Title of Invention	APPARATUS AND METHOD FOR AUTOMATIC GAIN CONTROL
Abstract	The present application discloses an apparatus configured to control a gain value of a variable gain amplifier for a received signal, wherein an outcome signal is processed based on the received signal. The apparatus comprises a burst signal detector configured to detect a burst signal in said outcome signal, if said burst signal is detected, the burst signal detector sets a burst indication signal to a first particular value which indicate an active said burst signal is received, if said burst signal is not detected, force a burst indication signal to a second particular value which indicates an inactive said burst signal is received. The apparatus also comprises a variable gain generator controlling apparatus configured to use a counter to count the number of the said burst indication signal with said second particular value for outputting a signal indication result configured to control the updating and saving the said gain value. The variable gain generator controlling apparatus further calculates the present needed gain value based on said burst indication signal and outputs a gain control word to adjust said gain value of said variable gain amplifier.

Title of Invention

APPARATUS AND METHOD FOR AUTOMATIC GAIN CONTROL

Abstract

The present application discloses an apparatus configured to control a gain value of a variable gain amplifier for a received signal, wherein an outcome signal is processed based on the received signal. The apparatus comprises a burst signal detector configured to detect a burst signal in said outcome signal, if said burst signal is detected, the burst signal detector sets a burst indication signal to a first particular value which indicate an active said burst signal is received, if said burst signal is not detected, force a burst indication signal to a second particular value which indicates an inactive said burst signal is received. The apparatus also comprises a variable gain generator controlling apparatus configured to use a counter to count the number of the said burst indication signal with said second particular value for outputting a signal indication result configured to control the updating and saving the said gain value. The variable gain generator controlling apparatus further calculates the present needed gain value based on said burst indication signal and outputs a gain control word to adjust said gain value of said variable gain amplifier.

Full Text	FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See section 10, Rule 13] APPARATUS AND METHOD FOR AUTOMATIC GAIN CONTROL; VIA TECHNOLOGIES , INC., A CORPORATION ORGANIZED AND EXISTING UNDER THE LAWS OF TAIWAN, R.O.C., WHOSE ADDRESS IS 8F, 535, CHUNG-CHENG RD., HSIN-TIEN, TAIPEI, TAIWAN, R.O.C. THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. BACKGROUND INFORMATION Field of the Invention The present invention generally relates to the signal processing in the receiving end of the wireless communication system and more particularly to the automatic gain control apparatus and method of the received signal for signal burst detection. Background of the Invention In a digital receiving process of a wireless communication system, the dynamic range of A/D (analog to digital) converter is limited by the power of received signal. In a wireless receiver, by reason of the various effects of the electrical characteristics and propagation path, the power of received signal varies from time to time. When the power of digital signal exceeds the dynamic range of the wireless receiver, the distortion and error receiving of signal may occur. The power of the received signal needs also to be adjusted to accommodate the dynamic range of A/D converting. Thus it is useful to employ the automatic gain controller in the synchronous demodulation devices of wireless communication system to calculate current gain according to RSSI (Received Signal Strength Indication), and to adjust the received signal power to adapt to A/D dynamic range for reducing noise level and overflow. This method is applied to RF (radio frequency) and baseband processing of the GSM (Global System for Mobile Communications) and other system. A basic 2 concept for the wireless transmission of GSM is that a transmission unit which is about 100 modulation bits sequence is called a "burst". The "burst" is the basic unit for data transmission. For receiver, complicated wireless communication channel environment as well as the noise and other electrical interference leads to changes of burst signal power. Meanwhile, different logic channels, such as control channel and traffic channel, are defined by different payload types. The burst powers transmitted on the traffic channel and control channel are different; therefore when transmission switches from control channel to traffic channel, the received signal power may be changed accordingly. In the existed AGC (automatic gain control) system, when the transmitted signal power lowers, this sudden decrease of the received signal power may be considered as results of the cease transmission or interference caused by other factors, and request of resending lost signal and/or rebuilding a connection may be sent by the receiver. It may result in resources waste and inefficiency. The change of the power may drive signal amplitude beyond the A/D dynamic range and may cause performance deteriorated as well as reconnection. In the existed GSM communications system receiver, there are two common circumstances. First, BS (base station) sends control information through control channel and switches to traffic channel having comparatively lower power. This may result in the need of different signal gain; second, after a period of silence, BS resumes transmission via control channel to MS (mobile station) with the same power, the resending means the information may contain key information such as 3 control signaling. Both of the two circumstances above give certain requirements to AGC and burst signal detection. In the first circumstance, the sudden decrease of the received signal power does not mean no signal sent at all. Instead, there are signals which may be sent by lower power via traffic channel than control channel around 30dB. Under the conditions of low-power transmission, it is needed to adopt effective burst detection method to deal with inherent high error ratio. In the second circumstance, it is useful to compute a new gain to control RF power based on the received signal power. If the transmission of control channel is stopped by transmitter while the AGC controller of receiver is still working, the received signal is mainly consisted of noise and interference since there is no reception of burst. Therefore the AGC raises the gain because of low power of effective signal. It does useless amplification for the system and reduces the life for use of amplifiers. In the very beginning of the resumed transmission, the gain value and the amplified power of signal is remained at a higher level. At this stage, saturation distortion may be brought up by sudden increase of the amplified power of signal, and error codes in the receiver as a result may lead to lose some key information. A handover or a reselection procedure of BS may be forcedly executed by receiver. Figure 1 is a diagram illustrating for an existed AGC system. After processing in a tuner 102, the received signal is amplified by a variable gain amplifier 104 based on a present gain value, and the output signal of the amplifier 104 may be provided to a AGC device 120 and a filter 112 through the processes of a mixer 106 4 and an A/D converter 108. The filtered signal may be sent to a demodulator 114 and a decoder 116 to produce data which is to be received. The AGC device 120 comprises a gain generator 122 and a gain control word generator 124. The gain generators 122 calculated and send the current gain to gain control word generator 124 according to the strength of received signal and produce a gain control word signal. The gain control word signal is a feedback of the variable gain amplifier 104 in order to control the gain value of the variable gain amplifier 104 according to the present signal. As mentioned above, the gain control word signal is an input to the variable gain amplifier 104 in the form of a control word. Those skilled in the art can comprehend that any signal which is not limited in the form to control the variable gain amplifier. However., it is not taken into consideration of the impact to AGC and correct reception due to sudden power decrease of the burst signal in the prior art, namely the second circumstance. Especially when the sudden signals cease to be transmitted , the AGC device 120 remain computing of the gain value based on received signal power. When no transmission of the burst signal but noise signal is received, this automatic gain control devices 120 may still amplify signal. This amplification is not required by the system, it may result in amplifying noise interference and taxing system resources. Figure 2 is a diagram illustrating the second circumstance mentioned above by relating received RF signal power and the amplifier gain value. Figure 2 shows the three variables: the RF signal power level 210, the gain value 230 from the variable gain amplifier 104 and the amplified signal power level 240. It may be categorized into 3 phases of the time axial in Figure 2: phase A 222, B 224, and C 226. 5 With reference to the block diagram Figure l,when the sudden decrease in the RF receiver signal power 210 at the transiting from phase A to B, automatic gain control device 120 conducts the gain adjustment to the variable gain amplifier 104 according to the change in the RF signal power 210. That is to increase the gain value 230 of the variable gain amplifier. However, when no signal transmitted, for example, no burst transmitted, a sudden decrease of RF signal power 210 may appear in the phase B 224.That means the sudden decrease is not from the effective transmission. At that time, the variable gain amplifier 104 still does the action of automatic gain control and remains a high gain value which may result in power waste. After the transition from phase B 224 to C 226, the amplifier gain value is remained high. Furthermore, a burst appears again and the received signal power may be amplified at a considerably high gain. Then a power distortion 242 may arise. This distortion 242 may exceed the A/D dynamic range, and lead to the saturation distortion in the receiver. The purpose of this invention is to resolve the problem above and to provide an apparatus and method to detect the burst signals and allow the automatic gain control to the received signals. The device and method may implement AGC operation, and do the burst detection. Especially in the sudden reducing of the signal power, It also may provide a stable output gains as well as low-power signals to afford the correct judgment reception. Automatic gain control operation as well as burst signal detection could be done by the apparatus and method for providing stable output gains and correct reception of low power signal, especially in response to a sudden decrease of received RF signal power. 6 SUMMARY OF THE INVENTION Systems and methods for implementing automatic gain control are presented below. In one aspect of the present invention, it is disclosed that an apparatus configured to control a gain value of a variable gain amplifier for a received signal, wherein an outcome signal is processed based on the received signal, the apparatus comprising a burst signal detector configured to detect a burst signal in said outcome signal, if said burst signal is detected, the burst signal detector sets a burst indication signal to a first particular value which indicate an active said burst signal is received, if said burst signal is not detected, force a burst indication signal to a second particular value which indicates an inactive said burst signal is received; and a variable gain generator controlling apparatus configured to use a counter to count the number of the said burst indication signal with said second particular value for outputting a signal indication result configured to control the updating and saving the said gain value, the variable gain generator controlling apparatus further calculates the present needed gain value based on said burst indication signal and outputs a gain control word to adjust said gain value of said variable gain amplifier. Another aspect of the present invention concerns a control apparatus configured to conduct automatic gain control to adjust a gain value of a variable gain amplifier and receive a burst indication signal that comprising a first particular value and a second particular value, the control apparatus comprising a variable gain 7 generator controlling apparatus configured to use a counter to count the number of the said burst indication signal with said second particular value for outputting a signal indication result configured to control the updating and saving the said gain value, the variable gain generator controlling apparatus further calculates the present needed gain value based on said burst indication signal and outputs a gain control word to adjust said gain value of said variable gain amplifier. A third aspect of the invention disclosed a method sconfigured to control a gain value of a variable gain amplifier for a received signal, wherein an outcome signal is processed based on the received signal, the method comprising detecting a burst signal of said signal and conducting the burst signal detection, if said burst signal is active, setting a burst indication signal to a first particular value and employing a first operation, if said burst signal is inactive, setting a burst indication signal to a second particular value and employing a counting operation with a counter; setting a signal indication result to a first result value when said counter value is not less than a reference value, Setting the signal indication result as a second result value when said counter value is less than the reference value; and adjusting the gain value of said variable gain amplifier. The present invention also concerns a method for automatic gain control configured to control a gain value of a variable gain amplifier for a received signal, detect a burst signal and get a burst indication signal, and use a counter to calculate the number of continuous said burst indication signal with a second particular value, the method comprising setting a signal indication result as a first 8 result value when said counter value is not less than a reference value, stops updating the variable gain, and employs the backup gain value as the output of the present variable gain amplifier; and setting the signal indication result as a second result value when said counter value is less than the reference value, begins the updating of the variable gain amplifier. BRIEF DESCRIPTION OF THE DRAWINGS Features, aspects, and embodiments of the inventions are described in conjunction with the attached drawings, in which: Figure 1 is a block diagram illustrating an AGC system structure in the prior art. Figure 2 is a timing diagram illustrating the received signal relationship of the AGC system especially the status change of the system gainD when a sudden power decrease occurs in the prior art. Figure 3 is a block diagram illustrating an example of this invention for the AGC system with burst detection in accordance with one embodiment. Figure 4 is a block diagram illustrating an example of signal status relationship of the AGC system with burst detection in accordance with one embodiment. Figure 5 is a flow diagram illustrating an example method of this invention for signal detection and AGC in a wireless communication system in accordance with one embodiment. 9 While the invention is susceptible to various modification and alternative forms, specific embodiments thereof are shown by way of example in the drawings and herein may be described in detail. It should be understood, however, that the drawings and detailed description there are not intended to limited to the invention to the particular form disclosed of the invention, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the present invention as defined by the appended claims. DETAILED DESCRIPTION The main purpose of the following description is to enable one of the skilled in the art to make and use the present invention to meet a particular application and requirement. However, various modifications to the preferred embodiment may be apparent to one skilled in the art, and general principles defined herein may be applied to other embodiment. Thus the present invention is not limited to the particular embodiment described followed, but it is to be accorded the widest scope consistent with the principles and novel features disclosed herein. The invention brings forth a burst signal detection device for RF receiver. The present amplifier gain is continually updated according to RSSI, and the results of the burst signal detection is to achieve system requirements, Figure 3 to figure 5 of the invention involve a particular embodiment. 10 Figure 3 mainly describes a method exemplary of the invention for the receiver apparatus. After processing in a tuner 302, the receiving processing result signal is amplified by a variable gain amplifier 304 based on a present gain value. In the present embodiment, the output signal may be provided to a controllable gain control devices 320 and a filter 312 through the process of a mixer 306 and a D/A converter 308. Meanwhile the signal may be send to a demodulator 314 after filtered. The demodulating result may be an input of a decoder 316 and a burst detector 330. A burst indication signal may be generated after the detection of the received signal by the burst detector 330 and provided to a controllable gain generator 320, and then a gain value of the variable gain amplifier is calculated based on the burst indication signal and RSSI. In one embodiment, a RF amplifier gain may be implemented by multi-component. For example, a gain control word output gain of 90dB, which may be consisted of 40dB from low-noise amplifier, 30dB from a mixer and 20dB from a LPF (low-pass filter), the gain may be developed by the above apparatus which collectively produce the gain needed. In another embodiment, a gain processing module may be introduced to achieve the function of the tuner 302, the variable gain amplifier 304 and the mixer 306. The reception and processing may be realized by this module which may be controlled by the controllable gain generator 320. In one embodiment, the result signal may be the data output of -the demodulator 314. In other embodiment, it may be the output of the decoder 316, and/or the filter 312 after correlatively coding. The selection of the received signal processing depends on the detection method employed in the burst detector 330 which is beyond 11 the scope of this invention; the introduction may not be necessarily made in this description. The burst detector 330 works at making out whether a burst with a relative low power level is in the output signal of the receiving processing. The function of the burst detection 330 is to avoid mistaking the low-power burst for the noise. When received the burst signal, the burst indication signal is indicated as a value like 1, in the following description, the value 1 indicates that an active signal may be detected. For illustration, the value 0 indicates no active signal detected. It can be understood by the skilled in the art that other values may be available in the scope of the present invention, and the other signals may change correspondingly. Alternatively, the controllable gain generator 320 includes a counter. If the burst indication signal indicates 1, which means an active burst signal is received currently..The counter is cleared with a default value. In this embodiment, the default value may be 0. If the burst indication is 0, that means no active burst signal is received or no signal is sent. If the counter value is less than a reference value, the counter value increases. If the counter is not less than the reference value, the counter value maintains as the reference value. It can be understood by one skilled in the art that the reference value is to determine a holding period of the burst indication signal. The reference value which is related to the system parameter which is a positive integer. In one embodiment, the reference value is corresponding to a plurality of single burst periods. After received an active burst, if the counter value is less than the reference value, set the signal indication result to 1, otherwise remain 0. 12 In this embodiment, the counter may be operated in an incremental mode in which the counter increases from the default value to the reference value the ordinary in the art can comprehended that a detrimental mode in which the counter decreased from the reference value to the default value may work as well. Figure 4 shows the status relationship of a. received signal power 410, a gain value of a variable gain amplifier 420, an amplified signal power 430 and burst indication signal 440 and an indication result 450 in this embodiment, whereby the amplitude of the received signal power 410 indicates the variation of the signal power level. As shown in figure 4, in accordance with the received signal power change, it may be categorized into 3 phase: phase A 460, phase B 470 and phase C 480. In phase A 460, an active burst may be received, then generate the gain value of the variable Gain amplifier 420. The gain value may be various with the received signal power 410 and the present gain value 420 is saved as a backup continuously. In one embodiment, the gain value 420 of the variable gain amplifier adopts the form of a gain control word. In phase A 460, the burst indication signal 440 indicates 1, the signal detection result indicates 1, and the counter indicates 0. The controllable gain generator 320 shown in figure 3 continuously updates and computes the current gain value and output the gain control word according to the received signal power. At a beginning point 472 of the transition from phase A 460 to phase B 470, a sudden decrease appears in the received signal povyer 410. The sudden decrease may be caused by a transmission silence and/or the handover on the channel. At that time, the burst indication signal 440 changes to 0 and the counter value is less than the 13 reference value which maintains the signal detection result as 1, the counter remains increasing and stopping saving the gain value 420 as the backup value. In phase B 470, there is no burst signal sent and/or the received signal power was too low to process, during the period from time 472 to time 474, the variable gain amplifier continuously calculates the current received signal gain needed without backup the gain value 420. The gain value 420 of the variable gain amplifier increases constantly. The burst indication signal 440 remains 0 before the counter number of the continuous 0 of the burst indication signal 440 achieves the reference value. After the counter value reaching the reference value, the burst indication signal 440 change to 0, then the counter stops increasing and maintains the reference value until the burst indication signal 440 turns to 1. In the embodiment, the reference value is 4. If the burst indication signal 440 and the signal detection result change to 0, the variable gain amplifier amplifies with the backup gain value concurrently. At the point 476, the system receives an active burst signal. The burst indication signal 440 indicates 1 which makes the counter returns to the default value. Apparently the default value is less than the reference value, the signal detection result changes to 1 and the gain value 420 updates. The variable gain amplifier 304 showed in the figure 3 works on this value. In the phase C 480, the value updates according to the received signal power. Figure 5 shows the method flow exemplary introduced in the present invention of AGC with burst detection and signal detection. In different embodiments, 14 some method steps may be implemented concurrently, and/or adopts a flow which is not shown in the figures or some steps may be combined. In the step 502, the burst signal detection may be implemented as the received processing result signal. In the step 506, if there is an active burst, the burst indication signal is set to 1 which means an active signal transmission and then pursues the step 510. In the step 510, the counter returns the reference value and saves the current gain as a backup value. The gain calculates based on the current received signal power. If an active burst signal is detected which indicates no effective signal or heavy error code transmission and incorrect decoding executed in the receiver, the burst indication changes to 0. When the counter works at an incremental mode, the counter value N may be increased by 1 in the step 514. In the beginning of the processing, the counter default value may be 0. In the step 518, when the counter value N is less than the reference value, the gain value of the variable gain amplifier may be updated and computed; meanwhile the signal detection result indicates 1. Processing the next received burst indication signal may be implemented in the step 502. In the step 518, when the counter value N is not less than the reference value, changes the signal detection result to 0 in the step 526, and stops the gain value computing. The backup value gain may be adopted and then process the next burst indication signal. Compared with the prior art, the present invention provides the method and device of AGC with the burst detection. As the described above, the invention 15 intends to provide an embodiment of the burst detection and AGC device in RF receiver, however the method introduced herein may be applied in baseband receiver as well. While certain embodiments of the inventions have been described above, it will be understood that the embodiments described are by way of examples only. Numerous variations and modifications can be apparent to those skilled in the art. Accordingly, the inventions should not be limited based on the described embodiments. Rather, the scope of the inventions herein described should only be limited in the claims that follow when taken in conjunction with the above description and accompanying drawings. 16 We Claim : 1. An apparatus, configured to control a gain value of a variable gain amplifier for a received signal, wherein an outcome signal is processed based on the received signal, the apparatus comprising: a burst signal detector configured to detect a burst signal in said outcome signal, if said burst signal is detected, the burst signal detector sets a burst indication signal to a first particular value which indicate an active said burst signal is received, if said burst signal is not detected, force a burst indication signal to a second particular value which indicates an inactive said burst signal is received; and a variable gain generator controlling apparatus configured to use a counter to count the number of the said burst indication signal with said second particular value for outputting a signal indication result configured to control the updating and saving the said gain value, the variable gain generator controlling apparatus further calculates the present needed gain value based on said burst indication signal and outputs a gain control word to adjust said gain value of said variable gain amplifier. 2. The apparatus of claim 1, wherein said counter compares the number of the continuous said burst indication signal with said second particular value to a reference value, if the number is less than said reference value, said signal indication result is output as a first value, if the number is not less than said reference value, output said signal indication result is output as a second value. 3. The apparatus of claim 1, wherein said signal indication result configured to determine whether the recalculation of the gain value is said variable gain 17 amplifier is needed, if the signal indication result is said first value, said variable gain generator controlling apparatus begins the automatic gain control and update the calculation of said gain value of said variable gain amplifier; if the signal indication result is said second value, said variable gain generator controlling apparatus stops updating and calculating of said gain value. 4. The apparatus of claim 1, wherein when the burst indication signal is said first particular value, save the gain value of said variable gain amplifier as a backup gain value, when the burst indication signal is said second particular value, employ the latest saved said backup gain value as the gain value of said variable gain amplifier. 5. A control apparatus configured to conduct automatic gain control to adjust a gain value of a variable gain amplifier and receive a burst indication signal that comprising a first particular value and a second particular value, the control apparatus comprising: a variable gain generator controlling apparatus configured to use a counter to count the number of the said burst indication signal with said second particular value for outputting a signal indication result configured to control the updating and saving the said gain value, the variable gain generator controlling apparatus further calculates the present needed gain value based on said burst indication signal and outputs a gain control word to adjust said gain value of said variable gain amplifier. 6. A method configured to control a gain value of a variable gain amplifier for a received signal, wherein an outcome signal is processed based on the received 18 signal, the method comprising: detecting a burst signal of said signal and conducting the burst signal detection, if said burst signal is active, setting a burst indication signal to a first particular value and employing a first operation, if said burst signal is inactive, setting a burst indication signal to a second particular value and employing a counting operation with a counter; setting a signal indication result to a first result value when said counter value is not less than a reference value, setting the signal indication result as a second result value when said counter value is less than the reference value; and adjusting the gain value of said variable gain amplifier. 7. The method of claim 6, wherein said the first operation further comprising: setting the counter value to the default counter value and saving present said gain value of said variable gain amplifier as a backup gain value. 8. The method of claim 6, wherein said counting operation further comprising: if said burst indication signal is said second particular value, the counter begins to run; If said counter works on an increment mode, a unit value is increased, If said counter works on an decrement mode, a unit value is decreased. 9. The method of claim 6, wherein said signal indication result is said first value, said variable gain generator controlling apparatus stops updating and calculating of said gain value of said variable gain amplifier and employs said backup gain value as the current output of said variable gain amplifier; if the signal indication result is said second value, said variable gain generator controlling apparatus 19 begins the updating and calculating. 10. a method for automatic gain control configured to control a gain value of a variable gain amplifier for a received signal, detect a burst signal and get a burst indication signal, and use a counter to calculate the number of continuous said burst indication signal with a second particular value, the method comprising: setting a signal indication result as a first result value when said counter value is not less than a reference value, stopping updating the variable gain, and employing the backup gain value as the output of the present variable gain amplifier; and setting the signal indication result ass a second result value when said counter value is less than the reference value and updating the variable gain amplifier. Dated this 1st day of October, 2008 FOR VIA TECHNOLOGIES, INC. By their Agent (MADHURI RAMESHCHANDRA TAWRI) KRISHNA & SAURASTRI 20

Full Text

FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
& THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
APPARATUS AND METHOD FOR AUTOMATIC GAIN CONTROL;

VIA TECHNOLOGIES , INC., A
CORPORATION ORGANIZED AND
EXISTING UNDER THE LAWS OF TAIWAN, R.O.C., WHOSE ADDRESS IS 8F, 535, CHUNG-CHENG RD., HSIN-TIEN, TAIPEI, TAIWAN, R.O.C.

THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

BACKGROUND INFORMATION Field of the Invention
The present invention generally relates to the signal processing in the receiving end of the wireless communication system and more particularly to the automatic gain control apparatus and method of the received signal for signal burst detection.
Background of the Invention
In a digital receiving process of a wireless communication system, the
dynamic range of A/D (analog to digital) converter is limited by the power of received
signal. In a wireless receiver, by reason of the various effects of the electrical
characteristics and propagation path, the power of received signal varies from time to
time. When the power of digital signal exceeds the dynamic range of the wireless
receiver, the distortion and error receiving of signal may occur. The power of the
received signal needs also to be adjusted to accommodate the dynamic range of A/D
converting. Thus it is useful to employ the automatic gain controller in the
synchronous demodulation devices of wireless communication system to calculate
current gain according to RSSI (Received Signal Strength Indication), and to adjust the
received signal power to adapt to A/D dynamic range for reducing noise level and
overflow. This method is applied to RF (radio frequency) and baseband processing of
the GSM (Global System for Mobile Communications) and other system. A basic
2

concept for the wireless transmission of GSM is that a transmission unit which is about 100 modulation bits sequence is called a "burst". The "burst" is the basic unit for data transmission. For receiver, complicated wireless communication channel environment as well as the noise and other electrical interference leads to changes of burst signal power. Meanwhile, different logic channels, such as control channel and traffic channel, are defined by different payload types. The burst powers transmitted on the traffic channel and control channel are different; therefore when transmission switches from control channel to traffic channel, the received signal power may be changed accordingly.
In the existed AGC (automatic gain control) system, when the transmitted signal power lowers, this sudden decrease of the received signal power may be considered as results of the cease transmission or interference caused by other factors, and request of resending lost signal and/or rebuilding a connection may be sent by the receiver. It may result in resources waste and inefficiency. The change of the power may drive signal amplitude beyond the A/D dynamic range and may cause performance deteriorated as well as reconnection.
In the existed GSM communications system receiver, there are two common circumstances. First, BS (base station) sends control information through control channel and switches to traffic channel having comparatively lower power. This may result in the need of different signal gain; second, after a period of silence, BS resumes transmission via control channel to MS (mobile station) with the same power, the resending means the information may contain key information such as
3

control signaling. Both of the two circumstances above give certain requirements to AGC and burst signal detection.
In the first circumstance, the sudden decrease of the received signal power does not mean no signal sent at all. Instead, there are signals which may be sent by lower power via traffic channel than control channel around 30dB. Under the conditions of low-power transmission, it is needed to adopt effective burst detection method to deal with inherent high error ratio.
In the second circumstance, it is useful to compute a new gain to control RF power based on the received signal power. If the transmission of control channel is stopped by transmitter while the AGC controller of receiver is still working, the received signal is mainly consisted of noise and interference since there is no reception of burst. Therefore the AGC raises the gain because of low power of effective signal. It does useless amplification for the system and reduces the life for use of amplifiers. In the very beginning of the resumed transmission, the gain value and the amplified power of signal is remained at a higher level. At this stage, saturation distortion may be brought up by sudden increase of the amplified power of signal, and error codes in the receiver as a result may lead to lose some key information. A handover or a reselection procedure of BS may be forcedly executed by receiver.
Figure 1 is a diagram illustrating for an existed AGC system. After processing in a tuner 102, the received signal is amplified by a variable gain amplifier 104 based on a present gain value, and the output signal of the amplifier 104 may be provided to a AGC device 120 and a filter 112 through the processes of a mixer 106
4

and an A/D converter 108. The filtered signal may be sent to a demodulator 114 and a decoder 116 to produce data which is to be received. The AGC device 120 comprises a gain generator 122 and a gain control word generator 124. The gain generators 122 calculated and send the current gain to gain control word generator 124 according to the strength of received signal and produce a gain control word signal. The gain control word signal is a feedback of the variable gain amplifier 104 in order to control the gain value of the variable gain amplifier 104 according to the present signal. As mentioned above, the gain control word signal is an input to the variable gain amplifier 104 in the form of a control word. Those skilled in the art can comprehend that any signal which is not limited in the form to control the variable gain amplifier. However., it is not taken into consideration of the impact to AGC and correct reception due to sudden power decrease of the burst signal in the prior art, namely the second circumstance. Especially when the sudden signals cease to be transmitted , the AGC device 120 remain computing of the gain value based on received signal power. When no transmission of the burst signal but noise signal is received, this automatic gain control devices 120 may still amplify signal. This amplification is not required by the system, it may result in amplifying noise interference and taxing system resources.
Figure 2 is a diagram illustrating the second circumstance mentioned above by relating received RF signal power and the amplifier gain value. Figure 2 shows the three variables: the RF signal power level 210, the gain value 230 from the variable gain amplifier 104 and the amplified signal power level 240. It may be categorized into 3 phases of the time axial in Figure 2: phase A 222, B 224, and C 226.
5

With reference to the block diagram Figure l,when the sudden decrease in the RF receiver signal power 210 at the transiting from phase A to B, automatic gain control device 120 conducts the gain adjustment to the variable gain amplifier 104 according to the change in the RF signal power 210. That is to increase the gain value 230 of the variable gain amplifier. However, when no signal transmitted, for example, no burst transmitted, a sudden decrease of RF signal power 210 may appear in the phase B 224.That means the sudden decrease is not from the effective transmission. At that time, the variable gain amplifier 104 still does the action of automatic gain control and remains a high gain value which may result in power waste. After the transition from phase B 224 to C 226, the amplifier gain value is remained high. Furthermore, a burst appears again and the received signal power may be amplified at a considerably high gain. Then a power distortion 242 may arise. This distortion 242 may exceed the A/D dynamic range, and lead to the saturation distortion in the receiver.
The purpose of this invention is to resolve the problem above and to provide an apparatus and method to detect the burst signals and allow the automatic gain control to the received signals. The device and method may implement AGC operation, and do the burst detection. Especially in the sudden reducing of the signal power, It also may provide a stable output gains as well as low-power signals to afford the correct judgment reception. Automatic gain control operation as well as burst signal detection could be done by the apparatus and method for providing stable output gains and correct reception of low power signal, especially in response to a sudden decrease of received RF signal power.
6

SUMMARY OF THE INVENTION
Systems and methods for implementing automatic gain control are presented below.
In one aspect of the present invention, it is disclosed that an apparatus configured to control a gain value of a variable gain amplifier for a received signal, wherein an outcome signal is processed based on the received signal, the apparatus comprising a burst signal detector configured to detect a burst signal in said outcome signal, if said burst signal is detected, the burst signal detector sets a burst indication signal to a first particular value which indicate an active said burst signal is received, if said burst signal is not detected, force a burst indication signal to a second particular value which indicates an inactive said burst signal is received; and a variable gain generator controlling apparatus configured to use a counter to count the number of the said burst indication signal with said second particular value for outputting a signal indication result configured to control the updating and saving the said gain value, the variable gain generator controlling apparatus further calculates the present needed gain value based on said burst indication signal and outputs a gain control word to adjust said gain value of said variable gain amplifier.
Another aspect of the present invention concerns a control apparatus configured to conduct automatic gain control to adjust a gain value of a variable gain amplifier and receive a burst indication signal that comprising a first particular value and a second particular value, the control apparatus comprising a variable gain
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generator controlling apparatus configured to use a counter to count the number of the said burst indication signal with said second particular value for outputting a signal indication result configured to control the updating and saving the said gain value, the variable gain generator controlling apparatus further calculates the present needed gain value based on said burst indication signal and outputs a gain control word to adjust said gain value of said variable gain amplifier.
A third aspect of the invention disclosed a method sconfigured to control a gain value of a variable gain amplifier for a received signal, wherein an outcome signal is processed based on the received signal, the method comprising detecting a burst signal of said signal and conducting the burst signal detection, if said burst signal is active, setting a burst indication signal to a first particular value and employing a first operation, if said burst signal is inactive, setting a burst indication signal to a second particular value and employing a counting operation with a counter; setting a signal indication result to a first result value when said counter value is not less than a reference value, Setting the signal indication result as a second result value when said counter value is less than the reference value; and adjusting the gain value of said variable gain amplifier.
The present invention also concerns a method for automatic gain control configured to control a gain value of a variable gain amplifier for a received signal, detect a burst signal and get a burst indication signal, and use a counter to calculate the number of continuous said burst indication signal with a second particular value, the method comprising setting a signal indication result as a first
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result value when said counter value is not less than a reference value, stops updating the variable gain, and employs the backup gain value as the output of the present variable gain amplifier; and setting the signal indication result as a second result value when said counter value is less than the reference value, begins the updating of the variable gain amplifier.
BRIEF DESCRIPTION OF THE DRAWINGS
Features, aspects, and embodiments of the inventions are described in conjunction with the attached drawings, in which:
Figure 1 is a block diagram illustrating an AGC system structure in the prior art.
Figure 2 is a timing diagram illustrating the received signal relationship of the AGC system especially the status change of the system gainD when a sudden power decrease occurs in the prior art.
Figure 3 is a block diagram illustrating an example of this invention for the AGC system with burst detection in accordance with one embodiment.
Figure 4 is a block diagram illustrating an example of signal status relationship of the AGC system with burst detection in accordance with one embodiment.
Figure 5 is a flow diagram illustrating an example method of this invention for signal detection and AGC in a wireless communication system in accordance with one embodiment.
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While the invention is susceptible to various modification and alternative forms, specific embodiments thereof are shown by way of example in the drawings and herein may be described in detail. It should be understood, however, that the drawings and detailed description there are not intended to limited to the invention to the particular form disclosed of the invention, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the present invention as defined by the appended claims.
DETAILED DESCRIPTION
The main purpose of the following description is to enable one of the skilled in the art to make and use the present invention to meet a particular application and requirement. However, various modifications to the preferred embodiment may be apparent to one skilled in the art, and general principles defined herein may be applied to other embodiment. Thus the present invention is not limited to the particular embodiment described followed, but it is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
The invention brings forth a burst signal detection device for RF receiver. The present amplifier gain is continually updated according to RSSI, and the results of the burst signal detection is to achieve system requirements, Figure 3 to figure 5 of the invention involve a particular embodiment.
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Figure 3 mainly describes a method exemplary of the invention for the receiver apparatus. After processing in a tuner 302, the receiving processing result signal is amplified by a variable gain amplifier 304 based on a present gain value. In the present embodiment, the output signal may be provided to a controllable gain control devices 320 and a filter 312 through the process of a mixer 306 and a D/A converter 308. Meanwhile the signal may be send to a demodulator 314 after filtered. The demodulating result may be an input of a decoder 316 and a burst detector 330. A burst indication signal may be generated after the detection of the received signal by the burst detector 330 and provided to a controllable gain generator 320, and then a gain value of the variable gain amplifier is calculated based on the burst indication signal and RSSI. In one embodiment, a RF amplifier gain may be implemented by multi-component. For example, a gain control word output gain of 90dB, which may be consisted of 40dB from low-noise amplifier, 30dB from a mixer and 20dB from a LPF (low-pass filter), the gain may be developed by the above apparatus which collectively produce the gain needed. In another embodiment, a gain processing module may be introduced to achieve the function of the tuner 302, the variable gain amplifier 304 and the mixer 306. The reception and processing may be realized by this module which may be controlled by the controllable gain generator 320.
In one embodiment, the result signal may be the data output of -the
demodulator 314. In other embodiment, it may be the output of the decoder 316, and/or
the filter 312 after correlatively coding. The selection of the received signal processing
depends on the detection method employed in the burst detector 330 which is beyond
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the scope of this invention; the introduction may not be necessarily made in this description. The burst detector 330 works at making out whether a burst with a relative low power level is in the output signal of the receiving processing. The function of the burst detection 330 is to avoid mistaking the low-power burst for the noise. When received the burst signal, the burst indication signal is indicated as a value like 1, in the following description, the value 1 indicates that an active signal may be detected. For illustration, the value 0 indicates no active signal detected. It can be understood by the skilled in the art that other values may be available in the scope of the present invention, and the other signals may change correspondingly.
Alternatively, the controllable gain generator 320 includes a counter. If the burst indication signal indicates 1, which means an active burst signal is received currently..The counter is cleared with a default value. In this embodiment, the default value may be 0. If the burst indication is 0, that means no active burst signal is received or no signal is sent. If the counter value is less than a reference value, the counter value increases. If the counter is not less than the reference value, the counter value maintains as the reference value. It can be understood by one skilled in the art that the reference value is to determine a holding period of the burst indication signal. The reference value which is related to the system parameter which is a positive integer. In one embodiment, the reference value is corresponding to a plurality of single burst periods. After received an active burst, if the counter value is less than the reference value, set the signal indication result to 1, otherwise remain 0.
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In this embodiment, the counter may be operated in an incremental mode in which the counter increases from the default value to the reference value the ordinary in the art can comprehended that a detrimental mode in which the counter decreased from the reference value to the default value may work as well.
Figure 4 shows the status relationship of a. received signal power 410, a gain value of a variable gain amplifier 420, an amplified signal power 430 and burst indication signal 440 and an indication result 450 in this embodiment, whereby the amplitude of the received signal power 410 indicates the variation of the signal power level. As shown in figure 4, in accordance with the received signal power change, it may be categorized into 3 phase: phase A 460, phase B 470 and phase C 480. In phase A 460, an active burst may be received, then generate the gain value of the variable Gain amplifier 420. The gain value may be various with the received signal power 410 and the present gain value 420 is saved as a backup continuously. In one embodiment, the gain value 420 of the variable gain amplifier adopts the form of a gain control word. In phase A 460, the burst indication signal 440 indicates 1, the signal detection result indicates 1, and the counter indicates 0. The controllable gain generator 320 shown in figure 3 continuously updates and computes the current gain value and output the gain control word according to the received signal power.
At a beginning point 472 of the transition from phase A 460 to phase B 470, a sudden decrease appears in the received signal povyer 410. The sudden decrease may be caused by a transmission silence and/or the handover on the channel. At that time, the burst indication signal 440 changes to 0 and the counter value is less than the
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reference value which maintains the signal detection result as 1, the counter remains increasing and stopping saving the gain value 420 as the backup value.
In phase B 470, there is no burst signal sent and/or the received signal power was too low to process, during the period from time 472 to time 474, the variable gain amplifier continuously calculates the current received signal gain needed without backup the gain value 420. The gain value 420 of the variable gain amplifier increases constantly. The burst indication signal 440 remains 0 before the counter number of the continuous 0 of the burst indication signal 440 achieves the reference value. After the counter value reaching the reference value, the burst indication signal 440 change to 0, then the counter stops increasing and maintains the reference value until the burst indication signal 440 turns to 1. In the embodiment, the reference value is 4. If the burst indication signal 440 and the signal detection result change to 0, the variable gain amplifier amplifies with the backup gain value concurrently.
At the point 476, the system receives an active burst signal. The burst indication signal 440 indicates 1 which makes the counter returns to the default value. Apparently the default value is less than the reference value, the signal detection result changes to 1 and the gain value 420 updates. The variable gain amplifier 304 showed in the figure 3 works on this value. In the phase C 480, the value updates according to the received signal power.
Figure 5 shows the method flow exemplary introduced in the present invention of AGC with burst detection and signal detection. In different embodiments,
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some method steps may be implemented concurrently, and/or adopts a flow which is not shown in the figures or some steps may be combined.
In the step 502, the burst signal detection may be implemented as the received processing result signal. In the step 506, if there is an active burst, the burst indication signal is set to 1 which means an active signal transmission and then pursues the step 510. In the step 510, the counter returns the reference value and saves the current gain as a backup value. The gain calculates based on the current received signal power.
If an active burst signal is detected which indicates no effective signal or heavy error code transmission and incorrect decoding executed in the receiver, the burst indication changes to 0. When the counter works at an incremental mode, the counter value N may be increased by 1 in the step 514. In the beginning of the processing, the counter default value may be 0.
In the step 518, when the counter value N is less than the reference value, the gain value of the variable gain amplifier may be updated and computed; meanwhile the signal detection result indicates 1. Processing the next received burst indication signal may be implemented in the step 502. In the step 518, when the counter value N is not less than the reference value, changes the signal detection result to 0 in the step 526, and stops the gain value computing. The backup value gain may be adopted and then process the next burst indication signal.
Compared with the prior art, the present invention provides the method and device of AGC with the burst detection. As the described above, the invention
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intends to provide an embodiment of the burst detection and AGC device in RF receiver, however the method introduced herein may be applied in baseband receiver as well.
While certain embodiments of the inventions have been described above, it will be understood that the embodiments described are by way of examples only. Numerous variations and modifications can be apparent to those skilled in the art. Accordingly, the inventions should not be limited based on the described embodiments. Rather, the scope of the inventions herein described should only be limited in the claims that follow when taken in conjunction with the above description and accompanying drawings.
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We Claim :
1. An apparatus, configured to control a gain value of a variable gain amplifier for a
received signal, wherein an outcome signal is processed based on the received
signal, the apparatus comprising:
a burst signal detector configured to detect a burst signal in said outcome signal, if said burst signal is detected, the burst signal detector sets a burst indication signal to a first particular value which indicate an active said burst signal is received, if said burst signal is not detected, force a burst indication signal to a second particular value which indicates an inactive said burst signal is received; and
a variable gain generator controlling apparatus configured to use a counter to count the number of the said burst indication signal with said second particular value for outputting a signal indication result configured to control the updating and saving the said gain value, the variable gain generator controlling apparatus further calculates the present needed gain value based on said burst indication signal and outputs a gain control word to adjust said gain value of said variable gain amplifier.
2. The apparatus of claim 1, wherein said counter compares the number of the continuous said burst indication signal with said second particular value to a reference value, if the number is less than said reference value, said signal indication result is output as a first value, if the number is not less than said reference value, output said signal indication result is output as a second value.
3. The apparatus of claim 1, wherein said signal indication result configured to determine whether the recalculation of the gain value is said variable gain
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amplifier is needed, if the signal indication result is said first value, said variable gain generator controlling apparatus begins the automatic gain control and update the calculation of said gain value of said variable gain amplifier; if the signal indication result is said second value, said variable gain generator controlling apparatus stops updating and calculating of said gain value.
4. The apparatus of claim 1, wherein when the burst indication signal is said first particular value, save the gain value of said variable gain amplifier as a backup gain value, when the burst indication signal is said second particular value, employ the latest saved said backup gain value as the gain value of said variable gain amplifier.
5. A control apparatus configured to conduct automatic gain control to adjust a gain value of a variable gain amplifier and receive a burst indication signal that comprising a first particular value and a second particular value, the control apparatus comprising:
a variable gain generator controlling apparatus configured to use a counter to count the number of the said burst indication signal with said second particular value for outputting a signal indication result configured to control the updating and saving the said gain value, the variable gain generator controlling apparatus further calculates the present needed gain value based on said burst indication signal and outputs a gain control word to adjust said gain value of said variable gain amplifier.
6. A method configured to control a gain value of a variable gain amplifier for a
received signal, wherein an outcome signal is processed based on the received
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signal, the method comprising:
detecting a burst signal of said signal and conducting the burst signal detection, if said burst signal is active, setting a burst indication signal to a first particular value and employing a first operation, if said burst signal is inactive, setting a burst indication signal to a second particular value and employing a counting operation with a counter;
setting a signal indication result to a first result value when said counter value is not less than a reference value, setting the signal indication result as a second result value when said counter value is less than the reference value; and
adjusting the gain value of said variable gain amplifier.
7. The method of claim 6, wherein said the first operation further comprising: setting the counter value to the default counter value and saving present said gain value of said variable gain amplifier as a backup gain value.
8. The method of claim 6, wherein said counting operation further comprising: if said burst indication signal is said second particular value, the counter begins to run; If said counter works on an increment mode, a unit value is increased, If said counter works on an decrement mode, a unit value is decreased.
9. The method of claim 6, wherein said signal indication result is said first value, said variable gain generator controlling apparatus stops updating and calculating of said gain value of said variable gain amplifier and employs said backup gain value as the current output of said variable gain amplifier; if the signal indication result is said second value, said variable gain generator controlling apparatus
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begins the updating and calculating.
10. a method for automatic gain control configured to control a gain value of a
variable gain amplifier for a received signal, detect a burst signal and get a burst
indication signal, and use a counter to calculate the number of continuous said
burst indication signal with a second particular value, the method comprising:
setting a signal indication result as a first result value when said counter value is
not less than a reference value, stopping updating the variable gain, and employing
the backup gain value as the output of the present variable gain amplifier; and
setting the signal indication result ass a second result value when said counter
value is less than the reference value and updating the variable gain amplifier.
Dated this 1st day of October, 2008
FOR VIA TECHNOLOGIES, INC.
By their Agent

(MADHURI RAMESHCHANDRA TAWRI) KRISHNA & SAURASTRI
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Patent Number

259616

Indian Patent Application Number

2115/MUM/2008

PG Journal Number

12/2014

Publication Date

21-Mar-2014

Grant Date

20-Mar-2014

Date of Filing

01-Oct-2008

Name of Patentee

VIA TECHNOLOGIES, INC.

Applicant Address

8F, 535, CHUNG-CHENG RD., HSIN-TIEN, TAIPEI, R.O.C.

Inventors:

#	Inventor's Name	Inventor's Address
1	LIJUN ZHANG	8F, 535, CHUNG-CHENG RD., HSIN-TIEN, TAIPEI, R. O. C.
2	JERVI ZHANG	8F, 535, CHUNG-CHENG RD., HSIN-TIEN, TAIPEI, R. O. C.
3	ORVILLE YI	8F, 535, CHUNG-CHENG RD., HSIN-TIEN, TAIPEI, R. O. C.
4	YAN WU	8F, 535, CHUNG-CHENG RD., HSIN-TIEN, TAIPEI, R. O. C.
5	MIN LEI	8F, 535, CHUNG-CHENG RD., HSIN-TIEN, TAIPEI, R. O. C.

PCT International Classification Number

H03G3/20

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	200710152468.2	2007-10-15	Chinese Taipei