I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation

Abstract

The invention discloses an I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation. The I / Q imbalance distortion suppression phase demodulation system comprises an I / Q mixer, an I channel conditioning circuit, a Q channel conditioning circuit, an I channel analog-to-digital converter, a Q channel analog-to-digital converter, a direct digital frequency synthesizer and a microcontroller, the microcontroller comprises an arc tangent module, a carrier frequency generation module, a residual phase calibration module, a feedback control output module and a demodulation phase output module. According to the I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation, the target of closed-loop control is modified, and on the basis of tracking the phase of an input signal, the mixed signal is modulated on one frequency through feedback control, so that on one hand, the signal is separated from low-frequency noise, and on the other hand, the frequency of the signal is reduced; and on the other hand, the nonlinear harmonic is modulated on the carrier frequency, so that the amplitude of the nonlinear harmonic component is greatly reduced, low-frequency noise floor deterioration is avoided, and signal detection and extraction are facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of phase demodulation detection, and in particular relates to an I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation. Background Art

[0002] In advanced sensor systems, phase modulation sensors convert target signals into phase modulation signals, which have the advantages of high sensitivity and strong anti-interference ability. They can achieve high-precision detection of tiny physical quantities, vibrations, pressure and other parameters, and are widely used in aerospace, precision manufacturing, earthquake monitoring, biomedicine and other fields. Therefore, the application of phase modulation sensors puts forward higher requirements for accuracy, real-time and robustness of phase demodulation technology to ensure the reliability and stability of signal detection, and further promote the technical development and practical application of advanced sensor systems.

[0003] In the field of phase demodulation detection technology, phase demodulation structures based on orthogonal I / Q signals are widely used, which are further subdivided into direct digital sampling structures and zero intermediate frequency structures. The direct digital sampling structure directly samples the RF signal through a high-speed A / D converter, and completes phase demodulation by combining the digital local oscillator signal with a digital phase-locked loop (DPLL). This structure simplifies the hardware design and avoids the impact of analog device defects on the signal, but the sampling noise and bandwidth limitations of the high-speed A / D converter reduce its application in high-performance sensing systems. The zero intermediate frequency structure directly converts the RF signal into a baseband I / Q signal through an analog orthogonal local oscillator, and performs digital phase demodulation after sampling by a high-performance A / D converter. Although its sampling resolution and noise performance are better than those of the direct digital sampling structure, the imbalance of the analog I / Q path will destroy the orthogonality of the signal, and the low-frequency 1 / f noise of the analog device will alias the signal, causing problems such as image interference, noise increase, and reduced detection signal-to-noise ratio. At present, there is a lack of in-depth analysis on the problem of detection performance degradation caused by I / Q imbalance in sensor systems, and there is a lack of effective measures to improve the degradation of analog signal I / Q imbalance on high-performance phase demodulation detection, which limits the performance improvement of advanced sensor systems. Summary of the invention

[0004] The present invention provides an I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation to solve the above-mentioned technical problems, and specifically adopts the following technical solutions:

[0005] An I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation, comprising: an I / Q mixer, an I channel conditioning circuit, a Q channel conditioning circuit, an I channel analog-to-digital converter, a Q channel analog-to-digital converter, a direct digital frequency synthesizer and a microcontroller;

[0006] The I / Q mixer modulates the phase of the signal to be measured. The direct digital frequency synthesizer generates a reference local oscillator signal Perform mixing operation to output orthogonal I / Q two-way analog signal, the phase modulation signal to be measured The phase modulation part is expressed as ;

[0007] The I / Q two-way analog signals are amplified and filtered by the I / Q channel conditioning circuit respectively, and then transmitted to the analog-to-digital converter for sampling and quantization to obtain digital I / Q voltage signals. and , transmitted to the microcontroller;

[0008] The microcontroller comprises an inverse tangent module, a carrier frequency generation module, a residual phase calibration module, a feedback control output module and a demodulation phase output module;

[0009] The inverse tangent module performs digital quantization on the voltage signal and Perform inverse tangent phase calculation to extract the phase difference information contained in the I / Q signal The carrier frequency generation module uses a sampling rate For the beat, at a fixed frequency Generates a phase value accumulated over time , and output it to the residual phase calibration module for residual phase separation, removing the solved phase residual information In part, only the signal to be tested is retained Phase tracking residual caused by dynamics , phase tracking residual The feedback control output module is input to calculate the feedback control amount to configure the direct digital frequency synthesizer in real time, thereby controlling the real-time phase of the direct digital frequency synthesizer. To achieve phase tracking demodulation of the input signal, phase tracking residual Input demodulation phase output module, the demodulation phase output module combines the phase difference information and feedback control quantity to generate the final phase demodulation result .

[0010] Furthermore, the I / Q mixer modulates the phase of the signal to be measured. The reference local oscillator signal generated by the direct digital frequency synthesizer A mixing operation is performed to generate sum frequency and difference frequency components, wherein the difference frequency component converts the high-frequency signal to baseband to obtain two-way I / Q analog signals that are spatially orthogonal to each other for subsequent phase demodulation.

[0011] Furthermore, the I / Q channel conditioning circuit amplifies and low-pass filters the I / Q signal output by the I / Q mixer, amplifies the signal level to adapt to the input level range of the subsequent analog-to-digital converter, improves detectability, and filters out the mixer sum frequency component while achieving anti-aliasing filtering and retains the difference frequency component.

[0012] Further, the I / Q channel analog-to-digital converter has a sampling rate of The I / Q voltage output by the conditioning circuit is quantized and sampled to obtain a digitally quantized voltage signal.

[0013] Furthermore, the direct digital frequency synthesizer dynamically adjusts the phase-frequency characteristics of its output in real time under the digital control of the microcontroller, and the digital control frequency and sampling frequency are The adjustment method of the direct digital frequency synthesizer is to use only frequency control, through each control cycle The integration of the frequency adjustment amount obtains the phase adjustment amount, thereby realizing the tracking of the phase modulation part of the signal to be measured.

[0014] Furthermore, a reconstruction filter is cascaded at the output end of the direct digital frequency synthesizer, and the bandwidth covers the output nominal frequency, so as to effectively remove possible spurious signals and noise, thereby improving the signal quality and spectrum purity of the output end of the direct digital frequency synthesizer.

[0015] Furthermore, the I / Q channel conditioning circuit and the I / Q channel analog-to-digital converter maintain consistency in device selection and maintain symmetry in circuit design, thereby reducing the imbalance of the I / Q signal and avoiding excessive degradation of the orthogonality of the I / Q signal.

[0016] Furthermore, the analog bandwidth design of the I / Q channel conditioning circuit comprehensively considers the feedback control algorithm design of the microcontroller. The phase part of the I / Q channel signal in the closed-loop system is represented by the superposition of the residual phase and the linear growth phase introduced by the control carrier frequency, that is, The maximum frequency deviation caused by this phase part can be expressed as , the bandwidth of the analog conditioning is greater than or equal to .

[0017] Furthermore, the inverse tangent module performs inverse tangent calculation on the quantized I / Q voltage signal, using the Arctangent function to achieve Phase calculation of the range to obtain the phase difference information contained in the I / Q signal .

[0018] The carrier frequency generation module is further configured to generate a sampling rate For the beat, at a fixed frequency Generates a phase value accumulated over time ;

[0019] The phase accumulation module is at a sampling rate As the beat, a phase value accumulated over time is generated, which is then output to the feedback control output module for feedback control quantity calculation;

[0020] The feedback control output module combines the phase difference information obtained by the inverse tangent module with the phase accumulation value output by the phase accumulation module to calculate the feedback control amount and feed it back to the direct digital frequency synthesizer, dynamically adjusts the phase-frequency characteristics output by the direct digital frequency synthesizer, on the one hand, tracks the phase modulation part of the signal to be measured, and on the other hand, introduces a control carrier frequency into the I / Q signal output by the mixer to form a carrier frequency modulation of the I / Q signal;

[0021] The demodulation phase output module combines the phase difference information obtained by the inverse tangent module with the feedback control amount output by the feedback control output module to restore and estimate the phase modulation information of the signal to be measured, thereby realizing phase demodulation and output.

[0022] The I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation of the present application modifies the target of closed-loop control. On the basis of tracking the phase of the input signal, the mixed signal is modulated on a frequency through feedback control. On the one hand, the signal is distinguished from the low-frequency noise, and on the other hand, the nonlinear harmonics are modulated on this carrier frequency, thereby greatly reducing the amplitude of the nonlinear harmonic components. The combination of the two avoids the deterioration of the low-frequency noise floor and is beneficial to signal detection and extraction.

[0023] The I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation of the present application introduces a direct digital frequency synthesizer to generate the local oscillator signal on the basis of the traditional zero intermediate frequency I / Q phase demodulation structure. The local oscillator signal generated by the DDS dynamically adjusts its phase and frequency in real time under the control of the controller, accurately tracks the phase modulation part of the signal to be detected, thereby effectively suppressing the phase fluctuation in the analog I / Q signal and compressing the bandwidth of the I / Q signal. This method significantly suppresses the nonlinear distortion caused by I / Q imbalance, and at the same time reduces the bandwidth requirements of the analog signal acquisition circuit by compressing the signal bandwidth. On the one hand, the use of low-noise analog devices (such as op amps and ADCs) helps to optimize the detection noise of the system; on the other hand, it simplifies the design of analog conditioning circuits, avoids dependence on high-speed ADCs, and reduces the design cost of the demodulation system.

[0024] The benefit of the present invention lies in the I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation provided, which combines analog zero-difference carrier phase tracking with residual carrier frequency modulation, combines the advantages of zero-difference closed-loop tracking in the expansion of detection dynamic range and nonlinear improvement, and combines the carrier frequency modulation method to modulate the phase residual after zero-difference closed-loop tracking to a fixed carrier frequency to construct a carrier frequency closed-loop phase demodulation structure. This structure effectively eliminates the problems of I / Q imbalance, local oscillator leakage, low-frequency flicker noise and image interference caused by analog components in the I / Q channel, thereby suppressing the detection noise floor in the entire frequency range and ensuring high-precision detection and extraction of signals. This structure does not require complex I / Q imbalance digital estimation and compensation algorithms, reduces the requirements for algorithm performance and ensures real-time performance. At the same time, the carrier frequency closed-loop phase demodulation structure effectively compresses the bandwidth of the I / Q signal by suppressing the phase fluctuation in the analog I / Q signal, and reduces the requirements for the bandwidth of the analog signal acquisition circuit. On the one hand, the use of low-noise analog devices (such as op amps and ADCs) helps optimize the detection noise of the system; on the other hand, it simplifies the design of analog conditioning circuits, avoids dependence on high-speed ADCs, and reduces the design cost of the demodulation system. In summary, the proposed I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation, combined with the control algorithm, introduces the control carrier frequency on the basis of tracking the phase modulation of the signal to be measured, and finally realizes the carrier frequency closed-loop tracking demodulation of the baseband I / Q signal, successfully solves the signal demodulation distortion problem caused by I / Q signal imbalance, and improves the system detection signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0026] Figure 1 It is a schematic diagram of an I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation of the present invention;

[0027] Figure 2 It is a schematic diagram of an embodiment of an I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation of the present invention;

[0028] Figure 3 This is a frequency domain simulation diagram of the phase detection result of an embodiment of the present invention, including a comparison with a traditional zero-IF phase detection structure.

[0029] An I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation includes a phase modulation signal input 1, an I / Q mixer 2, an I channel conditioning circuit 3, a Q channel conditioning circuit 4, an I channel analog-to-digital converter (ADC) 5, a Q channel analog-to-digital converter (ADC) 6, a direct digital frequency synthesizer (DDS) 7, a microcontroller 8, an inverse tangent module 801, a carrier frequency generation module 802, a residual phase calibration module 803, a feedback control output module 804 and a demodulation phase output module 805. DETAILED DESCRIPTION

[0030] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0031] like Figure 1 As shown, an I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation of the present application comprises: a phase modulation signal input 1, an I / Q mixer 2, an I channel conditioning circuit 3, a Q channel conditioning circuit 4, an I channel analog-to-digital converter (ADC) 5, a Q channel analog-to-digital converter (ADC) 6, a direct digital frequency synthesizer (DDS) 7 and a microcontroller 8. Among them, the microcontroller 8 comprises an inverse tangent module 801, a carrier frequency generation module 802, a residual phase calibration module 803, a feedback control output module 804 and a demodulation phase output module 805. The I / Q mixer 2 converts the phase modulation signal 1 to be measured into a phase modulation signal 1. The reference local oscillator signal generated by the direct digital synthesizer (DDS) 7 Perform mixing operation and output a pair of orthogonal voltage signals ( and ), the I channel conditioning circuit 3 and the Q channel conditioning circuit 4 perform signal conditioning on the I / Q voltage signal, complete the amplification and low-pass filtering of the analog signal, amplify the signal level to adapt to the input level range of the subsequent ADC, improve the detectability, and obtain the I / Q voltage output by the conditioning circuit ( and ), the I channel analog-to-digital converter (ADC) 5 and the Q channel analog-to-digital converter (ADC) 6 digitally sample the conditioned analog I / Q voltage signal to obtain a digitally quantized voltage signal ( and ), which is transmitted to the microcontroller 8. The microcontroller 8 is responsible for digital logic operations, wherein the inverse tangent module 801 performs digital quantization on the voltage signal ( and ) to perform phase calculation to extract the phase difference information contained in the I / Q signal The carrier frequency generation module 802 uses a sampling rate For the beat, at a fixed frequency Generates a phase value accumulated over time ( ), and output it to the residual phase calibration module 803 for residual phase separation, removing the calculated phase residual information In part, only the signal to be tested is retained Phase tracking residual caused by dynamics . Then, The input feedback control output module 804 calculates the feedback control amount to configure the DDS in real time, thereby controlling the real-time phase of the DDS ( ) to achieve phase tracking demodulation of the input signal. At the same time, Input demodulation phase output module 805, by combining the control output and the phase tracking residual, generates the final phase demodulation result .

[0032] Specifically, the phase difference between the measured signal and the local oscillator signal is obtained by solving the four-quadrant inverse tangent algorithm: The obtained phase difference is further transmitted to the closed-loop controller, which calculates the feedback control output based on the control algorithm and dynamically adjusts the phase of the DDS output signal in real time. The control objective of closed-loop control combines zero-difference phase closed-loop tracking with residual phase carrier frequency modulation. On the one hand, the DDS dynamically adjusts the output signal phase. To implement the phase modulation part of the input PM signal to be measured Real-time tracking of The dynamic adjustment part should be consistent with The fluctuations of On the other hand, based on the zero-difference phase closed-loop tracking, carrier frequency generation and residual phase carrier frequency modulation are introduced to further modulate the residual phase under the above-mentioned zero-difference phase closed-loop tracking at a fixed carrier frequency. On, the signal to be tested With the local oscillator signal Maintain a stable frequency difference between , thus realizing the closed-loop tracking demodulation of the carrier frequency of the input signal to be measured. At this time, the closed-loop residual phase contains two parts at the same time, The tracking residual part and the control carrier frequency The linear growth phase introduced is Finally, the demodulation phase output module combines the phase difference information calculated by the inverse tangent solution with the feedback control output information to output the phase demodulation result of the PM signal to be measured. Compared with the existing I / Q phase demodulation structure based on zero intermediate frequency, in the present invention, the local oscillator signal generator adopts DDS to realize dynamic phase-frequency modulation signal output, and the control algorithm introduces a control carrier frequency on the basis of tracking the phase modulation of the signal to be measured, which combines the advantages of zero-difference closed-loop tracking in the expansion of detection dynamic range and nonlinear improvement, and combines the carrier frequency modulation method to secondary modulate the phase residual after zero-difference closed-loop tracking on the fixed carrier frequency, construct a carrier frequency closed-loop phase demodulation structure, realize the carrier frequency closed-loop tracking and demodulation of the baseband I / Q signal, and specifically solve the signal demodulation distortion problem caused by I / Q signal imbalance.

[0033] like Figure 2 The figure shows an embodiment of the I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation of the present invention. The I / Q mixer 2 converts the phase modulation signal 1 to be measured into The reference local oscillator signal generated by the direct digital synthesizer (DDS) 7 Perform a mixing operation to obtain the orthogonal signal of the mixing output ( and ), including sum frequency component and difference frequency component. The phase modulation signal to be measured can be expressed as The orthogonal reference local oscillator signal generated by DDS can be expressed in complex form .in, and represents the voltage amplitude of the signal used for mixing, represents the nominal carrier frequency of the signal, represents the phase part of the phase modulated signal to be detected, It represents the phase part of the reference local oscillator signal generated by DDS. The difference frequency component in the mixer output converts the carrier signal into a baseband signal to obtain a pair of mutually orthogonal I / Q signals for subsequent phase demodulation. The sum frequency component is not a signal required for phase detection and is filtered out by the low-pass filter at the rear stage of the I / Q mixer.

[0034] The I channel conditioning circuit 3 and the Q channel conditioning circuit 4 condition the I / Q signal output by the I / Q mixer, complete the amplification and low-pass filtering of the analog signal, amplify the signal level to match the input level range of the subsequent ADC, improve the detectability, and obtain the I / Q voltage output by the conditioning circuit. At the same time, while realizing the anti-aliasing filtering before signal sampling, the mixer and frequency components are further filtered out, and the difference frequency components are retained. Due to the imperfections of the analog devices themselves and the error limitations of processing, the I / Q channel output has unavoidable amplitude imbalance, phase imbalance and DC offset, and the orthogonality is degraded. At this time, the I / Q voltage output by the conditioning circuit ( and ) is affected by the I / Q channel imbalance and noise, and is expressed as follows. represents the low-pass filter function, represents the gain imbalance coefficient, represents the phase imbalance coefficient, and represents the DC bias voltage of the I / Q signal, and Indicates an independent noise signal superimposed on the I / Q signal.

[0035]

[0036] The I / Q channel conditioning circuit and the I / Q channel analog-to-digital converter maintain consistency in device selection and maintain symmetry in circuit design, thereby reducing the imbalance of the I / Q signal and avoiding excessive degradation of the orthogonality of the I / Q signal.

[0037] The analog bandwidth design of the I / Q channel conditioning circuit comprehensively considers the feedback control algorithm design of the microcontroller. The phase part of the I / Q channel signal in the closed-loop system is expressed as the superposition of the residual phase and the linear growth phase introduced by the control carrier frequency, that is, The maximum frequency deviation caused by this phase part can be expressed as , the bandwidth of the analog conditioning is greater than or equal to .

[0038] The I channel analog-to-digital converter (ADC) 5 and the Q channel analog-to-digital converter (ADC) 6 are configured to be sampled at a rate of The I / Q voltage output by the conditioning circuit ( and ) to perform quantization sampling and obtain the digitally quantized voltage signal ( and ), where n represents the nth sampling moment, that is, , Corresponding to the sampling interval, the voltage signal after digital quantization is expressed as follows.

[0039]

[0040] The microcontroller 8 first performs an inverse tangent calculation on the quantized I / Q voltage signal through the inverse tangent module 801 to obtain the phase difference information contained in the I / Q signal. , expressed as: The Atan2 function is a four-quadrant inverse tangent function. It can calculate the polar coordinate angle (in radians) relative to the origin based on the input I / Q value. The phase detection range is , which can solve the quadrant identification problem.

[0041] Furthermore, the carrier frequency generation module 802 uses a sampling rate For the beat, at a fixed frequency Generates a phase value accumulated over time ( ), specifically, the carrier frequency generation module uses a digitally controlled oscillator (NCO) for generation. The digitally quantized phase accumulation output is , indicating the The phase accumulation value at each sampling moment.

[0042] Furthermore, the residual phase calibration module 803 integrates the residual phase information output by the inverse tangent module 801 The phase information output by the carrier frequency generation module 802 , perform residual phase separation and remove the solved phase residual information In part, only the signal to be tested is retained Phase tracking residual caused by dynamics Specifically, the residual phase after separation is expressed as .

[0043] Furthermore, the feedback control output module 804 is based on the separated residual phase , calculate the feedback control quantity. The feedback control quantity is used to configure the DDS in real time, thereby controlling the real-time phase of the DDS ( ) to achieve phase tracking demodulation of the input signal. Specifically, the real-time phase output of DDS is an integral output, and the control output of each sampling cycle is It can be expressed as the following formula. Under the control output accumulation in each sampling cycle, the real-time phase output of DDS As shown in the following formula.

[0044]

[0045] Furthermore, the demodulation phase output module 805 generates the final phase demodulation result by combining the control output and the phase tracking residual. Specifically, the final phase demodulation result is expressed as .

[0046] Furthermore, the direct digital frequency synthesizer (DDS) 7 dynamically modulates its output phase and frequency under the real-time control of the microcontroller 8. A reconstruction filter is cascaded at its output end, and the bandwidth covers the output nominal frequency to effectively remove possible spurious signals and noise, thereby improving the signal quality and spectrum purity at the output end of the direct digital frequency synthesizer (DDS) 7. The adjustment method of the direct digital frequency synthesizer (DDS) 7 is to use only frequency control, and each control cycle The integration of the frequency adjustment amount obtains the phase adjustment amount, thereby realizing the tracking of the phase modulation part of the signal to be measured.

[0047] Furthermore, the real-time phase output of the direct digital synthesizer (DDS) 7 It also includes the input phase modulation part to be measured The residual error of the tracking and the fixed frequency introduced by the phase accumulation module At this time, compared with the traditional zero-IF structure, the phase tracking residual is modulated at a fixed frequency On, that is A fixed frequency is superimposed on . DC bias voltage of I / Q signal and and independent noise signals superimposed on the I / Q signals and It can be separated from the signal in the frequency domain, thus avoiding the deterioration of the detection signal-to-noise ratio due to noise coupling. At the same time, due to the closed-loop frequency modulation, the nonlinear effect caused by the unbalanced nonlinearity of the I / Q signal is reduced, so that the intensity of the nonlinear harmonic component in the detection spectrum is greatly attenuated, thereby ensuring the total harmonic distortion of the detection and improving the detection performance.

[0048] The frequency domain simulation diagram of the phase detection result of one embodiment of the present invention is as follows: Figure 3 As shown in Figure 1, it includes a comparison with the traditional zero-IF phase detection results. The phase part of the phase modulation signal to be detected is , that is, the modulation frequency is 57 Hz, and the modulation depth is 1 radian. The phase spectrum curve obtained by demodulation based on the zero intermediate frequency method is represented by a black dotted line, and the phase spectrum curve obtained by demodulation based on the carrier frequency closed-loop modulation method of the present invention is represented by a black solid line. It can be seen that there are a large number of 57 Hz nonlinear distortion harmonics in the result obtained by phase demodulation based on the zero intermediate frequency method, while there are only clean 57 Hz spectral lines in the result obtained by phase demodulation based on the carrier frequency closed-loop modulation method of the present invention. At the same time, it can be seen from the signal detection noise floor in the low-frequency band that the carrier frequency closed-loop modulation method based on the present invention can achieve a lower detection noise floor and have a higher phase detection signal-to-noise ratio, thereby ensuring the weak signal detection performance of the phase modulation type advanced sensing system.

[0049] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. An I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation, characterized in that: include: I / Q mixer, I channel conditioning circuit, Q channel conditioning circuit, I channel analog-to-digital converter, Q channel analog-to-digital converter, direct digital frequency synthesizer and microcontroller; The I / Q mixer modulates the phase of the signal to be measured. The reference local oscillator signal generated by the direct digital frequency synthesizer is mixed to output orthogonal I / Q two-way analog signals, the phase modulation signal to be measured The phase modulation part is expressed as ; The I / Q two-way analog signals are amplified and filtered by the I / Q channel conditioning circuit respectively, and then transmitted to the analog-to-digital converter for sampling and quantization to obtain digital I / Q voltage signals. and , transmitted to the microcontroller; The microcontroller comprises an inverse tangent module, a carrier frequency generation module, a residual phase calibration module, a feedback control output module and a demodulation phase output module; The inverse tangent module performs digital quantization on the voltage signal and Perform inverse tangent phase calculation to extract the phase difference information contained in the I / Q signal The carrier frequency generation module uses a sampling rate For the beat, at a fixed frequency Generates a phase value accumulated over time , and output it to the residual phase calibration module for residual phase separation, removing the solved phase residual information In part, only the signal to be tested is retained Phase tracking residual caused by dynamics , phase tracking residual The feedback control output module is input to calculate the feedback control amount to configure the direct digital frequency synthesizer in real time, thereby controlling the real-time phase of the direct digital frequency synthesizer. To achieve phase tracking demodulation of the input signal, phase tracking residual Input demodulation phase output module, the demodulation phase output module combines the phase difference information and feedback control quantity to generate the final phase demodulation result .

2. The I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation according to claim 1, characterized in that: The I / Q mixer is a phase modulated signal to be measured. The reference local oscillator signal generated by the direct digital frequency synthesizer A mixing operation is performed to generate sum frequency and difference frequency components, wherein the difference frequency component converts the high-frequency signal to baseband to obtain two-way I / Q analog signals that are spatially orthogonal to each other for subsequent phase demodulation.

3. The I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation according to claim 1, characterized in that: The I / Q channel conditioning circuit amplifies and low-pass filters the I / Q signal output by the I / Q mixer, amplifies the signal level to adapt to the input level range of the subsequent analog-to-digital converter, and filters out the mixer sum frequency component while realizing anti-aliasing filtering and retaining the difference frequency component.

4. The I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation according to claim 1, characterized in that: The I / Q channel analog-to-digital converter is sampled at a rate The I / Q voltage output by the conditioning circuit is quantized and sampled to obtain a digitally quantized voltage signal.

5. The I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation according to claim 1, characterized in that: The direct digital frequency synthesizer dynamically adjusts the phase-frequency characteristics of its output in real time under the digital control of the microcontroller, and the digital control frequency and sampling frequency The adjustment method of the direct digital frequency synthesizer is to use only frequency control, through each control cycle The integral of the frequency adjustment amount is used to obtain the phase adjustment amount, thereby tracking the phase modulation part of the signal to be measured.

6. The I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation according to claim 1, characterized in that: A reconstruction filter is cascaded at the output end of the direct digital frequency synthesizer, and the bandwidth covers the output nominal frequency.

7. The I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation according to claim 1, characterized in that: The I / Q channel conditioning circuit and the I / Q channel analog-to-digital converter are consistent in device selection and symmetrical in circuit design.

8. The I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation according to claim 1, characterized in that: The analog bandwidth design of the I / Q channel conditioning circuit comprehensively considers the feedback control algorithm design of the microcontroller. The phase part of the I / Q channel signal in the closed-loop system is represented by the superposition of the residual phase and the linear growth phase introduced by the control carrier frequency, that is, The maximum frequency deviation caused by this phase part can be expressed as , the bandwidth of the analog conditioning is greater than or equal to .

9. The I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation according to claim 1, characterized in that: The inverse tangent module performs inverse tangent calculation on the quantized I / Q voltage signal using the Arctangent function to achieve Phase calculation of the range to obtain the phase difference information contained in the I / Q signal .

10. The I / Q imbalance distortion suppression phase demodulation system based on carrier frequency closed-loop modulation according to claim 1, characterized in that: The carrier frequency generation module uses the sampling rate For the beat, at a fixed frequency Generates a phase value accumulated over time ; The phase accumulation module is at a sampling rate As the beat, a phase value accumulated over time is generated, which is then output to the feedback control output module for feedback control quantity calculation; The feedback control output module combines the phase difference information obtained by the inverse tangent module with the phase accumulation value output by the phase accumulation module to calculate the feedback control amount and feed it back to the direct digital frequency synthesizer, dynamically adjusts the phase-frequency characteristics output by the direct digital frequency synthesizer, on the one hand, tracks the phase modulation part of the signal to be measured, and on the other hand, introduces a control carrier frequency into the I / Q signal output by the mixer to form a carrier frequency modulation of the I / Q signal; The demodulation phase output module combines the phase difference information obtained by the inverse tangent module with the feedback control amount output by the feedback control output module to restore and estimate the phase modulation information of the signal to be measured, thereby realizing phase demodulation and output.

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