CN115604063B - Demodulation method of high-speed maglev train communication system based on frequency-phase conversion - Google Patents
Demodulation method of high-speed maglev train communication system based on frequency-phase conversion Download PDFInfo
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Abstract
The invention discloses a demodulation method of a high-speed magnetic levitation train communication system based on frequency-phase conversion, which comprises the steps of firstly processing received signals by using a frequency-phase conversion technology, converting signal frequency differences corresponding to different code elements into differences in signal phases, then converting the differences in signal phases corresponding to different code elements into differences in voltage by using a phase discriminator, inputting the demodulated signals into a sampling detection module, comparing and judging whether the demodulation is abnormal or not by using a logic circuit, and controlling a frequency-phase conversion network to timely modulate abnormal conditions by using a control module to complete demodulation of CPFSK signals of the high-speed magnetic levitation train communication system. The method of the invention realizes the automation of CPFSK demodulation and detection and adjustment thereof, reduces the complexity and error rate of the system, enhances the reliability of the system, has the advantages of high efficiency, accuracy and rapidness, and ensures the correct information transfer of the magnetic levitation train in the running process.
Description
Technical Field
The invention belongs to the technical field of digital communication CPFSK signal modulation and demodulation, and particularly relates to a demodulation method of a high-speed magnetic levitation train communication system based on frequency-phase conversion.
Background
In the high-speed magnetic levitation train-ground communication system, a ground fixed base station and a vehicle-mounted mobile base station perform data interaction through wireless millimeter wave signals. The communication system has higher requirements on performances such as transmission delay, error rate, system reliability and the like, and the modulation and demodulation of wireless signals have larger influence on the communication performance.
In the normal operation process of the magnetic suspension train, the ground fixed base station receives the operation information sent by the vehicle-mounted mobile equipment, the operation information is transmitted to the ground partition control system, the ground control center returns the control information to the vehicle-mounted mobile equipment, and data interaction is carried out between the ground control center and the vehicle-mounted mobile equipment through a wireless channel, so that the modulation and demodulation of signals are of great importance.
CPFSK signals are modulation modes of the existing high-speed magnetic levitation train-ground communication system, have the characteristics of continuous phase change and insensitivity to frequency deviation caused by Doppler effect, and have the problems of high complexity, low frequency spectrum utilization rate, high error rate, high delay and the like because the existing method for researching CPFSK signals demodulation in the magnetic levitation train-ground communication system is relatively less in China and internationally.
In the existing CPFSK signal demodulation method, the coherent demodulation method multiplies the received signal with the carrier signal to transfer the information on the signal frequency to the amplitude of the signal, but the method needs to provide a local coherent carrier strictly synchronous with the received modulated signal at the receiving end of the system, so that the complexity of a demodulation part can be increased; the incoherent demodulation method, namely the envelope detection method, the CPFSK signal is regarded as superposition of two ASK signals, the two paths of the CPFSK signal are divided and are respectively distinguished by using envelope detection, the envelope detector usually comprises a full-wave rectifier and a low-pass filter, the method does not need a local coherent carrier, but the demodulation effect is sensitive to the signal-to-noise ratio of the input signal, the threshold effect exists, and the influence of a channel is larger when the method demodulates, so that the error rate of the demodulation process is higher; the zero-crossing detection method distinguishes two signal code elements with different frequencies by detecting the number of zero-crossing points, the method is more dependent on the performance of a zero-crossing detection circuit and is easy to be interfered, and in addition, the channel bandwidth required to be used is larger in order to ensure that the error rate of the zero-crossing detection method meets the requirement, so that the frequency spectrum utilization rate is low.
Disclosure of Invention
In order to solve the technical problems, the invention provides a demodulation method of a high-speed magnetic levitation train communication system based on frequency-phase conversion.
The invention adopts the technical scheme that: a demodulation method of a high-speed magnetic levitation train communication system based on frequency-phase conversion comprises the following specific steps:
S1, after the CPFSK signal is input into a demodulation device, the CPFSK signal is subjected to primary demodulation through a frequency-phase conversion device and a phase discriminator;
s2, detecting whether demodulation system demodulates normally or not through a sampling detection module, and judging whether adjustment is needed or not;
s3, the control module receives the instruction and the data sent by the sampling detection module and controls the frequency-phase conversion module to adjust;
And S4, after the frequency-phase conversion module is adjusted, repeating the steps S2 and S3 until the control module no longer receives an instruction needing adjustment, completing the adjustment process and outputting a demodulation signal.
Further, in the step S1, the specific steps are as follows:
s11, after receiving the signal, the demodulation device inputs the signal into the frequency-phase conversion module;
The frequency-phase conversion module is composed of a plurality of groups of adjustable resonators, different phase offsets are added to signals with different frequencies, and the phase offset is added to signals with the frequency of omega 1 The signal with frequency omega 2 increases the phase offset/>Thereby distinguishing between different frequencies.
S12, the output signal after the frequency-phase conversion module is input into the phase discrimination device together with the original signal;
In the phase detector, different phase-shifted signals will output different levels, the level of the output signal is proportional to the phase difference of the two input signals, and the phase shift is The level of the signal output is V 1, and the phase offset is/>The level of the signal output is V 2, the two levels have larger phase difference, and code element information carried by the signal is extracted according to the level size, so that decoding is finished.
Further, in the step S2, the specific steps are as follows:
S21, sampling the demodulation signal output by the phase demodulation module by the sampling detection module to obtain a sampling signal, and further judging whether the demodulation process is abnormal or not;
S22, comparing the magnitude of a sampling level V n of a certain sampling point with the magnitude of a standard level median V mid, and dividing the sampling level V n into a low-level sampling point and a high-level sampling point;
Firstly, setting a standard level median value V mid and V mid＝0.5(V1stand+V2stand), wherein V 1stand and V 2stand are standard values of a low level and a high level respectively, and if V n＜Vmid, determining that the sampling level at the sampling point corresponds to the low level; if V n＞Vmid, the sample level at that sample point is deemed to correspond to a high level. Transmitting a signal TYPE for discriminating the level TYPE to the backward detection circuit, wherein the signal TYPE is invalid and indicates a low level, and executing step S23; comparing the sampled level V n with the low level primary threshold V 1test and the low level secondary threshold V 1max, and if the signal TYPE is valid, indicating a high level, executing step S24, and comparing V n with the high level primary threshold V 2test and the low level secondary threshold V 2min.
S23, a first-level detection threshold V 1test、V2test and a second-level detection threshold V 1max、V2min corresponding to the low-level standard value V 1stand and the high-level standard value V 2stand are respectively set, a low-level abnormal sampling point counting parameter A and an upper limit A max thereof are set, and a high-level abnormal sampling point counting parameter B and an upper limit B max thereof are set.
If V n＜V1test is found that the low-level signal at the sampling point is normal, a command is not required to be sent to the control circuit to control the frequency-phase conversion module to adjust, the abnormal sampling point counting parameter A is reset to 0, and the same judgment is directly carried out on the sampling level V n+1 of the next sampling point; if V 1max＞Vn＞V1test is detected, the low level signal under the sampling point is abnormal, the counting parameter A of the low level abnormal sampling point is changed into A+1, then the sizes of A and A max are judged, if the value of A does not exceed the limit A max, the error code is not generated in low level demodulation temporarily, and the sampling level V n+1 of the next sampling point is judged in the same way; if the value of A exceeds the limit A max, the low level in the demodulated signal is considered to be immediately bit error, and a signal LWRONG needing to adjust the low level is sent to the control module; if V 1max＜Vn, the sampling level is considered to be very different from the standard low level, and error code is immediately generated, and a signal LWRONG for adjusting the low level is sent to the control module.
S24, if V n＞V2test is met, the high-level signal under the sampling point is considered to be normal, an instruction is not required to be sent to the control circuit to control the frequency-phase conversion module to adjust, the abnormal sampling point counting parameter B is reset to 0, and the same judgment is directly carried out on the sampling level V n+1 of the next sampling point; if V 2test＞Vn＞V2min is detected, the high level signal under the sampling point is abnormal, the counting parameter B of the high level abnormal sampling point is changed into B+1, then the sizes of B and B max are judged, if the value of B does not exceed the limit B max, the high level in the demodulation signal is considered to have error code for a period of time, and a command is not required to be sent to a control circuit to control a frequency-phase conversion module to adjust, so that the sampling level V n+1 of the next sampling point is directly judged to be the same; if the value of B exceeds the limit B max, the high level in the demodulated signal is considered to be immediately bit error, and a signal HWRONG needing to adjust the high level is sent to the control module; if V n＜V2min, the sampling level is considered to be very different from the standard high level, and error code is immediately generated, and a signal HWRONG for adjusting the high level is sent to the control module.
Further, in the step S3, the specific steps are as follows:
S31, if the control module receives an instruction of low level to be adjusted, the control module compares a level value V n of a sampling point at the effective moment of the instruction with a standard low level value V 1stand;
Calculating the difference value |V n-V1stand |, and then reversely deducing the phase difference needing to be adjusted and compensated by the relation between the output voltage of the phase discriminator and the phase difference of the input signal And further, according to the intermediate frequency phase transfer characteristic curve of the frequency phase conversion module, reversely calculating the frequency delta omega 1 needing to be offset, and then controlling the frequency phase conversion module to generate corresponding delta omega 1 offset to finish compensation.
S32, if the control module receives an instruction of high level to be adjusted, the control module compares a level value V n of a sampling point at the effective moment of the instruction with a standard high level value V 2stand;
Calculating the difference value |V n-V2stand |, and then reversely deducing the phase difference needing to be adjusted and compensated by the relation between the output voltage of the phase discriminator and the phase difference of the input signal And further, according to the intermediate frequency phase transfer characteristic curve of the frequency phase conversion module, reversely calculating the frequency delta omega 2 needing to be offset, and then controlling the frequency phase conversion module to generate corresponding delta omega 2 offset to finish compensation.
The invention has the beneficial effects that: the method of the invention firstly uses the frequency-phase conversion technology to process the received signals, converts the signal frequency difference corresponding to different code elements into the difference in signal phase, then uses the phase discriminator to convert the difference in signal phase corresponding to different code elements into the difference in voltage, and the demodulation result can deviate from the expected value gradually due to the unavoidable influence of environmental error and system error when the magnetic levitation train-ground communication system is in operation, the demodulated signals are required to be timely adjusted, the demodulated signals are input into the sampling detection module, the logic circuit is used for comparing and judging whether the demodulation is abnormal, and the control module is used for controlling the frequency-phase conversion network to timely modulate the abnormal situation, thus completing the demodulation of CPFSK signals of the high-speed magnetic levitation train-ground communication system. The method of the invention realizes the automation of CPFSK demodulation and detection and adjustment thereof, reduces the complexity and error rate of the system, enhances the reliability of the system, has the advantages of high efficiency, accuracy and rapidness, and ensures the correct information transfer of the magnetic levitation train in the running process.
Drawings
Fig. 1 is a flow chart of a demodulation method of a high-speed magnetic levitation train communication system based on frequency-phase conversion.
Fig. 2 is a system structure block diagram of a demodulation method of a high-speed magnetic levitation train communication system based on frequency-phase conversion.
Fig. 3 is a schematic diagram of a CPFSK signal frequency-phase transfer curve and a pressure-phase transfer curve according to an embodiment of the present invention.
Fig. 4 is a flowchart of CPFSK signal sampling detection decision adjustment according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of CPFSK signal adjustment compensation according to an embodiment of the present invention.
Detailed Description
Embodiments of the present invention are further described below with reference to the accompanying drawings.
As shown in fig. 1, the demodulation method flow chart of the high-speed magnetic levitation train communication system based on frequency-phase conversion comprises the following specific steps:
The system structure block diagram in this embodiment is shown in fig. 2, and includes the following components: the device comprises a frequency-phase conversion module, a phase discrimination module, a sampling detection module and a control module.
In this embodiment, the demodulation device of the maglev train-ground communication system receives CPFSK signals with frequencies ω 1 and ω 2, respectively: Or/> Wherein M is the amplitude of CPFSK signal to be demodulated, t is time variable,/>In order to detect the initial phase of the CPFSK signal to be demodulated in real time in the demodulation process, a demodulation system is adjusted, and the demodulation is ensured to be carried out smoothly.
S1, after the CPFSK signal is input into a demodulation device, the CPFSK signal is subjected to primary demodulation through a frequency-phase conversion device and a phase discriminator;
s2, detecting whether demodulation system demodulates normally or not through a sampling detection module, and judging whether adjustment is needed or not;
S3, the control module receives the signal transmitted by the sampling detection circuit and controls the frequency-phase conversion module to adjust according to the signal type;
and S4, after the frequency-phase conversion module is adjusted, repeating the steps S2 and S3 until the control module no longer receives LWRONG or HWRONG signals, and outputting demodulation signals again.
In this embodiment, in the step S1, the following is specifically described:
s11, after receiving the CPFSK signal, the demodulation device inputs the CPFSK signal into the frequency-phase conversion module;
the frequency-phase conversion module is composed of a plurality of groups of adjustable resonators, two signals with different frequencies generate different phase offsets in the frequency transfer module, so that different frequencies are distinguished, and the output signals are Or (b)
S12, outputting signals after passing through the frequency phase transfer moduleAnd the original signalInputting the two components into a phase discrimination device;
In the phase detector, the signals with different phase offsets output different levels, the level of the output signal is proportional to the phase difference of the two input signals, and when the frequency is omega 1, the phase difference is Level V 1, phase difference/>, when frequency is omega 2 The level is V 2, as shown in fig. 3, the level V 1、V2 has a larger phase difference, and the symbol information carried by the signal is extracted according to the level size, so that decoding is completed.
In this embodiment, in the step S2, as shown in fig. 4, the flowchart specifically includes:
S21, sampling the demodulation signals output by the phase demodulation device by a sampling detection module to obtain the level V t1、Vt2、Vt3......Vtn-1、Vtn of n sampling points, and further judging whether the demodulation process is abnormal or not;
S22, comparing the level V ti (i=1, 2,3 … n) of each sampling point with the standard level median V mid, and dividing the level V ti into a low-level sampling point and a high-level sampling point;
Wherein, median value of standard level V mid＝0.5(V1stand+V2stand), if V ti＞Vmid, the i-th sampling level is considered as high level; if V ti＜Vmid, the ith sample level is considered to be low. Transmitting a signal TYPE for discriminating the level TYPE to the backward detection circuit, wherein the signal TYPE is invalid and indicates a low level, and executing step S23; comparing the sampled level V ti with the low level primary threshold V 1test and the low level secondary threshold V 1max, and if the signal TYPE is valid, indicating a high level, executing step S24, and comparing V ti with the high level primary threshold V 2test and the low level secondary threshold V 2min.
S23, a first-level detection threshold V 1test、V2test and a second-level detection threshold V 1max、V2min corresponding to the low-level standard value V 1stand and the high-level standard value V 2stand are respectively set, a low-level abnormal sampling point counting parameter A and an upper limit A max thereof are set, and a high-level abnormal sampling point counting parameter B and an upper limit B max thereof are set.
If V ti＜V1test, considering the sampling level of the sampling point to be normal, i=i+1, resetting A=0 by the low-level abnormal sampling point counting parameter A, and judging the sampling level of the next sampling point; if V 1max＞Vti＞V1test is found that the sampling level of the sampling point is abnormal, the counting parameter A=A+1 of the low-level abnormal sampling point is judged, then the sizes of A and A max are judged, if A does not exceed the upper limit of the A, the error code is found for a period of time in the low level of the demodulation signal, and a command is not required to be sent to a control circuit to control a frequency-phase conversion module to adjust, and the detection of the i+1th sampling point is continued; if A exceeds the upper limit, the low level in the demodulation signal is considered to continuously generate abnormal level for a long time, the low level in the demodulation signal is immediately bit error, and a signal LWRONG needing to adjust the low level is sent to the control module; if V ti＞V1max is found that the sampling level of the sampling point is greatly different from the quasi-low level, error code immediately occurs, and a signal LWRONG needing to adjust the low level is directly sent to the control module.
S24, if V ti＞V2test, considering that the sampling level of the sampling point is normal, i=i+1, resetting B=0 by using the counting parameter B of the high-level abnormal sampling point, and judging the sampling level of the next sampling point; if V 2test＞Vti＞V2min is detected, the sampling level of the sampling point is considered to be abnormal, the counting parameter B=B+1 of the high-level abnormal sampling point is judged, then the sizes of B and B max are judged, if B does not exceed the upper limit of the B, the high-level demodulation is considered to be temporarily free from error code, and the detection of the (i+1) th sampling point is continued; if B exceeds the upper limit, the high level in the demodulation signal is considered to continuously generate abnormal level for a long time, the error code is generated immediately in the high level in the demodulation signal, and a signal HWRONG needing to adjust the high level is sent to the control module; if V ti＜V2min is found that the sampling level of the sampling point is larger than the standard high level, error code will occur immediately, and a signal HWRONG for adjusting the high level is directly sent to the control module.
In this embodiment, in the step S3, the following is specifically described:
S31, when the control module receives the signal LWRONG, calculating a difference value DeltaV 1＝|V1fin-V1stand I between the sampling point level V 1fin and the low level standard level V 1stand at the moment;
As shown in fig. 5, the phase difference to be adjusted and compensated is reversely deduced according to the phase-pressure transfer characteristic curve in the phase discriminator Further according to the frequency-phase transfer characteristic curve of the frequency-phase transfer module, reversely deducing the frequency delta omega 1 needing to be adjusted, finally adjusting the frequency-phase transfer module to make the frequency offset of delta omega 1 generated by the frequency-phase transfer characteristic curve of the frequency-phase transfer module complete compensation, wherein,/>For the sampling level V 1fin, according to the phase shift corresponding to the phase-pressure transfer characteristic curve, ω' 1 is/>And according to the signal frequency corresponding to the frequency-phase transfer characteristic curve.
S32, when the control module receives the signal HWRONG, calculating the difference value DeltaV 2＝|V2fin-V2stand I between the sampling point level V 2fin and the high level standard level V 2stand at the moment;
As shown in fig. 5, the phase difference to be adjusted and compensated is reversely deduced according to the phase-pressure transfer characteristic curve in the phase discriminator Further according to the frequency-phase transfer characteristic curve of the frequency-phase transfer module, reversely deducing the frequency delta omega 2 needing to be adjusted, finally adjusting the frequency-phase transfer module to make the frequency offset of delta omega 2 generated by the frequency-phase transfer characteristic curve of the frequency-phase transfer module complete compensation, wherein,/>For the sampling level V 2fin, according to the phase shift corresponding to the phase-pressure transfer characteristic curve, ω' 2 is/>And according to the signal frequency corresponding to the frequency-phase transfer characteristic curve.
The demodulation signals which are re-output after being adjusted by the frequency-phase conversion module through the detection module and the control module are more approximate to the standard demodulation signals, so that the demodulation signals are more stable and more accurate, and the performance of a demodulation system is improved.
In summary, the key point of the method of the invention is to use the frequency-phase conversion technology to demodulate, detect and automatically adjust the demodulation result by the sampling detection and control circuit, and use the method of the invention to demodulate CPFSK signals of the high-speed maglev train-ground communication system.
Claims (3)
1. A demodulation method of a high-speed magnetic levitation train communication system based on frequency-phase conversion comprises the following specific steps:
S1, after the CPFSK signal is input into a demodulation device, the CPFSK signal is subjected to primary demodulation through a frequency-phase conversion device and a phase discriminator;
s2, detecting whether demodulation system demodulates normally or not through a sampling detection module, and judging whether adjustment is needed or not;
s3, the control module receives the instruction and the data sent by the sampling detection module and controls the frequency-phase conversion module to adjust;
S4, after the frequency-phase conversion module is adjusted, repeating the steps S2 and S3 until the control module no longer receives an instruction to be adjusted, completing the adjustment process and outputting a demodulation signal;
in the step S2, the specific steps are as follows:
S21, sampling the demodulation signal output by the phase demodulation module by the sampling detection module to obtain a sampling signal, and further judging whether the demodulation process is abnormal or not;
S22, comparing the magnitude of a sampling level V n of a certain sampling point with the magnitude of a standard level median V mid, and dividing the sampling level V n into a low-level sampling point and a high-level sampling point;
Firstly, setting a standard level median value V mid and V mid＝0.5(V1stand+V2stand), wherein V 1stand and V 2stand are standard values of a low level and a high level respectively, and if V n＜Vmid, determining that the sampling level at the sampling point corresponds to the low level; if V n＞Vmid, the sampling level at the sampling point is considered to correspond to a high level; transmitting a signal TYPE for distinguishing level TYPEs to the backward detection circuit, wherein when the signal TYPE is invalid, the signal TYPE represents a low level, executing step S23, and comparing the sampled level V n with a low-level primary threshold V 1test and a low-level secondary threshold V 1max; if the signal TYPE is valid, the signal TYPE is high level, step S24 is executed, and the magnitudes of V n, the high-level primary threshold V 2test and the low-level secondary threshold V 2min are compared;
S23, respectively setting a first-level detection threshold V 1test、V2test and a second-level detection threshold V 1max、V2min corresponding to a low-level standard value V 1stand and a high-level standard value V 2stand, setting a low-level abnormal sampling point counting parameter A and an upper limit A max thereof, and setting a high-level abnormal sampling point counting parameter B and an upper limit B max thereof;
If V n＜V1test is found that the low-level signal at the sampling point is normal, a command is not required to be sent to the control circuit to control the frequency-phase conversion module to adjust, the abnormal sampling point counting parameter A is reset to 0, and the same judgment is directly carried out on the sampling level V n+1 of the next sampling point; if V 1max＞Vn＞V1test is detected, the low level signal under the sampling point is abnormal, the counting parameter A of the low level abnormal sampling point is changed into A+1, then the sizes of A and A max are judged, if the value of A does not exceed the limit A max, the error code is not generated in low level demodulation temporarily, and the sampling level V n+1 of the next sampling point is judged in the same way; if the value of A exceeds the limit A max, the low level in the demodulated signal is considered to be immediately bit error, and a signal LWRONG needing to adjust the low level is sent to the control module; if V 1max＜Vn is found, the sampling level is far different from the standard low level, and error code is immediately generated, and a signal LWRONG needing to adjust the low level is sent to the control module;
S24, if V n＞V2test is met, the high-level signal under the sampling point is considered to be normal, an instruction is not required to be sent to the control circuit to control the frequency-phase conversion module to adjust, the abnormal sampling point counting parameter B is reset to 0, and the same judgment is directly carried out on the sampling level V n+1 of the next sampling point; if V 2test＞Vn＞V2min is detected, the high level signal under the sampling point is abnormal, the counting parameter B of the high level abnormal sampling point is changed into B+1, then the sizes of B and B max are judged, if the value of B does not exceed the limit B max, the high level in the demodulation signal is considered to have error code for a period of time, and a command is not required to be sent to a control circuit to control a frequency-phase conversion module to adjust, so that the sampling level V n+1 of the next sampling point is directly judged to be the same; if the value of B exceeds the limit B max, the high level in the demodulated signal is considered to be immediately bit error, and a signal HWRONG needing to adjust the high level is sent to the control module; if V n＜V2min, the sampling level is considered to be very different from the standard high level, and error code is immediately generated, and a signal HWRONG for adjusting the high level is sent to the control module.
2. The demodulation method of the high-speed magnetic levitation train communication system based on frequency-phase conversion according to claim 1, wherein in the step S1, the specific steps are as follows:
s11, after receiving the signal, the demodulation device inputs the signal into the frequency-phase conversion module;
The frequency-phase conversion module is composed of a plurality of groups of adjustable resonators, different phase offsets are added to signals with different frequencies, and the phase offset is added to signals with the frequency of omega 1 The signal with frequency omega 2 increases the phase offset/>Distinguishing between different frequencies;
s12, the output signal after the frequency-phase conversion module is input into the phase discrimination device together with the original signal;
In the phase detector, different phase-shifted signals will output different levels, the level of the output signal is proportional to the phase difference of the two input signals, and the phase shift is The level of the signal output is V 1, and the phase offset is/>The signal output level of the (2) is V 2, and code element information carried by the signal is extracted according to the level size, so that decoding is finished.
3. The demodulation method of the high-speed magnetic levitation train communication system based on frequency-phase conversion according to claim 1, wherein in the step S3, the specific steps are as follows:
S31, if the control module receives an instruction of low level to be adjusted, the control module compares a level value V n of a sampling point at the effective moment of the instruction with a standard low level value V 1stand;
Calculating the difference value |V n-V1stand |, and then reversely deducing the phase difference needing to be adjusted and compensated by the relation between the output voltage of the phase discriminator and the phase difference of the input signal Further, according to the intermediate frequency phase transfer characteristic curve of the frequency phase conversion module, reversely calculating the frequency delta omega 1 needing to be offset, and then controlling the frequency phase conversion module to generate corresponding delta omega 1 offset to finish compensation;
S32, if the control module receives an instruction of high level to be adjusted, the control module compares a level value V n of a sampling point at the effective moment of the instruction with a standard high level value V 2stand;
Calculating the difference value |V n-V2stannd |, and then reversely deducing the phase difference needing to be adjusted and compensated by the relation between the output voltage of the phase discriminator and the phase difference of the input signal And further, according to the intermediate frequency phase transfer characteristic curve of the frequency phase conversion module, reversely calculating the frequency delta omega 2 needing to be offset, and then controlling the frequency phase conversion module to generate corresponding delta omega 2 offset to finish compensation.
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