Title of Invention

METHOD AND APPARATUS FOR ACCURATELY DETECTING VALIDITY OF A RECEIVED SIGNAL

Abstract The present invention relates to a method for accurately detecting validity of a received signal, the method comprising: performing an autocorrelation on the received signal to produce an autocorrelation resultant (110) by delaying the received signal by a period of a valid signal (120), periodically measuring the cumulative energy level of the delayed signal over a time interval related to said period and, when a peak cumulative energy level is detected that indicates a valid signal, correlating the received signal with the delayed signal (122); performing a cross correlation of the received signal with a reference signal to produce a cross correlation resultant; determining a reference autocorrelation level based on an autocorrelation of a known input (126); normalizing the autocorrelation resultant with reference to the reference autocorrelation (128) to produce a normalized autocorrelation resultant; scaling a ratio of the cross correlation resultant and the autocorrelation resultant based on the normalized autocorrelation resultant (130) to produce an output; and comparing the output with a valid signal threshold (132) to indicate whether or not the signal is valid.
Full Text BACKGROUND OF THE INVENTION
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to wireless communication systems and more
particularly to receiving transmissions within such wireless communication systems.
DESCRIPTION OF RELATED ART
Figure 1 is a schematic block diagram of a prior art radio receiver that includes a tuned
preamplifier, a mixer, tuned local oscillator, 1st IF filter stage, another mixer, a local
oscillation reference (LOg), a 2nd IF filter, a demodulator, a synchronization detect module,
clock tracking module and automatic gain control (AGC) processor, The tuned preamplifier
receives incoming RF signals via the antenna to produce an RF signal. The frequency
spectrum of the RF signal is shown in Figure 2 for multi-channel RF communications such as
those prescribed within the IEEE 802.11 standard. As shown in Figure 2, the RF signal may
include a plurality of channels, in this example 4. The center of the RF signal is an
intermediate frequency above the local oscillation (LO1) produced by the tuned local
oscillator. Note that, in the alternative, the center of the RF signal is an intermediate
frequency below the local oscillation (LO1).
Returning to the description of Figure 1, the mixer, mixes the RF signal with the tuned
local oscillation (LO1) to produce an intermediate frequency (IF) signal. The frequency
spectrum of the IF sigual is shown in Figure 3. As shown in Figure 3, the IF signal includes
the 4 channels centered about the intermediate frequency (IF). In addition, an image of the IF
signal is produced and is centered about the negative IF. In this example, the desired channel
corresponds to channel 3 and the undesired channels are channels 1, 2 and 4. Returning to the
description of Figure 1, the 1st IF filter stage filters the IF signal to produce a filtered IF
signal The 1st IF filter is typically a SAW filter and has a frequency response as illustrated in
Figure 3. The frequency spectrum of the resulting filtered IF signal is shown in Figure 4, As
shown in Figure 4, the desired channel 3 passes through the filter while channels 1 and 4 of
the undesired channels are completely attenuated and a portion of channel 2 is attenuated.
This also occurs on the image side of the filtered IF signal.

Returning to the discussion of Figure 1,.the next mixer, mixes the filtered IF signal
with a 2nd local oscillation (LO2) to produce a baseband signal. The baseband signal is
subsequently filtered by the 2nd IF filter stage to produce a filtered baseband signal. With
reference to Figures 5 and 6, Figure 5 illustrates the frequency spectrum of the baseband
signal including the desired channel 3, the image of the undesired channel 2 overlapping and
the image of the desired channel 3 overlapping with the undesired channel 2. When this is
filtered, as shown in Figure 6, the resulting filtered baseband signal includes the desired
channel 3 and the image of the undesired channel 2.
When the desired channel 3 is actually a valid signal, the inclusion of the image of the
undesired channel 2 presents minimal problems. If, however, there is no desired channel 3,
but only the image of the undesired channel 2, the sync detect and corresponding clock
tracking may indicate that a valid signal is present and activate the entire receiver to recapture
the data from the filtered baseband signal, However, since this data corresponds to undesired
information, the recovered data will be useless.
In general, the sync detect may be a correlation, which compares the incoming
baseband signal to a stored representation of a valid preamble. If the beginning portion of the
incoming baseband signal (e.g., the portion mat would correlate to a preamble of a valid
signal) matches the stored valid preamble, the correlator indicates that the signal is valid.
If the correlator falsely identifies a valid signal, the subsequent processing by the
receiver is wasted. For portable wireless communication devices, wasted receiver processing
corresponds to wasted power, winch reduces the battery life of a wireless communication
device, and reduced data throughput. Such false identifications occur more frequently as the
signal strength of the received RF signal decreases. As such, many wireless communication
devices have a minimum signal strength requirement to reduce the number of false,
identifications, but do so at the cost of .limiting the range of the wireless communication
device and data throughput.
Therefore, a need exists for a method and apparatus to accurately detect the presence
of a valid signal in view of undesired signals,
BRIEF SUMMARY OF THE INVENTION
The method and apparatus for accurately detecting the validity of a received signal of
the present invention substantially meets these needs and others. In an embodiment, a method

begins by performing an auto-correlation on the received, signal to produce an auto-correlation
resultant. The process continues by performing a cross-correlation on the receive signal with
a reference signal to produce a cross-correlation resultant. The process then continues by
mathematically relating the auto-correlation resultant with the cross-correlation resultaut to
produce a mathematical correlation relationship. The process then proceeds by interpreting
the mathematical correlation relationship to indicate whether the receive signal is valid or not.
With such a method and apparatus, in the absence of a valid signal, the image of an undesired
channel will not falsely trigger the indication of a valid signal, thus a greater level of accuracy
. is achieved in detecting the presence of a valid signal,

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF ACCOMPANYING THE DRAWINGS
Figure 1 is a schematic block diagram of a prior art radio receiver;
Figures 2-6 illustrate frequency domain representations of the signals within the prior
art receiver of Figure 1;
Figure 7 is a schematic block diagram of a radio receiver in accordance with the
present invention;
Figure 8 is a functional diagram of the data detection module of the radio receiver of
Figure 7;
Figure 9 is a timing relationship corresponding to the functional diagram of Figure 8;
and
Figure 10 is a logic diagram of a method for accurately detecting validity of a received
signal.
DETAILED DESCRIPTION OF THE INVENTION
Figure 7 illustrates a schematic block diagram of a radio receiver 10 that includes a
low noise amplifier 12, a down conversion module 14, a low pass filter 16, an analog to
digital converter 20, a local oscillator 24, and a data recovery module 26. The data recovery
module 26 includes low IF mixers 28 and 30, low pass filters 32 and 34, a demodulation
module 36 and a data detection module 38. The data detection module 3,8 includes a
processing module 40 and memory 42. The processing module 40 may be a single
processing device or a plurality of processing devices. Such a processing device may be a

microprocessor, micro-controller, digital signal processor, microcomputer, central processing
unit, field programmable gate array, programmable logic device, state machine, logic
circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog
and/or digital) based on operational instructions. The memory 42 may be a single memory
device or a plurality of memory devices. Such a memory device may be a read-only memory,
random access memory, volatile memory, non-volatile memory, static memory, dynamic
memory, flash memory, and/or any device that stores digital information. Note that when the
processing module 40 implements one or more of its functions via a state machine, analog
circuitry, digital circuitry, and/or logic circuitry, the memory storing the corresponding
operational instructions is embedded with the circuitry comprising the state machine, analog
circuitry, digital circuitry, and/or logic circuitry. The memory 42 stores, and the processing
module 40 executes, operational instructions corresponding to at least some of the steps
and/or functions illustrated in Figures 7-10.
In operation, the radio receiver 10 receives a radio frequency (RF) signal 44 via an
antenna, which provides the RF signal 44 to the low noise amplifier 12. The low noise
amplifier 12 amplifies the RF signal 44 to produce an amplified RF signal 46. As one of
average skill in the art will appreciate, a bandpass filter may precede and/or follow the low
noise amplifier to tune the radio receiver to a particular radio frequency.
. The down conversion module 14 mixes the amplified RF signal 28 with a local
oscillation provided by the local oscillator 24 to produce an intermediate frequency (IF) signal
48. The down conversion module 14 may include one or more intermediate frequency stages
to step down the carrier frequency from that of the radio frequency to the intermediate
frequency. Low pass filter 16 filters the IF signal 48 to produce a filtered IF signal 50. The
analog to digital converter 20 converts the filtered IF signal 50 into a digital IF signal.
The data recovery module 26 receives the digital IF signal via the low IF mixers 28
and 30. The low IF mixers 28 and 30 mix the digital IF signal with a low IF local oscillation
and. a 90° phase shifted representation thereof, respectively, to produce a complex baseband
signal 52 (i.e., a baseband signal that includes an in-phase (I) component and a quadrature (Q)
component). The low pass filters 32 and 34 filter the complex baseband signal 52 to produce
a complex filtered baseband signal 54.

The data detection module 38 interprets the complex filtered baseband signal 54, as
will be described in greater detail with reference to Figures 8 - 10, to determine whether the
complex filtered baseband signal 54 is a valid signal. If so, the data detection module 38
generates a valid signal indication signal 56, which is provided to the demodulation module
36. In response to the valid signal indication signal 56, the demodulation module 36
demodulates the complex filtered baseband signal 54 to recapture data 58.
Figure 8 illustrates a functional diagram of the data detection module 38 that includes
a complex conjugate module 60, a multiplier 62, a real time energy filter 64, a 2nd complex
conjugate module 82, a one-period delay module 84, a 2nd multiplier 86, a delayed energy
filter 80, a state machine 66, an absolute value module 78, a gain module 72, a coarse
correlation module 68, an interpreting module 70, a second absolute value module 74, and a
moving average module 76.
The filtered baseband signal 54 is a complex signal that is provided to the complex
conjugate modules 60 and 82. The complex conjugate module 60 performs a complex
conjugate function on filtered baseband signal 54 to produce a conjugate value. The
multiplier 62 multiplies the filtered baseband signal 54 with the complex conjugate 60's
output to produce a real energy input. For example, if the filtered baseband input 56 is
represented by (Real component + Imaginary component) then the complex conjugate module
produces the conjugate value of (Real component - imaginary component) and the multiplier
62 produces the real energy input of (R2+I2).
i
The real time energy filter 64 receives real energy input from multiplier 62 and
produces a real time energy value 98. The real time energy filter 64 is essentially a low pass
filter that may have its impulse response adjusted in accordance with an impulse response
adjust signal 100. For instance, during early detection of a valid signal, the impulse response
of the real time energy filter may be fast and then slowed as the likelihood that the input is a
valid signal. This allows the real time energy to reach an appropriate level quickly for valid
signals and reduce the deviation of the level as the likelihood of the input being valid
increases. The real time energy filter 64 provides the real time energy level 98 to the state
machine 66, which determines the valid signal indication 56 as will be discussed below.
The complex conjugate module 82 performs a complex conjugate function on the
filtered baseband signal 54 to produce a complex conjugate input. The one period delay

module 84 delays the complex conjugate input to produce a delayed complex conjugate input
The multiplier 86 multiplies the filtered baseband signal 54 with the delayed complex
conjugate input to produce a correlated input 92. If the filtered baseband signal 54 is valid,
the correlated input 92 will resemble the output of multiplier 48 but delayed by one period of
a repetitive signal in the preamble of a valid signal. If the filtered baseband signal 54 is not a
valid signal, the correlated input 92 will resemble noise. For example, for an IEEE802.11a
compliant wireless communication device, the preamble includes a short training sequence
and a long .framing sequence. The short training sequence includes repetitive signals that are
16 samples in length while the long training period includes repetitive signals that are 64
samples in length. As such, during the short training sequence, the one period delay is set to
correspond to 16 samples and for the long training sequence is set to correspond to 64
samples. Thus, for the short training sequence, the correlated input 92 will resemble the
output of multiplier 62 with the addition of a noise term.
The multiplier 86 provides the correlated input 92 to the moving average module 76
. and to the delayed energy filter 80. The delayed energy filter 80 filters the correlated input 92
to produce an energy level of the correlated input. The absolute value module 78 generates an
absolute value for the energy level of the correlated input and provides it to the gain module
72.
The gain module 72 adjusts the magnitude of the energy level of the correlated input
based on a coarse probability 90 to produce the delayed energy level 96. The generation of
the coarse probability 90 will be discussed subsequently. The state machine 66 receives the
delayed energy level 96 and compares it with the real time energy level 98 to produce a
probability of the input signal being a valid signal. The state machine 66 also receives a
moving average 94, which it uses in comparison with the real rime energy 98 to conclusively
determine whether the filtered baseband signal 54 is a valid signal or not. If the filtered
baseband signal 54 is a valid signal, the state machine 66 generates a valid signal indication
56, If the filtered baseband signal 54 is not a valid signal, the state machine 66 does not
generate the valid signal indication 56 and the demodulation module 36 is not enabled. Thus,
power consumption is reduced since the data detection module 38 has substantially reduced
and/or eliminated false identifications of valid signals.
The moving average module 76 produces a moving average of the correlated input 92.
The absolute value module 74 provides an absolute value of the output of the moving average

module 76 to produce the moving average 94. The state machine 66 interprets the moving
average with respect to the real time energy level at the end of an initialization sequence (e.g.,
the end of the short training sequence and/or long training sequence for an 802.11a
implementation). The state machine 66 then indicates that the input signal is valid when the
interpretation of the moving average 94 with the respect to the real time energy level 98 was
favorable. This will be discussed in greater detail with reference to Figure 9.
The coarse correlation module 68. receives the complex digital signal 74 and produces
a coarse correlation value 88. The coarse correlation module 68 is providing a simple
correlation function that compares the complex digital signal 74 with a stored representation
of a valid preamble of a signal. The interpreting module 70 receives the coarse correlation 88
and generates a coarse probability 90 therefrom. In general, the interpreting module 70 is
interpreting the coarse correlation 88 to determine the likelihood that the filtered baseband
signal 54 is valid and to establish the gain level for the gain module 72 proportional to the
likelihood. The more likely the input is valid, the greater the coarse probability 90 will be,
thus the greater the gain level of the gain module 72 will be.
Figure 9 illustrates a graphical representation of the signals produced by the data
detection module 38 of Figure 8. The baseband signal 54 includes a noise section and a valid
signal portion. The valid signal portion, for 802.1 la implementation includes a short trdning
sequence, a guard band, a long training sequence, a 2nd guard band and data. During the noise
portion of the baseband signal 54, i.e., when no data is being received, the real time energy
filter 64 is producing real time energy level 98, which is relatively low and corresponds to the
energy level of me noise. Similarly, the delayed energy level 96 is initially low due to the
noise. When the 1st short training sequence signal is received (i.e., the first 16 samples block
of the STS), the real time energy filter is in a fast impulse response mode and ramps up
quickly to indicate the energy of the first short training sequence signal. Simultaneously, the
coarse correlation signal 88 is generated to indicating that there is energy in the baseband
signal that correlates to the stored representation on a valid preamble.
For the 1st short training sequence signal, the delayed energy 96 remains low. This is
due to the one period delay module 84, which for an IEEE 802.1 la implementation is initially
set to provide a delay equivalent to 16 samples. After the one period delay, the delayed
energy 96 rises correspondingly to the gain of the gain module 72 as well as the energy within
the short' training sequence signals,

The coarse correlation 88 continues to indicate that a signal is present and that it
correlates with the stored valid preamble. As such, the interpreting module 70 is increasing
the coarse probability 90. As such, the gain for the delayed energy path via the gain module
72 is increasing and the magnitude of the delayed energy. 96 increases and exceeds the
magnitude of the real time energy level 98, which provides a good first indication that the
baseband signal 54 is currently providing a valid signal. As shown in Figure 9, the cross
correlation 88 and the cross, or coarse, probability 90 each includes a solid line waveform and
a dashed-line waveform. The solid line waveform corresponds to a signal associated with a
desired channel and the dashed line waveform corresponds to a signal associated with an
undesired channel in the absence of a signal of the desired channel. Refer to the discussions
of Figures 2 - 6 for a description of a desired channel and an undesired channel.
The moving average 94, which represents an autocorrelation, is increasing as the valid
preamble is detected until the end of the short training sequence. At that time, the moving
average 94 begins to decay. At a predetermined time after 'the end of the short training
sequence has been indicated, the current moving average 94, which represents the cumulative
energy level of the plurality of repetitive signals of the STS, is compared with the peak value
of the moving average. If the moving average 94 has decayed sufficiently from its peak at the
predetermined time (which indicates that a signal was the cause for the rise in the moving
average and not some random occurrence of energy bursts that would continue to increase, or
at least keep from decaying, the moving average) the comparison is favorable and the state
machine increases the probability that the input is a valid signal. If the magnitude of the
moving average 94 has not sufficiently decayed from its peak value, the state machine
indicates that the signal is invalid and the processing starts all over.
When the probability that the input is valid is generated, the data detection module
switches into processing the long training sequence of the preamble of the valid signal. As
such, the moving average path, having the one period delay changed from 16 samples to 64
samples within delay module 84 produces a new moving average 94. The new moving
average 94 represents a cumulative energy level of the LTS and is interpreted to determine the
end of the long training sequence. At the end of the long training sequence, the state machine
compares the magnitude of the moving average 94 with the magnitude of the real time energy
98. If the moving average 94 is greater than the real time energy 98, the state machine.

conclusively determines that the signal is valid. If the moving average 94 is less than the real
time energy 98 the state machine indicates that the signal is not valid.
This occurs equally for the signal of the desired channel and the signal of the
imdesired channel in the absence of a desired channel. However, as shown, the cross
correlation 88 and the corresponding probability. 90 have a lower magnitude for the signal of
the undesired channel in the absence of a desired channel than the signal of the desired
channel. The auto correlation, or the moving average, has essentially the same magnitude for
the signal of the undesired channel in the absence of a desired channel than the signal of the
desired channel. Thus, based on the difference in magnitude of the cross correlation with
respect to the auto correlation, a determination can be made as to whether the signal being
analyzed is one from a desired channel or from an undesired channel in the absence of a
desired channel. Such a determination is based on a mathematical relationship between the
auto correlation and the cross correlation at the end of the STS, which may be expressed as

wherein the autocorr corresponds to the autocorrelation resultant, the refcorr corresponds to a
reference autocorrelation, the xcorr corresponds to the cross correlation resultant, and the K
corresponds to a valid signal threshold. As such, the data detection module 38 provides a
conclusive determination whether the baseband signal 54 is valid before subsequent digital
processing is activated. As such, power consumption is reduced, the range of wireless
communication devices is increased, and data throughput is increased since the data detection
1
module 38 is extremely sensitive in detecting the validity of incoming signals and can do so
when the signal strength is low.
Figure 10 is a logic diagram of a method for accurately detecting validity of a received
signal The process begins at Step 110 where an auto-correlation is performed on the receive
signal producing an auto-correlation resultant. This may be done as illustrated in Steps 120-
124, At Step 120, the receive signal is delayed by a period of the valid signal. The process
then proceeds to Step 122 where the receive signal is correlated with the delayed signal. The
process then proceeds to Step 124 where a moving average, or auto-correlation, is determined,
which, represents the energy of the correlated signal.

From Step 110, the process proceeds to Step 112 where a cross-correlation is
performed on the receive signal with a reference signal to produce a cross-correlation
resultant. This may be done as shown in Steps 126-130. At Step 126, a reference auto-
correlation level is determined based on a fixed length of the auto-correlation of a known
input. The process then proceeds to Step 128 where the auto-correlation resultant is
normalized with reference to a reference auto-correlation. The process then proceeds to Step
130 where a ratio of the cross-correlation resultants and the auto-correlation resultants are
scaled based on the normalized auto-correlation resultant. This was graphically illustrated
with reference to Figure 9.
From Step 112, the process proceeds to Step 114 where the auto-correlation resultant
is mathematically related to the cross-correlation resultant to produce a mathematical
correlation relationship. This may be done as illustrated in Steps 132-136. At Step 132, the
mathematical correlation relationship is compared with a difference threshold. The process
proceeds to Step 134 when the comparison is favorable, indicating that the receive signal is
valid, At Step 136, if the comparison was unfavorable indicating that the receive signal is not
valid. Alternatively, the mathematical relationship may be achieved as

wherein the autocorr corresponds to the autocorrelation resultant, the refcorr corresponds to a
reference autocorrelation, the xcorr corresponds to the cross correlation resultant, and the K
corresponds to a valid signal threshold.
From Step 114, the process proceeds to Step 116 where the mathematical correlation
relationship is interpreted to indicate whether the receive signal is valid or not.
As one of average skill in the art will appreciate, the term "substantially" or
"approximately", as may be used herein, provides an industry-accepted tolerance to its
corresponding term. Such an industry-accepted tolerance ranges from less than one percent to
twenty percent and corresponds to, but is not limited to, component values, integrated circuit
process variations, temperature variations, rise and fall times, and/or thermal noise. As one of
average skill in the art will further appreciate, the term "operably coupled", as may be used
herein, includes direct coupling and indirect coupling via another component, element, circuit,

or module where, for indirect coupling, the intervening component, element, circuit, or
module does not modify the information of a signal but may adjust its current level, voltage
level, and/or power level. As one of average skill in the art will also appreciate, inferred
coupling (i.e., where one element is coupled to another element by inference) includes direct
and. indirect coupling between two elements in the same manner as "operably coupled". As
one of average skill in the art will further appreciate, the term "compares favorably", as may
be used herein, indicates that a comparison between two or more elements, items, signals,
etc., provides a desired relationship. For example, when the desired relationship' is that signal
1 has a greater magnitude than signal, 2, a favorable comparison may be achieved when the
magnitude of signal 1 is. greater than that of signal 2 or when the magnitude of signal 2 is less
than that of signal 1.
The preceding discussion has presented a method and apparatus for accurately
determining the validity of a receive signal.. As one of average skill in the art will appreciate,
other embodiments may be derived from the teachings of the present invention without
deviating from the scope of the claims.

We Claim :
1. A method for accurately detecting validity of a received signal, the method comprising:
performing an autocorrelation on the received signal to produce an autocorrelation
resultant by delaying the received signal by a period of a valid signal, periodically measuring the
cumulative energy level of the delayed signal over a time interval related to said period and,
when a peak cumulative energy level is detected that indicates a valid signal, correlating the
received signal with the delayed signal;
performing a cross correlation of the received signal with a reference signal to produce a
cross correlation resultant; determining a reference autocorrelation level based on an
autocorrelation of a known input; normalizing the autocorrelation resultant with reference to the
reference autocorrelation to produce a normalized autocorrelation resultant;
scaling a ratio of the cross correlation resultant and the autocorrelation resultant based on
the normalized autocorrelation resultant to produce an output; and
comparing the output with a valid signal threshold to indicate whether or not the signal is
valid.
2. The method as claimed in claim 1, wherein the determining the reference autocorrelation
level is based on a fixed length of the autocorrelation of the known input.
3. The method as claimed in claim 1, wherein the autocorrelation resultant and the cross
correlation resultant for a valid signal are related by:

wherein K corresponds to the valid signal threshold.
4. The method as claimed in claim 3, which involves determining the reference
autocorrelation based on a fixed length of the autocorrelation of a known input.

5. An apparatus for accurately detecting validity of a received signal, the apparatus
comprising:
processing module; and
memory operably coupled to the processing module, wherein the memory includes
operational instructions that cause the processing module to:
delay the received signal by a period of a valid signal, periodically measure the
cumulative energy level of the delayed signal over a time interval related to said period and,
when a peak cumulative energy level is detected that indicates a valid signal, correlate the
received signal with the delayed signal to produce an autocorrelation resultant;
perform a cross correlation of the received signal with a reference signal to produce a
cross correlation resultant;
determine a reference autocorrelation level based on an autocorrelation of a known input;
normalize the autocorrelation resultant with reference to the reference autocorrelation to
produce a normalized autocorrelation resultant;
scale a ratio of the cross correlation resultant and the autocorrelation resultant based on
the normalized autocorrelation resultant to produce an output; and
compare the output with a valid signal threshold to indicate whether or not the signal is
valid.
6. The apparatus as claimed in claim 5, wherein the memory comprises operational
instructions that cause the processing module to determine the reference autocorrelation level
based on a fixed length of the autocorrelation of a known input.
7. The apparatus as claimed in claim 5, wherein the memory comprises operational
instructions that cause the processing module to indicate a valid signal when:

wherein the autocorr corresponds to the autocorrelation resultant, the refcorr corresponds
to a reference autocorrelation, the xcorr corresponds to the cross correlation resultant, and the K
corresponds to the valid signal threshold.

8. The apparatus as claimed in claim 7, wherein the memory comprises operational
instructions that cause the processing module to determine the reference autocorrelation based on
a fixed length of the autocorrelation of a known input.
9. A radio receiver comprising:
low noise amplifier operably coupled to amplify a radio frequency (RF) signal to produce
an amplified RF signal;
down conversion module operably coupled to convert the amplified RF signal into a
baseband signal;
data recovery module operably coupled to recapture data from the baseband signal,
wherein the data recovery module comprises:
data detection module operably coupled to detect validity of the baseband signal to
produce a valid signal indication; and
demodulation module operably coupled to demodulate the baseband signal to produce the
data in accordance with the valid signal indication, wherein the data detection module comprises:
processing module; and
memory operably coupled to the processing module, wherein the memory comprises
operational instructions that cause the processing module to:
delay the received signal by a period of a valid signal, to periodically measure the
cumulative energy level of the delayed signal over a time interval related to said period and,
when a peak cumulative energy level is detected that indicates a valid signal, to correlate the
received signal with the delayed signal to produce an autocorrelation resultant;
perform a cross correlation of the received signal with a reference signal, to produce a
cross correlation resultant;
determine a reference autocorrelation level based on an autocorrelation of a known input;
normalize the autocorrelation resultant with reference to the reference autocorrelation to produce
a normalized autocorrelation resultant;
scale a ratio of the cross correlation resultant and the autocorrelation resultant based on
the normalized autocorrelation resultant to produce an output; and

compare the output with a valid signal threshold to indicate whether or not the signal is
valid.
10. The radio receiver as claimed in claim 9, wherein the memory comprises operational
instructions that cause the processing module to determine a reference autocorrelation level
based on a fixed length of the autocorrelation of a known input.
11. The radio receiver as claimed in claim 9, wherein the memory comprises operational
instructions that cause the processing module to indicate a valid signal when:

wherein the autocorr corresponds to the autocorrelation resultant, the refcorr corresponds
to a reference autocorrelation, the xcorr corresponds to the cross correlation resultant, and the K
corresponds to the valid signal threshold.
12. The radio receiver as claimed in claim 11, wherein the memory comprises operational
instructions that cause the processing module to determine the reference autocorrelation based on
a fixed length of the autocorrelation of a known input.

Documents:

00990-kolnp-2006 abstract.pdf

00990-kolnp-2006 claims.pdf

00990-kolnp-2006 correspondence others.pdf

00990-kolnp-2006 description (complete).pdf

00990-kolnp-2006 drawings.pdf

00990-kolnp-2006 form-1.pdf

00990-kolnp-2006 form-3.pdf

00990-kolnp-2006 form-5.pdf

00990-kolnp-2006 international publication.pdf

00990-kolnp-2006 international search authority report.pdf

00990-kolnp-2006 pct form.pdf

00990-kolnp-2006-claims-1.1.pdf

00990-kolnp-2006-correspondence others-1.1.pdf

00990-kolnp-2006-correspondence-1.2.pdf

00990-kolnp-2006-form-13.pdf

00990-kolnp-2006-form-18.pdf

00990-kolnp-2006-form-3-1.1.pdf

00990-kolnp-2006-priority document.pdf

990-KOLNP-2006-ABSTRACT 1.1.pdf

990-KOLNP-2006-ASSIGNMENT.pdf

990-KOLNP-2006-CLAIMS.pdf

990-KOLNP-2006-CORRESPONDENCE 1.1.pdf

990-KOLNP-2006-CORRESPONDENCE.pdf

990-kolnp-2006-correspondence1.2.pdf

990-KOLNP-2006-DESCRIPTION (COMPLETE) 1.1.pdf

990-KOLNP-2006-DRAWINGS 1.1.pdf

990-KOLNP-2006-EXAMINATION REPORT REPLY RECIEVED.pdf

990-kolnp-2006-examination report.pdf

990-KOLNP-2006-FORM 1.1.pdf

990-kolnp-2006-form 13.1.pdf

990-KOLNP-2006-FORM 13.pdf

990-kolnp-2006-form 18.pdf

990-KOLNP-2006-FORM 2.pdf

990-KOLNP-2006-FORM 3.1.pdf

990-kolnp-2006-form 3.pdf

990-kolnp-2006-form 5.pdf

990-KOLNP-2006-FORM-27.pdf

990-kolnp-2006-granted-abstract.pdf

990-kolnp-2006-granted-claims.pdf

990-kolnp-2006-granted-description (complete).pdf

990-kolnp-2006-granted-drawings.pdf

990-kolnp-2006-granted-form 1.pdf

990-kolnp-2006-granted-form 2.pdf

990-kolnp-2006-granted-specification.pdf

990-KOLNP-2006-OTHERS 1.1.pdf

990-KOLNP-2006-OTHERS.pdf

990-kolnp-2006-others1.2.pdf

990-KOLNP-2006-PA.pdf

990-kolnp-2006-pa1.1.pdf

990-KOLNP-2006-PETITION UNDER RULE 137-1.1.pdf

990-KOLNP-2006-PETITION UNDER RULE 137.pdf

990-kolnp-2006-reply to examination report.pdf

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Patent Number 247875
Indian Patent Application Number 990/KOLNP/2006
PG Journal Number 22/2011
Publication Date 03-Jun-2011
Grant Date 30-May-2011
Date of Filing 19-Apr-2006
Name of Patentee VIXS SYSTEMS, INC.
Applicant Address PARKWAY PLACE, 245 CONSUMERS ROAD, SUITE 301, TORONTO, ONTARIO M2J 1R3, CANADA
Inventors:
# Inventor's Name Inventor's Address
1 ASTRACHAN PAUL MORRIS 804, CRYSTAL MOUNTAIN, AUSTIN, TEXAS 78733
PCT International Classification Number H04B 1/00
PCT International Application Number PCT/CA2004/001815
PCT International Filing date 2004-10-08
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/683,062 2003-10-10 U.S.A.