CN111049487A - Automatic gain control circuit and control method - Google Patents
Automatic gain control circuit and control method Download PDFInfo
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- CN111049487A CN111049487A CN201911293451.8A CN201911293451A CN111049487A CN 111049487 A CN111049487 A CN 111049487A CN 201911293451 A CN201911293451 A CN 201911293451A CN 111049487 A CN111049487 A CN 111049487A
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- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers
- H03G3/20—Automatic control
- H03G3/30—Automatic control in amplifiers having semiconductor devices
- H03G3/3036—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers
- H03G3/3042—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers in modulators, frequency-changers, transmitters or power amplifiers
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Abstract
The disclosure provides an automatic gain control circuit and a control method, and belongs to the technical field of wireless communication. The automatic gain control circuit comprises a first-stage automatic gain module, a second-stage automatic gain module and a logarithmic amplifier module, wherein the logarithmic amplifier module is formed by connecting three series-connection cascade logarithmic amplifiers in parallel; the first-stage automatic gain module is used for amplifying or reducing the input signal to obtain a first signal with the same gain control range as that of the second-stage automatic gain module and outputting the first signal to the second-stage automatic gain module; the second-stage automatic gain module is used for amplifying or reducing the first signal to obtain a second signal which is the same as the gain control range of the logarithmic amplifier, and outputting the second signal to the logarithmic amplifier; and the logarithmic amplifier module is used for amplifying or reducing the second signal to obtain a desired output signal and outputting the desired output signal. The automatic gain control circuit can reduce harmonic distortion and improve the input dynamic range of the automatic gain control circuit.
Description
Technical Field
The present disclosure relates to the field of wireless communications technologies, and in particular, to an automatic gain control circuit and a control method.
Background
In a ship-aircraft communication system, an automatic gain control circuit is often arranged in a receiver, and when an input signal is very weak, the gain of the receiver is large, and the automatic gain control circuit does not work. When the input signal is strong, the automatic gain control circuit controls to reduce the gain of the receiver. Thus, the voltage or power at the output of the receiver is substantially constant or remains constant as the received signal strength varies.
The automatic gain control circuit generally includes a feedback type automatic gain control circuit and a feedforward type automatic gain control circuit. In the current ship and aircraft communication system, a feedforward type automatic gain control circuit is generally adopted. When the feedforward type automatic gain control circuit processes signals, an input signal is usually separated into two paths, one path is sent to a variable gain amplifier for amplification, the other path enters a peak detector and a signal power estimator, the peak detector detects the input signal, the signal power estimator estimates the power of the input signal in a short time, and then the variable gain amplifier is adjusted according to the difference value between the estimated signal power and the final expected signal power.
In the existing ship-airplane communication process, the distance between an airplane and a ship can be changed continuously, and the power of an input signal can also be changed continuously. Therefore, after receiving an input signal, the signal power estimator of the feedforward type automatic gain control circuit estimates the signal power a plurality of times in a short time. In the process of ship-aircraft communication, the signal peak-to-average ratio of an input signal is generally high, the dynamic range of the signal is large, and the error between the signal power estimation in a short time and the actual signal average power is necessarily large. The fast and stable convergence of the variable gain amplifier is realized under the condition of inaccurate power estimation, and the problems of large harmonic distortion and small linear dynamic range exist.
Disclosure of Invention
The embodiment of the disclosure provides an automatic gain control circuit and a control method, which can reduce harmonic distortion, improve the input dynamic range of the automatic gain control circuit, and simultaneously shorten the adjustment time of automatic gain. The technical scheme is as follows:
in a first aspect, an automatic gain control circuit is provided, the automatic gain control circuit comprises a first-stage automatic gain module, a second-stage automatic gain module and a logarithmic amplifier module, wherein the logarithmic amplifier module is formed by connecting three series-connected cascade logarithmic amplifiers in parallel;
the first-stage automatic gain module is used for amplifying or reducing an input signal to obtain a first signal with the same gain control range as that of the second-stage automatic gain module and outputting the first signal to the second-stage automatic gain module;
the second-stage automatic gain module is used for amplifying or reducing the first signal to obtain a second signal which is the same as the gain control range of the logarithmic amplifier, and outputting the second signal to the logarithmic amplifier;
and the logarithmic amplifier module is used for amplifying or reducing the second signal to obtain an expected output signal and outputting the expected output signal.
Optionally, the logarithmic amplifier module comprises a first preamplifier, a second preamplifier, a third preamplifier, a first cascaded logarithmic amplifier, a second cascaded logarithmic amplifier, a third cascaded logarithmic amplifier and a parallel summing unit;
the input ends of the first preamplifier, the second preamplifier and the third preamplifier are all connected with the output end of the second-stage automatic gain module, the output end of the first preamplifier is connected with the output end of the first cascade logarithmic amplifier, the output end of the second preamplifier is connected with the output end of the second cascade logarithmic amplifier, and the output end of the third preamplifier is connected with the output end of the third cascade logarithmic amplifier;
the output ends of the first cascade logarithmic amplifier, the second cascade logarithmic amplifier and the third cascade logarithmic amplifier are all connected with the parallel summing unit, and the parallel summing unit is used for summing and outputting the outputs of the first cascade logarithmic amplifier, the second cascade logarithmic amplifier and the third cascade logarithmic amplifier.
Optionally, the first cascaded logarithmic amplifier is formed by cascading two limiting amplifiers in series, and the second cascaded logarithmic amplifier and the third cascaded logarithmic amplifier are formed by cascading five limiting amplifiers in series.
Optionally, the first-stage automatic gain module includes a first detector, a first electrically-tuned attenuator, and a first amplifier;
the first detector is used for detecting the input signal, comparing the voltage of the input signal with a reference voltage stored in the first detector to obtain a first control signal, and sending the first control signal to the first electrically-controlled attenuator;
the first electrically-adjusted attenuator is used for controlling the magnification or reduction times of the first amplifier according to the received first control signal;
the first amplifier is used for amplifying or reducing the input signal to obtain the first signal.
Optionally, the control voltage of the first electrically-adjustable attenuator is-3-0V.
Optionally, the second-stage automatic gain module includes a second electrically-tuned attenuator, a second amplifier, and a second detector;
the second detector is used for detecting the first signal, comparing the voltage of the first signal with a reference voltage stored in the second detector to obtain a second control signal, and sending the second control signal to the second electrically-controlled attenuator;
the second electrically-adjusted attenuator is used for controlling the magnification or reduction times of the second amplifier according to the received second control signal;
the second amplifier is used for amplifying or reducing the first signal to obtain the second signal.
Optionally, the automatic gain control system further comprises an attenuator disposed between the output of the primary automatic gain module and the input of the secondary automatic gain module.
Optionally, the automatic gain control system further comprises a pre-amplification module and a filter;
the pre-amplification module is used for amplifying the input signal and outputting the amplified input signal to the filter;
the filter is used for filtering the amplified interference signals in the input signals and outputting the interference signals to the first-stage automatic gain module.
Optionally, the automatic gain control system further includes a demodulation module for demodulating and outputting the signal output by the logarithmic amplifier.
In a second aspect, there is provided an automatic gain control method using the automatic gain control circuit according to the first aspect, the automatic gain control method comprising:
acquiring the input signal;
outputting the input signal to the first-stage automatic gain module for first-stage amplification or reduction to obtain a first signal;
outputting the first signal to the secondary automatic gain module for secondary amplification or reduction to obtain a second signal;
and outputting the second signal to the logarithmic amplifier module for three-stage amplification or reduction to obtain an expected output signal.
The technical scheme provided by the embodiment of the disclosure has the following beneficial effects:
by arranging the automatic gain control system, when an input signal is received, the input signal can be amplified or reduced in two stages through the first-stage automatic gain module and the second-stage automatic gain module, and finally amplified or reduced in three stages through the logarithmic amplifier module. The logarithmic amplifier module is formed by connecting three series-connection logarithmic amplifiers in parallel, the logarithmic function is realized by the way of parallel summation of the three series-connection logarithmic amplifiers, and the input dynamic range of the logarithmic amplifier module far exceeds that of a single chip series-connection logarithmic amplifier, so that the input dynamic range of the automatic gain control circuit can be greatly improved, the dynamic range of input signals can be large, the output basically keeps constant, and the harmonic distortion is small. Meanwhile, the automatic gain adjustment time of the logarithmic amplifier module is faster and can reach a millisecond pole, so that the automatic gain adjustment time can be shortened.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an automatic gain control circuit according to an embodiment of the present disclosure;
FIG. 2 is a graph of gain dynamic range provided by embodiments of the present disclosure;
fig. 3 is a control circuit diagram of a first-stage automatic gain module and a second-stage automatic gain module provided in the embodiment of the present disclosure;
fig. 4 is a schematic structural diagram of a logarithmic amplifier provided by an embodiment of the present disclosure;
FIG. 5 is a circuit diagram of a parallel summing circuit of logarithmic amplifier modules provided by an embodiment of the present disclosure;
fig. 6 is a flowchart of a method of automatic gain control according to an embodiment of the present disclosure.
Detailed Description
To make the objects, technical solutions and advantages of the present disclosure more apparent, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of an automatic gain control circuit provided in an embodiment of the present disclosure, and as shown in fig. 1, the automatic gain control circuit includes a first-stage automatic gain module 10, a second-stage automatic gain module 20, and a logarithmic amplifier module 30. The logarithmic amplifier module 30 is formed by connecting three series-connected cascaded logarithmic amplifiers in parallel.
The first-stage automatic gain module 10 is configured to amplify or reduce an input signal to obtain a first signal having the same gain control range as that of the second-stage automatic gain module 20, and output the first signal to the second-stage automatic gain module 20.
The two-stage automatic gain module 20 is configured to amplify or reduce the first signal to obtain a second signal with the same gain control range as that of the logarithmic amplifier 30, and output the second signal to the logarithmic amplifier 30.
The logarithmic amplifier module 30 is used for amplifying or reducing the second signal to obtain a desired output signal and outputting the desired output signal.
Wherein the desired output signal is an output signal of constant amplitude.
By arranging the automatic gain control system, when an input signal is received, the input signal can be subjected to secondary amplification or reduction through the primary automatic gain module and the secondary automatic gain module, and finally subjected to tertiary amplification or reduction through the logarithmic amplifier module. The logarithmic amplifier module is formed by connecting three series-connection logarithmic amplifiers in parallel, the logarithmic function is realized by the way of parallel summation of the three series-connection logarithmic amplifiers, and the input dynamic range of the logarithmic amplifier module far exceeds that of a single chip series-connection logarithmic amplifier, so that the input dynamic range of the automatic gain control circuit can be greatly improved, the dynamic range of input signals can be large, the output basically keeps constant, and the harmonic distortion is small. Meanwhile, the automatic gain adjustment time of the logarithmic amplifier module is faster and can reach a millisecond pole, so that the automatic gain adjustment time can be shortened.
In this embodiment, the gain of the input signal is-80 dBm-0 dBm, the control-start point of the first-stage automatic gain module 10 is-8 dB, and the dynamic range is 20 dB. The start control point of the secondary automatic gain module 20 is-19 dB, and the dynamic range is 20 dB. The start-up point of the logarithmic amplifier module 30 is-38 dBm with a dynamic range of 40 dB. After an input signal passes through the first-stage automatic gain module 10, a first signal with the same gain control range as that of the second-stage automatic gain module 20 is obtained, and the gain of the first signal is-68 dBm to-8 dBm; attenuation is 3 dB: -71 to-11 dBm. The first signal passes through the second-stage automatic gain module 20 to obtain a second signal with the same gain control range as that of the logarithmic amplifier 30, and the gain of the second signal is-59 dBm to-19 dBm. The second signal passes through the logarithmic amplifier module 30 to obtain the desired signal, which has a gain of-38 dBm.
Fig. 2 is a diagram of a gain dynamic range provided by an embodiment of the present disclosure, and as shown in fig. 2, a gain of an input signal is-80 dBm to 0dBm, and a desired signal with a gain of-38 dBm is finally obtained after passing through an automatic gain control circuit provided by the embodiment of the present disclosure.
Optionally, the first-stage automatic gain module 10 includes a first detector 11, a first electrically-tunable attenuator 12, and a first amplifier 13.
The first detector 11 is configured to detect an input signal, compare a voltage of the input signal with a reference voltage stored inside the first detector 11 to obtain a first control signal, and send the first control signal to the first electrically-controlled attenuator 12.
And the first electrically-adjusted attenuator 12 is used for controlling the magnification or reduction factor of the first amplifier 13 according to the received first control signal.
The first amplifier 13 is configured to amplify or reduce the input signal to obtain a first signal.
In this embodiment, the control voltage of the first electrically-tunable attenuator 12 is-3 to 0V.
The control voltage of the first electrically-adjustable attenuator is negative voltage from-3V to 0V, the high-speed operational amplifier changes the positive voltage output by the detection into the required negative voltage, and meanwhile, the amplification factor is adjustable, so that the debugging is facilitated. The first electrically-adjustable attenuator is a positive slope control attenuation, namely, the attenuation is increased along with the increase of the control voltage, so that the first electrically-adjustable attenuator and the fixed gain amplifier are equivalent to a variable gain amplifier forming a negative slope (the higher the control voltage is, the lower the gain is), a detection circuit with a positive slope response is required (the higher the input signal power is, the higher the detection output voltage is), a differential amplification circuit is designed, and the negative slope response of the detection output can be changed into the positive slope response by providing a proper reference voltage.
The input of each stage should not exceed the requirement of the compression point of the active device, so as to prevent signal distortion, and preferably, sufficient margin is left, and the input of each stage backs by 6-10 dB at the compression point, so as to meet the index of linearity. The input signal of the amplifier can not exceed the requirement of the compression point, and the first amplifier 13 in the first-stage automatic gain module 10 should select a pipe with high compression point and good linearity, and the requirement can be met by setting the control point of the automatic gain module during debugging. The design can realize electrically-tuned attenuation by using a field effect transistor when the electrically-tuned attenuator is selected.
Optionally, the two-stage automatic gain module 20 includes a second electrically-tuned attenuator 21, a second amplifier 22 and a second detector 23.
The second detector 21 is configured to detect the first signal, compare the voltage of the first signal with a reference voltage stored inside the second detector 21 to obtain a second control signal, and send the second control signal to the second electrically-controlled attenuator 22.
And the second electrically-adjusted attenuator 22 is used for controlling the magnification or reduction factor of the second amplifier 23 according to the received second control signal.
And a second amplifier 23 for amplifying or reducing the first signal to obtain a second signal.
In this embodiment, the control voltage of the second electrically-controlled attenuator 22 is-3 to 0V.
Fig. 3 is a control circuit diagram of a first-stage automatic gain module and a second-stage automatic gain module according to an embodiment of the present disclosure, and as shown in fig. 3, an input signal may be output to obtain a second signal through the circuit structures of the first-stage automatic gain module 10 and the second-stage automatic gain module 20 shown in fig. 3.
Optionally, the automatic gain control system further comprises an attenuator 40 disposed between the output of the first stage automatic gain module 10 and the input of the second stage automatic gain module 20 to enhance the stability of the circuit.
Optionally, the automatic gain control system further comprises a pre-amplification module 50 and a filter 60.
And the preamplification module 50 is used for amplifying the input signal and outputting the amplified signal to the filter.
And the filter 60 is configured to filter an interference signal in the amplified input signal, and output the interference signal to the first-stage automatic gain module.
Optionally, the automatic gain control system further comprises a demodulation module 70 for demodulating and outputting the signal output by the logarithmic amplifier 30.
Fig. 4 is a schematic structural diagram of a logarithmic amplifier provided by an embodiment of the present disclosure, and as shown in fig. 4, the logarithmic amplifier module 30 includes a first preamplifier 311, a second preamplifier 312, a third preamplifier 313, a first cascaded logarithmic amplifier 321, a second cascaded logarithmic amplifier 322, a third cascaded logarithmic amplifier 323, and a parallel summing unit 33.
The input ends of the first preamplifier 311, the second preamplifier 312 and the third preamplifier 313 are all connected with the output end of the two-stage automatic gain module 20, the output end of the first preamplifier 311 is connected with the output end of the first cascaded logarithmic amplifier 321, the output end of the second preamplifier 312 is connected with the output end of the second cascaded logarithmic amplifier 322, and the output end of the third preamplifier 313 is connected with the output end of the third cascaded logarithmic amplifier 323.
The output ends of the first cascaded logarithmic amplifier 321, the second cascaded logarithmic amplifier 322 and the third cascaded logarithmic amplifier 323 are all connected with the parallel summing unit 33, and the parallel summing unit 33 is used for summing and outputting the outputs of the first cascaded logarithmic amplifier 321, the second cascaded logarithmic amplifier 322 and the third cascaded logarithmic amplifier 323.
Fig. 5 is a circuit diagram of a parallel summing circuit of a logarithmic amplifier module according to an embodiment of the present disclosure, and as shown in fig. 5, three input signals are summed and output after passing through the circuit of the logarithmic amplifier module 30 shown in fig. 5. For a signal with a rapidly changing input signal, a multistage logarithmic amplifier cascade technique is generally adopted in order to realize a large dynamic range of a logarithmic amplifier. Each logarithmic amplifier is a limiting amplification unit, which is used to process one section of the logarithmic amplifier, and the output of the logarithmic amplifier unit is summed to obtain a large dynamic range of the synthesis.
The logarithmic amplifier module 30 adopts a three-channel monolithic series cascaded logarithmic amplifier parallel summation mode. The input signal is firstly amplified by a three-channel preamplifier, the amplified signals are respectively sent to a series cascade pair amplifier for amplitude limiting amplification, the outputs of the amplitude limiters are summed, and the summation result is the output logarithm value of the single-chip series cascade logarithmic amplifier. Then the output logarithm value of the cascade logarithmic amplifier is summed in parallel by the parallel summation circuit of the large dynamic range logarithmic amplifier, and an output signal which is approximately logarithmic to the input is obtained at the parallel summation output end of the circuit as long as the gain of each preamplifier in the circuit is properly selected. The output signal is the logarithmic value of the input signal of the logarithmic amplifier with the expanded dynamic range, so that the input dynamic range capacity of the circuit is greatly improved, and the dynamic range of the three-channel parallel summation structure is greatly expanded by 2.5 times compared with that of a single-chip cascade logarithmic amplifier.
Alternatively, the amplification factors of the first preamplifier 311, the second preamplifier 312 and the third preamplifier 313 are a-2、A0And A5. Where a denotes the gain of each preamplifier, the gain of each preamplifier being the same.
Alternatively, the first cascaded logarithmic amplifier 321 is formed by cascading two limiting amplifiers in series, and the second cascaded logarithmic amplifier 322 and the third cascaded logarithmic amplifier 323 are formed by cascading five limiting amplifiers in series. When the logarithmic amplifiers are arranged as series cascade logarithmic amplifiers, the number of stages is not too large, and the bandwidth and the circuit stability are affected by too much stages, so that the first cascade logarithmic amplifier 321 is formed by adopting two limiting amplifiers in series cascade, and the second cascade logarithmic amplifier 322 and the third cascade logarithmic amplifier 323 are formed by connecting five limiting amplifiers in series cascade, on one hand, the dynamic range of the logarithmic amplifier module can be expanded, and on the other hand, the bandwidth and the circuit stability can be ensured.
Fig. 6 is a flowchart of a method of an automatic gain control method according to an embodiment of the present disclosure, and as shown in fig. 6, an automatic gain control circuit according to the embodiment is used, the automatic gain control method includes:
In the present embodiment, the input signal is obtained by using a directional coupling method. A directional coupler is a device with a resistance of 50 omega and its structure determines that the RF signal flows from the input to the output with minimal insertion loss and only a small part of the signal is tapped off the main line.
Illustratively, step 601 may include:
A) determining coupler metrics including coupling coefficient C (dB), characteristic impedance Z of each port0(omega), center frequency fcSubstrate parameter (. epsilon.)r，h)。
B) Computing odd and even mode impedances Z0eAnd Z0o。
C) Calculating Z by software according to the substrate parameters0e、Z0oCoupled with the line width and spacing (W, S) and the length P of a quarter wavelength.
D) And finally, carrying out simulation analysis and fine adjustment.
Further, before performing step 601, the automatic gain control method may further include:
the amplitude value of the input signal is detected by a peak detector.
In this embodiment, the peak detector performs detection on the sampled small rf signal and outputs a voltage or current proportional to the power of the sampled signal.
The signal is input into the cascaded amplifying units, and because the gain of each amplifying unit is in direct current coupling, the signal is amplified step by step when passing through the amplifying units. A detector with square law effect is arranged at each gain output end to shape the signal, and a compensation feedback circuit is arranged to compensate the signal. The output signal is made very accurate by a series of measures. Therefore, the input signal voltage is converted into a differential current signal which changes along with the amplitude of the input signal after being amplified, and the average value of the differential current signal is different along with the difference of the level of the input radio frequency. The current waveform is shaped and filtered, and then converted into voltage for output.
Further, the method may further include:
and amplifying and filtering the input signal.
The low-pass filter is used for filtering noise and interference in the output signal of the detector. The filter must filter out the modulated signal leaving only a signal level representative of the strength of the intermediate frequency carrier to control the gain. The filter bandwidth is narrow (time constant is large) and the lowest modulated signal frequency should be excluded.
In this embodiment, it is assumed that the gain of the input signal is-80 dBm to 0dBm, the start-control point of the first-stage automatic gain module 10 is-8 dB, and the dynamic range is 20 dB. After an input signal passes through the first-stage automatic gain module 10, a first signal with the same gain control range as that of the second-stage automatic gain module 20 is obtained, and the gain of the first signal is-68 dBm to-8 dBm; attenuation is 3 dB: -71 to-11 dBm.
In this embodiment, the start-control point of the second-stage automatic gain module 20 is-19 dB, and the dynamic range is 20 dB. The first signal passes through the second-stage automatic gain module 20 to obtain a second signal with the same gain control range as that of the logarithmic amplifier 30, and the gain of the second signal is-59 dBm to-19 dBm.
And step 604, outputting the second signal to a logarithmic amplifier module for three-stage amplification or reduction to obtain an expected output signal.
In this embodiment, the start-up point of the logarithmic amplifier module 30 is-38 dBm, and the dynamic range is 40 dB. The second signal passes through the logarithmic amplifier module 30 to obtain the desired signal, which has a gain of-38 dBm.
For a signal with a rapidly changing input signal, in order to realize a large dynamic range of the logarithmic amplifier, a multi-stage logarithmic amplifier unit cascade technology is generally adopted. Each stage of logarithmic amplifier unit is a limiting amplifier unit, which is used to process one section of the logarithmic amplifier unit, and the output of the logarithmic amplifier unit is summed to obtain the synthesized large dynamic range.
By arranging the automatic gain control system, when an input signal is received, the input signal can be amplified or reduced in two stages through the first-stage automatic gain module and the second-stage automatic gain module, and finally amplified or reduced in three stages through the logarithmic amplifier module. The logarithmic amplifier module is formed by connecting three series-connection logarithmic amplifiers in parallel, the logarithmic function is realized by the way of parallel summation of the three series-connection logarithmic amplifiers, and the input dynamic range of the logarithmic amplifier module far exceeds that of a single chip series-connection logarithmic amplifier, so that the input dynamic range of the automatic gain control circuit can be greatly improved, the dynamic range of input signals can be large, the output basically keeps constant, and the harmonic distortion is small. Meanwhile, the automatic gain adjustment time of the logarithmic amplifier module is faster and can reach a millisecond pole, so that the automatic gain adjustment time can be shortened.
The above description is intended to be exemplary only and not to limit the present disclosure, and any modification, equivalent replacement, or improvement made without departing from the spirit and scope of the present disclosure is to be considered as the same as the present disclosure.
Claims (10)
1. An automatic gain control circuit is characterized by comprising a first-stage automatic gain module (10), a second-stage automatic gain module (20) and a logarithmic amplifier module (30), wherein the logarithmic amplifier module (30) is formed by connecting three cascaded logarithmic amplifiers in parallel;
the primary automatic gain module (11) is configured to amplify or reduce an input signal to obtain a first signal having the same gain control range as that of the secondary automatic gain module (20), and output the first signal to the secondary automatic gain module (20);
the two-stage automatic gain module (20) is used for amplifying or reducing the first signal to obtain a second signal with the same gain control range as that of the logarithmic amplifier (30), and outputting the second signal to the logarithmic amplifier (30);
the logarithmic amplifier module (30) is used for amplifying or reducing the second signal to obtain a desired output signal and outputting the desired output signal.
2. The automatic gain control circuit according to claim 1, wherein the logarithmic amplifier module (30) comprises a first preamplifier (311), a second preamplifier (312), a third preamplifier (313), a first cascaded logarithmic amplifier (321), a second cascaded logarithmic amplifier (322), a third cascaded logarithmic amplifier (323), and a parallel summing unit (33);
the input ends of the first preamplifier (311), the second preamplifier (312) and the third preamplifier (313) are all connected with the output end of the two-stage automatic gain module (20), the output end of the first preamplifier (311) is connected with the output end of the first cascade logarithmic amplifier (321), the output end of the second preamplifier (312) is connected with the output end of the second cascade logarithmic amplifier (322), and the output end of the third preamplifier (313) is connected with the output end of the third cascade logarithmic amplifier (323);
the output ends of the first cascaded logarithmic amplifier (321), the second cascaded logarithmic amplifier (322) and the third cascaded logarithmic amplifier (323) are all connected with the parallel summing unit (33), and the parallel summing unit (33) is used for summing and outputting the outputs of the first cascaded logarithmic amplifier (321), the second cascaded logarithmic amplifier (322) and the third cascaded logarithmic amplifier (323).
3. The automatic gain control circuit according to claim 2, wherein the first cascaded logarithmic amplifier (321) is formed by cascading two limiting amplifiers in series, and the second cascaded logarithmic amplifier (322) and the third cascaded logarithmic amplifier (323) are formed by cascading five limiting amplifiers in series.
4. The automatic gain control circuit according to claim 1, wherein the first-stage automatic gain module (10) comprises a first detector (11), a first electrically-tuned attenuator (12), and a first amplifier (13);
the first detector (11) is used for detecting the input signal, comparing the voltage of the input signal with a reference voltage stored in the first detector (11) to obtain a first control signal, and sending the first control signal to the first electrically-controlled attenuator (12);
the first electrically-adjusted attenuator (12) is used for controlling the magnification or reduction factor of the first amplifier (13) according to the received first control signal;
the first amplifier (13) is used for amplifying or reducing the input signal to obtain the first signal.
5. The automatic gain control circuit according to claim 4, wherein the control voltage of the first electrically adjustable attenuator (12) is-3-0V.
6. The automatic gain control circuit according to claim 1, wherein the secondary automatic gain module (20) comprises a second electrically-tuned attenuator (21), a second amplifier (22) and a second detector (23);
the second detector (21) is configured to detect the first signal, compare the voltage of the first signal with a reference voltage stored in the second detector (21), obtain a second control signal, and send the second control signal to the second electrically-controlled attenuator (22);
the second electrically-adjusted attenuator (22) is used for controlling the magnification or reduction times of the second amplifier (23) according to the received second control signal;
the second amplifier (23) is used for amplifying or reducing the first signal to obtain the second signal.
7. The automatic gain control circuit according to any one of claims 1 to 6, wherein the automatic gain control system further comprises an attenuator (40) disposed between an output of the primary automatic gain module (10) and an input of the secondary automatic gain module (20).
8. The automatic gain control circuit according to any one of claims 1 to 6, wherein the automatic gain control system further comprises a pre-amplification module (50) and a filter (60);
the pre-amplification module (50) is used for amplifying the input signal and outputting the amplified input signal to the filter;
and the filter (60) is used for filtering the interference signals in the amplified input signals and outputting the interference signals to the first-stage automatic gain module.
9. The automatic gain control circuit according to any one of claims 1 to 6, wherein the automatic gain control system further comprises a demodulation module (70) for demodulating and outputting the signal output by the logarithmic amplifier (30).
10. An automatic gain control method using the automatic gain control circuit according to any one of claims 1 to 9, wherein the automatic gain control method comprises:
acquiring the input signal;
outputting the input signal to the first-stage automatic gain module for first-stage amplification or reduction to obtain a first signal;
outputting the first signal to the secondary automatic gain module for secondary amplification or reduction to obtain a second signal;
and outputting the second signal to the logarithmic amplifier module for three-stage amplification or reduction to obtain an expected output signal.
Priority Applications (1)
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Cited By (2)
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| CN111901726A (en) * | 2020-07-29 | 2020-11-06 | 广州市迪士普音响科技有限公司 | Automatic silent sound preamplifier system and control method thereof |
| CN112838874A (en) * | 2021-01-04 | 2021-05-25 | 北京全路通信信号研究设计院集团有限公司 | AGC control method and system based on directional coupler |
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