CN111049487B - Automatic gain control circuit and control method - Google Patents
Automatic gain control circuit and control method Download PDFInfo
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- CN111049487B CN111049487B CN201911293451.8A CN201911293451A CN111049487B CN 111049487 B CN111049487 B CN 111049487B CN 201911293451 A CN201911293451 A CN 201911293451A CN 111049487 B CN111049487 B CN 111049487B
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- 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 primary automatic gain module, a secondary automatic gain module and a logarithmic amplifier module, wherein the logarithmic amplifier module is formed by connecting three serially cascaded 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 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 with the same gain control range as the logarithmic amplifier, and outputting the second signal to the logarithmic amplifier; 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 dynamic range of the input 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 machine communication system, an automatic gain control circuit is often arranged in a receiver, and when an input signal is 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. In this way, 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 machine communication system, a feedforward type automatic gain control circuit is generally adopted. When the feedforward automatic gain control circuit processes signals, the input signals are usually split into two paths, one path is sent to the variable gain amplifier for amplifying, the other path is sent to the peak detector and the signal power estimator, the peak detector detects the signals, the signal power estimator estimates the power of the input signals 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.
Because the distance between the aircraft and the ship can be changed continuously in the existing ship-to-ship communication process, the power of the input signal can be changed continuously. Therefore, the signal power estimator of the feedforward type automatic gain control circuit makes multiple estimates of the signal power in a short time after receiving the input signal. In the process of warship communication, the peak-to-average ratio of the input signal is generally higher, the dynamic range of the signal is larger, and the error between the signal power estimation in a short time and the average power of the actual signal is necessarily larger. The problem of large harmonic distortion and small linear dynamic range exists in the case of realizing the rapid and stable convergence of the variable gain amplifier under the condition of inaccurate power estimation.
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 dynamic range of the input of the automatic gain control circuit, and shorten the adjustment time of the automatic gain. The technical scheme is as follows:
in a first aspect, an automatic gain control circuit is provided, where the automatic gain control circuit includes a first-stage automatic gain module, a second-stage automatic gain module, and a logarithmic amplifier module, where the logarithmic amplifier module is formed by connecting three serially cascaded 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 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 with the same gain control range as the logarithmic amplifier, and outputting the second signal to the logarithmic amplifier;
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.
Optionally, the logarithmic amplifier module includes 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 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 cascade connection of two limiting amplifiers in series, and the second cascaded logarithmic amplifier and the third cascaded logarithmic amplifier are formed by cascade connection of five limiting amplifiers in series.
Optionally, the first-stage automatic gain module comprises a first detector, a first electrically tunable 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-tunable attenuator;
the first electrically-controlled attenuator is used for controlling the amplification or reduction multiple of the first amplifier according to the received first control signal;
the first amplifier is configured to amplify or reduce the input signal to obtain the first signal.
Optionally, the control voltage of the first electrically-controlled attenuator is-3-0V.
Optionally, the second automatic gain module includes a second electrically tunable attenuator, a second amplifier, and a second detector;
the second detector is configured to detect the first signal, compare the voltage of the first signal with a reference voltage stored in the second detector, obtain a second control signal, and send the second control signal to the second electrically tunable attenuator;
the second electrically-controlled attenuator is used for controlling the amplification or reduction multiple of the second amplifier according to the received second control signal;
and 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-amplifying module is used for amplifying the input signal and outputting the amplified signal to the filter;
the filter is used for filtering interference signals in the amplified input signals and outputting the interference signals to the primary automatic gain module.
Optionally, the automatic gain control system further comprises 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 employing the automatic gain control circuit as described in the first aspect, the automatic gain control method comprising:
acquiring the input signal;
outputting the input signal to the primary automatic gain module for primary amplification or reduction to obtain a first signal;
outputting the first signal to the second automatic gain module for second-stage 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 a desired output signal.
The technical scheme provided by the embodiment of the disclosure has the beneficial effects that:
by setting 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 serially connected logarithmic amplifiers in parallel, the logarithmic function is realized by the mode of summing the three serially connected logarithmic amplifiers in parallel, and the input dynamic range of the logarithmic amplifier module is far more than that of a single-chip serially connected logarithmic amplifier, so that the input dynamic range of an automatic gain control circuit can be greatly improved, the dynamic range of an input signal can be greatly increased, the output is basically kept constant, and the harmonic distortion is small. Meanwhile, the automatic gain adjustment time of the logarithmic amplifier module is faster, and can reach millisecond level, so that the automatic gain adjustment time can be shortened.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and other drawings may be obtained according to these drawings without inventive effort for a person of ordinary skill in the art.
Fig. 1 is a schematic 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 an embodiment of the present disclosure;
FIG. 3 is a control circuit diagram of a primary automatic gain module and a secondary automatic gain module provided by an embodiment of the present disclosure;
FIG. 4 is a schematic diagram of a logarithmic amplifier provided by an embodiment of the disclosure;
FIG. 5 is a parallel summing circuit diagram of a logarithmic amplifier module provided by an embodiment of the disclosure;
fig. 6 is a method flowchart of an automatic gain control method according to an embodiment of the present disclosure.
Detailed Description
For the purposes of clarity, technical solutions and advantages of the present disclosure, the following further details the embodiments of the present disclosure with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of an automatic gain control circuit according to an embodiment of the present disclosure, and as shown in fig. 1, the automatic gain control circuit includes a primary automatic gain module 10, a secondary automatic gain module 20, and a logarithmic amplifier module 30. The logarithmic amplifier module 30 is formed by connecting three serially cascaded logarithmic amplifiers in parallel.
The first automatic gain module 10 is configured to amplify or reduce an input signal to obtain a first signal with the same gain control range as the second automatic gain module 20, and output the first signal to the second 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 the logarithmic amplifier 30, and output the second signal to the logarithmic amplifier 30.
The logarithmic amplifier module 30 is configured to amplify or reduce the second signal to obtain a desired output signal and output the desired output signal.
Wherein the desired output signal is an output signal of constant amplitude.
According to the embodiment of the disclosure, by setting 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 serially connected logarithmic amplifiers in parallel, the logarithmic function is realized by the mode of summing the three serially connected logarithmic amplifiers in parallel, and the input dynamic range of the logarithmic amplifier module is far more than that of a single-chip serially connected logarithmic amplifier, so that the input dynamic range of an automatic gain control circuit can be greatly improved, the dynamic range of an input signal can be greatly increased, the output is basically kept constant, and the harmonic distortion is small. Meanwhile, the automatic gain adjustment time of the logarithmic amplifier module is faster, and can reach millisecond level, 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 starting point of the primary automatic gain module 10 is-8 dB, and the dynamic range is 20dB. The starting control point of the two-stage automatic gain module 20 is-19 dB, and the dynamic range is 20dB. The starting point of the logarithmic amplifier module 30 is-38 dBm and the dynamic range is 40dB. The input signal passes through the first-stage automatic gain module 10 to obtain a first signal with the same gain control range as the second-stage automatic gain module 20, wherein the gain of the first signal is-68 to-8 dBm; attenuation 3dB: -71 to-11 dBm. After the first signal passes through the two-stage automatic gain module 20, a second signal with the same gain control range as the logarithmic amplifier 30 is obtained, and the gain of the second signal is-59 to-19 dBm. The second signal is passed through the logarithmic amplifier module 30 to obtain the desired signal with a gain of-38 dBm.
Fig. 2 is a gain dynamic range diagram provided by an embodiment of the present disclosure, as shown in fig. 2, where the gain of the input signal is-80 dBm to 0dBm, and after the gain is passed through the automatic gain control circuit provided by the embodiment of the present disclosure, the desired signal with a gain of-38 dBm is finally obtained.
Optionally, the primary 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 level of the input signal with a reference voltage stored in the first detector 11, obtain a first control signal, and send the first control signal to the first electrically tunable attenuator 12.
A first electrically tunable attenuator 12 for controlling the amplification 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 an input signal to obtain a first signal.
In the present embodiment, the control voltage of the first electrically tunable attenuator 12 is-3 to 0V.
Because the control voltage of the first electrically-controlled attenuator is negative voltage of-3 to 0V, the high-speed operational amplifier changes the positive voltage of the detection output into the required negative voltage, and meanwhile, the amplification factor is provided with adjustable amplification factor, so that the debugging is convenient. The first electrically tunable attenuator is a positive slope controlled attenuation, i.e., the attenuation increases with the increase of the control voltage, thus, together with the fixed gain amplifier, the first electrically tunable attenuator is equivalent to a variable gain amplifier (the higher the control voltage is, the lower the gain is) which forms a negative slope, a detection circuit with positive slope response (the higher the input signal power is, the higher the detection output voltage is) is required, and a differential amplifying circuit is designed, so that the negative slope response of the detection output can be converted into the positive slope response by providing a suitable reference voltage.
The input of each stage should not exceed the compression point requirement of the active device, so as to prevent signal distortion, and preferably, a sufficient margin is left, and the input is retracted by 6-10 dB at the compression point so as to meet the index of linearity. The input signal of the amplifier cannot exceed the requirement of the compression point, the first amplifier 13 in the first-stage automatic gain module 10 is required to select a pipe with high compression point and good linearity, and the requirement can be met by setting the starting control point of the automatic gain module during debugging. The design can realize the electric tuning attenuation by selecting the electric tuning attenuator to use a field effect transistor.
Optionally, the two-stage automatic gain module 20 comprises a second electrically tunable 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 tunable attenuator 22.
A second electrically tunable attenuator 22 for controlling the amplification or reduction factor of the second amplifier 23 in response to the received second control signal.
And a second amplifier 23 for amplifying or reducing the first signal to obtain a second signal.
In the present embodiment, the control voltage of the second electrically tunable 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, as shown in fig. 3, an input signal may be output to obtain a second signal through a circuit structure 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 arranged between the output of the primary automatic gain module 10 and the input of the secondary 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.
The pre-amplification module 50 is configured to amplify the input signal and output the amplified signal to the filter.
The filter 60 is configured to filter the interference signal in the amplified input signal, and output the filtered 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 diagram of a logarithmic amplifier according to an embodiment of the 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 second 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 cascade logarithmic amplifier 321, the second cascade logarithmic amplifier 322 and the third cascade logarithmic amplifier 323 are all connected with a parallel summing unit 33, and the parallel summing unit 33 is used for summing and outputting the outputs of the first cascade logarithmic amplifier 321, the second cascade logarithmic amplifier 322 and the third cascade logarithmic amplifier 323.
Fig. 5 is a parallel summing circuit diagram of a logarithmic amplifier module according to an embodiment of the disclosure, and as shown in fig. 5, three-way input signals are summed and output after passing through the circuit of the logarithmic amplifier module 30 as shown in fig. 5. For input signals that are rapidly varying, multistage logarithmic amplifier cascading techniques are typically employed in order to achieve a large dynamic range of logarithmic amplifiers. Each logarithmic amplifier is a limiting amplifying unit, which is used to process one section of the logarithmic amplifier unit, and the outputs of the logarithmic amplifier units are summed to obtain the synthesized large dynamic range.
The logarithmic amplifier module 30 adopts a three-channel monolithic series cascade logarithmic amplifier parallel summation mode. The input signal is amplified by the three-channel pre-amplifier, the amplified signals are respectively sent to the serial cascade amplifier for limiting amplification, the output of each limiter is summed, and the summation result is the output logarithmic value of the single-chip serial cascade logarithmic amplifier. And then the output logarithmic value of the cascade logarithmic amplifier is summed in parallel through a parallel summing circuit of the logarithmic amplifier with a large dynamic range, and an output signal which is approximately logarithmic with the input is obtained at a parallel summing output end of the circuit as long as the gain of each preamplifier in the circuit is properly selected. The output signal is actually the logarithmic value of the input signal of the logarithmic amplifier with the dynamic range enlarged, thus greatly improving the capability of the input dynamic range of the circuit, and the parallel summation structure of three channels greatly enlarges the dynamic range by nearly 2.5 times compared with the monolithic cascade logarithmic amplifier.
Optionally, the first pre-amplifier 311, the second pre-amplifier 312 and the third pre-amplifier 313 have amplification factors a respectively -2 、A 0 And A 5 . Where a represents the gain of each preamplifier, the gain of each preamplifier being the same.
Optionally, the first cascaded logarithmic amplifier 321 is formed by cascade connection of two limiting amplifiers in series, and the second cascaded logarithmic amplifier 322 and the third cascaded logarithmic amplifier 323 are formed by cascade connection of five limiting amplifiers in series. When the logarithmic amplifiers are arranged into the series cascade logarithmic amplifiers, the number of stages is not excessive, and the excessive number of stages can affect the bandwidth and the circuit stability, so that the first cascade logarithmic amplifier 321 is designed to be formed by cascade connection of two limiting amplifiers in series, and the second cascade logarithmic amplifier 322 and the third cascade logarithmic amplifier 323 are formed by cascade connection of five limiting amplifiers in series, so that the dynamic range of the logarithmic amplifier module can be enlarged, and 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 above embodiment is used, where the automatic gain control method includes:
step 601, acquiring an input signal.
In this embodiment, an input signal is acquired by a directional coupling method. A directional coupler is a device with a resistance of 50Ω whose structure determines that the RF signal flows from the input to the output with minimal insertion loss and that only a small part of the signal is tapped off from the main line.
Illustratively, step 601 may include:
a) Determining coupler metrics, including coupling coefficient C (dB), characteristic impedance Z for each port 0 (Ω), center frequency f c Substrate parameter (. Epsilon.) r ，h)。
B) Calculating odd and even mode impedances Z 0e And Z 0o 。
C) Calculating Z by software according to the substrate parameters 0e 、Z 0o Microstrip coupling line width and spacing (W, S) and quarter wavelength length P.
D) And finally, performing simulation analysis and fine adjustment.
Further, before performing step 601, the automatic gain control method may further include:
the peak detector is used to detect the amplitude value of the input signal.
In this embodiment, the peak detector detects the sampled small rf signal and outputs a voltage or current proportional to the sampled signal power.
The signal is input into the cascade of amplifying units, and the signal is amplified step by step as it passes through the amplifying units, since the gain of each amplifying unit is dc coupled. A square law detector is provided at each gain output to shape the signal and a compensation feedback circuit is provided to compensate the signal. The output signal is made very accurate by a series of measures. The input signal voltage is converted into a differential current signal with the amplitude of the input signal after amplification, and the average value of the differential current signal is different according to the level of the input radio frequency. The current waveform is shaped and filtered and then converted into a voltage 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 the signal level representing 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 from the band.
Step 602, outputting the input signal to a first-stage automatic gain module for first-stage amplification or reduction, so as to obtain a first signal.
In this embodiment, the gain of the input signal is assumed to be-80 dBm-0 dBm, the starting point of the stage-one automatic gain module 10 is-8 dB, and the dynamic range is 20dB. The input signal passes through the first-stage automatic gain module 10 to obtain a first signal with the same gain control range as the second-stage automatic gain module 20, wherein the gain of the first signal is-68 to-8 dBm; attenuation 3dB: -71 to-11 dBm.
And 603, outputting the first signal to a second automatic gain module for second-stage amplification or reduction to obtain a second signal.
In this embodiment, the starting point of the two-stage automatic gain module 20 is-19 dB and the dynamic range is 20dB. After the first signal passes through the two-stage automatic gain module 20, a second signal with the same gain control range as the logarithmic amplifier 30 is obtained, and the gain of the second signal is-59 to-19 dBm.
Step 604, outputting the second signal to the logarithmic amplifier module for three-stage amplification or reduction, so as to obtain the desired output signal.
In this embodiment, the starting point of the logarithmic amplifier module 30 is-38 dBm and the dynamic range is 40dB. The second signal is passed through the logarithmic amplifier module 30 to obtain the desired signal with a gain of-38 dBm.
For input signals that are rapidly varying, multistage logarithmic amplifier cell cascading techniques are typically employed in order to achieve a large dynamic range of logarithmic amplifiers. Each logarithmic amplifier unit is a limiting amplifying unit, which is used for processing one section of the logarithmic amplifier units, and the outputs of the logarithmic amplifier units are summed to obtain the synthesized large dynamic range.
According to the embodiment of the disclosure, by setting 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 serially connected logarithmic amplifiers in parallel, the logarithmic function is realized by the mode of summing the three serially connected logarithmic amplifiers in parallel, and the input dynamic range of the logarithmic amplifier module is far more than that of a single-chip serially connected logarithmic amplifier, so that the input dynamic range of an automatic gain control circuit can be greatly improved, the dynamic range of an input signal can be greatly increased, the output is basically kept constant, and the harmonic distortion is small. Meanwhile, the automatic gain adjustment time of the logarithmic amplifier module is faster, and can reach millisecond level, so that the automatic gain adjustment time can be shortened.
The foregoing description of the preferred embodiments of the present disclosure is provided for the purpose of illustration only, and is not intended to limit the disclosure to the particular embodiments disclosed, but on the contrary, the intention is to cover all modifications, equivalents, alternatives, and alternatives falling within the spirit and principles of the disclosure.
Claims (8)
1. The automatic gain control circuit is characterized by comprising a primary automatic gain module (10), a secondary automatic gain module (20) and a logarithmic amplifier module (30), wherein the logarithmic amplifier module (30) is formed by connecting three serially cascaded logarithmic amplifiers in parallel;
the first-stage automatic gain module (11) is used for amplifying or reducing an input signal to obtain a first signal with the same gain control range as the second-stage automatic gain module (20), and outputting the first signal to the second-stage 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 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;
the gain of the input signal is-80 dBm-0 dBm; the starting control point of the primary automatic gain module is-8 dB, and the dynamic range is 20dB; the starting control point of the two-stage automatic gain module is-19 dB, and the dynamic range is 20dB; the starting control point of the logarithmic amplifier module is-38 dBm, and the dynamic range is 40dB; the gain of the first signal is-68 to-8 dBm; the gain of the second signal is-59 to-19 dBm; the gain of the desired output signal is-38 dBm;
the primary automatic gain module (10) comprises a first detector (11), a first electrically-controlled attenuator (12) and a first amplifier (13);
the first detector (11) is configured to detect the input signal, compare the voltage of the input signal with a reference voltage stored in the first detector (11), obtain a first control signal, and send the first control signal to the first electrically tunable attenuator (12);
the first electrically tunable attenuator (12) is configured to control an amplification 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;
the second-stage automatic gain module (20) comprises a second electrically-tunable 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 tunable attenuator (22);
-said second electrically tunable attenuator (22) for controlling an amplification or reduction factor of said second amplifier (23) in dependence of said received second control signal;
the second amplifier (23) is configured to amplify or reduce the first signal to obtain the second signal.
2. The automatic gain control circuit of 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 connected with the output end of the second-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 cascade logarithmic amplifier (321), the second cascade logarithmic amplifier (322) and the third cascade logarithmic amplifier (323) are connected with the parallel summing unit (33), and the parallel summing unit (33) is used for summing and outputting the outputs of the first cascade logarithmic amplifier (321), the second cascade logarithmic amplifier (322) and the third cascade logarithmic amplifier (323).
3. The automatic gain control circuit according to claim 2, wherein the first cascaded logarithmic amplifier (321) is formed by cascade-connecting two limiting amplifiers in series, and the second cascaded logarithmic amplifier (322) and the third cascaded logarithmic amplifier (323) are each formed by cascade-connecting five limiting amplifiers in series.
4. An automatic gain control circuit according to claim 1, characterized in that the control voltage of the first electrically tunable attenuator (12) is-3-0V.
5. The automatic gain control circuit of any one of claims 1 to 4, wherein the automatic gain control system further comprises an attenuator (40) disposed between the output of the primary automatic gain module (10) and the input of the secondary automatic gain module (20).
6. The automatic gain control circuit of any one of claims 1 to 4, wherein the automatic gain control system further comprises a pre-amplifier module (50) and a filter (60);
-the pre-amplification module (50) for amplifying the input signal and outputting to the filter;
the filter (60) is used for filtering interference signals in the amplified input signals and outputting the interference signals to the primary automatic gain module.
7. The automatic gain control circuit of any one of claims 1 to 4, wherein the automatic gain control system further comprises a demodulation module (70) for demodulating and outputting a signal output from the logarithmic amplifier (30).
8. An automatic gain control method employing an automatic gain control circuit according to any one of claims 1 to 7, characterized in that the automatic gain control method comprises:
acquiring the input signal;
outputting the input signal to the primary automatic gain module for primary amplification or reduction to obtain a first signal;
outputting the first signal to the second automatic gain module for second-stage 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 a desired output signal.
Priority Applications (1)
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| 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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