CN113702701B - Amplitude-phase characteristic measurement method based on comb wave signals - Google Patents
Amplitude-phase characteristic measurement method based on comb wave signals Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
- G01R23/06—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage by converting frequency into an amplitude of current or voltage
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R25/00—Arrangements for measuring phase angle between a voltage and a current or between voltages or currents
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Abstract
The invention provides a method for measuring amplitude-phase characteristics based on comb wave signals, wherein a signal source and a frequency analyzer are used in the measuring process, and the method comprises the following steps: setting the bandwidth of a channel to be measured of the frequency analyzer and the frequency stepping parameters of the comb wave signal, generating the comb wave signal with consistent amplitude and consistent initial phase or known initial phase through a signal source, and sending the comb wave signal into the channel to be measured of the frequency analyzer; the frequency analyzer performs data acquisition and analysis of amplitude-phase characteristics.
Description
Technical Field
The invention belongs to the technical field of electronic signal measurement, and particularly relates to a method for measuring amplitude-phase characteristics based on comb wave signals.
Background
The amplitude flatness and the phase linearity are important factors influencing the improvement of the performance of the receiver, and after the design of the receiving system is finished, how to test the two indexes effectively with high precision is always a difficult problem for testers. When the vector signal analyzer performs demodulation analysis, even very small amplitude fluctuation and phase nonlinear fluctuation cause great errors on the measurement result, so that the amplitude-phase characteristic measurement of the receiving channel is a necessary and key step.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for measuring amplitude-phase characteristics based on comb signals, wherein a signal source and a frequency analyzer are used in the measuring process of the measuring method, and the method comprises the following steps:
step 1, setting the bandwidth of a channel to be measured of a frequency analyzer and the frequency stepping parameters of a comb wave signal;
Step 2, generating comb wave signals with the same amplitude and the same primary phase or known primary phase through a signal source, and sending the comb wave signals into a channel to be measured of a frequency analyzer;
and 3, the frequency analyzer performs data acquisition and amplitude-phase characteristic analysis.
Further, the step 1 includes the sub-steps of:
step 1.1, setting initial amplitude coincidence of comb wave signals:
A0＝A1＝…＝AN
Initial phase agreement:
The resulting comb calibration signal time domain expression is:
Step 1.2, after the comb calibration signal passes through the channel, it is:
Wherein p n is the phase of each frequency component added after passing through the channel, α n is the amplitude value of each frequency component, n=0, 1,2, …, N;
Step 1.3, the frequency analyzer collects the comb wave calibration signal after passing through the channel at time t 0, and the phase of each frequency component has the following formula:
pn＝Wn·t0+θn
Where ω n·t0 refers to the phase of the current frequency component ω n that is increased by the delay t 0 and θ n refers to the additional phase of the current channel to the frequency component ω n.
Further, the measuring of the amplitude-phase curve in the step 3 comprises the following substeps:
step 3.1, performing Fast Fourier Transform (FFT) on the acquired signals to obtain amplitude values and phase values corresponding to the current frequency components;
and 3.2, measuring the phase error by adopting a three-point method, and calculating a phase error curve of each frequency component.
Further, step 3.2 comprises the sub-steps of:
Step 3.21, calculating a phase error E 3 at the frequency point f 3 based on f 1 and f 5:
Step 3.22 calculates an initial phase error E 2 at frequency point f 2 based on f 1 and f 3:
Step 3.23, because of the phase error at f 3, the superposition error at frequency point f 2 is E' 2:
Step 3.24, calculating an initial phase error E 4 at the frequency point f 4 based on f 3 and f 5:
Step 3.25, since the phase at f 3 has an error, the superposition error at the frequency point f 4 is E' 4:
Step 3.26, calculating the phase error at the frequency point f 2,f3,f4:
Δ2＝E2+E′2
△3＝E3
Δ4＝E4+E′4
Where f i is the selected frequency point.
Further, selecting different frequency points, repeating the steps 3.21 to 3.26, and calculating the phase errors of all the frequency components to be calculated.
The method can be used for off-line calibration and on-line calibration, has high algorithm measurement accuracy and high speed, and can be suitable for signal processing processes with high speed and real-time performance.
Drawings
FIG. 1 is a schematic diagram of three-point method for measuring phase error;
FIG. 2 is a schematic diagram of a three-point method for measuring phase errors with 5 frequency components;
FIG. 3 is a channel amplitude versus frequency curve setting;
FIG. 4 is a channel phase frequency curve setup;
Fig. 5 is a received baseband comb frequency spectrum;
FIG. 6 is a comparison of amplitude versus frequency curve measurements and true values;
FIG. 7 is a phase frequency curve measurement and true value comparison;
fig. 8 is a graph of error linearity analysis between measured and true values.
Detailed Description
The invention provides a comb wave signal-based amplitude-phase characteristic measuring method, which can analyze the amplitude-phase characteristic curve of the current channel only through one-time signal acquisition, can be used for subsequent channel calibration, and has the advantages of small calculated amount, high speed and easy engineering realization. The conventional channel phase measurement method needs a trigger signal to synchronize a source and a receiver, and cannot acquire the phase frequency characteristic in the whole frequency band at one time. The measuring method can be used for off-line calibration and on-line calibration, has high algorithm measuring precision and high speed, and can be suitable for a signal processing process with high speed and real-time performance.
The following detailed description of specific embodiments of the invention refers to the accompanying drawings.
The invention is realized by the following steps:
(1) Setting parameters such as bandwidth of a channel to be measured, frequency stepping of a comb wave signal and the like;
(2) Generating comb wave signals with consistent amplitude, initial phase or known comb wave signals and sending the comb wave signals to a channel to be measured;
(3) And (5) data acquisition and amplitude-phase characteristic analysis.
A. signal model
The comb time domain expression is:
wherein ω n＝ω1 + (n-1) Δω, For the initial phase of each frequency component, a n is the initial amplitude value of each frequency component, n=0, 1,2,3, …, N.
(1) Setting initial parameters of comb signal
The initial amplitude is set to unity: a 0＝A1＝…＝AN
The initial phase is set to unity:
The resulting comb calibration signal time domain expression is:
(2) After the comb calibration signal passes through the channel, the comb calibration signal is:
Wherein the frequency component omega n,pn is the phase of each frequency component increased after passing through the channel, alpha n is the amplitude value of each frequency component, n=0, 1,2, …, N
(3) Assume that the signal is acquired at time t 0
The phase of each frequency component has the following formula:
pn＝Wn·t0+θn
Where ω n·t0 refers to the phase of the current frequency component ω n that is increased by the delay t 0 and θ n refers to the additional phase of the current channel to the frequency component ω n. Omega 0·t0,ω1·t0,...,ωN·t0 varies linearly, then theta n is the channel phase nonlinearity to be measured, and alpha n is the channel amplitude nonlinearity to be measured.
B. Amplitude-phase curve measurement
(1) And carrying out Fourier transform (FFT) on the acquired signals to obtain amplitude values and phase values corresponding to the current frequency components.
The amplitude value obtained at this time is the measured channel amplitude-frequency curve.
(2) Phase error curve measurement
The phase error is measured using a three-point method.
Assume that the three-point frequency f 1,f2,f3 satisfies the following equation:
f2-f1＝f3-f2
the corresponding measured phase values are p 1,p2,p3, assuming that p 1,p3 has no error, p 1 and p 3 are taken as reference points, the ideal channel is a linear phase, then p 1,p2,p3 is theoretically on a straight line, when p 2 is not on the p 1,p3 straight line, the current channel is not the ideal channel, the phase is distorted, and then the phase error at the frequency f 2 is:
When the number of comb-shaped wave frequency points is greater than 3, for example, when the number of frequency components is 5, the error calculation schematic diagram is shown in fig. 2.
Assuming that p 1,p5 has no error, a straight line is drawn by taking p 1 and p 5 as reference points, and the ideal channel has a linear phase, then p 1,p2,p3,p4,p5 is theoretically on a straight line, when the channel has different distortions for each frequency component phase, as shown in fig. 3, p 1,p2,p3,p4,p5 is not on the same straight line, and the phase error calculation method at the frequency point f 2,f3,f4 is as follows:
(1) Calculating the phase error E at the frequency point f 3 by taking f 1 and f 5 as references 3
(2) Calculating an initial phase error E at a frequency point f 2 by taking f 1 and f 3 as references 2
(3) Because of the error of the phase at f 3, the superposition error at the frequency point f 2 is
(4) Calculating initial phase error at frequency point f 4 based on f 3 and f 5
(5) Because of the error of the phase at f 3, the superposition error at the frequency point f 4 is
The phase error at the frequency point f 2,f3,f4 is calculated by this:
Δ2＝E2+E′2
△3＝E3
Δ4＝E4+E′4
Similarly, the phase errors of all the desired frequency components can be calculated.
C. Simulation of
Assuming that the initial amplitude and phase curve of the channel is as shown in fig. 3 and 4, this curve is loaded into the comb signal during the simulation.
The received baseband signal is subjected to FFT, the amplitude value of each frequency component is calculated, and the phase error curve of each frequency component is calculated, as shown in fig. 5 to 8.
From simulation results, it can be seen that the obtained amplitude-frequency curve is basically consistent with the set channel amplitude-frequency curve, the obtained phase-frequency curve fluctuation trend is opposite to that of the actually set channel phase-frequency curve, and the sum of the obtained amplitude-frequency curve and the actually set channel phase-frequency curve is a linear value, because the phase error value is obtained by subtracting the actual measured value from the ideal linear value, which represents the phase value required by the channel to reach the ideal linear phase, and because the head-to-tail frequency component error is assumed to be 0 and is not consistent with the actual, the actual head-to-tail phase error is uniformly distributed in the whole bandwidth, so that the measured phase-frequency curve and the actual phase-frequency curve are different to be a linear curve, and as can be seen from fig. 6, the linear phase-frequency curve does not affect the signal quality for the channel, and only has one relative signal delay, so that the measured phase curve can be used to represent the amplitude-phase characteristic of the current channel.
The comb wave signal generated in the simulation example has larger signal peak-to-average ratio because the initial phase is set to 0, a known initial phase curve can be set to load on each frequency component of the comb wave when the actual engineering is used, and the phase frequency curve of the channel can be obtained by removing the initial value of the part of the measured phase frequency curve. … … A
Finally, it should be noted that the above-mentioned embodiments are merely for illustrating the technical solution of the embodiment of the present invention, and not for limiting, and although the embodiment of the present invention has been described in detail with reference to the above-mentioned preferred embodiments, it should be understood by those skilled in the art that modifications and equivalent substitutions can be made to the technical solution of the embodiment of the present invention without departing from the spirit and scope of the technical solution of the embodiment of the present invention.
Claims (1)
1. A method for measuring amplitude-phase characteristics based on comb signals, wherein a signal source and a frequency analyzer are used in the measuring process of the measuring method, and the method is characterized by comprising the following steps:
step 1, setting the bandwidth of a channel to be measured of a frequency analyzer and the frequency stepping parameters of a comb wave signal;
step 2, generating comb wave signals with consistent amplitude and known primary phase or primary phase through a signal source, and sending the comb wave signals into a channel to be measured of a frequency analyzer;
step 3, the frequency analyzer performs data acquisition and performs amplitude-phase characteristic analysis;
The step 2 comprises the following substeps:
step 2.1, setting initial amplitude coincidence of comb wave signals:
A0＝A1＝…＝AN＝1
Initial phase agreement:
The resulting comb calibration signal time domain expression is:
Step 2.2, after the comb wave calibration signal passes through a channel to be measured of the frequency analyzer, the comb wave calibration signal is as follows:
Wherein p n is the phase of each frequency component after passing through a channel to be measured of the frequency analyzer, alpha n is the amplitude value of each frequency component, and n=0, 1,2, … and N;
Step 2.3, the frequency analyzer collects comb wave calibration signals after passing through a channel to be measured of the frequency analyzer at time t 0, and the phase of each frequency component is calculated according to the following formula:
pn＝wn·t0+θn
Wherein w n·t0 refers to the phase of the current frequency component w n increased by the delay t 0, and θ n refers to the additional phase of the channel to be measured of the current frequency analyzer to the frequency component w n;
the amplitude and phase curve measurement in step 3 comprises the following sub-steps:
Step 3.1, performing fast Fourier transform FFT on the acquired signals to obtain amplitude values and phase values corresponding to the current frequency components;
Step 3.2, measuring phase errors by adopting a three-point method, and calculating a phase error curve of each frequency component;
Step 3.2 comprises the sub-steps of:
Step 3.21, when the number of the frequency components w n is 5, calculating the phase error E 3 at w 3 based on w 1 and w 5:
Step 3.22 calculates an initial phase error E 2 at w 2 based on w 1 and w 3:
Step 3.23, since there is an error in the phase at w 3, the overlay error at w 2 is E' 2:
Step 3.24, based on w 3 and w 5, calculate an initial phase error E 4 at w 4:
Step 3.25, since there is an error in the phase at w 3, the overlay error at w 4 is E' 4:
step 3.26, calculating the phase error at w 2、w3、w4:
Δ2＝E2+E′2
Δ3＝E3
Δ4＝E4+E′4
And selecting different frequency components, repeating the steps 3.21 to 3.26, and calculating the phase errors of all the frequency components to be calculated.
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