Title of Invention

"APPARATUS AND METHOD FOR CONTROLLING ADAPTIVE CIRCUITS"

Abstract A feed-forward amplifier (20) having a signal cancellation loop including a cancellation node, and an error pathway (73), comprising: a first gain controller (C1) and a first phase controller (C2), each controller for providing a discrete tap steering signal and modulating the respective tap steering signal with a discrete low level signal that takes on a preselected sequence of values, the sequence chosen so that each low level signal is mutually orthogonal to each other low level signal over a preselected period; a first gain and phase adjuster (GPA1) connected to the outputs of the first gain controller (C1) and the first phase controller (C2) for providing a controlled gain change and phase shift in the signal cancellation loop, the magnitude of the gain change and phase shift controlled by the corresponding tap steering signals presented to the first gain and phase adjuster (GPA1) by the first gain controller and the first phase controller; and a first detector (D1), the input of which is connected to the cancellation node and the output of which is connected to the first gain controller (C1) and the first phase controller (C2), the first detector (D1) outputting a sequence of values of a characteristic of the signal at the cancellation node sampled over the preselected period and corresponding to the preselected sequences of values, wherein after the preselected period new values for the tap steering signals presented to the first gain and phase adjuster (GPA1) by the first gain controller (C1) and the first phase controller (C2) are obtained by multiplying term-by-term the sequence of values of the first detector output by the respective preselected sequences of values of the low level signals, each over the respective preselected period, summing each resulting series of products, and changing the tap steering signals to be modulated and presented to the first gain and phase adjuster (GPA1) based upon the values of the respective sums so as to maximize signal cancellation at said cancellation node. Figure: 1
Full Text The present invention relates to an apparatus and method for controlling adaptive circuits
FIELD OF THE INVENTION
The present invention relates to adaptive circuits. More specifically, the present invention relates to an apparatus and method for controlling adaptive circuits, such as controlling gain and phase adjustments in a feed forward amplifier circuit.
BACKGROUND OF THE INVENTION
Adaptive circuits are well known and used in a variety of applications. One well-known example of an adaptive circuit is the feed forward amplifier ("FFA"). In order to achieve linearity in a feed forward amplifier, careful control of the amplifier circuitry is required. In particular, in FFAs two or more gain and phase adjusters are often employed and the taps of each of these adjusters are carefully steered to achieve linearity through the amplifier.
Within the art of FFAs, it is known to use detector-controller circuits, one for each gain-and-phase adjuster. Each detector-controller circuit is operable to steer the taps of its respective gain-and-phase adjuster in the FFA so that the main amplifier and correctional amplifier can properly cooperate in order to reduce error introduced by the main amplifier and, should a pilot tone be used in the FFA, to also reduce the output residue of the pilot tone injected prior to the main amplifier.
In certain prior art detector-controller circuits, once the detector portion of the detector-controller circuit has indicated that the associated controller portion should make an adjustment, the controller arbitrarily steers the taps of the gain-and-phase adjuster in a direction to either increase or decrease the input to the tap, without knowing which of an increase or decrease will actually achieve the desired effect. In order to verify whether the controller steered the tap in the correct direction (e.g., to increase the signal to the tap), after the correction has been applied the detector circuit ascertains whether the direction of the variation brought about the desired effect, and, if so, instructs the controller circuit to continue steering in the same direction, if necessary. If, however, the detector circuit ascertains that the steering direction brought about an undesired result, then the detector instructs to the controller to try steering the tap in the opposite direction
(e.g., to decrease the signal to the tap).
In flic prior art, each detector-controller circuit works independently of each other, and therefore, achieving convergence towards m optimum level for each tap of each adjuster can be difficult For example, rapid changes is the strength of the input signal being amplified by the 5 FFA can make it difficult for the detector-controller circuits to respond quickly enough to converge the tap levels of each gain-and-phase adjuster towards the respective optimum levels. Furthermore, the adjustment of one tap of a gain-and-phase adjuster can disrupt an optimum or near optimum input level achieved at another tap, therefore cascading disruptions through all of the taps.
The inventor of the present invention also believes that a further problem is that such
prior art controller circuits can sometimes result in taps being steered to levels that are levels corresponding to local minima for the input signal, missing a global optimum for the input signal.
SUMMARY OF TOE INVENTION
It is an object of the present invention to provide a novel apparatus and method for
controlling an adaptive circuit mat obviates or mitigates at least one of the above-identified disadvantages of the prior art It is a further object of the present invention to provide a novel feed forward amplifier mat obviates or mitigates at least one of the above-identified disadvantages of the prior art.
According to an aspect of the present invention, mere is provided a feed-forward amplifier having a signal cancellation loop including a cancellation node that includes a gain controller and a phase controller. Each controller provides a discrete tap steering signal and modulates the corresponding tap steering signal with a discrete tracer signal mat takes on a preselected sequence of values. The sequence chosen so that the tracer signal is mutually orthogonal to each 25 other tracer signal over a preselected period. A gain and phase adjuster connected to the outputs of the controllers provides a controlled jam change and phase shift m the signal cancellation loop, the magnitude of the gain change and phase shift controlled by the corresponding tap steering signals presented to the gain and phase adjuster by the controllers. A detector, the input of which is connected to the cancellation node and the output of wMch is connected to the 30 controllers, outputs a measure of the envelope of me signal at the cancellation node. After the preselected period new values for the tap steering signals presented to the gam and phase adjuster by the controllers are obtained by moMplymg detector output by tfae respective tracer

signal, each ova- the respective preselected period, summing each resutong series of values, and changing the tap steering signals to be modulated and presented to the gam and phase adjuster in accordance with the values of the respective sums. Optionally, each tap steering signal may be increased or decreased depending upon the polarity of the corresponding sum, or the tap steering 5 signal presented to the gain and phase adjuster is left unchanged if tie corresponding sum is zero or within a preselected range about zero but, if the corresponding sum is outside the preselected range about zero, is increased or decreased depending upon the polarity of the corresponding sum. Also, each tap steering signal is increased if the corresponding sum is positive and decreased if the corresponding sum is negative. In any of the embodiments discussed above, the 10 tracer signals vary in polarity but not in magnitude and may be chosen to be pseudo noise sequences or Walsh codes.
According to another aspect of the present invention, there is provided a feed-forward amplifier that includes:
an input port;
a first main path splitter, the input of which is connected to the input port so that when an
input signal applied to the input port it is split by the first main path, splitter into a main
signal and a feed-forward signal;
a mam signal path gain and phase adjuster, the input of which is connected to the first
output of tins first main path splitter, the main signal path gain and phase adjuster having
a gain-control input tap and a phase-control input tap configured so that the voltage levels
on the taps control the amplitude and phase of the main signal;
a main amplifier, the input of which is connected to the output of the main signal path
gain and phase adjuster;
a second main path splitter, the input of which is connected to the output of the main
amplifier;
15 a feed-forward signal path delay element, the input of which is connected to the second
output of the first main path splitter, the delay imposed by the feed-forward signal path
delay element selected to approximately match the delay in the main signal caused by the
main amplifier,
a feed-forward path coupler, the first input of which is connected to the output of the
20 feed-forward signal path delay element;
a connector/atteiiuator connecting the second output of the second main path splitter to

the second input of the feed-forward path coupler, the attenuation selected so that the undistorted portion of the main signal provided to the feed-lorward path coupler is approximately cancelled out by the feed-forward signal;
a feed-forward path splitter, the input of which is connected to die output of the feed-
5 forward path coupler,
a detector, the input of which is connected to the second output of the feed-forward path splitter;
a gain controller, the input of which is connected to the output of the detector and the
output of which is connected to the gain-control input tap; and
10 a phase controller, the input of which is connected to the output of the detector and the
output of which is connected to the phase-control input tap, wherein:
each of the controllers modulates the voltage level on its respective output with a discrete low level signal that takes on a preselected sequence of values, the sequence chosen so that each low 1S level signal is mutually orthogonal to each other low level signal over a preselected period; the detector outputs a measure of the envelope of the signal at the cancellation node; and each controller multiples the signal received from the detector by the low level signal with which it modulated the tap to which it is connected, in each case over the preselected period, sums the resulting series of values over tune, and changes the voltage level on its respective tap in 20 accordance with the value of the sum.
Optionally, each voltage level is increased or decreased depending upon the polarity of the corresponding sum or the voltage level presented to the gain and phase adjuster is left unchanged if the corresponding sum is zero or within a preselected range about zero but, if the corresponding sum is outside the preselected range about zero, is increased or decreased 25 depending upon the polarity ofthe corresponding sum. Also, each voltage level may be increased if the corresponding sum is positive and decreased if the corresponding sum is negative and each output voltage level may be changed in proportion to magnitude ofthe respective sum.
In any ofthe embodiments discussed above, the low level signals vary in polarity but not 30 in magnitude and the low level signals may be chosen to be pseudo noise sequences or Walsh codes.
According to yet another aspect of the present invention, there is provided a feed-forward

amplifier having a signal cancellation loop including a cancellation node at which a signal is to be minimized, including:
a controller for providing a tap steering signal and undulating the tap steering signal with a tracer signal that takes on a preselected sequence of values; 5 an adjuster connected to the output of the controller for providing a controlled change in a
characteristic of lite signal cancellation loop that results in a change in a measure of the envelope of the signal at the cancellation node, toe magnitude of the change in the characteristic controlled by Hie modulated tap steering signal presented to me adjuster by the controller, and a detector, file input of which is connected to the cancellation node and the output of which is
10 connected to the controller, the detector for outputting the measure of the envelope of the signal at the cancellation node,
wherein after the preselected period a new setting for the tap steering signal is obtained by multiplying Hie detector output by the tracer signal, summing the resulting series of values, and changing the tap steering signal to be modulated and provided to the adjuster in accordance with
15 the value of the sum.
Optionally, the tap steering signal may be increased or decreased depending upon the polarity of the corresponding sum, or tibe tap steering signal presented to the gain and phase adjuster is left unchanged if the corresponding sum is zero or within a preselected range about zero but, if the corresponding sum is outside the preselected range about zero, is increased or
20 ' decreased depending upon me polarity of Ihe corresponding sum. Also, the tap steering signal is increased if the corresponding sun is positive and decreased if the corresponding sum is negative, hi any of the embodiments discussed above, the tracer signal vary in polarity but not in magnitude and may be chosen to be pseudo noise sequences or Walsh codes.
According to yet another aspect of the present invention, there is provided a circuit
25 having a node at which a signal is adaptrvery minimized by the circuit, comprising:
a controller providing an output voltage level, the output voltage level modulated by a low level signal that takes on a preselected sequence of values over a preselected period; an adjuster connected to the output of the controller for providing a controlled change in a characteristic of ttie adaptive circuit that results in a change in a measure of the envelope of the
30 signal at the node, the magnitude of me change in the characteristic controlled by the voltage level presented to the adjuster by the controller; and a detector, the input of which is connected to the node and the output of which is connected to

the controler, the detector outputting the measure of the envelope of the signal at the node, wherein after the preselected period a new setting for the voltage level presented to the adjuster by the controller is obtained by multiplying toe detector output by the low level signal, summing the resulting series of values, and changing the voltage level presented to the adjuster in 5 accordance with the value of the sum.
Optionally, each voltage level is increased or decreased depending upon the polarity of the corresponding sum or the voltage level presented to the adjuster is left unchanged if the corresponding sum is zero or within a preselected range about zero but, if the corresponding sum is outside the preselected range about zero, is increased or decreased depending upon the polarity 10 of the corresponding sum. Also, each voltage level may be increased if the corresponding sum is positive and decreased if the corresponding sum is negative and each output voltage level may be changed in proportion to magnitude of the respective sum.
According to yet another aspect of the present invention, more is provided a feed forward amplifier comprising:
an amplifier portion including a coupler, first and second gain and phase adjusters, first and second delay elements, a main amplifier and a correctional amplifier, the coupler providing an input signal to said amplifier portion to a first signal path including the first gain and phase adjuster, the main amplifier and the first delay element and an output and the coupler providing the input signal to a second signal path including the second delay element, the second gain and phase adjuster sad the correctional amplifier having a first signal path for carrying an input signal to a first gain-and-phase adjuster aad a main-amplifier, said first gain-and-phase adjuster having a pair of taps for steering said first adjuster, said amplifier portion having a second signal path for carrying a sample of said input signal generated to a second gain-and-phase adjuster and a correctional-amplifier, said second gain-and-phase adjuster having a pair of taps for steering said adjuster; and
a detector-controller portion having a first detector for receiving a detected signal from said first signal path and a second detector for receiving a detected signal from said second 15 signal path, said detector-controller portion further comprising a first pair of controllers for receiving said detected signal from said first detector and a second pair of controllers for receiving said detected signal from said second detector, said controllers each operable to steer a respective one of said taps based on said received detected signals, each of said controllers further operable to inject tracer-signals into its respective tap, said tracer-signals for carrying

through said amplifier portion and modulating said detected signals, said controllers each operable to extract from its respective detected signals a tap-signal by using its respective said tracer-signal, said controllers each further operable to utilize said extracted tap-signal to determine a desired direction for steering its respective tap and to output, substantially 5 simultaneously with each other controller, a signal to steer said respective tap.
According to yet another aspect of fins present invention, there is provided a feed forward amplifier comprising: an amplifier portion including:
(a) a first signal path having a first gain and phase adjuster, a mam amplifier and a
delay element; and
(b) a second signal path having a delay element, a second gain and phase adjuster and
a correctional amplifier, each gain and phase adjuster including a control input tap to
accept an input to alter the phase response of the gain and phase adjuster and a control
input tap to accept an input to alter the gain response of the gain and phase adjuster, the
first and second signal paths having a common signal input and a common signal output;
and
a detector portion including:
(c) a first detector to receive a signal from the common signal output and to provide
the received signal to a first controller operable to create an input to the gain tap of the
second gain and phase adjuster and to provide tie received signal to a second controller
operable to create an input to me phase tap of the seamd gam and priase adjuster; and
(d) a second detector to receive a signal from the second signal path before the
second gain and phase adjuster and to provide the received signal to a first controller
10 operable to create an input to me gam tap ofme first gain and phase adjuster and to
provide the received signal to a second controller operable to create an input to the phase tap of the first gain and phase adjuster, each controller responsive to a component in said received signals which is orthogonal to the components to which each other controller are responsive to and all the created inputs being applied to the taps substantially
15 simultaneously and altering the operation of said feed forward amplifier to linearize the
amplification of the input signal through the feed forward amplifier. According to yet another aspect of the present invention, there is provided a method for operating am adaptive control circuit having a plurality of control input taps, said method

comprising, for each said control input, the steps of: detecting a signal, including a tracer signal, from said circuit; extracting a measurement from the tracer signal in said detected signal; determining an appropriate input to be applied to said control input to improve operation of said adaptive circuit; creating a tracer signal for said control input, said created tracer signal being orthogonal to the tracer signals created for each other control input; and combining said tracer signal and said determined input and applying the resulting signal to said control input.
An apparatus and method for operating an adaptive circuit includes injecting a set of orthogonal tracer signals into the circuit. The tracers' signals are extracted after modification during operation of at least a portion of the circuit and are examined by respective controllers to modify operation of the circuit
5 in one embodiment, the invention is incorporated into a feed forward amplifier in which
a set of orthogonal tracer signals is applied to the amplifier. A detector controller detects a signal including as components the orthogonal tracer signals as modified by portions of the amplifier. Each controller portion of the detector controller extracts a measurement relative to its respective tracer signal from the detected signal and modifies its output to control a portion of 10 the amplifier accordingly. The controllers apply their outputs to the respective portions of the amplifier at substantially the same time, leading to quick convergence of the operating point of the amplifier to an optimal, or near-optimal, configuration. Injection of the tracer signals into the amplifier is accomplished by dithering the controller outputs by the respective orthogonal tracer signals.
According to yet another aspect of the present invention, there is provided an adaptive circuit comprising:
at least two adjusters, each adjuster including at least one control input to alter the operation of the circuit;
at least one signal generator to create at least one tracer signal, each created tracer signal being orthogonal to each other created tracer signal;
at least two controllers, each controller operable to output a control signal to at least a respective one of the control inputs of the at least two adjusters, a different orthogonal tracer signal from said at least one signal generator being applied to each respective control signal as a dither; and
15 at least one detector operable to extract a composite signal from the circuit and to apply
the composite signal to the at least two controllers, each controller being responsive to the

applied signal to extract at least one orthogonal tracer and alter the respective control signal to converge operation of the circuit to an optimal or near optimal configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the present invention will now be described, by way of 5 example only, with reference to the attached Figures, wherein:
Figure 1 is a block diagram of a feed forward amplifier in accordance with an embodiment of the present invention;
Figure 2 is a block diagram of a detector-controller portion of the amplifier shown in Figure 1;
10 Figure 3 is a flow chart showing a method of controlling the gain and phase adjustment
of the amplifier of Figure 1;
Figure 4 is an exemplary set of Walsh codes for use in the detector-controller portion of the amplifier of Figures 1 and 2;
Figure 5 shows an example of the operation of two of the controllers shown in Figure 2 15 using the method of Figure 3, during an initial power-on of the amplifier of Figure 1; and
Figure 6 shows an example of the operation of the controllers shown in Figure 5 during a subsequent iteration through the method shown of Figure 3.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to Figure 1, a forward feed amplifier ("FFA") in accordance with an 20 embodiment ofthe invention is indicated generally at 20. FFA 20 comprises an amplifier
portion 24 and a detector-controller portion 28. Amplifier portion 24 includes a coupler 36 mat is connected to an input signal path 40. Coupler 36 is operable to split an incoming signal from path 40 into a main amplifier signal path 44 and a correctional amplifier signal path 48.
Main amplifier signal path 44, which carries the main signal from coupler 36, includes a 25 gain and phase adjuster GPAi, amain amplifier 56 and a delay element 60 that outputs to an output signal path 6*4. GPAi includes a gain control input tap Ti, and a phase control input tap T2, each of which can be steered so mat GPAi operates to yield maximum signal cancellation at the output of coupler 82 and the input of coupler 104, as discussed below. The location in the circuit at which maximum signal cancellation is to occur is sometimes referred to as the 30 "cancellation node".
Correctional amplifier signal path 48 which carries a sample, generated by coupler 36, of the signal from input signal path 40 includes a delay element 68, a gain and phase adjuster GPA2

and a correctional amplifier 74, the output of which connects to output signal path 64 via a coupler 76. GPA2 includes a gain control input tap T3, and a phase control input tap T4} each of which can be steered so that GPAa is adjusted to require a minimum, or near minimum, amount of power to be delivered to me correctional amplifier 74. As used herein, the terms "steer", "steered" and "steering" are intended to comprise all suitable methods of adjusting and/or controlling of the taps respective to a gain and phase or other suitable adjuster. In the embodiment of the invention discussed below, taps T1, T2, T3, and T4, are steered by changing the voltage levels applied to each of them respectively.
As will be apparent to those of skill in the art, GPA2 and correctional amplifier 74 form 10 an error pathway 73 within amplifier portion 24. Accordingly, when the output of correctional amplifier 74 is coupled to the output of delay 60, errors and pilot tones, if used, are substantially eliminated from the output signal path 64, such that the output signal path 64 presents a substantially linear amplification of the signal from input signal path 40.
Amplifier portion 24 is further characterized by a coupled path 79 mat interconnects a 15 first coupler 80, which is connected to the output of main amplifier 56, and a second coupler 82, which is connected to the output of delay element 68, in order to provide a sample of the error introduced by main amplifier 56" to the error pathway 73, commencing at GPA2. Attenuation may be provided in coupled path 73, if not already provided by the first coupler 80.
The main amplifier signal path 44, the correctional amplifier signal path 48, and the 20 coupled path 79 together are sometimes referred to as a "signal cancellation loop".
In the illustrated embodiment, amplifier portion 24 further includes a pilot tone generator 86 that is coupled, via a coupler 90, to the input of main amplifier 56. Pilot tone generator 86 generates a pilot tone for use by error pathway 73 in the usual manner for reducing error introduced by main amplifier 56. By the same token, amplifier portion 24 further includes a 25 pilot tone receiver 94 that is coupled, via a coupler 98, to output signal path 64. Pilot tone
receiver 94 is operable to measure any remaining pilot tone present along output signal path 64 for eventual use by error pathway 73 to introduce a signal at coupler 76 that will reduce the pilot tone in output signal path 64.
Detector-controller portion 28 connects to amplifier portion 24 through various inputs 30 and various outputs, as described herein. Specifically, a coupler 104 connected just prior to error pathway 73 delivers an input signal to a first detector Dx, which in turn presents a detector-outoat to a gain controller Ci and a phase controller C2. hi the illustrated embodiment, the

detector-output is a measure of the amplitude of the envelope of the input signal applied to it. However, it is within the scope of the invention to provide as a detector-output a signal proportional to the log of the IMS value of the envelope of the input signal or proportional to peaks of the envelope of the input signal, as well as any other measure or signal that will occur 5 to those skilled in the art Wherever in the following or in the claims that reference is made to the detector-output being the amplitude of the envelope of the input signal applied to it, it should be understood that such other signals or measures are also intended.
Similarly, pilot tone receiver 94 delivers an output signal to a second detector D2, which in turn presents a detector-output to a gain controller C3 and a phase controller C4. Again, 10 detector D2 outputs the amplitude ofthe envelope ofthe input signal applied to it. As will be discussed in greater detail below, controllers Q, C2, C3 and Q are operable to steer taps Ti, T2, T3 and T4, respectively, based on the signals received from their respective detectors D, in order to find optimum (or otherwise desired) pin and phase adjustments for each of adjusters GPAi and GPA2.
15 In the illustrated embodiment, tracer signals are applied to each of main amplifier signal
path 44 and correctional amplifier signal path 48 by using them to modulate the voltage levels applied to the taps Ti, T2, T3, and T4, respectively. Those voltage levels are also referred to as tap steering signals and the modulated voltage levels as modulated tap steering signals. Each tracer signal, because it rapidly but slightly changes either the gain or the phase m the signal
20 cancellation loop, causes variations in the amplitude ofthe envelope ofthe input signal applied to one ofthe detectors D| and D2. The detected amplitudes ofthe envelopes ofthe signals applied to the detectors Dj and D2 are passed to the respective controllers C. Each controller C extracts the variation in the detector output caused by the tracer signal applied to the corresponding tap and steers the tap accordingly. The variations in the detector outputs caused
25 by the tracer signals «m be separated from each other because each tracer signal is selected to be orthogonal to each other tracer signal As described below, to achieve orthogonality in the illustrated embodiment each tracer signal is a Walsh code, but other techniques, such as selecting appropriate pseudo noise sequences as the tracer signals will be apparent to those of skill in the art As will become apparent to those of skill in the art from the discussion herein,
30 the present invention will operate wifli tracer signals tot are not totally orthogonal to each other, although better performance will be obtained when using signals as orthogonal as possible. Accordingly, as used herein, the term orthogonal is intended to include both perfectly orthogonal

signals, such as Walsh codes, and near-orthogonal signals, for example pseudo noise sequences taken over a time period that provides approximately orthogonal results. The general criterion is that the mere uncorrelated tracer signals are over an appropriate time period the better the results.
5 Before going into the details, as an overview, consider an idealized situation that may
help in understanding the embodiment of the invention described herein. To aid in understanding, we assume that the main amplifier does not distort the input signal at all and we start with adjusting only one tap steering signal. We begin by setting a tap steering signal at a particular voltage level. If that voltage level is applied to a tap of an adjuster, a particular level
10 of signal cancellation at the cancellation node results. If the voltage level is optimal (so that the amplitude of envelope of the signal at the cancellation node is zero), dithering of the voltage level by a tracer signal that has an avenge value of zero (as do orthogonal and pseudo noise sequences over appropriate periods) wit result in slight excursions in the amplitude of envelope of the signal at the cancellation node above and below zero, but the sum of all the excursions
15 will be zero. Now suppose mat the voltage level is not optimal. Then the slight excursions in the amplitude of the envelope of the signal at the cancellation node will be to levels above and below the amplitude of envelope of the signal at the cancellation node that would occur if no dither were applied. The result will be a non-zero sum with a polarity, or sign, the same as the polarity of the amplitude of the envelope of the signal at the cancellation node would be if no
20 dither were applied. So far we have assumed that there is only one tap. If there are more taps, thenby using orthogonal or pseudo noise sequences over appropriate periods as tracer signals, the excursions in the amplitude of envelope of the signal at the cancellation node caused by dithering of each tap can be extracted separately from the amplitude of envelope of the signal at the cancellation node, summed, and used to adjust the corresponding tap steering signals
25 simultaneously.
Referring now to Figure 2, detector-controller portion 28 will now be discussed m greater detail. As shown, controllers d, Cz, C3 and C4 each include the same components. Each controller C includes a multiplier 200 fiiat receives a detector-output ftom a respective detector D. Controllers C are operable to utilize fte detector-output to determine how to steer their
30 respective tap T. In the present embodiment, each detector-ou^wt is the amplitude of the envelope of the signal received by a respective detector D and carries combined information about the effects of dithering (modulating) the respective tap steering signals with the respective

tracer signals on me amplitude of the envelope of the signal received by the respective detector D. The information carried about the effect of the dithering of each tap steering signal with a tracer signal may be separately extracted from the detector-o»$>ut in the manner discussed in greater detail further below.
5 To extract &e effect of the tracer signal injected by tap T for the controller C, each
multiplier 200 receives its Walsh code from a Walsh code generator 204. Each Walsh code generator 204j, 2042,2043 and 2044, generates a unique Walsh code, which, as is understood by those of skill in the art, is a preselected pattern of one or more logical ones and/or logical zeroes that repeat over a given period and is orthogonal to each other Walsh code. As will be 10 discussed in greater detail below, when the detector-output from a respective detector D is multiplied by multiplier 200 with a respective Walsh code, only the portion of the detector-output resulting from the tracer signal injected at the respective tap T will be output from the respective multiplier 200.
Controllers C also each include an integrator 208 which is operable to sum the results
15 from multiplier 200, which represent the effect of tracer signal for the respective tap T on the
respective detector-output, for each penoi and output those summed results to an adjuster 212
which is operable to determine from the summed result whether the tap T it is responsible for is
properly steered. If an adjuster 212 determines that its corresponding tap T was steered in the
proper direction, then adjuster 212 outputs a signal mat continues to steer that tap T in the same
20 direction. If adjuster 212 determines that its corresponding tap T was steered in the wrong
direction, then adjuster 212 outputs a signal that steers that tap T in the opposite direction.
Adjuster 212 can also determine that the tap T is at an optimum level, in which case adjuster 212
does not steer tap T at all, but leaves the tap steering signal at the existing level. Further details
of adjuster 212 will be discussed in greater detail below.
25 To inject the tracer signal for a controller C into amplifier portion 24, the signal
outputted from adjuster 212 is modulated, using a summer 216, with the Walsh code generated at Walsh code generator 204, the Walsh code having first been attenuated through an attenuator 220 by a factor A. The Walsh code is attenuated, by fetor A, to a level that provides a suitable "dither" or '^perturbance" that can be summed with the control signal from adjuster 212 for the 30 respective tap T. The voltage level of the resulting modulated signal is at a level that will generally yield a niiniiHuni reliably detectable signal at the output of detector D.
As will be apparent to those of still in me art, in order for the Walsh code to behave as a

good dither, each Walsh code for each controller C is selected to have as many transitions as possible, while still bemg orthogonal to fee Walsh codes of the other controllers C. Also, as the tracer signal is averaged over a suitable period of time to reduce the effects of noise in the detected signal, it is desired to choose a Walsh code, or other orthogonal signal, with a suitably long length. It is presently preferred that a length for the Walsh codes is selected which is at least twice the number taps T to be controlled, i.e. — in the embodiment of Figure 1, the shortest desired length of Walsh codes would be an eight chip code and, in feet, it is presently preferred to use a Walsh code length of sixty-four chips for a feed forward amplifier with four taps T.
The output of each summer 216 is then presented to its respective tap T, thereby steering each respective tap T accordingly and injecting the respective tracer signal.
A method of controlling the gain and phase adjustment of feed forward amplifier 20 will now be discussed with reference to Figure 3. The flow-chart in Figure 3 shows a sequence of steps which can be used to operate, for example, each controller C of detector-controller portion 28, thereby steering each tap T. In other words, fee sequence of steps in Figure 3 will be performed, in parallel, for each controller C.
Although, as mentioned above, in a presently preferred embodiment each Walsh code is actually sixty-four chips in length, for simplicity while explaining fee method, it will be assumed feat each Walsh code Wt, W2, W3 and W4, is only eight chips in length. Each Walsh code W,, W2, W3 asd W4 is generated by a respective Walsh code generators 204i, 2042,2043 and 2044 and is shown in Table I and illustrated in fee pulse-waveforms shown in Figure 4. From fee waveforms shown therein, it is to be understood feat a "1" means a logical "1", and "-1" means a logical "0".
Table I
(Table Removed)
Again for simplicity, fee method of Figure 3 will only be discussed in detail wife reference to controllers d and C2 and feek associated detector Dt. The method begins at step

300 where a signal is detected at detector Di from the amplifier portion 24 of feed forward amplifier 20. To illustrate how this step can be accomplished according to a present embodiment, it will be assumed that feed forward amplifier 20 has just been activated (i.e. initialized), but that so input signal is present along input signal path 40, and accordingly no 5 output signal is present along output signal path 64.
The activity in feed forward amplifier 20 at this point in the method is illustrated in Figure 5, where detector Dj, controlter Ci and conlmllar C2 are shown. As there is no input signal along input signal path 40, detector Di detects this and outputs a corresponding waveform, which is represented in Figure 5 as a detector-output waveform 400a, which in turn is 10 inputted into multiplier 200i and multiplier 2OQ2.
By way of further background tofhe operation of the present embodiment, it will be apparent to those of skill in the art that the tracer signal being applied to the taps T of gain and phase adjuster GPAi, whether a Walsh code or any other dither, will only be detectable at detector D] where there is an input signal along input signal path 40 as the tracer signal is a 15 modulation of the input signal. Similarly, ifapilot tone is being injected at coupler 90, then the tracer signal applied at the tips T of GP A2 will be detectable at detector D?. as modulation of the pilot tone detected at detector D2. As there is as yet no input signal in Figure 5, detector-output waveform 400a is all zeros, as shown.
Referring again to Figure 3, the method then advances to step 320 where the tracer signal 20 for the tap Tj respective to the controller Q is extracted from the signal detected at step 300. In a present embodiment, this signal is extracted from detector-output waveform 400a using multiplier 200 and integrator 208. First, multiplier 200 multiplies the Walsh code output from Walsh code generator 204 with the detector-output waveform 400a to extract the tracer signal. The product waveform is presented to integrator 208, which sums each pulse in the waveform 25 over the number of chips in the Walsh code. The output for each integrator 208 u 2082 are represented on Figure S as items 404ai and 404%, respectively.
Specifically, for controller C«, since flic detector-output 400a = {0,0,0,0, 0,0,0,0}, and since the output of Walsh code generator 204i can be represented by the series Wi={l, -1, -1,1,-1,1,1,-1}, then the output of multiplier 200i can be represented as {0,0,0,0,0,0,0,0} 30 x {1, -1, -1,1, -1,1,1, -1} - (0,0,0,0,0,0,0,0). The result 404at, from integrator 208t can be represented as 404ai = (0,0,0,0,0,0,0,0) - 0.
Similarly, for controller Cz» since detector-outouF400a== {0,0,0,0, 0,0,0,0} and since

the output of Walsh-code generator 204z can be represented by the series Wf* {1, -1,1, -1,1, -1, 1, -1}, then flieoutptttofmuhqjKeraOOicanbereiHi^enled as {0,0,0,0, 0,0,0,0} x {1, -1,1, -1,1,-1,1,-1}- (0,0,0,0,0,0,0,0). The result 404&2, from integrator 208a can be represented as 404a2 - (0,0,0, 0,0,0,0,0) « 0.
5 Referring again to Figure 3, the method ten advances to step 340 where the appropriate
steering signal for the tap T; respective to a given controller Q is determined. In the present embodiment, this step is performed by adjuster 212. Continuing with the above example being discussed with reference to Figure 5, flic result 404a from each integrator 208 is then passed to its respective adjuster 212. As shows in fee example of Figure 5, the result 404a from each 10 integrator 20S was "0", and this value is passed to adjuster 212.
In the present embodiments, adjuster 212 includes digital signal processing circuitry that is operable to make the determination of whether and how to steer the tap T based on the result 404a passed irons its respective integrator 208. Adjuster 212 determines from the received "0" input that no steering of a tap T is required and the method advances to step 360, wherein no 15 adjustment is made to the steering signal applied to the respective tap T.
If adjuster 212 had received a positive or negative input from the result 404a, men an appropriate adjustment to the tap steering signal would be determined and the method would have advanced to step 360 where the appropriate adjustment of the steering signal is applied to the respective tap T.
20 Continuing with the example being discussed in conjunction with Figure 5, as it was
determined at step 340 mat no adjustment to the steering signal was required, and as feed forward amplifier 20 has just been activated, adjuster 212 determines mat the tap T for its respective controller C should remain in tt* nominal position. Each adjuster 212 then outputs a corresponding tap steering signal, indicated on Figure 5 as signals 408aI and 408a2. The exact 25 format oftapsteermg signals 408 can be generated usmg known meam and circuitry and need only correspond with the format required to control the specific type of gain and phase adjusters used within amplifier portion 24.
Tap steering signals 408a are then presented to their respective summer 216, which sums the tap steering signal 408a with an attenuated version AW of the Walsh code W. This 30 attenuated WaMi code is indicated on Figure 5 as items AWi and AW2 and is the tracer signal to be injected in me signal paths of amplifier portion 24 for fee next iteration of the control method, fi will be apparent to those of skill in fee art that fee factors A for each attenuator 220

can differ from each other. Attenuated Walsh codes AW are attenuated by factors A to a level, appropriate far me specific O»A employed, so they act as a "dither" modulated on top of its tap steering signal 408a and that operation of the gain and phase GPA is not impeded by the dither. Attenuated Walsh codes AW are produced by attenuators 220, which simply receive the 5 output of their respective Walsh code generator 204 and generate and output an attenuated version thereof to their respective summers 216. Thus, each tap steering signal 408a and respective attenuated Walsh code AW are combined by their respective summer 216, to create a dithered tap steering signal, indicated on Figure 5 as items 412ai and 412a2. At step 360, the dithered tap steering signals 412ai, 412% are then presented to their respective taps Tt, T2 of 10 GPAi and the method then returns to step 300, where another iteration of the method begins.
As mentioned above, the method shown in Figure 3 operates simultaneously for detector D2 and controllers C3 and Q in the same manner as that described above for detector Di and controllers Ci and Q. Thus, steering adjustments can be effected at each tap T at the same tune. An example of a second iteration through the method of Figure 3 will now be discussed 15 with reference to Figure 6. It is assumed that, prior to this iteration an input signal is being input along input signal pain 40. Figure 6 again shows detector D1 and controllers C1 and C2. This iteration commences with step 300 again being performed by detector Di. As mere is now an input signal along input signal path 40, detector D1 now detects the tracer signal (dither) mat has been applied to at least one of the gain and phase adjusters and reflects this detection in detector-20 output waveform 400b. For purposes of explaining the present embodiment, it will be assumed mat detector-output waveform 400b is {-3, -1,0,2, -3,0, -1,1} and waveform 400b is input to multipliers 200) and 2OO2.
Referring again to Figure 3, the method then advances to step 320 where the tap measurement for the tap T, respective to the controller C, is extracted from the signal detected at 25 step 300. In the present example discussed in conjunction with Figure 6, tilts signal is extracted from detector-output waveform 400b using multiplier 200, and integrator 208, of each controller Q. First, multiplier 200 multiplies the Walsh code output from Walsh code generator 204 with the detector-output waveform 400b. The product waveform is then presented to integrator 208, which sums each pulse in the waveform over the number chips in the Walsh code. The results 30 from each integrator 2081,2O82 are represented on Figure 6 as items 404bi and 404b2, respectively.
Specifically, for controller Cj, since the detector-output 400b = {-3, -1, 0, 2, -3, 0, -1,1},

and since the output of Walsh-code generator 204, Wi-{1, -1, -1,1, -1,1,1, -1}, then the output of multiplier 200! can be represented as {-3, -1,0,2, -3, 0, -1,1} x {1, -I, -1,1, -1,1,1, -1} = (-3,1,0,2, 3,0, -1, -1). The result for integrator 208] can be represented as 404b, = (-3, 1, 0, 2,3,0, -1, -1) - 1. Similarly, for controller C2,400b - {-3, -1, 0,2, -3,0, -1,1} and since the 5 output of Walsh-code generate 2042 Wz- {1, -1,1, -1,1, -1,1, -1}, then the output of multiplier 2002 can be represented as {-3, -1,0,2, -3,0, -1,1} x {1, -1,1, -1,1, -1,1, -1} = (-3,1, 0, -2, -3, 0, -1, -1). Tfceresult for integrator 2O82 can be repre^oted as 404b2== (-3,1,0, -2, -3,0, -1, -1) - -9.
The method then advances to step 340 where the appropriate steering signal for the tap T 10 respective to a given controller C is determined. Continuing with the above example being
discussed with reference to Figure 6, the result 404b for each integrator 208 is then passed to its respective adjuster 212. In this example, the result 404b produced by integrator 2081 was "1" and this value is passed to adjuster 212b. The result 404b2 produced by integrator 2O82 was "-9", and this value is passed to adjuster 2122- In each case, the sign of the integrator output 15 determines which way the respective tap T is adjusted.
As previously discussed, adjusters 212 include digital signal processing circuitry which is operable to make the determination of whether to steer the tap T based on the result 404b passed from its respective integrator 208. hi the present embodiment, adjusters 212 are configured so mat, if the received input from its respective integrator 208 does not equal "0", then it is 20 determiDed that steering of its respective tap T is required. Accordingly, in the example of Figure 6 adjusters 212i and 2122 both determine that steering of the respective taps Ti, T2 is required.
For controller Ci, adjuster 212i has received a "1", and thereby detetmines that the tap steering signal 408b 1 to tap Tj should be increased and accordingly, the output tap steering signal 25 408bi is increased by a preselected increment from the previous signal mat was used during the previous iteration through the method of Figure 3. For controller C2, adjuster 2122 has received a "-9", and thereby determines mat the tap steering signal 408b2 to tap T2 should be decreased and accordingly, the output tap steering signal 408t>2 is decreased by a preselected increment from the previous signal that was used during the previous iteration through the method of 30 Figure 3. Tap steering signals 408b are men presented to their respective summer 216, which sums the tap steering signal 408a with the respective attenuated Walsh code AW. Thus, each tap steering signal 408a and attenuated Walsh code AW are summed together by their respective

summer 216, to create a dithered tap steering signal, indicated on Figure 6 as items 412bi and 412ba. The dithered tap steering signals 412b are flien presented to their respective taps T of their respective GPA at step 360.
Iterations through tibe method of Figure 3 repeat continuously for each controller C, 5 increasing or decreasing each tap output signal 412 until an optimum level for a respective tap T is reached, at which point the respective controller C simply mamtarns the tap output signal 412 at its current level (i.e. - the result from integrator 208 of the product from multiplier 200 of waveform 400 and Walsh code W is "0*0 until, during a subsequent iteration through the method of Figure 3, further steering of the respective tap T is required.
10 While the embodiments discussed herein are directed to specific implementations of the
invention, it will be understood that combinations, sub-sets and variations of the embodiments are within the scope of the invention. For example, it will now be apparent to those of skill in the art that amplifier portion 24 is a substantially known configuration for one type of amplifier portion of a feed forward amplifier, yet other configurations of amplifier portion 24 are within
15 the scope of the invention. Other such configurations are discussed in a co-pending U.S. patent application 09/715,085, assigned to the assignee of the present invention, the contents of which are incorporated herein by reference. In particular, this application teaches a feed forward amplifier with a single pilot tone generator receiver, which is also suitable for incorporation into the present invention. A general discussion of feed forward amplifiers instructive to those of
20 skill in the art for the design of amplifier portions is discussed in U.S. Patent 3,471,798, the contents of which are also incorporated herein by reference.
As will also be apparent to those of skill in the art, feed forward amplifiers can include more than two gain and phase adjusters, hi such a case, a detector-controller circuit can be employed for each gain and phase adjuster and a separate orthogonal tracer signal employed for
25 each tap T.
Further, while the embodiments discussed herein refer specifically to FFAs having a pilot tone, it is to be understood that the present invention is also applicable to FFAs that do not use pilot tone, but use some other method, for example such as measuring intermodulation energy at detector D2.
30 While the embodiments discussed herein refer to gain and phase adjusters having gam
and phase taps T, it is to be understood that the present invention is not so limited and can be applied to other types of adjusters, such as phase and gain adjusters having in phase T and

quadrature "Q" taps. Furthermore, while the embodiments discussed herein refer to controHing gain and phase adjustments in FFAs, it is to be understood thai the apparatus and method discussed herein can be modified for use with any appropriate circuit where adaptive control is used, such as feed forward circuits, etc.
5 It is also to be understood that while the embodiments discussed herein refer to Walsh
codes, any type of orthogonal tracer-signal, such as suitable length pseudo noise sequences or the like can be used, with appropriate modifications to other aspects of the remainder of the circuit. Additionally, while the number of chips of the Walsh codes used in the exemplary embodiments discussed herein corresponds to the period of the puke wave-form of the detector-output, it will 10 be understood that these periods need not correspond at all. to general, it is to be understood that any means or method for extracting a particular tap measurement from a detector-output can be used, such as using frequency division multiplexing.
While presently less preferred due to increased complexity, it is contemplated that the magnitude of the output of integrator 208 could also be used to provide further information to 15 determine the amount by which each tap T is to be steered, in addition to using the polarity of the integrated signal to determine the direction the tap T should be steered. In such a case, instead of adjusting the amount by a preselected increment, a variable increment can be selected depending upon the magnitude of the output.
It is also contemplated that the size of the increment can vary, in a preselected manner, 20 between start up of the adaptive circuit and normal operation of the adaptive circuit. For
example, at start up and for a given number of iterations, amplifier 20 of Figure 1 can employ an increment/decrement size of 5 unite, followed by an increment/decrement size of 3 units for another given number of iterations, then followed by an increment/decrement size of 2 units for another given number of iterations, after which an increment/decrement size of 1 unit is 25 employed. This should allow faster convergence of the ampUfier at start up.
The present invention provides a novel feed forward amplifier that includes a method and apparatus for steering the gam and phase adjustment such mat each tap within the gain and phase adjusters is adjusted at substantially the same time to converge towards an optimum operating setting. Convergence towards me optimum settings are therefore obtained 30 substantially faster and/or more accurately than prior art feedforward amplifiers. Bach tap can have a tracer signal, which is orthogonal to other tracer signals, applied to the signal paths through the amplifier. The respective tap measurement is extracted and employed by each tap

controller to appropriately alter the respective tap steering signal.
The above-described embodiments of the invention are intended to be examples of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention which is defined solely by the claims appended hereto.















We claim:
1. A feed-forward amplifier (20) having a signal cancellation loop including a cancellation
node, and an error pathway (73), comprising:
a first gain controller (C1) and a first phase controller (C2), each controller for providing a discrete tap steering signal and modulating the respective tap steering signal with a discrete low level signal that takes on a preselected sequence of values, the sequence chosen so that each low level signal is mutually orthogonal to each other low level signal over a preselected period;
a first gain and phase adjuster (GPA1) connected to the outputs of the first gain controller (C1) and the first phase controller (C2) for providing a controlled gain change and phase shift in the signal cancellation loop, the magnitude of the gain change and phase shift controlled by the corresponding tap steering signals presented to the first gain and phase adjuster (GPA1) by the first gain controller and the first phase controller; and
a first detector (D1), the input of which is connected to the cancellation node and the output of which is connected to the first gain controller (C1) and the first phase controller (C2), the first detector (D1) outputting a sequence of values of a characteristic of the signal at the cancellation node sampled over the preselected period and corresponding to the preselected sequences of values,
wherein after the preselected period new values for the tap steering signals presented to the first gain and phase adjuster (GPA1) by the first gain controller (C1) and the first phase controller (C2) are obtained by multiplying term-by-term the sequence of values of the first detector output by the respective preselected sequences of values of the low level signals, each over the respective preselected period, summing each resulting series of products, and changing the tap steering signals to be modulated and presented to the first gain and phase adjuster (GPA1) based upon the values of the respective sums so as to maximize signal cancellation at said cancellation node.
2. The feed-forward amplifier (20) as claimed in claim 1, wherein said error pathway (73)
includes a correctional amplifier (74), the feed-forward amplifier (20) additionally
comprising:
a second gain controller (C3) and a second phase controller (C4), each such controller for providing a discrete tap steering signal and modulating the respective tap steering signal with a discrete low level signal that takes on a preselected sequence of values, the sequence chosen so that each low level signal is mutually orthogonal to each other low level signal over a preselected period;
a second gain and phase adjuster (GPA2) connected to the outputs of the second gain controller (C3) and a second phase controller (C4) for providing a controlled gain change and phase shift in the error pathway, the magnitude of the gain change and phase shift controlled by the corresponding tap steering signals presented to the second gain and phase adjuster (GPA2) by the second gain controller (C3) and a second phase controller (C4); and
a second detector (D2), the input of which is connected to the output of the feed-forward amplifier (20) and the output of which is connected to the second gain controller (C3) and a second phase controller (C4), the second detector (D2) outputting a sequence of values of a characteristic of the signal at the output of the feed-forward amplifier (20) sampled over the preselected period and corresponding to the preselected sequences of values,
wherein after the preselected period new values for the tap steering signals presented to the second gain and phase adjuster (GPA2) by the second gain controller (C3) and the second phase controller (C4) are obtained by multiplying term-by-term the sequence of values of the second detector output by the respective preselected sequences of values of the low level signals, each over the respective preselected period, summing each resulting series of products, and changing the tap steering signals to be modulated and presented to the second gain and phase adjuster (GPA2) based upon the values of the respective sums.
3. The feed-forward amplifier (20) as claimed in claim 1 or claim 2, wherein each tap steering signal is increased or decreased depending upon the polarity of the corresponding sum.
4. The feed-forward amplifier (20) as claimed in any one of claims 1-3, wherein a tap steering signal presented to a gain and phase adjuster is left unchanged if the corresponding sum is zero or within a preselected range about zero but, if the corresponding sum is outside the preselected range about zero, is increased or decreased depending upon the polarity of the corresponding sum.
5. The feed-forward amplifier (20) as claimed in any one of claims 1 - 4, wherein a tap steering signal is increased if the corresponding sum is positive and decreased if the corresponding sum is negative.
6. The feed-forward amplifier (20) as claimed in any one of claims 1 to 5, wherein the low level signals vary in polarity but not in magnitude.
7. The feed-forward amplifier (20) as claimed in any one of claims 1 to 6, wherein the low level signals are chosen to be pseudo noise sequences or Walsh codes.
8. The feed-forward amplifier (20) as claimed in any one of claims 1 to 7, wherein the characteristic of each signal detected by a detector is the amplitude of the envelope of the signal.
9. A method of controlling a feed-forward amplifier (20) having a signal cancellation loop including a cancellation node, and an error pathway (73), comprising:
generating two discrete low level signals that each take on a preselected sequence of values, the sequence chosen so that each low level signal is mutually orthogonal to each other low level signal over a preselected period;
generating a gain control tap steering signal and a phase control tap steering signal each modulated with a different one of the low level signals;
providing a controlled gain change and phase shift in the signal cancellation loop, the magnitude of the gain change and phase shift controlled by the respective tap steering signals;
detecting a measure of the envelope of a signal at the cancellation node and outputting a sequence of values of that measure sampled over the preselected period and corresponding to the preselected sequences of values; and
after the preselected period, calculating new values for the tap steering signals by multiplying term-by-term the sequence of values of the detector output by the respective preselected sequences of values of the low level signals, each over the respective preselected period, summing each resulting series of products, and changing the tap steering signals based upon the values of the respective sums so as to maximize signal cancellation at said cancellation node.
10. The method as claimed in claim 9, comprising:
generating two additional discrete low level signals that each take on a preselected sequence of values, the sequence chosen so that each low level signal is mutually orthogonal to each other low level signal over the preselected period;
generating an additional gain control tap steering signal and an additional phase control tap steering signal each modulated with a different one of the additional low level signals;
providing a controlled gain change and phase shift in the error pathway, the magnitude of the gain change and phase shift controlled by the respective additional tap steering signals;
detecting a measure of the envelope of a signal at the output of the feed-forward amplifier and outputting a sequence of values of that measure sampled over the preselected period and corresponding to the preselected sequences of values; and
after the preselected period, calculating new values for the additional tap steering signals by multiplying term-by-term the sequence of values of the detector output by the respective preselected sequences of values of the additional low level signals, each over the respective preselected period, summing each resulting series of products, and changing the additional tap steering signals based upon the values of the respective sums.
11. The method as claimed in claim 9 or claim 10, wherein each tap steering signal is increased or decreased depending upon the polarity of the corresponding sum.
12. The method as claimed in any one of claims 9-11, wherein a tap steering signal is left unchanged if the corresponding sum is zero or within a preselected range about zero but, if the corresponding sum is outside the preselected range about zero, is increased or decreased depending upon the polarity of the corresponding sum.
13. The method as claimed in any one of claims 9-12, wherein a tap steering signal is increased if the corresponding sum is positive and decreased if the corresponding sum is negative.
14. The method as claimed in any one of claims 9 to 13, wherein the low level signals vary in polarity but not in magnitude.
15. The method as claimed in any one of claims 9 to 14, wherein the low level signals are chosen to be pseudo noise sequences or Walsh codes.
16. The method as claimed in any one of claims 9 to 15, wherein the characteristic of each signal detected is the amplitude of the envelope of the signal.

Documents:

00626-delnp-2004-form-13-(03-04-2006).pdf

626-DELNP-2004-Abstract-(01-07-2010).pdf

626-delnp-2004-abstract.pdf

626-DELNP-2004-Claims-(01-07-2010).pdf

626-delnp-2004-claims.pdf

626-DELNP-2004-Correspondence-Others-(01-07-2010).pdf

626-delnp-2004-correspondence-others.pdf

626-DELNP-2004-Description (Complete)-(01-07-2010).pdf

626-delnp-2004-description (complete).pdf

626-DELNP-2004-Drawings-(01-07-2010).pdf

626-delnp-2004-drawings.pdf

626-DELNP-2004-Form-1-(01-07-2010).pdf

626-delnp-2004-form-1.pdf

626-delnp-2004-form-13.pdf

626-delnp-2004-form-18.pdf

626-delnp-2004-form-2.pdf

626-DELNP-2004-Form-3-(01-07-2010).pdf

626-delnp-2004-form-3.pdf

626-delnp-2004-form-5.pdf

626-DELNP-2004-GPA-(01-07-2010).pdf

626-delnp-2004-gpa.pdf

626-delnp-2004-pct-210.pdf

626-delnp-2004-pct-220.pdf

626-delnp-2004-pct-304.pdf

626-delnp-2004-petition-138.pdf


Patent Number 259705
Indian Patent Application Number 626/DELNP/2004
PG Journal Number 13/2014
Publication Date 28-Mar-2014
Grant Date 24-Mar-2014
Date of Filing 11-Mar-2004
Name of Patentee SOMA NETWORKS, INC
Applicant Address SUITE 2000, WHARFSIDE BUILDING CHINA BASIN LANDING, 185 BERRY STREET, SAN FRANCISCO, CALIFORNIA 94107, U.S.A.
Inventors:
# Inventor's Name Inventor's Address
1 JAMES R. BLODGETT 73 CASTLE ROCK ROAD, WALNUT CREEK, CALIFORNIA 94598, U.S.A.
PCT International Classification Number H04L
PCT International Application Number PCT/US02/25557
PCT International Filing date 2002-08-12
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/311,358 2001-08-13 U.S.A.
2 10/016,691 2001-12-17 U.S.A.