A method and apparatus for calibrating modulation depth of an AM transmitting signal

Abstract

The application discloses an AM transmitting signal modulation depth calibration method and device, and relates to the technical field of communication. The method comprises the following steps: initializing and configuring an AM transmitting link according to a control signal sent by an AM detection control link to obtain an initial AM amplitude modulation signal; performing signal conversion on the initial AM amplitude modulation signal to obtain an AM envelope digital signal, and performing preliminary AM carrier signal and modulation signal amplitude calibration according to the AM envelope digital signal to obtain a preliminary amplitude calibration result; generating a control signal of the AM transmitting link, traversing a working frequency range of the AM transmitting link according to the control signal of the AM transmitting link, and performing S2 to complete the AM modulation depth calibration point by point. The application can make the modulation depth of the AM transmitting signal meet the corresponding standard requirements, thereby improving the transmission quality and power utilization rate of the AM transmitting signal and ensuring the signal transmission efficiency.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and more specifically, to an AM transmission signal modulation depth calibration method and apparatus. Background Technology

[0002] AM modulation is widely used in broadcasting for transmitting voice signals. It modulates the voice signal onto the amplitude of a carrier wave, ultimately transmitting it as electromagnetic waves to radios or other receiving devices. Modulation depth indicates the degree to which the voice signal modulates the carrier amplitude. The magnitude of the modulation depth determines the quality of the voice signal and the power utilization of the transmitting equipment. If the modulation depth is too large, the voice signal will become distorted or clipped; if the modulation depth is too small, the anti-interference capability is weakened, the equipment's transmission power cannot be effectively utilized, and the signal transmission efficiency is reduced. Therefore, calibrating the modulation depth for AM transmission signals is crucial.

[0003] The modulation depth of amplitude modulation (AM) is the ratio of the modulating signal amplitude to the carrier signal amplitude in an AM signal. The modulation depth is determined by both the carrier signal amplitude and the modulating signal amplitude; therefore, modulation depth calibration requires two steps: carrier amplitude calibration and modulating signal amplitude calibration. Currently, there is limited material available on AM transmit signal modulation depth calibration. The current state of AM transmit signal modulation depth calibration technology can be briefly described from two aspects: carrier signal amplitude (i.e., transmit power) calibration and modulating signal amplitude calibration.

[0004] I. For carrier signal amplitude calibration, AM transmit signal carrier amplitude (i.e., transmit power) calibration often employs external calibration methods. For example, patent CN202422115851 proposes an AM transmit power calibration method and device, the calibration principle block diagram of which is as follows: Figure 8 As shown, this method uses a power meter and a spectrum analyzer to measure the AM signal power at the transmit port of the AM transmitter and the input port of the power amplifier unit. The measured power values ​​are then fed back to the computer. The computer compares the measured power values ​​with the target power values ​​and outputs a control signal to control the output signal power of the excitation unit in the AM transmitter, thereby achieving the purpose of calibrating the AM transmit signal carrier amplitude.

[0005] II. Regarding modulation signal amplitude calibration, there is a lack of relevant materials. Patent CN202410024225 proposes an AM modulation depth control method. The control method involves calculating the broadcast signal power and clutter power of AM audio sampling data within a bandwidth of 20Hz to 20kHz and a bandwidth of 20kHz to 60kHz using an FFT algorithm. Then, the target power ratio of the broadcast signal power to the clutter power is calculated, and the target modulation degree corresponding to the target power ratio is matched from a preset modulation degree lookup table. If the target modulation degree exceeds a first modulation degree threshold, the amplitude of the input audio signal corresponding to the AM audio sampling data is reduced.

[0006] In summary, existing AM transmit signal modulation depth calibration techniques have the following drawbacks:

[0007] The AM carrier signal amplitude (i.e., transmit power) calibration method requires the use of test instruments such as spectrum analyzers and power meters. However, these test instruments are expensive, and the calibration system is costly to set up, making it unsuitable for large-scale deployment on production lines.

[0008] There are few technologies related to AM modulation signal amplitude calibration. The AM modulation depth control method proposed in patent CN202410024225 uses a 65536-point FFT algorithm to calculate the power of the AM signal. However, the 65536-point FFT calculation time is long, and the bandwidth for calculating power is wide, resulting in large noise power. This leads to poor accuracy of the calculated power value, affecting the control accuracy of AM modulation depth.

[0009] There are currently no effective solutions to the problems in the relevant technologies. Summary of the Invention

[0010] To address the problems in related technologies, this invention proposes an AM transmission signal modulation depth calibration method and apparatus to overcome the aforementioned technical problems existing in the prior art.

[0011] Therefore, the specific technical solution adopted by the present invention is as follows:

[0012] According to one aspect of the present invention, an AM transmit signal modulation depth calibration method is provided, the method comprising the following steps:

[0013] S1. Initialize the AM transmission link according to the control signal sent by the AM detection and control link to obtain the initial AM amplitude modulation signal;

[0014] S2. Perform signal conversion on the initial AM amplitude modulation signal to obtain the AM envelope digital signal, and perform preliminary AM carrier signal and modulation signal amplitude calibration based on the AM envelope digital signal to obtain preliminary amplitude calibration results.

[0015] S3. Based on the preliminary amplitude calibration results, generate the control signal for the AM transmission link. According to the control signal of the AM transmission link, traverse the working frequency range of the AM transmission link and execute S2 point by point to complete the AM modulation depth calibration.

[0016] Furthermore, the control signals sent by the AM detection and control link include carrier frequency control signals, frequency hopping filter segment code control signals, digital potentiometer range control signals, digital-to-analog converter gain control signals, and automatic gain control circuit gain control signals.

[0017] Furthermore, the initial AM amplitude-modulated signal is converted to obtain an AM envelope digital signal, and preliminary amplitude calibration of the AM carrier signal and modulation signal is performed based on the AM envelope digital signal to obtain preliminary amplitude calibration results, including:

[0018] S21. Perform a coupling operation on the initial AM amplitude modulation signal, obtain the AM envelope signal using a detector based on the coupling operation result, and perform signal conversion on the AM envelope signal to obtain the AM envelope digital signal.

[0019] S22. Perform digital downsampling and filtering on the AM envelope digital signal to obtain the carrier signal amplitude voltage, and perform AM transmit power detection on the carrier signal amplitude voltage. Based on the detection results, perform preliminary AM carrier signal amplitude calibration to obtain the interactive signal.

[0020] S23. Based on the interactive signal, the AM modulation depth of the AM envelope digital signal is detected to obtain the AM modulation depth. Based on the AM modulation depth, the amplitude of the AM modulation signal is preliminarily calibrated to obtain the preliminary AM modulation signal amplitude calibration result.

[0021] Furthermore, the AM envelope digital signal is digitally downsampled and filtered to obtain the carrier signal amplitude voltage. The AM transmit power of the carrier signal amplitude voltage is then detected. Based on the detection results, preliminary AM carrier signal amplitude calibration is performed, resulting in the following interactive signals:

[0022] S221. Digitally downsample the AM envelope digital signal to obtain the downsampled AM envelope digital signal, and use a digital low-pass filter to filter the downsampled AM envelope digital signal to obtain the carrier signal amplitude voltage.

[0023] S222. Initialize the number of AM transmit power detections, and set the AGC control gain for AM transmit power detection based on the number of detections. Perform AM transmit power detection on the carrier signal amplitude voltage to obtain the detection result.

[0024] S223. Calculate the power difference based on the detection results, and make a power fluctuation judgment on the power difference. Based on the power fluctuation judgment result, perform preliminary AM carrier signal amplitude calibration to obtain the interactive signal.

[0025] Furthermore, based on the power fluctuation judgment results, preliminary AM carrier signal amplitude calibration is performed to obtain the interaction signal, which includes:

[0026] If the power fluctuation judgment result is that the power difference meets the power fluctuation requirements, then the setting parameters of the AGC control gain are stored in the storage medium to complete the preliminary carrier signal amplitude calibration and obtain the interactive signal.

[0027] If the power fluctuation judgment result is that the power difference does not meet the power fluctuation requirements, then it is determined whether the number of AM transmit power detections is greater than or equal to the maximum value of the number of AM transmit power detections.

[0028] If the number of AM transmit power detections is greater than or equal to the maximum number of AM transmit power detections, the setting parameters of the AGC control gain are stored in the storage medium to complete the initial carrier signal amplitude calibration and obtain the interactive signal.

[0029] If the number of AM transmit power detections is less than the maximum number of AM transmit power detections, then the gradient descent method is used to update the AGC control gain to obtain the updated AGC control gain.

[0030] The updated AGC control gain is dynamically ranged, and the updated AGC control gain is adjusted based on the dynamic range judgment result to obtain the adjusted AGC control gain.

[0031] After the AGC control gain is updated and adjusted, the number of AM transmit power detections is updated, and the power fluctuation judgment and AGC control gain update process are repeated to obtain the final AGC control gain.

[0032] The final AGC control gain settings are stored in the storage medium to complete the initial carrier signal amplitude calibration and obtain the interactive signal.

[0033] Furthermore, AM modulation depth is detected based on the interactive signal of the AM envelope digital signal to obtain the AM modulation depth. Preliminary AM modulation signal amplitude calibration is then performed based on the AM modulation depth, yielding preliminary AM modulation signal amplitude calibration results, including:

[0034] S231. Based on the interactive signal, set the number of AM modulation depth detections and the number of DAC output gain adjustments;

[0035] S232. Set the adjusted DAC output gain according to the number of DAC output gain adjustments; and set the digital potentiometer setting for AM modulation depth detection according to the number of AM modulation depth detections.

[0036] S233. Perform AM modulation depth detection on the AM envelope digital signal to obtain the AM modulation depth, calculate the modulation depth difference based on the AM modulation depth, and judge the modulation depth fluctuation of the modulation depth difference.

[0037] S234. Based on the modulation depth fluctuation judgment result, perform preliminary AM modulation signal amplitude calibration to obtain preliminary AM modulation signal amplitude calibration result.

[0038] Furthermore, based on the modulation depth fluctuation judgment results, preliminary AM modulation signal amplitude calibration is performed, and the preliminary AM modulation signal amplitude calibration results include:

[0039] If the modulation depth fluctuation judgment result is that the modulation depth meets the modulation depth fluctuation requirement, the adjusted DAC output gain and the setting parameters of the digital potentiometer range are stored in the storage medium to complete the preliminary modulation signal amplitude calibration and obtain the preliminary AM modulation signal amplitude calibration result.

[0040] If the modulation depth fluctuation judgment result is that the modulation depth does not meet the modulation depth fluctuation requirement, then it is determined whether the number of AM modulation depth detections is greater than or equal to the maximum value of the number of AM modulation depth detections.

[0041] If the number of AM modulation depth detections is less than the maximum number of AM modulation depth detections, the gradient descent method is used to update the digital potentiometer range, and the updated digital potentiometer range is judged and adjusted to obtain the adjusted digital potentiometer range.

[0042] If the number of AM modulation depth detections is greater than or equal to the maximum number of AM modulation depth detections, then determine whether the adjusted DAC output gain is less than or equal to the minimum DAC output gain.

[0043] If the adjusted DAC output gain is less than or equal to the minimum DAC output gain, the adjusted DAC output gain and the setting parameters of the digital potentiometer range are stored in the storage medium to complete the preliminary modulation signal amplitude calibration and obtain the preliminary AM modulation signal amplitude calibration result.

[0044] If the adjusted DAC output gain is greater than the minimum DAC output gain, then the adjusted DAC output gain is subtracted from the DAC gain adjustment step, and the updated DAC output gain is range-determined and adjusted to obtain the adjusted DAC output gain.

[0045] Based on the adjusted digital potentiometer setting and the adjusted DAC output gain, the modulation depth fluctuation judgment and digital potentiometer setting and DAC output gain update processing are repeatedly performed to complete the preliminary modulation signal amplitude calibration and obtain the preliminary AM modulation signal amplitude calibration result.

[0046] According to another aspect of the present invention, an AM transmission signal modulation depth calibration device is provided, the AM transmission signal modulation depth calibration device comprising: an AM transmission link and an AM detection and control link;

[0047] The AM transmit link is used to receive the control signal output from the AM detection and control link and output the AM amplitude modulation signal.

[0048] The AM detection and control link is used to generate control signals for controlling the AM transmit link and to complete modulation depth calibration.

[0049] One end of the AM transmit link is connected to one end of the AM detection and control link.

[0050] Furthermore, the AM transmit link includes: frequency hopping filter, power amplifier, automatic gain control circuit, automatic level control circuit, digital potentiometer, digital-to-analog converter, and radio frequency signal source;

[0051] A digital-to-analog converter (DAC) is used to receive a DAC gain control signal and a calibration sequence signal, and output a first modulation signal.

[0052] A digital potentiometer is used to receive a digital potentiometer range control signal and a first modulation signal, and output a second modulation signal;

[0053] Radio frequency signal source, used to receive carrier frequency control signals and output carrier signals;

[0054] Automatic level control circuit is used to receive the carrier signal and the filtered AM envelope signal to complete AM modulation;

[0055] Automatic gain control circuit, used to receive the gain control signal from automatic gain control circuit and amplify the AM amplitude modulation signal output by automatic level control circuit;

[0056] A power amplifier used to amplify the AM amplitude-modulated signal output from an automatic gain control circuit;

[0057] Frequency hopping filter is used to receive the frequency hopping filter segment code control signal and to filter out external interference signals from the AM amplitude modulation signal output by the power amplifier.

[0058] The first pin of the frequency hopping filter is connected to one end of the power amplifier, the other end of the power amplifier is connected to the first pin of the automatic gain control circuit, the second pin of the automatic gain control circuit is connected to the first pin of the automatic level control circuit, the second pin of the automatic level control circuit is connected to one end of the radio frequency signal source, the third pin of the automatic level control circuit is connected to the first pin of the digital potentiometer, and the second pin of the digital potentiometer is connected to the first pin of the digital-to-analog converter.

[0059] Furthermore, the AM detection and control link includes: a directional coupler, a detector, a low-pass filter, an analog-to-digital converter, a control processor, and a storage medium;

[0060] A directional coupler is used to couple AM ​​(amplitude modulated) signals and output the coupled AM signal.

[0061] The detector is used to receive the coupled amplitude-modulated signal and output two AM envelope signals.

[0062] A low-pass filter is used to filter the AM envelope signal and input it to the automatic level control circuit.

[0063] An analog-to-digital converter is used to convert AM envelope signals into AM envelope digital signals.

[0064] The control processor is used to perform AM modulation depth calibration on the received AM envelope digital signal and output carrier frequency control signal, frequency hopping filter segment code control signal, digital potentiometer range control signal, digital-to-analog converter gain control signal, calibration sequence signal, storage medium control signal and automatic gain control circuit gain control signal.

[0065] Storage medium, used to receive storage medium control signals and store control parameters for AM modulation depth calibration;

[0066] One end of the directional coupler is connected to the second pin of the frequency hopping filter, and the other end of the directional coupler is connected to one end of the detector. The other end of the detector is connected to one end of the low-pass filter and one end of the analog-to-digital converter. The other end of the low-pass filter is connected to the fourth pin of the automatic level control circuit. The other end of the analog-to-digital converter is connected to the first pin of the control processor. The second, third, and fourth pins of the control processor are connected to one end of the storage medium. The fifth pin of the control processor is connected to the third pin of the digital potentiometer. The sixth pin of the control processor is connected to the second pin of the digital-to-analog converter. The seventh pin of the control processor is connected to the third pin of the digital-to-analog converter. The eighth pin of the control processor is connected to the other end of the RF signal source. The ninth pin of the control processor is connected to the third pin of the frequency hopping filter. The tenth pin of the control processor is connected to the third pin of the automatic gain control circuit.

[0067] The beneficial effects of this invention are as follows:

[0068] 1. This invention achieves the required modulation depth of AM signals by calibrating both carrier signal amplitude and modulation signal amplitude, thereby improving the accuracy of AM transmitter transmission power and modulation depth, and ultimately enhancing the transmission quality and power utilization of AM signals, ensuring signal transmission efficiency.

[0069] 2. This invention employs a low-cost method for calibrating carrier signal amplitude and modulation signal amplitude within the range, eliminating the need for expensive instruments such as spectrum analyzers and power meters, making it suitable for large-scale deployment on production lines. Furthermore, by calibrating the carrier signal amplitude before calibrating the modulation signal amplitude, the automatic level control circuit ensures that the modulation signal amplitude is calibrated under an accurate power reference signal, significantly reducing the impact of AM transmit power fluctuations on AM modulation depth and improving the accuracy of AM modulation depth calibration.

[0070] 3. This invention uses digital downsampling and digital low-pass filters in the carrier signal amplitude calibration method, which filters out out-of-band noise while saving hardware resources, greatly reducing noise power and improving AM transmit power detection accuracy; and improves the calibration accuracy of carrier signal amplitude while ensuring optimization speed by optimizing AGC control gain through gradient descent method.

[0071] 4. In the modulation signal amplitude calibration, the present invention uses two-level control of DAC output gain and digital potentiometer range to perform calibration, which increases the total adjustment range of variables in the modulation signal amplitude calibration process, making the modulation signal amplitude calibration more accurate. At the same time, the adjustment of the digital potentiometer range uses the gradient descent method, which improves the calibration accuracy of the modulation signal amplitude while ensuring the optimization speed. Attached Figure Description

[0072] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0073] Figure 1 This is a flowchart of an AM transmit signal modulation depth calibration method according to an embodiment of the present invention;

[0074] Figure 2 This is a schematic diagram of an AM transmission signal modulation depth calibration device according to an embodiment of the present invention;

[0075] Figure 3 This is a schematic diagram of AM modulation depth calibration in an AM transmit signal modulation depth calibration method according to an embodiment of the present invention;

[0076] Figure 4 This is a schematic diagram of carrier signal amplitude calibration processing in an AM transmit signal modulation depth calibration method according to an embodiment of the present invention;

[0077] Figure 5 This is a flowchart of carrier signal amplitude calibration in an AM transmit signal modulation depth calibration method according to an embodiment of the present invention;

[0078] Figure 6 This is a schematic diagram of modulation signal amplitude calibration in an AM transmission signal modulation depth calibration method according to an embodiment of the present invention;

[0079] Figure 7 This is a flowchart of the modulation signal amplitude calibration process in an AM transmit signal modulation depth calibration method according to an embodiment of the present invention;

[0080] Figure 8 It is a principle block diagram of the AM carrier signal amplitude external calibration method in patent CN202422115851. Detailed Implementation

[0081] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention.

[0082] According to an embodiment of the present invention, an AM transmission signal modulation depth calibration method and apparatus are provided.

[0083] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figure 1 As shown, according to an embodiment of the present invention, an AM transmit signal modulation depth calibration method is provided, the method comprising the following steps:

[0084] An AM transmit signal modulation depth calibration method, characterized in that the method includes:

[0085] S1. Initialize the AM transmission link according to the control signal sent by the AM detection and control link to obtain the initial AM amplitude modulation signal.

[0086] Specifically, the control signals sent by the AM detection and control link include carrier frequency control signals, frequency hopping filter segment code control signals, digital potentiometer range control signals, digital-to-analog converter gain control signals, and automatic gain control circuit gain control signals.

[0087] Specifically, such as Figure 2As shown, the AM transmission signal modulation depth calibration device proposed in this invention consists of two parts: an amplitude modulation (AM) transmission link and an AM detection and control link. One end of the AM transmission link is connected to the other end of the AM detection and control link. The AM transmission link consists of a frequency hopping filter, a power amplifier, an automatic gain control circuit (AGC), an automatic level control circuit (ALC), a digital potentiometer, a digital-to-analog converter (DAC), and an RF signal source. The AM detection and control link consists of a directional coupler, a detector, a low-pass filter, an analog-to-digital converter (ADC), a control processor, and a storage medium. The control processor consists of an AM modulation depth calibration processing module and a control module. The AM modulation depth calibration processing module consists of a modulation signal amplitude calibration processing module and a carrier signal amplitude calibration processing module, and the modulation signal amplitude calibration processing module and the carrier signal amplitude calibration processing module are connected.

[0088] In this invention, the AM transmit link and the AM detection and control link constitute a closed loop for AM transmit signal modulation depth calibration. In the AM transmit link, the RF signal source outputs a carrier signal with stable but low power, and the DAC and digital potentiometer output a modulation signal. The ALC module uses the signal output by the low-pass filter as a power reference signal to complete AM modulation and output a low-power AM amplitude modulation signal. The low-power AM amplitude modulation signal is amplified by AGC and a power amplifier and then input to a frequency hopping filter. After filtering out out-of-band interference signals, it outputs an AM amplitude modulation signal with the corresponding power. The AM amplitude-modulated signal transmitted by the AM transmit link is coupled back to the AM detection and control link by a directional coupler. The coupled AM amplitude-modulated signal is then output by a detector as two identical AM envelope signals. One AM envelope signal is filtered by a low-pass filter and used as the power reference signal for the ALC module, adjusting the power of the AM amplitude-modulated signal output by the ALC module. The other AM envelope signal is input to the ADC module, converted into an AM envelope digital signal, and then input to the AM modulation depth calibration processing module in the control processor. The AM modulation depth calibration processing module in the control processor processes the input AM envelope digital signal and outputs control signals for the AGC, digital potentiometer, and DAC. It performs compensation control on the AGC, digital potentiometer, and DAC, and stores the control parameters of the AGC, digital potentiometer, and DAC in the storage medium, completing the modulation depth calibration of the AM transmit signal. In addition, the control processor also includes a control module that sends a carrier frequency control signal to control the operating frequency of the RF signal source output carrier signal, sends a frequency hopping filter segment code control signal to control the operating frequency band of the frequency hopping filter, and outputs a calibration sequence signal to the DAC to make the DAC output a sine wave signal of the corresponding frequency.

[0089] Specifically, such as Figure 3The diagram illustrates the specific process of AM modulation depth calibration. Initialization configuration (i.e., initial settings) involves the control processing module in the control processor sending a carrier frequency control signal to set the initial operating frequency of the RF signal source's output carrier signal, sending a frequency hopping filter segment code control signal to ensure the passband of the frequency hopping filter includes the operating frequency of the RF signal source's output carrier signal, and outputting a sinusoidal calibration sequence signal with a frequency range of 20Hz to 10.24kHz (1kHz is a typical frequency used in this invention). The AM modulation depth calibration processing module then sends a digital potentiometer range control signal to set the digital potentiometer's range to the middle range within its adjustment range, sends a DAC gain control signal to set the DAC's output gain to the maximum gain, and sends an AGC gain control signal to set the AGC's gain to the middle gain within its dynamic range.

[0090] S2. Perform signal conversion on the initial AM amplitude modulation signal to obtain the AM envelope digital signal, and perform preliminary AM carrier signal and modulation signal amplitude calibration based on the AM envelope digital signal to obtain preliminary amplitude calibration results.

[0091] Specifically, the initial AM amplitude modulated signal is converted to obtain an AM envelope digital signal, and preliminary amplitude calibration of the AM carrier signal and modulation signal is performed based on the AM envelope digital signal to obtain preliminary amplitude calibration results, including:

[0092] S21. Perform a coupling operation on the initial AM amplitude modulation signal, obtain the AM envelope signal using a detector based on the coupling operation result, and perform signal conversion on the AM envelope signal to obtain the AM envelope digital signal.

[0093] S22. Perform digital downsampling and filtering on the AM envelope digital signal to obtain the carrier signal amplitude voltage, and perform AM transmit power detection on the carrier signal amplitude voltage. Based on the detection results, perform preliminary AM carrier signal amplitude calibration to obtain the interactive signal.

[0094] Specifically, the AM envelope digital signal is digitally downsampled and filtered to obtain the carrier signal amplitude voltage. The AM transmit power of the carrier signal amplitude voltage is then detected. Based on the detection results, preliminary AM carrier signal amplitude calibration is performed to obtain the interactive signal, which includes:

[0095] S221. Digitally downsample the AM envelope digital signal to obtain the downsampled AM envelope digital signal, and use a digital low-pass filter to filter the downsampled AM envelope digital signal to obtain the carrier signal amplitude voltage.

[0096] S222. Initialize the number of AM transmit power detections, and set the AGC control gain for AM transmit power detection based on the number of detections. Perform AM transmit power detection on the carrier signal amplitude voltage to obtain the detection result.

[0097] S223. Calculate the power difference based on the detection results, and make a power fluctuation judgment on the power difference. Based on the power fluctuation judgment result, perform preliminary AM carrier signal amplitude calibration to obtain the interactive signal.

[0098] Specifically, based on the power fluctuation judgment results, preliminary AM carrier signal amplitude calibration is performed to obtain the following interactive signals:

[0099] If the power fluctuation judgment result is that the power difference meets the power fluctuation requirements, then the setting parameters of the AGC control gain are stored in the storage medium to complete the preliminary carrier signal amplitude calibration and obtain the interactive signal.

[0100] If the power fluctuation judgment result is that the power difference does not meet the power fluctuation requirements, then it is determined whether the number of AM transmit power detections is greater than or equal to the maximum value of the number of AM transmit power detections.

[0101] If the number of AM transmit power detections is greater than or equal to the maximum number of AM transmit power detections, the setting parameters of the AGC control gain are stored in the storage medium to complete the initial carrier signal amplitude calibration and obtain the interactive signal.

[0102] If the number of AM transmit power detections is less than the maximum number of AM transmit power detections, then the gradient descent method is used to update the AGC control gain to obtain the updated AGC control gain.

[0103] The updated AGC control gain is dynamically ranged, and the updated AGC control gain is adjusted based on the dynamic range judgment result to obtain the adjusted AGC control gain.

[0104] After the AGC control gain is updated and adjusted, the number of AM transmit power detections is updated, and the power fluctuation judgment and AGC control gain update process are repeated to obtain the final AGC control gain.

[0105] The final AGC control gain settings are stored in the storage medium to complete the initial carrier signal amplitude calibration and obtain the interactive signal.

[0106] Specifically, after initialization, the AM transmit link transmits an AM amplitude modulated signal. The AM detection and control link couples back the AM amplitude modulated signal transmitted by the AM transmit link, outputting an AM envelope signal through a detector. This AM envelope signal is then input to an ADC for sampling, quantization, and encoding, converting it into an AM envelope digital signal. This signal is then input to the AM modulation depth calibration processing module in the control processor. The module is divided into two paths: one for carrier signal amplitude calibration and the other for modulation signal amplitude calibration. A schematic diagram of the carrier signal amplitude calibration processing in the AM modulation depth calibration processing module is shown below. Figure 4 As shown, Figure 4 The AM modulation depth calibration processing module includes a carrier signal amplitude calibration processing module, which includes a digital downsampling module, a digital low-pass filter, and a carrier amplitude calibration module. The digital downsampling module receives the AM envelope digital signal, one end of which is connected to one end of the digital low-pass filter, and the other end of the digital low-pass filter is connected to one end of the carrier amplitude calibration module. The carrier amplitude calibration module outputs a storage medium control signal, an interactive signal, and an AGC gain control signal.

[0107] Typically, the sampling clock frequency of an ADC is much higher than the frequency of the AM envelope signal. To save hardware resources for the control processor and reduce the redundancy of the AM envelope digital signal data, the AM envelope digital signal is first digitally downsampled after input to the carrier signal amplitude calibration processing module, reducing the sampling frequency of the AM envelope signal to 5 to 8 times the AM envelope signal frequency. The downsampled AM envelope digital signal is then input to a digital low-pass filter. The passband cutoff frequency of the digital low-pass filter is much lower than the frequency of the AM envelope signal. After filtering out the AM envelope signal, the digital low-pass filter outputs a carrier signal amplitude voltage U to the carrier signal amplitude calibration module. The carrier signal amplitude calibration module uses voltage U to detect the AM transmit power. Based on the detected AM transmit power, it sends an AGC gain control signal to control the AGC gain until the AM transmit power meets the target power requirement. At this point, the carrier signal amplitude calibration module stops AGC gain control and sends a storage medium control signal to store the AGC gain control parameters in the storage medium, completing the carrier signal amplitude calibration. The carrier signal amplitude calibration flowchart is shown below. Figure 5 As shown, the detailed steps are as follows:

[0108] Step 2.1 sets the AM transmit power detection count i to an initial value of i=1.

[0109] Step 2.2 involves sending the AGC gain control signal and setting the AGC gain G during the i-th AM transmit power detection. i When i=1, the gain of AGC is set to the intermediate gain within the dynamic range.

[0110] Step 2.3 is to use the carrier signal amplitude voltage U output by the digital filter.m Perform the i-th AM transmit power detection and calculate the i-th AM transmit power P. i .

[0111] The formula for calculating AM transmit power is:

[0112] ;

[0113] In the formula, U m is the first n voltages received by the carrier amplitude calibration module after the start of the i-th AM transmit power calculation, in V; n is the total number of voltages used for power calculation; and At is the total link attenuation of the directional coupler and detector in the AM detection link, in dB.

[0114] Step 2.4 is to calculate the AM transmission power P of the i-th transmission. i With target power P opt The difference ∆P i =P i -P opt .

[0115] Step 2.5 is to determine the power difference ∆P obtained in the i-th iteration. i If the power fluctuation requirement is met, then send the storage medium control signal to increase the AGC gain G for the i-th iteration. i The settings parameters are stored in the storage medium to complete the carrier signal amplitude calibration and maintain the AGC gain at G. i The carrier signal amplitude calibration module sends an interactive signal to the modulation signal amplitude calibration module to inform the modulation signal amplitude calibration module to start the modulation signal amplitude calibration function; if the power fluctuation requirements are not met, proceed to step 2.6.

[0116] Step 2.6 is to determine whether the number of AM transmit power detections i is less than the maximum value i of the number of AM transmit power detections. max , if i max Then the cached AM detection power P of the i-th time i and AGC control gain G i Then proceed to steps 2.7~2.9; if i≥i max Then, the storage medium control signal will be sent to increase the AGC gain G of the i-th iteration. i The settings parameters are stored in the storage medium to complete the carrier signal amplitude calibration and maintain the AGC gain at G. i The carrier signal amplitude calibration module sends an interactive signal to the modulation signal amplitude calibration module, informing the modulation signal amplitude calibration module to start the modulation signal amplitude calibration function.

[0117] Step 2.7 involves using the gradient descent method to calculate the AGC control gain G for the (i+1)th iteration.​i+1 .

[0118] AGC control gain G i+1 The calculation expression is:

[0119] ;

[0120] In the formula, α i Let α be the step size. To ensure both optimization speed and accuracy, the step size is α. i The relationship between α and the number of tests i is an inverse proportional function, i.e., α i =δ / i, where δ is the initial step value. When i=1, P0=0 and G0=0.

[0121] Step 2.8 is to determine G i+1 Is it within the AGC gain adjustment range? If it is, G i+1 No adjustment is made; if it is outside the range, then G... i+1 The cutoff is within the AGC gain adjustment range and is related to G. i+1 The closest gain value.

[0122] Step 2.9 sets the number of AM transmit power detections to i=i+1, and repeats steps 2.2~2.5.

[0123] Carrier signal amplitude calibration is completed, and the carrier signal amplitude operates in calibration amplitude mode before modulation signal amplitude calibration begins. Controlling the AGC gain to the calibration gain ensures that carrier signal amplitude calibration is completed and the carrier signal amplitude operates in calibration amplitude mode before modulation signal amplitude calibration begins.

[0124] S23. Based on the interactive signal, the AM modulation depth of the AM envelope digital signal is detected to obtain the AM modulation depth. Based on the AM modulation depth, the amplitude of the AM modulation signal is preliminarily calibrated to obtain the preliminary AM modulation signal amplitude calibration result.

[0125] Specifically, AM modulation depth is detected based on the interactive signal of the AM envelope digital signal to obtain the AM modulation depth. Preliminary AM modulation signal amplitude calibration is then performed based on the AM modulation depth, yielding preliminary AM modulation signal amplitude calibration results, including:

[0126] S231. Based on the interactive signal, set the number of AM modulation depth detections and the number of DAC output gain adjustments;

[0127] S232. Set the adjusted DAC output gain according to the number of DAC output gain adjustments; and set the digital potentiometer setting for AM modulation depth detection according to the number of AM modulation depth detections.

[0128] S233. Perform AM modulation depth detection on the AM envelope digital signal to obtain the AM modulation depth, calculate the modulation depth difference based on the AM modulation depth, and judge the modulation depth fluctuation of the modulation depth difference.

[0129] S234. Based on the modulation depth fluctuation judgment result, perform preliminary AM modulation signal amplitude calibration to obtain preliminary AM modulation signal amplitude calibration result.

[0130] Specifically, based on the modulation depth fluctuation judgment results, preliminary AM modulation signal amplitude calibration is performed, and the preliminary AM modulation signal amplitude calibration results include:

[0131] If the modulation depth fluctuation judgment result is that the modulation depth meets the modulation depth fluctuation requirement, the adjusted DAC output gain and the setting parameters of the digital potentiometer range are stored in the storage medium to complete the preliminary modulation signal amplitude calibration and obtain the preliminary AM modulation signal amplitude calibration result.

[0132] If the modulation depth fluctuation judgment result is that the modulation depth does not meet the modulation depth fluctuation requirement, then it is determined whether the number of AM modulation depth detections is greater than or equal to the maximum value of the number of AM modulation depth detections.

[0133] If the number of AM modulation depth detections is less than the maximum number of AM modulation depth detections, the gradient descent method is used to update the digital potentiometer range, and the updated digital potentiometer range is judged and adjusted to obtain the adjusted digital potentiometer range.

[0134] If the number of AM modulation depth detections is greater than or equal to the maximum number of AM modulation depth detections, then determine whether the adjusted DAC output gain is less than or equal to the minimum DAC output gain.

[0135] If the adjusted DAC output gain is less than or equal to the minimum DAC output gain, the adjusted DAC output gain and the setting parameters of the digital potentiometer range are stored in the storage medium to complete the preliminary modulation signal amplitude calibration and obtain the preliminary AM modulation signal amplitude calibration result.

[0136] If the adjusted DAC output gain is greater than the minimum DAC output gain, then the adjusted DAC output gain is subtracted from the DAC gain adjustment step, and the updated DAC output gain is range-determined and adjusted to obtain the adjusted DAC output gain.

[0137] Based on the adjusted digital potentiometer setting and the adjusted DAC output gain, the modulation depth fluctuation judgment and digital potentiometer setting and DAC output gain update processing are repeatedly performed to complete the preliminary modulation signal amplitude calibration and obtain the preliminary AM modulation signal amplitude calibration result.

[0138] Specifically, after receiving the interactive signal from the carrier signal amplitude calibration module, the modulation signal amplitude calibration module initiates modulation signal amplitude calibration. A schematic diagram of the modulation signal amplitude calibration process in the AM modulation depth calibration processing module is shown below. Figure 6 As shown, Figure 6 The modulation signal amplitude calibration processing module is used to process AM envelope digital signals, storage medium control signals and interactive signals, and outputs DAC gain control signals, digital potentiometer control signals and interactive signals.

[0139] The modulation signal amplitude calibration module uses the AM envelope digital signal to detect the AM modulation depth. Based on the detected AM modulation depth, it sends a DAC gain control signal to control the DAC output gain and a digital potentiometer control signal to control the digital potentiometer's range, until the AM modulation depth meets the target depth requirement. Then, the modulation signal amplitude calibration module sends a storage medium control signal to store the DAC gain control parameters and the digital potentiometer range control parameters into the storage medium, completing the modulation signal amplitude calibration. The modulation signal amplitude calibration flowchart is shown below. Figure 7 As shown, the detailed steps are as follows:

[0140] Step 3.1 sets the AM modulation depth detection count k to an initial value of k=1 and the DAC output gain adjustment count q to an initial value of q=1.

[0141] Step 3.2 involves sending the DAC gain control signal to set the DAC output gain G for the qth adjustment. q When q=1, G q Set to the maximum value G of the DAC output gain max .

[0142] Step 3.3 involves sending a digital potentiometer control signal to set the digital potentiometer's position S during the k-th AM modulation depth detection. k .

[0143] Step 3.4 involves the modulation signal amplitude calibration module acquiring two cycles of AM envelope digital signal and then finding the maximum value EMAX of the two cycles of AM envelope digital signal. k and minimum value EMIN k Calculate the AM modulation depth MD of the k-th AM modulation depth detection. k The expression for calculating the AM modulation depth is:

[0144] .

[0145] Step 3.5 is to calculate the AM modulation depth MD of the kth detection. k With target modulation depth MD opt The difference ∆MD k =MDk -MD opt .

[0146] Step 3.6 is to determine the modulation depth difference ∆MD obtained from the k-th detection. k If the modulation depth fluctuation requirement is met, then the storage medium control signal is sent to adjust the DAC gain G at the qth iteration. q The setting parameters and the digital potentiometer setting S for the kth iteration k The settings parameters are stored in the storage medium to complete the modulation signal amplitude calibration; if the modulation depth fluctuation requirements are not met, proceed to step 3.7.

[0147] Step 3.7 is to determine whether the number of AM modulation depth detections k is less than the maximum value k of the number of AM modulation depth detections. max If k <k max Then cache the AM modulation depth detection value MD of the kth time. k and digital potentiometer range value S k Then proceed to steps 3.11 to 3.13; if k ≥ k max Proceed to step 3.8.

[0148] Step 3.8 is to determine the output gain G of the DAC. q Is it less than or equal to the minimum value G of the DAC output gain? min If G q ≤G min The DAC gain G at the qth iteration q The setting parameters and the digital potentiometer setting S for the kth iteration k The setting parameters are stored in the storage medium to complete the modulation signal amplitude calibration; if G q >G min Subtract the DAC gain adjustment step ∆G from the DAC output gain, i.e., G q+1 =G q -∆G.

[0149] Step 3.9 is to determine G q+1 Is it within the DAC gain adjustment range? If it is, G q+1 No adjustment is made; if it is outside the range, then G... q+1 The cutoff is within the AGC gain adjustment range and is related to G. q+1 The closest gain value.

[0150] Step 3.10 involves adjusting the AM modulation depth detection count k=1 and the DAC output gain setting count q=q+1, and then repeating steps 3.2 to 3.6.

[0151] Step 3.11 involves using the gradient descent method to calculate the (k+1)th digital potentiometer control position S.k+1 .

[0152] ;

[0153] In the formula, β k Let β be the step size. To ensure both optimization speed and accuracy, the step size is β. k The relationship between β and the number of tests k is an inverse proportional function, i.e., β k =γ / k, where γ is the initial step value. When k=1, MD0=0 and S0=0.

[0154] Step 3.12 is to determine S k+1 Is it within the adjustment range of the digital potentiometer? If it is, S k+1 No adjustment is made; if it is outside the range, then S... k+1 Cut off within the range of digital potentiometer adjustment and S k+1 The closest gear value;

[0155] Step 3.13 sets the number of AM modulation depth detections to k=k+1, and repeats steps 3.3 to 3.6.

[0156] S3. Based on the preliminary amplitude calibration results, generate the control signal for the AM transmission link. According to the control signal of the AM transmission link, traverse the working frequency range of the AM transmission link and execute S2 point by point to complete the AM modulation depth calibration.

[0157] Specifically, after completing the carrier signal amplitude calibration and modulation signal amplitude calibration of the initial carrier operating frequency of the AM transmit link, the control module sends the carrier frequency control signal and the frequency hopping filter segment code control signal (i.e., the control signal of the AM transmit link) to control the frequency of the carrier signal output by the radio frequency signal source and the passband range of the frequency hopping filter. It traverses the operating frequency band range of the AM transmit link and performs S2 calibration point by point to complete the carrier signal amplitude calibration and modulation signal amplitude calibration, thus completing the AM modulation depth calibration.

[0158] like Figure 2 As shown, according to another embodiment of the present invention, an AM transmission signal modulation depth calibration device is provided, the AM transmission signal modulation depth calibration device comprising: an AM transmission link and an AM detection and control link;

[0159] The AM transmit link is used to receive the control signal output from the AM detection and control link and output the AM amplitude modulation signal.

[0160] Specifically, the AM transmit link includes: frequency hopping filter, power amplifier, automatic gain control circuit, automatic level control circuit, digital potentiometer, digital-to-analog converter, and radio frequency signal source;

[0161] A digital-to-analog converter (DAC) is used to receive a DAC gain control signal and a calibration sequence signal, and output a first modulation signal.

[0162] A digital potentiometer is used to receive a digital potentiometer range control signal and a first modulation signal, and output a second modulation signal;

[0163] Radio frequency signal source, used to receive carrier frequency control signals and output carrier signals;

[0164] Automatic level control circuit is used to receive the carrier signal and the filtered AM envelope signal to complete AM modulation;

[0165] Automatic gain control circuit, used to receive the gain control signal from automatic gain control circuit and amplify the AM amplitude modulation signal output by automatic level control circuit;

[0166] A power amplifier used to amplify the AM amplitude-modulated signal output from an automatic gain control circuit;

[0167] Frequency hopping filter is used to receive the frequency hopping filter segment code control signal and to filter out external interference signals from the AM amplitude modulation signal output by the power amplifier.

[0168] The first pin of the frequency hopping filter is connected to one end of the power amplifier, the other end of the power amplifier is connected to the first pin of the automatic gain control circuit, the second pin of the automatic gain control circuit is connected to the first pin of the automatic level control circuit, the second pin of the automatic level control circuit is connected to one end of the radio frequency signal source, the third pin of the automatic level control circuit is connected to the first pin of the digital potentiometer, and the second pin of the digital potentiometer is connected to the first pin of the digital-to-analog converter.

[0169] The AM detection and control link is used to generate control signals for the AM transmit link and to complete modulation depth calibration.

[0170] Specifically, the AM detection and control link includes: directional coupler, detector, low-pass filter, analog-to-digital converter, control processor, and storage medium;

[0171] A directional coupler is used to couple AM ​​(amplitude modulated) signals and output the coupled AM signal.

[0172] The detector is used to receive the coupled amplitude-modulated signal and output two AM envelope signals.

[0173] A low-pass filter is used to filter the AM envelope signal and input it to the automatic level control circuit.

[0174] An analog-to-digital converter is used to convert AM envelope signals into AM envelope digital signals.

[0175] The control processor is used to perform AM modulation depth calibration on the received AM envelope digital signal and output carrier frequency control signal, frequency hopping filter segment code control signal, digital potentiometer range control signal, digital-to-analog converter gain control signal, calibration sequence signal, storage medium control signal and automatic gain control circuit gain control signal.

[0176] Storage medium, used to receive storage medium control signals and store control parameters for AM modulation depth calibration;

[0177] One end of the directional coupler is connected to the second pin of the frequency hopping filter, and the other end of the directional coupler is connected to one end of the detector. The other end of the detector is connected to one end of the low-pass filter and one end of the analog-to-digital converter. The other end of the low-pass filter is connected to the fourth pin of the automatic level control circuit. The other end of the analog-to-digital converter is connected to the first pin of the control processor. The second, third, and fourth pins of the control processor are connected to one end of the storage medium. The fifth pin of the control processor is connected to the third pin of the digital potentiometer. The sixth pin of the control processor is connected to the second pin of the digital-to-analog converter. The seventh pin of the control processor is connected to the third pin of the digital-to-analog converter. The eighth pin of the control processor is connected to the other end of the RF signal source. The ninth pin of the control processor is connected to the third pin of the frequency hopping filter. The tenth pin of the control processor is connected to the third pin of the automatic gain control circuit.

[0178] In summary, the AM transmit signal modulation depth calibration method and apparatus proposed in this invention are highly efficient, accurate, and low-cost. They can be applied to the calibration of transmit power and modulation depth of AM transmitters and are suitable for large-scale deployment on production lines. The key aspects lie in the carrier signal amplitude calibration method and the calibration of the modulation signal amplitude. Furthermore, the larger the dynamic range of the AGC in the apparatus, the higher the AM transmit power calibration accuracy; the larger the dynamic range of the DAC output gain, the smaller the gain adjustment step, and the more adjustable levels the digital potentiometer can have, the higher the AM modulation depth calibration accuracy.

[0179] In this invention, AM transmit power detection reduces the redundancy of the AM envelope digital signal data through digital downsampling, saving hardware resources of the control processor. Then, the digitally downsampled AM envelope digital signal is input into a digital low-pass filter, and the digital low-pass filter outputs the amplitude voltage U of the AM carrier signal. The AM transmit power is calculated using the mean square value of the amplitude voltage U of the carrier signal. The digital low-pass filter includes, but is not limited to, IIR filters and FIR filters. The sampling frequency of the digitally downsampled AM envelope digital signal only needs to satisfy the low-pass sampling theorem.

[0180] In this invention, the gradient descent method is used for carrier signal amplitude calibration, and the AM transmit power P detected twice is used. i Pi-1 The AGC gain G set before and after. i G i-1 Perform gradient calculation and detect power P i With target power P opt The difference ∆P i The sign of the gradient descent method determines the iterative optimization direction, and the step size α is... i The step size α is inversely proportional to the number of AM transmit power detections (i), ensuring both optimization speed and accuracy. i The relationship between the number of AM transmit power detections (i) and other functions includes, but is not limited to, an inverse proportional function relationship, requiring only a step α. i The value can be decreased as the number of AM transmit power detections (i) increases.

[0181] This invention calibrates the amplitude of the modulated signal through two-stage adjustment of the DAC output gain and the digital potentiometer range. The DAC output gain G... q Adjust the gain step ∆G with a negative slope to maintain the DAC output gain G. q With the setting unchanged, the gradient descent method is used to optimize the digital potentiometer setting S. k Using the AM modulation depth MD detected in the two tests before and after k MD k-1 and the digital potentiometer setting S before and after. k S k-1 Gradient calculation is performed to detect the modulation depth MD. k With target modulation depth MD opt The difference ∆MD k The sign of the gradient descent method determines the iterative optimization direction, and the step size β is... k The number of AM modulation depth detections, k, is also inversely proportional to the given number of detections, ensuring both optimization speed and accuracy. The step β... k The relationship between the number of AM modulation depth detections k and other functions includes, but is not limited to, an inverse proportional function relationship, requiring only a step β. k The value can be decreased as the number of AM modulation depth detections k increases.

[0182] In summary, by employing the above-mentioned technical solutions of this invention, the modulation depth of the AM transmitted signal meets the corresponding standard requirements through both carrier signal amplitude calibration and modulation signal amplitude calibration. This improves the accuracy of the AM transmitter's transmit power and modulation depth, thereby enhancing the transmission quality and power utilization of the AM transmitted signal and ensuring signal transmission efficiency. Furthermore, this invention utilizes a low-cost carrier signal amplitude and modulation signal amplitude calibration method, eliminating the need for expensive instruments such as spectrum analyzers and power meters, making it suitable for large-scale deployment on production lines. Moreover, by performing carrier signal amplitude calibration before modulation signal amplitude calibration, the automatic level control circuit ensures that modulation signal amplitude calibration is performed under an accurate power reference signal, significantly reducing the impact of AM transmit power fluctuations on the AM modulation depth. This invention improves the accuracy of AM modulation depth calibration by using digital downsampling and digital low-pass filters in the carrier signal amplitude calibration method. This reduces noise power and improves AM transmit power detection accuracy while saving hardware resources. Furthermore, it optimizes the AGC control gain using the gradient descent method, improving the calibration accuracy of the carrier signal amplitude while ensuring optimization speed. In the modulation signal amplitude calibration method, this invention increases the total adjustment range of variables during modulation signal amplitude calibration by using two-stage control of DAC output gain and digital potentiometer range, resulting in higher calibration accuracy. At the same time, the adjustment of the digital potentiometer range uses the gradient descent method, improving the calibration accuracy of the modulation signal amplitude while ensuring optimization speed.

[0183] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calibrating the modulation depth of an AM transmitted signal, characterized in that, The method includes: S1. Initialize the AM transmission link according to the control signal sent by the AM detection and control link to obtain the initial AM amplitude modulation signal; S2. Perform signal conversion on the initial AM amplitude modulation signal to obtain the AM envelope digital signal, and perform preliminary AM carrier signal and modulation signal amplitude calibration based on the AM envelope digital signal to obtain preliminary amplitude calibration results. S2 includes: S21. Perform a coupling operation on the initial AM amplitude modulation signal, obtain the AM envelope signal using a detector based on the coupling operation result, and perform signal conversion on the AM envelope signal to obtain the AM envelope digital signal. S22. Perform digital downsampling and filtering on the AM envelope digital signal to obtain the carrier signal amplitude voltage, and perform AM transmit power detection on the carrier signal amplitude voltage. Based on the detection results, perform preliminary AM carrier signal amplitude calibration to obtain the interactive signal. S22 includes: S221. Digitally downsample the AM envelope digital signal to obtain the downsampled AM envelope digital signal, and use a digital low-pass filter to filter the downsampled AM envelope digital signal to obtain the carrier signal amplitude voltage. S222. Initialize the number of AM transmit power detections, and set the AGC control gain for AM transmit power detection based on the number of detections. Perform AM transmit power detection on the carrier signal amplitude voltage to obtain the detection result. S223. Calculate the power difference based on the detection results, and make a power fluctuation judgment on the power difference. Based on the power fluctuation judgment result, perform preliminary AM carrier signal amplitude calibration to obtain the interactive signal. S23. Based on the interactive signal, the AM modulation depth of the AM envelope digital signal is detected to obtain the AM modulation depth. Based on the AM modulation depth, the amplitude of the AM modulation signal is preliminarily calibrated to obtain the preliminary AM modulation signal amplitude calibration result. S23 includes: S231. Based on the interactive signal, set the number of AM modulation depth detections and the number of DAC output gain adjustments; S232. Set the adjusted DAC output gain according to the number of DAC output gain adjustments, and set the digital potentiometer setting for AM modulation depth detection according to the number of AM modulation depth detections. S233. Perform AM modulation depth detection on the AM envelope digital signal to obtain the AM modulation depth, calculate the modulation depth difference based on the AM modulation depth, and judge the modulation depth fluctuation of the modulation depth difference. S234. Based on the modulation depth fluctuation judgment result, perform preliminary AM modulation signal amplitude calibration to obtain preliminary AM modulation signal amplitude calibration result; S3. Based on the preliminary amplitude calibration results, generate the control signal for the AM transmission link. According to the control signal of the AM transmission link, traverse the working frequency range of the AM transmission link and execute S2 point by point to complete the AM modulation depth calibration.

2. The AM transmission signal modulation depth calibration method according to claim 1, characterized in that, The control signals sent by the AM detection and control link include carrier frequency control signals, frequency hopping filter segment code control signals, digital potentiometer range control signals, digital-to-analog converter gain control signals, and automatic gain control circuit gain control signals.

3. The AM transmission signal modulation depth calibration method according to claim 1, characterized in that, The preliminary AM carrier signal amplitude calibration based on the power fluctuation judgment result yields the following interactive signals: If the power fluctuation judgment result is that the power difference meets the power fluctuation requirements, then the setting parameters of the AGC control gain are stored in the storage medium to complete the preliminary carrier signal amplitude calibration and obtain the interactive signal. If the power fluctuation judgment result is that the power difference does not meet the power fluctuation requirements, then it is determined whether the number of AM transmit power detections is greater than or equal to the maximum value of the number of AM transmit power detections. If the number of AM transmit power detections is greater than or equal to the maximum number of AM transmit power detections, the setting parameters of the AGC control gain are stored in the storage medium to complete the initial carrier signal amplitude calibration and obtain the interactive signal. If the number of AM transmit power detections is less than the maximum number of AM transmit power detections, then the gradient descent method is used to update the AGC control gain to obtain the updated AGC control gain. The updated AGC control gain is dynamically ranged, and the updated AGC control gain is adjusted based on the dynamic range judgment result to obtain the adjusted AGC control gain. After the AGC control gain is updated and adjusted, the number of AM transmit power detections is updated, and the power fluctuation judgment and AGC control gain update process are repeated to obtain the final AGC control gain. The final AGC control gain settings are stored in the storage medium to complete the initial carrier signal amplitude calibration and obtain the interactive signal.

4. The AM transmission signal modulation depth calibration method according to claim 1, characterized in that, The preliminary AM modulation signal amplitude calibration based on the modulation depth fluctuation judgment result yields the following preliminary AM modulation signal amplitude calibration results: If the modulation depth fluctuation judgment result is that the modulation depth meets the modulation depth fluctuation requirement, the adjusted DAC output gain and the setting parameters of the digital potentiometer range are stored in the storage medium to complete the preliminary modulation signal amplitude calibration and obtain the preliminary AM modulation signal amplitude calibration result. If the modulation depth fluctuation judgment result is that the modulation depth does not meet the modulation depth fluctuation requirement, then it is determined whether the number of AM modulation depth detections is greater than or equal to the maximum value of the number of AM modulation depth detections. If the number of AM modulation depth detections is less than the maximum number of AM modulation depth detections, the gradient descent method is used to update the digital potentiometer range, and the updated digital potentiometer range is judged and adjusted to obtain the adjusted digital potentiometer range. If the number of AM modulation depth detections is greater than or equal to the maximum number of AM modulation depth detections, then determine whether the adjusted DAC output gain is less than or equal to the minimum DAC output gain; if the adjusted DAC output gain is less than or equal to the minimum DAC output gain, then store the adjusted DAC output gain and the setting parameters of the digital potentiometer range in the storage medium to complete the preliminary modulation signal amplitude calibration and obtain the preliminary AM modulation signal amplitude calibration result. If the adjusted DAC output gain is greater than the minimum DAC output gain, then the adjusted DAC output gain is subtracted from the DAC gain adjustment step, and the updated DAC output gain is range-determined and adjusted to obtain the adjusted DAC output gain. Based on the adjusted digital potentiometer setting and the adjusted DAC output gain, the modulation depth fluctuation judgment and digital potentiometer setting and DAC output gain update processing are repeatedly performed to complete the preliminary modulation signal amplitude calibration and obtain the preliminary AM modulation signal amplitude calibration result.

5. An AM transmission signal modulation depth calibration apparatus, used to implement the AM transmission signal modulation depth calibration method according to any one of claims 1-4, characterized in that, The AM transmission signal modulation depth calibration device includes: an AM transmission link and an AM detection and control link; The AM transmission link is used to receive the control signal output by the AM detection and control link and output the AM amplitude modulation signal. The AM detection and control link is used to generate control signals to control the AM transmission link and complete modulation depth calibration; One end of the AM transmission link is connected to one end of the AM detection and control link.

6. The AM transmission signal modulation depth calibration device according to claim 5, characterized in that, The AM transmission link includes: a frequency hopping filter, a power amplifier, an automatic gain control circuit, an automatic level control circuit, a digital potentiometer, a digital-to-analog converter, and an RF signal source; The digital-to-analog converter is used to receive a digital-to-analog converter gain control signal and a calibration sequence signal, and to output a first modulation signal; The digital potentiometer is used to receive a digital potentiometer range control signal and a first modulation signal, and to output a second modulation signal; The radio frequency signal source is used to receive carrier frequency control signals and output carrier signals; The automatic level control circuit is used to receive the carrier signal and the filtered AM envelope signal to complete AM modulation; The automatic gain control circuit is used to receive the gain control signal from the automatic gain control circuit and amplify the AM amplitude modulation signal output by the automatic level control circuit. The power amplifier is used to amplify the AM modulation signal output by the automatic gain control circuit; The frequency hopping filter is used to receive the frequency hopping filter segment code control signal and to filter out external interference signals from the AM amplitude modulation signal output by the power amplifier. The first pin of the frequency hopping filter is connected to one end of the power amplifier, the other end of the power amplifier is connected to the first pin of the automatic gain control circuit, the second pin of the automatic gain control circuit is connected to the first pin of the automatic level control circuit, the second pin of the automatic level control circuit is connected to one end of the radio frequency signal source, the third pin of the automatic level control circuit is connected to the first pin of the digital potentiometer, and the second pin of the digital potentiometer is connected to the first pin of the digital-to-analog converter.

7. The AM transmission signal modulation depth calibration device according to claim 6, characterized in that, The AM detection and control link includes: a directional coupler, a detector, a low-pass filter, an analog-to-digital converter, a control processor, and a storage medium; The directional coupler is used to couple AM ​​amplitude-modulated signals and output the coupled amplitude-modulated signals. The detector is used to receive the coupled amplitude-modulated signal and output two AM envelope signals; The low-pass filter is used to filter the AM envelope signal and input it to the automatic level control circuit. The analog-to-digital converter is used to convert the AM envelope signal into an AM envelope digital signal; The control processor is used to perform AM modulation depth calibration on the received AM envelope digital signal and output carrier frequency control signal, frequency hopping filter segment code control signal, digital potentiometer range control signal, digital-to-analog converter gain control signal, calibration sequence signal, storage medium control signal and automatic gain control circuit gain control signal. The storage medium is used to receive storage medium control signals and store control parameters for AM modulation depth calibration. One end of the directional coupler is connected to the second pin of the frequency hopping filter, and the other end of the directional coupler is connected to one end of the detector. The other end of the detector is connected to one end of the low-pass filter and one end of the analog-to-digital converter. The other end of the low-pass filter is connected to the fourth pin of the automatic level control circuit. The other end of the analog-to-digital converter is connected to the first pin of the control processor. The second, third, and fourth pins of the control processor are connected to one end of the storage medium. The fifth pin of the control processor is connected to the third pin of the digital potentiometer. The sixth pin of the control processor is connected to the second pin of the digital-to-analog converter. The seventh pin of the control processor is connected to the third pin of the digital-to-analog converter. The eighth pin of the control processor is connected to the other end of the radio frequency signal source. The ninth pin of the control processor is connected to the third pin of the frequency hopping filter. The tenth pin of the control processor is connected to the third pin of the automatic gain control circuit.

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