CN104954033A - Rapid automatic gain control circuit and method for OFDM (orthogonal frequency division multiplexing) system - Google Patents
Rapid automatic gain control circuit and method for OFDM (orthogonal frequency division multiplexing) system Download PDFInfo
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- CN104954033A CN104954033A CN201510285016.6A CN201510285016A CN104954033A CN 104954033 A CN104954033 A CN 104954033A CN 201510285016 A CN201510285016 A CN 201510285016A CN 104954033 A CN104954033 A CN 104954033A
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Abstract
The invention belongs to the technical field of wireless communication, and particularly relates to a rapid automatic gain control method based on an OFDM (orthogonal frequency division multiplexing) system. An OFDM receiver model based on an AGC (automatic gain control) module is used, attenuation and distortion of received signals are unavoidable due to complex and changeful transmission channels in the transmission process of OFDM signals, and the AGC module is generated to solve the problem of signal attenuation. However, traditional AGC has the shortcomings of low convergence speed, gain jitter and incorrect empty time slot adjustment. The novel rapid automatic gain control method can effectively overcome the three shortcomings, and simulation is correspondingly performed. A device comprises a gain adjustment portion and an analog amplifier based on an OFDM receiver module with the AGC module.
Description
Technical field
The invention belongs to wireless communication technology field, be specifically related to a kind of speed automatic gain control circuit for ofdm system and method.
Background technology
The development that forth generation mobile communication system (4G) is following and evolution issues become the focus of current research.In the key technology that 4G adopts, OFDM technology is most important beyond doubt.The main thought of OFDM technology is exactly, in frequency domain, given channel is divided into many narrow orthogonal sub-channels, uses a subcarrier to modulate on each of the sub-channels, and each subcarrier parallel transmission, therefore can interference greatly between erasure signal waveform.OFDM can also distribute transmission load on different sub-channels adaptively, can optimize total transmission rate like this.In addition, OFDM can also contrary frequency Selective intensity or arrowband interference.Carrier wave in an ofdm system due to each sub-channels is mutually orthogonal, and their frequency spectrum is overlapped, so not only reduces the mutual interference between subcarrier, turn improves the availability of frequency spectrum simultaneously.
But in ofdm signal transmitting procedure, because transmission channel is complicated and changeable, inevitably there is decay and the distortion of Received signal strength, AGC(automatic growth control) generation of module is exactly to solve problem of signal attenuation.AGC module can by carrying out adaptive adjustment to received signal, thus the dynamic range of stable output signal, to reduce due to too small or the excessive and quantization error that is that cause of dynamic range of signals.
Traditional AGC adopts fixed step size method of adjustment mostly, when running into channel and significantly changing, cannot rapid adjustment gain parameter, and need just can converge to stationary value for a long time; And adopt the method for adjustment of fixed step size easily to cause yield value to shake.In addition, because traditional AGC does not consider the problem of empty slot, to not having the time slot of actual data transfer to carry out unnecessary adjustment, the raising of error rate of system may be caused.
The present invention is directed to these shortcomings of traditional AGC, propose a kind of rapid automatic gain control method, and correspondingly to emulate, prove that this new method effectively can overcome this three shortcomings.
Summary of the invention
The speed automatic gain for ofdm system that the object of the invention is to propose controls (Automatic Gain Control, AGC) circuit module and rapid automatic gain control method.
OFDM receiver module with agc circuit module as shown in Figure 1.Wherein, agc circuit module is made up of analogue amplifier and Gain tuning two parts; Before analogue amplifier part is arranged at the A/D module of OFDM receiver, signal for receiving antenna amplifies, thus make the dynamic range of Received signal strength be stabilized in a fixed range, to prevent the too little dropout caused of Received signal strength, and the excessive saturation distortion caused of Received signal strength; After gain adjusting part is arranged at the A/D module of OFDM receiver, for receiving the output signal of the A/D module of OFDM receiver, and signal level is calculated and compares, the yield value of adjustment analogue amplifier, to tackle the change of the Received signal strength dynamic range that channel variation produces.Herein, before gain adjusting part also can be arranged on the A/D module of OFDM receiver, directly receive the output signal of analogue amplifier, but Gain tuning now need use analog circuit to realize, cost comparatively digital circuit wants high.
The rapid automatic gain control method based on above-mentioned speed automatic gain control circuit module that the present invention proposes, concrete steps are as follows:
step 1:for AGC module installation gain initial value.AGC gain initial value can be set to any reasonable value in 20dB ~ 40dB.The preferred value of AGC gain initial value is 30dB.
step 2:measure the average power signal of each frequency.To sample each frequency
before
the energy of individual data, will
individual data point energy
d j root mean square as frequency
average power signal.Wherein,
for detecting data length.Therefore, frequency
average power signal
computing formula as follows:
。
step 3:judge whether power average value is less than noise gate, if so, then think that the signal received is white noise, Gain tuning is not carried out to it, skip AGC gain value adjustment member simultaneously, skip to step 7.Otherwise think normal data-signal, carry out Gain tuning to received signal, and continue step 4.
Wherein, noise gate can arrange any reasonable value higher than white noise average power, and concrete numerical value is limited by the anti-noise level of receiver preamplifier.
step 4:the maximum of average power signal and target power value are compared, its difference is that AGC adjusts increment.Wherein, target power value can be set to be any reasonable value that saturation distortion does not occur signal.Its preferred value is 0dB, that is: the saturation power of signal.
step 5:if AGC adjusts increment exceed adjustment thresholding, then AGC gain value is adjusted.Otherwise will not adjust.Wherein, the effect adjusting thresholding is adjusting frequency of control AGC.Adjustment thresholding arranges larger, then what the generation of AGC gain value was finely tuned may be lower, namely decreases adjusting frequency of AGC gain value, but also can cause AGC gain value now and non-optimal simultaneously, cannot adjust Received signal strength to best dynamic range.Otherwise, then can improve signal adjustment quality, but the frequent adjustment of AGC gain value can be caused.This is decided according to the actual requirements.
step 6:if AGC gain value exceeds AGC gain range, then AGC gain value is set to AGC gain range.Otherwise keep current AGC gain value.When AGC gain value exceeds the maxgain value that reality can reach, that is:, during gain range, system mistake may be caused.Therefore interpolation judges to ensure that AGC gain value is in normal range (NR) all the time herein.
step 7:complete AGC process, the Received signal strength after output gain adjustment is to rear class process.
So far, the process of an AGC process terminates.
The inventive method can adjust the yield value of AGC flexibly and rapidly, thus ensures that the signal power after AGC adjustment is stabilized in an optimum range, reduces the quantization error of rear class.
Accompanying drawing explanation
The OFDM receiver model of Fig. 1: band AGC module.
Fig. 2: rapid automatic gain control method flow chart.
Fig. 3: the fast A GC performance under awgn channel.
Embodiment
Below in conjunction with drawings and Examples, specifically describe the present invention further.
As shown in Figure 1, be the OFDM receiver of band agc circuit module.Wherein, agc circuit module is made up of analogue amplifier and Gain tuning two parts; Before analogue amplifier part is arranged at the A/D module of OFDM receiver, signal for receiving antenna amplifies, thus make the dynamic range of Received signal strength be stabilized in a fixed range, to prevent the too little dropout caused of Received signal strength, and the excessive saturation distortion caused of Received signal strength; After gain adjusting part is arranged at the A/D module of OFDM receiver, for receiving the output signal of the A/D module of OFDM receiver, and signal level is calculated and compares, the yield value of adjustment analogue amplifier, to tackle the change of the Received signal strength dynamic range that channel variation produces.
The rapid automatic gain control method based on above-mentioned speed automatic gain control circuit module that the present invention proposes, concrete steps are as follows:
step 1:for AGC module installation gain initial value.AGC gain initial value can be set to any reasonable value in 20dB ~ 40dB.The preferred value of AGC gain initial value is 30dB.
step 2:measure the average power signal of each frequency.To sample each frequency
before
the energy of individual data, will
individual data point energy
d j root mean square as frequency
average power signal.Wherein,
for detecting data length.Therefore, frequency
average power signal
computing formula as follows:
。
step 3:judge whether power average value is less than noise gate, if so, then think that the signal received is white noise, Gain tuning is not carried out to it, skip AGC gain value adjustment member simultaneously, skip to step 7.Otherwise think normal data-signal, carry out Gain tuning to received signal, and continue step 4.
Wherein, noise gate can arrange any reasonable value higher than white noise average power, and concrete numerical value is limited by the anti-noise level of receiver preamplifier.
step 4:the maximum of average power signal and target power value are compared, its difference is that AGC adjusts increment.Wherein, target power value can be set to be any reasonable value that saturation distortion does not occur signal.Its preferred value is 0dB, that is: the saturation power of signal.
step 5:if AGC adjusts increment exceed adjustment thresholding, then AGC gain value is adjusted.Otherwise will not adjust.Wherein, the effect adjusting thresholding is adjusting frequency of control AGC.Adjustment thresholding arranges larger, then what the generation of AGC gain value was finely tuned may be lower, namely decreases adjusting frequency of AGC gain value, but also can cause AGC gain value now and non-optimal simultaneously, cannot adjust Received signal strength to best dynamic range.Otherwise, then can improve signal adjustment quality, but the frequent adjustment of AGC gain value can be caused.This is decided according to the actual requirements.
step 6:if AGC gain value exceeds AGC gain range, then AGC gain value is set to AGC gain range.Otherwise keep current AGC gain value.When AGC gain value exceeds the maxgain value that reality can reach, that is:, during gain range, system mistake may be caused.Therefore interpolation judges to ensure that AGC gain value is in normal range (NR) all the time herein.
step 7:complete AGC process, the Received signal strength after output gain adjustment is to rear class process.
So far, the process of an AGC process terminates.
In step 3, judge whether power average value is less than noise gate and adopts with the following method:
Step 3.1: the quantity that a counter records the power points higher than noise gate is set, and is reset.
Step 3.2: the power average value of each frequency and noise gate are compared successively, if higher than noise gate, then adds one by counter.
Step 3.3: if counter values is greater than frequency sum
, then judge whether power average value is greater than noise gate, otherwise then judge to be less than noise gate.
any reasonable value in 50% ~ 80% can be set to.
Fig. 3 is the systematic function of OFDM receiver under awgn channel that have employed fast A GC.Can find, when fading channel is very little, due to the function that the analogue amplifier in the fast A GC of emulation does not make signal reduce, therefore cause certain saturation distortion, but this phenomenon can be solved by the gain parameter of adjustment analogue amplifier.
Claims (3)
1., for a speed automatic gain control circuit module for ofdm system, it is characterized in that being made up of analogue amplifier and Gain tuning two parts; Wherein, before analogue amplifier part is arranged at the A/D module of OFDM receiver, signal for receiving antenna amplifies, thus make the dynamic range of Received signal strength be stabilized in a fixed range, to prevent the too little dropout caused of Received signal strength, and the excessive saturation distortion caused of Received signal strength; After gain adjusting part is arranged at the A/D module of OFDM receiver, for receiving the output signal of the A/D module of OFDM receiver, and signal level is calculated and compares, the yield value of adjustment analogue amplifier, to tackle the change of the Received signal strength dynamic range that channel variation produces; Or, before gain adjusting part is arranged on the A/D module of OFDM receiver, directly receive the output signal of analogue amplifier.
2., based on the rapid automatic gain control method for ofdm system of circuit module described in claim 1, it is characterized in that concrete steps are:
Step 1: be AGC module installation gain initial value, this gain initial value is any reasonable value in 20dB ~ 40dB;
Step 2: the average power signal measuring each frequency: each frequency of sampling
before
the energy of individual data, will
individual data point energy
d j root mean square as frequency
average power signal; Wherein,
for detecting data length, frequency
average power signal
computing formula as follows:
Step 3: judge whether power average value is less than noise gate, if so, then thinks that the signal received is white noise, does not carry out Gain tuning to it, skip AGC gain value adjustment member simultaneously, skip to step 7; Otherwise think normal data-signal, carry out Gain tuning to received signal, and continue step 4; Wherein, described noise gate is set to any reasonable value higher than white noise average power;
Step 4: the maximum of average power signal and target power value are compared, its difference is that AGC adjusts increment; Wherein, target power value is set to be any reasonable value that saturation distortion does not occur signal;
Step 5: if AGC adjusts increment exceed adjustment thresholding, then AGC gain value is adjusted; Otherwise will not adjust; Wherein, adjust thresholding to set according to actual needs;
Step 6: if AGC gain value exceeds AGC gain range, then AGC gain value is set to AGC gain range; Otherwise keep current AGC gain value;
Step 7: complete AGC process, the Received signal strength after output gain adjustment is to rear class process.
3. the rapid automatic gain control method for ofdm system according to claim 2, is characterized in that in step 3, judge power average value whether be less than noise gate adopt method as follows:
Step 3.1: the quantity that a counter records the power points higher than noise gate is set, and is reset;
Step 3.2: the power average value of each frequency and noise gate are compared successively, if higher than noise gate, then adds one by counter;
Step 3.3: if counter values is greater than frequency sum
, then judge that power average value is greater than noise gate, otherwise then judge to be less than noise gate;
be set to any reasonable value in 50% ~ 80%.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108768425A (en) * | 2018-07-02 | 2018-11-06 | 成都国恒空间技术工程有限公司 | A kind of dynamic adjusting method of automatic growth control AGC |
| CN110474691A (en) * | 2019-08-09 | 2019-11-19 | 三维通信股份有限公司 | Gain control method and device |
| CN110620745A (en) * | 2019-09-12 | 2019-12-27 | 苏州门海微电子科技有限公司 | Digital front-end system for suppressing narrow-band interference and suppression method thereof |
| CN113014282A (en) * | 2021-02-18 | 2021-06-22 | 深圳捷扬微电子有限公司 | Automatic gain control method, device, receiver and ultra-wideband communication system |
| CN117580143A (en) * | 2024-01-15 | 2024-02-20 | 南京思宇电气技术有限公司 | Automatic gain control method and system based on dual-mode communication unit |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108768425A (en) * | 2018-07-02 | 2018-11-06 | 成都国恒空间技术工程有限公司 | A kind of dynamic adjusting method of automatic growth control AGC |
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| CN110474691A (en) * | 2019-08-09 | 2019-11-19 | 三维通信股份有限公司 | Gain control method and device |
| CN110620745A (en) * | 2019-09-12 | 2019-12-27 | 苏州门海微电子科技有限公司 | Digital front-end system for suppressing narrow-band interference and suppression method thereof |
| CN110620745B (en) * | 2019-09-12 | 2022-03-04 | 苏州门海微电子科技有限公司 | Digital front-end system for suppressing narrow-band interference and suppression method thereof |
| CN113014282A (en) * | 2021-02-18 | 2021-06-22 | 深圳捷扬微电子有限公司 | Automatic gain control method, device, receiver and ultra-wideband communication system |
| CN117580143A (en) * | 2024-01-15 | 2024-02-20 | 南京思宇电气技术有限公司 | Automatic gain control method and system based on dual-mode communication unit |
| CN117580143B (en) * | 2024-01-15 | 2024-03-22 | 南京思宇电气技术有限公司 | Automatic gain control method and system based on dual-mode communication unit |
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