Gain automatic control circuit applied to radio frequency receiving front-end channel

Abstract

The invention discloses an automatic gain control circuit applied to a radio frequency receiving front-end channel, and relates to the technical field of signal transmission. An input end of a coupling circuit (1) is connected with a radio frequency signal output end, a straight-through signal output end is connected with an input end of a low-noise amplification circuit, and a radio frequency coupling signal output end is connected with an input end of a coupling circuit (2); the output end of the low-noise amplification circuit is connected with the input end of the coupling circuit (2); the output end of the coupling circuit (2) is connected with the input end of the frequency conversion and ADC digital signal processing circuit; a gain control signal output end of the frequency conversion and ADC digital signal processing circuit is connected with a control input end of the amplifier modulation circuit, and a baseband signal output end is connected with an input end of the baseband circuit; the output end of the amplifier modulation circuit is connected with the power input end of the low-noise amplification circuit. The problems that an existing radio frequency front-end gain control mode is complex, a control circuit is complex, cost is high, and system integration and function multiplexing are not facilitated are solved.

Description

Technical Field

[0001] The present invention relates to the field of signal transmission technology, and in particular to an automatic gain control circuit applied to a radio frequency receiving front-end channel. Background Art

[0002] In recent years, with the rapid development of wireless communication and radar detection technology. Rapid control of channel gain in the RF receiving channel is particularly important. The low-noise amplifier in the RF front end generally works in the linear region. When amplifying the linear modulated signal, the RF signal needs to be linearly amplified to reduce signal distortion. Especially in complex electromagnetic environments, prevent large signals from blocking the channel and try to ensure that useful signals can be transmitted without distortion. It is usually required that within a certain bandwidth, the RF front-end link cannot be oversaturated, which puts higher requirements on the gain allocation of broadband RF front-end signal links. In addition, the link loss before the first-stage low-noise amplifier of the RF receiving link is directly related to the noise coefficient of the receiving system, which in turn affects the signal-to-noise ratio of the receiver. In order to improve the dynamic range and signal-to-noise ratio of the receiving system, it is necessary to realize dynamic control of the receiving channel gain. Therefore, dynamic control of the receiving channel gain is particularly important.

[0003] The existing RF front end usually adopts the traditional AGC automatic gain control method, and the circuit complexity is relatively high. For example, the dedicated AGC chip controls the gain of the intermediate frequency amplifier module after frequency conversion, thereby adjusting the dynamic range of reception; the RF signal is sampled and processed by separately setting the ADC device and the digital signal processor DSP. In today's miniaturized and low-cost application scenarios, its circuit structure is complicated. An RF front end gain automatic control circuit that can achieve broadband, low loss, and low cost plays a very important role in improving the sensitivity and dynamic range of the RF receiving system and realizing distortion-free transmission of RF signals. Summary of the invention

[0004] The present invention aims to provide an automatic gain control circuit for a radio frequency receiving front-end channel, so as to solve the problems that the existing radio frequency front-end gain control method is complex, the control circuit is complex, the cost is high, and it is not conducive to system integration and function reuse.

[0005] To achieve the above object, the present invention adopts the following technical solution: The present specification provides a gain automatic control circuit applied to a radio frequency receiving front-end channel, comprising a coupling circuit (1), a low noise amplifier circuit, a coupling circuit (2), a frequency conversion and ADC digital signal processing circuit and an amplifier modulation circuit, wherein: The input end of the coupling circuit (1) is connected to the radio frequency signal output end, the through signal output end of the coupling circuit (1) is connected to the input end of the low noise amplifier circuit, and the radio frequency coupling signal output end of the coupling circuit (1) is connected to the input end of the coupling circuit (2); the output end of the low noise amplifier circuit is connected to the input end of the coupling circuit (2); the output end of the coupling circuit (2) is connected to the input end of the frequency conversion and ADC digital signal processing circuit; the gain control signal output end of the frequency conversion and ADC digital signal processing circuit is connected to the control input end of the amplifier modulation circuit, and the baseband signal output end of the frequency conversion and ADC digital signal processing circuit is connected to the baseband circuit input end; the output end of the amplifier modulation circuit is connected to the power input end of the low noise amplifier circuit; The radio frequency signal is divided into a direct signal and a radio frequency coupling signal by a coupling circuit (1); when the low noise amplifier circuit is in an on state, the direct signal is subjected to low noise amplification processing by the low noise amplifier circuit and then output to the coupling circuit (2); the signal output by the low noise amplifier circuit is output to the frequency conversion and ADC digital signal processing circuit by the coupling circuit (2); and when the low noise amplifier circuit is in an off state, the radio frequency coupling signal is output to the frequency conversion and ADC digital signal processing circuit by the coupling circuit (2); the signal output by the coupling circuit (2) is subjected to frequency conversion, intermediate frequency amplification, sampling and signal processing in sequence by the frequency conversion and ADC digital signal processing circuit to form a baseband signal which is output to the input end of the baseband circuit, and a gain control signal is simultaneously formed which is output to the amplifier modulation circuit; the amplifier modulation circuit switches the working state of the low noise amplifier circuit in response to the gain control signal.

[0006] Based on the above technical solution, this specification can achieve the following technical effects: The automatic gain control circuit applied to the radio frequency receiving front-end channel provided by the present invention can realize the gain conversion of the radio frequency front-end channel, and achieve low noise coefficient and high dynamic response. Specifically: First, the coupling amplifier circuit forms two channel transmission modes by cascading the amplifier and the coupler, thereby realizing the RF front-end channel gain conversion; Secondly, the multiplexed channel communication link frequency conversion and ADC digital signal processing circuit only needs to perform amplitude judgment and output gain control signal when the subsequent FPGA circuit performs signal processing. The amplifier control circuit is controlled by the gain control signal output by the FPGA, and combined with the low-noise amplifier circuit, it can realize fast switching of RF channels, thereby meeting the fast gain switching requirements of the system; Thirdly, the use of a coupler can ensure low-loss transmission of weak signals, and at the same time, the coupling end can output a certain amount of coupled microwave signals, which are transmitted to the frequency conversion and ADC digital signal processing circuits to realize signal power detection and processing, thereby generating gain control signals. Fourthly, the amplifier control circuit adopts a drain modulator, which can respond to the gain control signal, thereby quickly controlling the operation and shutdown of the low-noise amplifier circuit, thereby realizing a closed-loop control system for fast switching of the RF receiving front-end gain.

[0007] The present invention has the following characteristics: simple circuit composition, high efficiency, low cost, strong versatility, easy implementation of logic control, real-time signal acquisition and processing, low latency of state control, flexible and controllable gain, and wide application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a schematic diagram of a structure of an automatic control circuit for a radio frequency receiving front-end channel gain provided in Example 1 of this specification; Figure 2 This is a schematic diagram of the composition of a circuit structure for automatic channel gain control applied to a radio frequency receiving front end provided in Example 2 of this specification. DETAILED DESCRIPTION

[0009] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are all in very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0010] It should be noted that, in order to clearly explain the content of the present invention, the present invention specifically cites multiple embodiments to further illustrate different implementations of the present invention, wherein the multiple embodiments are enumerated rather than exhaustive. In addition, for the sake of brevity of explanation, the contents mentioned in the previous embodiments are often omitted in the subsequent embodiments. Therefore, the contents not mentioned in the subsequent embodiments can refer to the previous embodiments accordingly.

[0011] Example 1 Please refer to Figure 1 , Figure 1 The figure shows a schematic diagram of a structure of a RF receiving front-end channel gain automatic control circuit provided by this embodiment. The circuit specifically includes: a coupling circuit 1, a low-noise amplifier circuit, a coupling circuit 2, a frequency conversion and ADC digital signal processing circuit and an amplifier modulation circuit, wherein: The input end of the coupling circuit 1 is connected to the RF signal output end, the through signal output end of the coupling circuit 1 is connected to the input end of the low-noise amplifier circuit, and the RF coupling signal output end of the coupling circuit 1 is connected to the input end of the coupling circuit 2; the output end of the low-noise amplifier circuit is connected to the input end of the coupling circuit 2; the output end of the coupling circuit 2 is connected to the input end of the frequency conversion and ADC digital signal processing circuit; the gain control signal output end of the frequency conversion and ADC digital signal processing circuit is connected to the control input end of the amplifier modulation circuit, and the baseband signal output end of the frequency conversion and ADC digital signal processing circuit is connected to the baseband circuit input end; the output end of the amplifier modulation circuit is connected to the power input end of the low-noise amplifier circuit.

[0012] The working principle of this circuit is: The coupling circuit 1 divides the RF signal outputted from the rear end of the antenna into a direct signal and a RF coupling signal. The direct signal is used as the input signal of the low noise amplifier circuit, and the RF coupling signal is used as the input signal of the coupling circuit 2; When the low-noise amplifier circuit is in the on state, the low-noise amplifier circuit performs low-noise amplification processing on the direct signal and outputs it to the coupling circuit 2, thereby linearly amplifying and outputting the RF small signal without distortion. The coupling circuit 2 transmits the signal output by the low-noise amplifier circuit to the subsequent circuit; When the low noise amplifier circuit is in the off state, the coupling circuit 2 transmits the RF coupling signal output by the coupling circuit 1 to the frequency conversion and ADC digital signal processing circuit; The frequency conversion and ADC digital signal processing circuit performs frequency conversion and intermediate frequency amplification on the RF signal output by the coupling circuit 2, and outputs a digital signal after sampling by the ADC, and completes signal processing and generates a gain control signal through the FPGA; The amplifier modulation circuit controls the working state of the low noise amplifier circuit in real time in response to the gain control signal, thereby controlling the gain switching of the radio frequency front end.

[0013] In summary, the automatic gain control circuit applied to the RF receiving front-end channel provided by the present invention can realize the RF front-end channel gain conversion, and achieve low noise coefficient and high dynamic response. Specifically: First, the coupling amplifier circuit forms two channel transmission modes by cascading the amplifier and the coupler, thereby realizing the RF front-end channel gain conversion; Secondly, the multiplexed channel communication link frequency conversion and ADC digital signal processing circuit only needs to perform amplitude judgment and output gain control signal when the subsequent FPGA circuit performs signal processing. The amplifier control circuit is controlled by the gain control signal output by the FPGA, and combined with the low-noise amplifier circuit, it can realize fast switching of RF channels, thereby meeting the fast gain switching requirements of the system.

[0014] The present invention has the following characteristics: simple circuit composition, high efficiency, low cost, strong versatility, easy implementation of logic control, real-time signal acquisition and processing, low latency of state control, flexible and controllable gain, and wide application range.

[0015] Example 2 Please refer to Figure 2 , Figure 2 The figure shows a schematic diagram of a circuit structure for automatic control of channel gain of a radio frequency receiving front end provided by this embodiment. The circuit structure includes: a coupling circuit 1, a low noise amplifier circuit, a coupling circuit 2, a frequency conversion and ADC digital signal processing circuit and an amplifier modulation circuit, wherein: The input end of the coupling circuit 1 is connected to the RF signal output end, the through signal output end of the coupling circuit 1 is connected to the input end of the low-noise amplifier circuit, and the RF coupling signal output end of the coupling circuit 1 is connected to the input end of the coupling circuit 2; the output end of the low-noise amplifier circuit is connected to the input end of the coupling circuit 2; the output end of the coupling circuit 2 is connected to the input end of the frequency conversion and ADC digital signal processing circuit; the gain control signal output end of the frequency conversion and ADC digital signal processing circuit is connected to the control input end of the amplifier modulation circuit, and the baseband signal output end of the frequency conversion and ADC digital signal processing circuit is connected to the baseband circuit input end; the output end of the amplifier modulation circuit is connected to the power input end of the low-noise amplifier circuit.

[0016] The frequency conversion and ADC digital signal processing circuit includes a mixing and amplifying filter circuit, an ADC sampling circuit and an FPGA circuit. The input end of the mixing and amplifying filter circuit is connected to the output end of the second coupling circuit, the output end of the mixing and amplifying filter circuit is connected to the input end of the ADC sampling circuit, the output end of the ADC sampling circuit is connected to the input end of the FPGA circuit, and the output end of the FPGA circuit is respectively connected to the control input end of the amplifier modulation circuit and the input end of the baseband circuit. Specifically: The signal output by the coupling circuit 2 is subjected to frequency conversion and intermediate frequency amplification processing by means of a mixing and amplifying filter circuit; The ADC sampling circuit samples the frequency-converted and intermediate-frequency-amplified signal and outputs the sampled digital signal; The digital signal is processed by the digital signal processing module and the detection control module of the FPGA circuit respectively to generate a baseband signal and a gain control signal. Among them, the digital signal processing module processes the sampled digital signal, generates a baseband signal and outputs it to the input end of the baseband circuit; the detection control module also performs frequency amplitude detection on the sampled digital signal, generates a gain control signal and outputs it to the amplifier modulation circuit. The method of controlling gain conversion according to the amplitude of the sampled signal specifically includes the following steps: First, the signal high threshold S is preset in the FPGA. H , signal low threshold SL , threshold error s; Secondly, check whether the signal frequency meets the working requirements, and then further check the amplitude.

[0017] Once again, compare the detected value with the threshold value. H +s, the output shutdown control signal is given to the amplifier modulation circuit, the amplifier does not work, and the RF signal is transmitted to the subsequent mixer sampling circuit through the coupling circuit 2; when the signal amplitude is less than the low threshold S L -s, the output start control signal is given to the amplifier modulation circuit, the amplifier works to output the first RF signal to the coupling circuit 2, and then to the subsequent frequency conversion and ADC digital signal processing circuit through the coupling circuit 2; when the signal amplitude is above the high threshold S H +s and low threshold S L -s, a default control signal is output to the amplifier modulation circuit. In this embodiment, the low noise amplifier is turned off by default.

[0018] Based on this, the frequency conversion and ADC digital signal processing circuit can be multiplexed with the communication. The frequency conversion and ADC digital signal processing circuit of the multiplexed channel communication link only needs to perform amplitude judgment and output gain control signals when the subsequent FPGA circuit performs signal processing. The amplifier control circuit is controlled by the gain control signal output by the FPGA, and combined with the low-noise amplifier circuit, it can realize fast switching of RF channels, thereby meeting the fast gain switching requirements of the system.

[0019] Preferably, the coupling circuit 1 adopts a directional coupler. The output end of the directional coupler includes a through end and a coupling end, specifically: The through end is connected to the input end of the low noise amplifier circuit, outputs a through signal to the low noise amplifier circuit, and is connected to the input end of the coupling circuit 2, outputs a radio frequency coupling signal to the coupling circuit 2. Based on this, the through path loss is small, the noise coefficient of the radio frequency receiving front end is improved, the coupling degree has a large variation range, and the required coupling amount can be adapted by changing the spacing, thereby changing the dynamic range.

[0020] The coupling end is connected to the input end of the coupling circuit 2, and outputs a radio frequency coupling signal to the coupling circuit 2. When the coupling circuit 1 receives a strong signal, the low noise amplifier circuit does not work, thereby forming a coupling path with attenuation characteristics. Based on this, a microwave signal with a certain coupling amount is output through the coupling end, and the microwave signal is transmitted to the frequency conversion and ADC digital signal processing circuit to realize signal power detection processing and thus realize the generation of a gain control signal.

[0021] Preferably, the coupling circuit 2 uses a 3dB coupler. The 3dB coupler includes a first input terminal and a second input terminal, wherein: The RF coupling signal output end of the coupling circuit 1 is connected to the first input end of the 3dB coupler, and the output end of the low noise amplifier circuit is connected to the second input end of the 3dB coupler. The first input end of the 3dB coupler is isolated from the second input end of the 3dB coupler. Based on this, the isolation of the two transmission paths can be improved, and the dynamic range extension is equal to the gain difference of the two paths.

[0022] Preferably, the directional coupler can be a microstrip coupler, which has a wide working bandwidth and good flatness, and its coupling degree can be designed as required.

[0023] Preferably, the 3dB coupler can also be designed and processed in the form of a microstrip circuit according to the microwave plate material, thereby reducing the device cost.

[0024] Preferably, the amplifier modulation circuit adopts a drain modulator, which can respond to the gain control signal to achieve rapid rise and fall of the voltage output to the power supply terminal of the low-noise amplifier, thereby indirectly and rapidly controlling the operation and shutdown of the low-noise amplifier circuit, thereby realizing a closed-loop control system for rapid gain switching of the RF receiving front end. The drain modulator can be composed of a transistor and a P-MOS.

[0025] The key components used in this embodiment are shown in Table 1 below: Table 1 Device List

[0026] It should be noted that the amplifier control circuit described in the present invention realizes the control of the working state of the low-noise amplifier in the radio frequency link. As long as the circuit can control the operation and shutdown of the amplifier, it is considered to be included in the protection scope of the present invention; the coupler described in the present invention has a signal distribution function, but the amplitude of the output signal is different. All microwave signal diversion devices, such as circulators, power dividers, etc., are considered to be included in the protection scope of the present invention.

[0027] In summary, the automatic gain control circuit applied to the RF receiving front-end channel provided in this embodiment can realize fast switching of the receiving channel gain and achieve dynamic expansion greater than 30dB, which can better meet the needs of most engineering applications. Specifically: First, the coupling amplifier circuit forms two channel transmission modes by cascading the amplifier and the coupler, thereby realizing the RF front-end channel gain conversion; Secondly, the multiplexed channel communication link frequency conversion and ADC digital signal processing circuit only needs to perform amplitude judgment and output gain control signal when the subsequent FPGA circuit performs signal processing. The amplifier control circuit is controlled by the gain control signal output by the FPGA, and combined with the low-noise amplifier circuit, it can realize fast switching of RF channels, thereby meeting the fast gain switching requirements of the system; Thirdly, the use of a coupler can ensure low-loss transmission of weak signals, and at the same time, the coupling end can output a certain amount of coupled microwave signals, which are transmitted to the frequency conversion and ADC digital signal processing circuits to realize signal power detection and processing, thereby generating gain control signals. Fourthly, the amplifier control circuit adopts a drain modulator, which can respond to the gain control signal, thereby quickly controlling the operation and shutdown of the low-noise amplifier circuit, thereby realizing a closed-loop control system for fast switching of the RF receiving front-end gain.

[0028] The present invention has the following characteristics: simple circuit composition, high efficiency, low cost, strong versatility, easy implementation of logic control, real-time signal acquisition and processing, low latency of state control, flexible and controllable gain, and wide application range.

[0029] The above description is only an embodiment of the present specification and is not intended to limit the present specification. For those skilled in the art, the present specification can be modified and varied in various ways. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present specification should be included in the scope of the claims of the present specification.

Claims

1. An automatic gain control circuit for a radio frequency receiving front end channel, characterized in that: It comprises a coupling circuit (1), a low-noise amplifier circuit, a coupling circuit (2), a frequency conversion and ADC digital signal processing circuit and an amplifier modulation circuit, wherein: The input end of the coupling circuit (1) is connected to the radio frequency signal output end, the through signal output end of the coupling circuit (1) is connected to the input end of the low noise amplifier circuit, and the radio frequency coupling signal output end of the coupling circuit (1) is connected to the input end of the coupling circuit (2); the output end of the low noise amplifier circuit is connected to the input end of the coupling circuit (2); the output end of the coupling circuit (2) is connected to the input end of the frequency conversion and ADC digital signal processing circuit; the gain control signal output end of the frequency conversion and ADC digital signal processing circuit is connected to the control input end of the amplifier modulation circuit, and the baseband signal output end of the frequency conversion and ADC digital signal processing circuit is connected to the baseband circuit input end; the output end of the amplifier modulation circuit is connected to the power input end of the low noise amplifier circuit; The radio frequency signal is divided into a direct signal and a radio frequency coupling signal by a coupling circuit (1); when the low noise amplifier circuit is in an on state, the direct signal is subjected to low noise amplification processing by the low noise amplifier circuit and then output to the coupling circuit (2); the signal output by the low noise amplifier circuit is output to the frequency conversion and ADC digital signal processing circuit by the coupling circuit (2); and when the low noise amplifier circuit is in an off state, the radio frequency coupling signal is output to the frequency conversion and ADC digital signal processing circuit by the coupling circuit (2); the signal output by the coupling circuit (2) is subjected to frequency conversion, intermediate frequency amplification, sampling and signal processing in sequence by the frequency conversion and ADC digital signal processing circuit to form a baseband signal which is output to the input end of the baseband circuit, and a gain control signal is simultaneously formed which is output to the amplifier modulation circuit; the amplifier modulation circuit switches the working state of the low noise amplifier circuit in response to the gain control signal.

2. The circuit according to claim 1, characterized in that The frequency conversion and ADC digital signal processing circuit includes a mixing and amplification filtering circuit, an ADC sampling circuit and an FPGA circuit, wherein: The input end of the mixing and amplifying filtering circuit is connected to the output end of the coupling circuit (2), the output end of the mixing and amplifying filtering circuit is connected to the input end of the ADC sampling circuit, the output end of the ADC sampling circuit is connected to the input end of the FPGA circuit, and the output end of the FPGA circuit is respectively connected to the control input end of the amplifier modulation circuit and the input end of the baseband circuit; The signal output by the coupling circuit (2) is subjected to frequency conversion and intermediate frequency amplification processing by a mixing and amplifying filtering circuit, the signal after frequency conversion and intermediate frequency amplification is sampled by an ADC sampling circuit, and a sampled digital signal is output, and the digital signal is processed by an FPGA circuit to generate a baseband signal and a gain control signal.

3. The circuit according to claim 2, characterized in that The FPGA circuit includes a digital signal processing module and a detection control module, wherein: The digital signal processing module is used to process the sampled digital signal, generate a baseband signal and output it to the baseband circuit input terminal; The detection control module is used to perform frequency and amplitude detection on the sampled digital signal, generate a gain control signal and output it to the amplifier modulation circuit.

4. The circuit according to claim 3, characterized in that The detection control module includes a frequency detection submodule and an amplitude detection submodule, wherein: The frequency detection submodule is used to detect whether the signal frequency meets the frequency required for work; The amplitude detection submodule is used to perform signal amplitude detection when the frequency detection meets the working requirements, and compare the amplitude detection value with the preset high threshold and the preset low threshold; when the amplitude detection value is greater than the preset high threshold, output a shutdown control signal to the amplifier modulation circuit; when the amplitude detection value is less than the preset low threshold, output an on control signal to the amplifier modulation circuit; when the amplitude detection value is between the preset high threshold and the preset low threshold, output a default control signal to the amplifier modulation circuit.

5. The circuit according to claim 1, characterized in that The coupling circuit (1) adopts a directional coupler, and the coupling circuit (2) adopts a 3dB coupler.

6. The circuit according to claim 5, characterized in that The output end of the directional coupler includes a through end and a coupling end, wherein: The through end is connected to the input end of the low-noise amplifier circuit and the input end of the coupling circuit (2), and the coupling end is connected to the input end of the coupling circuit (2); The through-port outputs a through-signal to the low-noise amplifier circuit and outputs a radio frequency coupling signal to the coupling circuit (2); The coupling end outputs a radio frequency coupling signal to the coupling circuit (2); when the coupling circuit (1) receives a strong signal, the low noise amplifier circuit does not work, thereby forming a coupling path with attenuation characteristics.

7. The circuit according to claim 5, characterized in that The 3dB coupler comprises a first input terminal and a second input terminal, wherein: The radio frequency coupling signal output end of the coupling circuit (1) is connected to the first input end of the 3dB coupler, and the output end of the low noise amplifier circuit is connected to the second input end of the 3dB coupler; The first input end of the 3dB coupler is isolated from the second input end of the 3dB coupler.

8. The circuit according to claim 5, characterized in that The directional coupler and the 3dB coupler are designed in the form of microstrip circuits.

9. The circuit according to claim 1, characterized in that The amplifier modulation circuit adopts a drain modulator, and the drain modulator is used to control the rapid rise and fall of the voltage output to the power supply terminal of the low-noise amplifier circuit in response to a gain control signal.

10. The circuit according to claim 1, characterized in that The low noise amplifier circuit adopts a low noise amplifier.

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