Analog adaptive filter circuit

Abstract

The invention provides an analog adaptive filter circuit, and relates to the technical field of microwave radio frequency solid-state circuits. The analog adaptive filter circuit comprises an electrically tunable filter, a coupling detection circuit and a voltage control circuit, the electrically tunable filter is used for filtering an input signal based on the working passband to obtain a filtered signal and outputting the filtered signal; the coupling detection circuit is used for extracting the voltage amplitude of the filtering signal and inputting the voltage amplitude and a preset threshold voltage into the voltage control circuit; and the voltage control circuit is used for generating a control signal of the electrically tunable filter based on the difference between the voltage amplitude and the preset threshold voltage, so that the working passband of the electrically tunable filter is matched with the frequency of the input signal. According to the invention, the working passband of the electrically tunable filter can be automatically adjusted to be near the frequency range of the main signal, the self-adaptive reconfiguration of the filter is realized, and the electrically tunable filter has the characteristic of continuous adjustability and has the advantages of simplicity, practicability, high reliability and low cost.

Description

Technical Field

[0001] This invention relates to the field of microwave radio frequency solid-state circuit technology, and in particular to an analog adaptive filter circuit. Background Technology

[0002] As a key component in the radio frequency (RF) link, filters play a crucial role in suppressing clutter signals and enhancing the suppression of useful signals and other signals. Filters are generally located in the local oscillator link, transmit link, and receive link. However, different link locations require filters with different operating frequencies or number of channels, necessitating the development of filters for different frequency bands or switching filter banks.

[0003] In traditional RF links, filtering is achieved by replacing different hardware or using externally controlled switching filter banks. However, in practical engineering applications, the hardware has poor reconfigurability, often requiring extensive redevelopment for different application scenarios. Summary of the Invention

[0004] This invention provides an analog adaptive filtering circuit to solve the problem of poor reconfigurability of filters in radio frequency links.

[0005] In a first aspect, embodiments of the present invention provide an analog adaptive filtering circuit, including an electrically tunable filter, a coupling detector circuit, and a voltage control circuit;

[0006] The input terminal of the electrically tunable filter forms the input terminal of the analog adaptive filter circuit, and the output terminal is connected to the input terminal of the coupling detector circuit. The first output terminal of the coupling detector circuit forms the input terminal of the analog adaptive filter circuit, and the second output terminal is connected to the control terminal of the electrically tunable filter through the voltage control circuit.

[0007] Electrically tunable filters are used to filter input signals based on the operating passband, obtain filtered signals, and output them.

[0008] The coupling detection circuit is used to extract the voltage amplitude of the filtered signal and input the voltage amplitude and the preset threshold voltage to the voltage control circuit.

[0009] The voltage control circuit is used to generate a control signal for the electrically tunable filter based on the difference between the voltage amplitude and a preset threshold voltage, so that the operating passband of the electrically tunable filter matches the frequency of the input signal.

[0010] In one possible implementation, the coupled detection circuit includes a coupler, a detection circuit, and a threshold setting circuit;

[0011] The input terminal of the coupler is connected to the output terminal of the electrically tunable filter, and the output terminal forms the output terminal of the analog adaptive filter circuit. The coupling terminal is connected to the input terminal of the detector circuit, the output terminal of the detector circuit is connected to the first input terminal of the voltage control circuit, and the output terminal of the threshold setting circuit is connected to the second input terminal of the voltage control circuit.

[0012] Couplers are used to transmit filtered signals to detection circuits and threshold setting circuits;

[0013] The detection circuit is used to extract the voltage amplitude of the filtered signal and input the voltage amplitude to the voltage control circuit;

[0014] The threshold setting circuit is used to input a preset threshold voltage to the voltage control circuit.

[0015] In one possible implementation, the detection circuit includes a first diode, a first resistor, a second resistor, and a first capacitor;

[0016] The positive terminal of the first diode is connected to the output terminal of the coupler and to the DC power supply through the first resistor. The negative terminal is connected to the first input terminal of the voltage control circuit. The first terminal of the second resistor and the first capacitor connected in parallel is connected to the negative terminal of the first diode, and the second terminal is grounded.

[0017] In one possible implementation, the threshold setting circuit includes a second diode, a third resistor, a fourth resistor, and a fifth resistor;

[0018] The positive terminal of the second diode is connected to the DC power supply through the third resistor and to the resistor setting terminal through the fourth resistor. The negative terminal is connected to the second input terminal of the voltage control circuit and to the ground through the fifth resistor.

[0019] In one possible implementation, the voltage control circuit includes an integrating operational amplifier;

[0020] The inverting input of the integrating operational amplifier is connected to the output of the detector circuit, the non-inverting input is connected to the output of the threshold setting circuit, and the output is connected to the control terminal of the electrically tunable filter.

[0021] In one possible implementation, the voltage control circuit also includes a seventh resistor, an eighth resistor, a ninth resistor, and a second capacitor;

[0022] The seventh resistor is connected between the non-inverting input of the integrating operational amplifier and the output of the threshold setting circuit; the eighth resistor is connected between the inverting input of the integrating operational amplifier and the output of the detector circuit; the ninth resistor is connected between the output of the integrating operational amplifier and the control terminal of the electrically tunable filter; and the second capacitor is connected between the inverting input and the output of the integrating operational amplifier.

[0023] In one possible implementation, a passband telemetry indication circuit is also included;

[0024] The input terminal of the passband telemetry indicator circuit is connected to the output terminal of the voltage control circuit, and the output terminal is used to connect to an external oscilloscope device.

[0025] The passband telemetry indicator circuit is used to input control signals to an external oscilloscope device and to isolate the voltage control circuit from the external oscilloscope device.

[0026] In one possible implementation, the passband telemetry indication circuit includes a proportional operational amplifier, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, and a third capacitor;

[0027] The inverting input of the proportional operational amplifier is connected to the output of the voltage control circuit through the tenth resistor. The non-inverting input is connected to the first ends of the eleventh and twelfth resistors. The second end of the eleventh resistor is connected to the DC power supply and grounded through the third capacitor. The second end of the twelfth resistor is grounded. The output of the proportional operational amplifier is connected to an external oscilloscope through the thirteenth resistor and to the inverting input through the fourteenth resistor.

[0028] In one possible implementation, the coupling detector circuit also includes a third diode, a fourth diode, and a fourth capacitor;

[0029] The positive terminal of the third diode is grounded, and the negative terminal is connected to the positive terminal of the second diode;

[0030] The positive terminal of the fourth diode is grounded, and the negative terminal is connected to the coupling terminal of the coupler. The fourth capacitor is connected between the coupling terminal of the coupler and the input terminal of the detector circuit.

[0031] In one possible implementation, a fifteenth resistor is also included; the first end of the fifteenth resistor is connected to the output of the voltage control circuit, and the second end is grounded.

[0032] This invention provides an analog adaptive filter circuit. By coupling a detector circuit and a voltage control circuit, the difference between the filtered signal obtained from the electrically tunable filter and a preset threshold voltage is identified. This difference is used to generate a control signal for closed-loop control of the electrically tunable filter. By reasonably setting the threshold voltage, the operating passband of the electrically tunable filter can be automatically adjusted to near the frequency range of the main signal, realizing the adaptive reconfigurability of the filter. It has continuously adjustable characteristics and does not require additional external control. The filter module product designed based on this filter circuit can be integrated into a small size based on chip and hybrid integration, and has the advantages of simplicity, practicality, high reliability and low cost. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the analog adaptive filter circuit provided in the embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the structure of the analog adaptive filter circuit provided in the embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram illustrating the working principle of the analog adaptive filter circuit provided in this embodiment of the invention. Detailed Implementation

[0036] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.

[0037] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.

[0038] The location of filters in the RF channel can be roughly divided into the following categories.

[0039] 1) Local Oscillator Link: Nonlinear devices with amplification characteristics, such as frequency sources or local oscillator frequency multipliers, often generate multiple signals, including fundamental and harmonic signals. To ensure that the main channel after mixing meets the noise suppression requirements, filters or switching filter banks are often placed to filter the main signal. However, for a wide local oscillator frequency band, the number of channels required for the switching filter bank is large, and the filter size will be very large. In engineering applications, it is necessary to develop switching filter banks with multiple channels for multiple frequency bands, which is not conducive to product reuse.

[0040] 2) Transmit Link: After the intermediate frequency (IF) signal is up-converted to radio frequency (RF) by the mixer, filters are needed to remove noise signals such as the local oscillator and image frequencies. If the suppression level is not high enough, such noise will cause power reduction of the useful signal and electromagnetic compatibility (EMC) problems in the transmit link. However, because the RF frequencies vary greatly in different application scenarios in RF systems, it is necessary to develop filters or switching filter banks for different frequency bands.

[0041] 3) Receiving Link: In the RF link, both spatial electromagnetic signals and interference signals enter the receiving system simultaneously. Filters are needed to suppress spatial electromagnetic signals and noise power at the image frequency. In the IF link, filters suppress IF harmonics and other clutter to ensure that the useful signal entering the AD converter achieves a certain degree of suppression compared to other signals, thereby improving receiver sensitivity and avoiding misinterpretations. However, since the IF frequencies differ across systems (e.g., 30MHz, 70MHz, 120MHz, 300MHz, and 1800MHz), filters of different frequencies need to be developed to meet system requirements.

[0042] To overcome the problem that filters require extensive new research and development and lack adaptive reconfigurability in different products or broadband circuits, this invention proposes a simple and applicable filter circuit capable of adaptive reconfigurability based on the input signal frequency. Employing an analog adaptive filter circuit, it achieves automatic passband adjustment based on the input signal frequency. This circuit features continuous adaptive adjustment of the filter band, superior reconfigurability, significantly reduces filter development work, expands the filter's applicability, achieves better filtering performance, improves the reusability of single filter circuits, and reduces the complexity of using reconfigurable filters.

[0043] The implementation of the present invention will be described in detail below with reference to the accompanying drawings:

[0044] Figure 1 This is a schematic diagram of an analog adaptive filter circuit provided in an embodiment of the present invention. (Refer to...) Figure 1 The analog adaptive filter circuit includes an electrically tunable filter 11, a coupling detector circuit 12, and a voltage control circuit 13.

[0045] The input terminal of the electrically tunable filter 11 forms the input terminal of the analog adaptive filter circuit, and the output terminal is connected to the input terminal of the coupling detector circuit 12. The first output terminal of the coupling detector circuit 12 forms the input terminal of the analog adaptive filter circuit, and the second output terminal is connected to the control terminal of the electrically tunable filter 11 through the voltage control circuit 13.

[0046] Electrically tunable filter 11 is used to filter the input signal based on the working passband, obtain the filtered signal and output it;

[0047] The coupling detection circuit 12 is used to extract the voltage amplitude of the filtered signal and input the voltage amplitude and the preset threshold voltage to the voltage control circuit 13;

[0048] The voltage control circuit 13 is used to generate a control signal for the electrically tunable filter 11 based on the difference between the voltage amplitude and the preset threshold voltage, so that the operating passband of the electrically tunable filter 11 matches the frequency of the input signal.

[0049] In this embodiment, the electrically tunable filter is a filter whose center frequency is continuously adjusted by an external voltage or current. In links where the main signal power is relatively fixed, such as the local oscillator link, the transmit link, and the receiver AGC output terminal, and where there is a certain power difference between the main signal and other harmonic and noise signals, a closed-loop control circuit is formed using the electrically tunable filter, the coupled detector circuit, and the voltage control circuit, enabling it to automatically adjust according to the input signal frequency. By setting a closed-loop lockout voltage threshold for the operational amplifier and through analog control of the electrically tunable filter and the operational amplifier, the passband of the electrically tunable filter is automatically adjusted to near the frequency range of the main signal, thereby achieving analog adaptive filtering.

[0050] The analog adaptive filter circuit provided in this embodiment of the invention identifies the difference between the filtered signal obtained by the electrically tunable filter and the preset threshold voltage through a coupled detection circuit and a voltage control circuit. It then generates a control signal to perform closed-loop control on the electrically tunable filter. By reasonably setting the threshold voltage, the operating passband of the electrically tunable filter can be automatically adjusted to near the frequency range of the main signal, realizing the adaptive reconfigurability of the filter and possessing continuous adjustable characteristics. No additional external control is required. The filter module product designed based on this filter circuit can be integrated into a small size based on chip and hybrid integration, and has the advantages of simplicity, practicality, high reliability, and low cost.

[0051] In one possible implementation, the coupled detection circuit includes a coupler, a detection circuit, and a threshold setting circuit;

[0052] The input terminal of the coupler is connected to the output terminal of the electrically tunable filter, and the output terminal forms the output terminal of the analog adaptive filter circuit. The coupling terminal is connected to the input terminal of the detector circuit, the output terminal of the detector circuit is connected to the first input terminal of the voltage control circuit, and the output terminal of the threshold setting circuit is connected to the second input terminal of the voltage control circuit.

[0053] Couplers are used to transmit filtered signals to detection circuits and threshold setting circuits;

[0054] The detection circuit is used to extract the voltage amplitude of the filtered signal and input the voltage amplitude to the voltage control circuit;

[0055] The threshold setting circuit is used to input a preset threshold voltage to the voltage control circuit.

[0056] In this embodiment, the specific structure of the analog adaptive filter circuit can be as follows: Figure 2 As shown, 1 is an electrically tunable filter; 2 is a filter passband telemetry indicator circuit; 3 is a coupling circuit; 4 is a voltage control circuit; 5 is a signal selection threshold setting circuit; 6 is a detection circuit; 7 is a signal input port; 8 is a signal output port; and 9 is the output voltage port of the filter passband telemetry indicator circuit.

[0057] The signal at input port 7 is a multi-tone signal. The amplitude of the useful signal to be retained can be roughly determined, while other harmonic and noise signals have a certain amplitude difference from the signal to be retained. After passing through port 7, the multi-tone signal enters the electrically tunable filter 1. The signal after filter 1 passes through coupler 3, and detector 6 generates a voltage of a certain amplitude. This voltage is compared with the threshold voltage set via port 5. When the detected voltage does not reach the preset threshold voltage, the output voltage of the operational amplifier will undergo integral change, meaning the control voltage of the electrically tunable filter 1 will continuously change. At this time, the power through coupler 3 increases, and the output voltage of detector 6 increases until the operating passband of the electrically tunable filter changes, adjusting the useful signal in the input multi-tone signal into the filter passband. At this point, the detected voltage of detector 6 is approximately equal to the voltage threshold set via port 5, completing the closed-loop control.

[0058] A schematic diagram illustrating the working principle of the analog adaptive filter circuit is shown below. Figure 3 In the diagram, the highest amplitude represents the useful signal that needs to be retained, while the others are harmonics and noise. Under the control of a preset threshold voltage, the operating passband of the electrically tunable filter will dynamically adjust to the frequency band where the useful signal is located, thereby filtering out harmonics and noise.

[0059] In one possible implementation, the detection circuit includes a first diode D3, a first resistor R3, a second resistor R13, and a first capacitor C2;

[0060] The positive terminal of the first diode D3 is connected to the output terminal of the coupler 3 and to the DC power supply VCC through the first resistor R3. The negative terminal is connected to the first input terminal of the voltage control circuit 4. The first terminal of the parallel connection of the second resistor R13 and the first capacitor C2 is connected to the negative terminal of the first diode D3, and the second terminal is grounded.

[0061] In this embodiment, the filtered signal is output from the coupling terminal of the coupler and reaches the first diode D3. Simultaneously, the voltage of the DC power supply VCC passes through the first resistor R3 and also reaches the first diode D3. The voltage at the positive terminal of the first diode D3 is the sum of the two voltages. After the voltage drop of the first diode D3 and the voltage divider of the second resistor R13, a voltage value related to the amplitude of the filtered signal is obtained and input to the first input terminal of the voltage control circuit.

[0062] In one possible implementation, the threshold setting circuit includes a second diode D2, a third resistor R2, a fourth resistor R8, and a fifth resistor R6.

[0063] The positive terminal of the second diode D2 is connected to the DC power supply VCC through the third resistor R2 and to the resistor setting terminal through the fourth resistor R8. The negative terminal is connected to the second input terminal of the voltage control circuit 4 and grounded through the fifth resistor R6.

[0064] In this embodiment, the structure of the threshold setting circuit is basically the same as that of the detection circuit. The voltage of the DC power supply VCC is divided by the third resistor R2 and the fourth resistor R8 to form a preset threshold voltage. The preset threshold voltage is then input to the second input terminal of the voltage control circuit after the voltage drop of the second diode D2 and the voltage division by the fifth resistor R6. Therefore, by reasonably setting the values ​​of the third resistor R2 and the fourth resistor R8, the preset threshold voltage can be adjusted.

[0065] In one possible implementation, the voltage control circuit 4 includes an integrating operational amplifier U2A;

[0066] The inverting input of the integrating operational amplifier U2A is connected to the output of the detector circuit 6, the non-inverting input is connected to the output of the threshold setting circuit 5, and the output is connected to the control terminal of the electrically tunable filter 1.

[0067] In this embodiment, the integrating operational amplifier U2A calculates the voltage difference between the detector circuit 6 and the threshold setting circuit 5, and integrates it to generate a gradually increasing control signal, thereby finely and gradually adjusting the operating passband of the electrically tunable filter. When the voltage difference between the detector circuit 6 and the threshold setting circuit 5 is sufficiently small, the control signal no longer changes, and the operating passband of the electrically tunable filter stabilizes within a certain range, ensuring that the main signal of the input signal falls within the operating passband of the electrically tunable filter, thus achieving dynamic and stable closed-loop control.

[0068] In one possible implementation, the voltage control circuit 4 also includes a seventh resistor R7, an eighth resistor R11, a ninth resistor R5, and a second capacitor C4.

[0069] The seventh resistor R7 is connected between the non-inverting input of the integrating operational amplifier U2A and the output of the threshold setting circuit 5. The eighth resistor R11 is connected between the inverting input of the integrating operational amplifier U2A and the output of the detector circuit 6. The ninth resistor R5 is connected between the output of the integrating operational amplifier U2A and the control terminal of the electrically tunable filter 1. The second capacitor C4 is connected between the inverting input and the output of the integrating operational amplifier U2A.

[0070] In this embodiment, the seventh resistor R7 and the eighth resistor R11 are used to convert the voltage input to the integrating operational amplifier U2A into an input current and to adjust the integration rate. The second capacitor C4 acts as a feedback capacitor to perform the integration operation and determines the integration gain. The ninth resistor R5 can provide impedance matching and current limiting protection for the control signal output by the integrating operational amplifier U2A.

[0071] In one possible implementation, a passband telemetry indication circuit 2 is also included;

[0072] The input terminal of the passband telemetry indicator circuit 2 is connected to the output terminal of the voltage control circuit 4, and the output terminal is used to connect to the external oscilloscope device 9;

[0073] The passband telemetry indicator circuit 2 is used to input control signals to an external oscilloscope device and to isolate the voltage control circuit 4 from the external oscilloscope device 9.

[0074] In this embodiment, the control signal output by the voltage control circuit 4 can be led to the outside of the analog adaptive filter circuit through the passband telemetry indicator circuit 2, and the external oscilloscope device is isolated from the voltage control circuit 4 to avoid the measurement and acquisition of the control signal affecting the working state of the electrically tunable filter.

[0075] By analyzing the control signals, we can better understand the operating state of the electrically tunable filter, which facilitates the optimization of the performance of the analog adaptive filter circuit.

[0076] In one possible implementation, the passband telemetry indicator circuit 2 includes a proportional operational amplifier U1A, a tenth resistor R9, an eleventh resistor R12, a twelfth resistor R14, a thirteenth resistor R10, a fourteenth resistor R4, and a third capacitor C2.

[0077] The inverting input of the proportional operational amplifier U1A is connected to the output of the voltage control circuit 4 through the tenth resistor R9. The non-inverting input is connected to the first end of the eleventh resistor R12 and the twelfth resistor R14. The second end of the eleventh resistor R12 is connected to the DC power supply VCC and grounded through the third capacitor C2. The second end of the twelfth resistor R14 is grounded. The output of the proportional operational amplifier U1A is connected to the external oscilloscope device 9 through the thirteenth resistor R10 and to the inverting input through the fourteenth resistor R4.

[0078] In this embodiment, the proportional operational amplifier U1A is the core component of the passband telemetry indicator circuit 2. The control signal output from the voltage control circuit 4 is input from the inverting input of the proportional operational amplifier U1A. The tenth resistor R9 converts it into current, which is then output after proportional calculation. The thirteenth resistor R10 provides impedance matching and current limiting protection for the output signal. The fourteenth resistor R4 is the feedback resistor. The non-inverting input of the proportional operational amplifier U1A is connected to the DC power supply VCC through the eleventh resistor R12 and grounded through the twelfth resistor R14 and the third capacitor C2. This reduces the influence of bias current and performs noise filtering, ensuring the signal quality of the control signal output to the external oscilloscope device 9.

[0079] In one possible implementation, the coupling detector circuit also includes a third diode D1, a fourth diode D4, and a fourth capacitor C1;

[0080] The positive terminal of the third diode D1 is grounded, and the negative terminal is connected to the positive terminal of the second diode D2;

[0081] The positive terminal of the fourth diode D4 is grounded, and the negative terminal is connected to the coupling terminal of coupler 3. The fourth capacitor C1 is connected between the coupling terminal of coupler 3 and the input terminal of detector circuit 6.

[0082] In this embodiment, the fourth capacitor C1 can convert the filtered signal into a voltage for detection, and the third diode D1 and the fourth diode D4 are used to protect the circuit from reverse voltage.

[0083] In one possible implementation, a fifteenth resistor R1 is also included; the first end of the fifteenth resistor R1 is connected to the output of the voltage control circuit 4, and the second end is grounded.

[0084] In this embodiment, the fifteenth resistor R1 is used to divide the control signal and adjust the amplitude of the control signal to a level suitable for the electrically tunable filter.

[0085] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An analog adaptive filter circuit, characterized in that, Includes electrically tunable filters, coupling detector circuits, and voltage control circuits; The input terminal of the electrically tunable filter constitutes the input terminal of the analog adaptive filter circuit, and the output terminal is connected to the input terminal of the coupling detector circuit. The first output terminal of the coupling detector circuit constitutes the input terminal of the analog adaptive filter circuit, and the second output terminal is connected to the control terminal of the electrically tunable filter through the voltage control circuit. The electrically tunable filter is used to filter the input signal based on the working passband, obtain the filtered signal, and output it. The coupling detection circuit is used to extract the voltage amplitude of the filtered signal and input the voltage amplitude and a preset threshold voltage to the voltage control circuit; The voltage control circuit is used to generate a control signal for the electrically tunable filter based on the difference between the voltage amplitude and a preset threshold voltage, so that the operating passband of the electrically tunable filter matches the frequency of the input signal.

2. The analog adaptive filter circuit as described in claim 1, characterized in that, The coupling detection circuit includes a coupler, a detection circuit, and a threshold setting circuit; The input terminal of the coupler is connected to the output terminal of the electrically tunable filter, and the output terminal constitutes the output terminal of the analog adaptive filter circuit. The coupling terminal is connected to the input terminal of the detector circuit, the output terminal of the detector circuit is connected to the first input terminal of the voltage control circuit, and the output terminal of the threshold setting circuit is connected to the second input terminal of the voltage control circuit. The coupler is used to transmit the filtered signal to the detection circuit and the threshold setting circuit; The detection circuit is used to extract the voltage amplitude of the filtered signal and input the voltage amplitude to the voltage control circuit; The threshold setting circuit is used to input a preset threshold voltage into the voltage control circuit.

3. The analog adaptive filter circuit as described in claim 2, characterized in that, The detection circuit includes a first diode, a first resistor, a second resistor, and a first capacitor; The positive terminal of the first diode is connected to the output terminal of the coupler and to the DC power supply through the first resistor. The negative terminal is connected to the first input terminal of the voltage control circuit. The first terminal of the second resistor and the first capacitor connected in parallel is connected to the negative terminal of the first diode, and the second terminal is grounded.

4. The analog adaptive filter circuit as described in claim 2, characterized in that, The threshold setting circuit includes a second diode, a third resistor, a fourth resistor, and a fifth resistor; The positive terminal of the second diode is connected to the DC power supply through the third resistor and to the resistor setting terminal through the fourth resistor. The negative terminal is connected to the second input terminal of the voltage control circuit and to the ground through the fifth resistor.

5. The analog adaptive filter circuit as described in claim 2, characterized in that, The voltage control circuit includes an integrating operational amplifier; The inverting input of the integrating operational amplifier is connected to the output of the detector circuit, the non-inverting input is connected to the output of the threshold setting circuit, and the output is connected to the control terminal of the electrically tunable filter.

6. The analog adaptive filter circuit as described in claim 5, characterized in that, The voltage control circuit also includes a seventh resistor, an eighth resistor, a ninth resistor, and a second capacitor; The seventh resistor is connected between the non-inverting input of the integrating operational amplifier and the output of the threshold setting circuit; the eighth resistor is connected between the inverting input of the integrating operational amplifier and the output of the detector circuit; the ninth resistor is connected between the output of the integrating operational amplifier and the control terminal of the electrically tunable filter; and the second capacitor is connected between the inverting input and the output of the integrating operational amplifier.

7. The analog adaptive filter circuit as described in claim 1, characterized in that, It also includes passband telemetry indication circuitry; The input terminal of the passband telemetry indicator circuit is connected to the output terminal of the voltage control circuit, and the output terminal is used to connect to an external oscilloscope device. The passband telemetry indication circuit is used to input the control signal into an external oscilloscope device and to isolate the voltage control circuit from the external oscilloscope device.

8. The analog adaptive filter circuit as described in claim 7, characterized in that, The passband telemetry indication circuit includes a proportional operational amplifier, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, and a third capacitor; The inverting input of the proportional operational amplifier is connected to the output of the voltage control circuit through the tenth resistor, the non-inverting input is connected to the first ends of the eleventh and twelfth resistors, the second end of the eleventh resistor is connected to the DC power supply and grounded through the third capacitor, the second end of the twelfth resistor is grounded, the output of the proportional operational amplifier is connected to an external oscilloscope through the thirteenth resistor and connected to the inverting input through the fourteenth resistor.

9. The analog adaptive filter circuit as described in claim 4, characterized in that, The coupling detection circuit also includes a third diode, a fourth diode, and a fourth capacitor; The positive terminal of the third diode is grounded, and the negative terminal is connected to the positive terminal of the second diode; The positive terminal of the fourth diode is grounded, and the negative terminal is connected to the coupling terminal of the coupler. The fourth capacitor is connected between the coupling terminal of the coupler and the input terminal of the detector circuit.

10. The analog adaptive filter circuit as described in claim 1, characterized in that, It also includes a fifteenth resistor; the first end of the fifteenth resistor is connected to the output terminal of the voltage control circuit, and the second end is grounded.

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