CN106199187B - A kind of test method of multi-tone signal relative phase - Google Patents

Abstract

The invention discloses a method for testing the relative phase of multi-tone signals, and relates to a method for testing the relative phase of multi-tone signals. A method for testing the relative phase of a multi-tone signal, which consists of two parts: building a test platform and solving the relative phase; its basic feature is that each single-tone component of the signal to be tested is successively compared with the same broadband signal or multiple broadband with the same spectrum information of the baseband For signal mixing, a sampling instrument is used to collect the mixed intermediate frequency components, and the relative phase of the signal to be measured is obtained by calculation. In the process of frequency down-conversion, the present invention uses a broadband signal as a frequency-mixing signal, and in the subsequent calculation process, uses a statistical average point of view to reduce calculation errors.

Description

A method for testing the relative phase of multi-tone signals

technical field

The invention designs a signal testing method, especially a testing method involving the relative phase of multi-tone signals.

Background technique

With the increasing demand of human beings for communication, communication technology is developing rapidly in the direction of multi-band and large data volume, and the instruments and methods for measuring communication systems have also made great progress. Multi-tone signals are often used in various communication systems. For example, the local oscillator signal of a compressed sensing receiver based on MWC architecture can be regarded as a multi-tone signal with a fixed frequency interval. However, measuring the relative phase of multi-tone signals has been perplexing researchers in related fields, and has become an important topic of related scientific research.

At present, the main test methods for the relative phase of multi-tone signals include direct measurement with a spectrum analyzer and indirect measurement with frequency mixing. Ordinary spectrum analyzers cannot accurately measure the absolute phase of the signal due to the random phase of the local oscillator signal and the uncertainty of the initial sampling phase. If the spectrum range of the tested multi-tone signal is narrow and does not exceed the bandwidth of the IF filter of the spectrum analyzer, adjust the down-conversion frequency inside the spectrum analyzer, and all the tones of the multi-tone signal can be sampled back by the spectrum analyzer at one time, so that The relative phase between each tone of the multi-tone signal can be calculated. However, if the frequency spectrum distributed by the multi-tone signal is wide and exceeds the bandwidth of the IF filter of the spectrum analyzer, its relative phase cannot be directly measured by the spectrum analyzer. Another test method is indirect measurement, which generates a group of multi-tone signals with known relative phases as the local oscillator, mixes with the multi-tone signal to be tested, and adjusts the frequency of each tone component of the local oscillator to ensure that each tone of the signal to be tested The components of the sound can be mixed to a lower intermediate frequency, and each sound does not generate aliasing at the intermediate frequency. The mixed signal can be sampled simultaneously by an ADC device or a spectrum analyzer at one time, and the relative frequency of the multi-tone signal can be obtained by calculation. phase. However, if there are too many multi-tone components in the signal to be tested and they are distributed in a wide frequency band, it is not easy to generate a multi-tone local oscillator signal with a known relative phase, and it is difficult to down-convert each tone component of the signal to be tested to an intermediate frequency at the same time. Instead, a one-time simultaneous sampling calculation is performed.

The signal to be tested applicable to the test method of the relative phase of the multi-tone signal proposed by the present invention has the following characteristics: each monotone component is relatively stable, and its signal overall presents obvious periodicity, and the spectrum distribution of the multi-tone signal is relatively wide, and its There are relatively many monophonic components, which cannot be directly measured by the above measurement methods. The present invention establishes a unified reference standard for multi-tone signals, measures each single-tone component separately, and finally calculates and processes according to the sampling value to obtain the relative phase. The invention not only overcomes the weakness of the narrow distribution of the frequency spectrum to be measured in the direct spectrum analyzer measurement, but also overcomes the weakness of the indirect measurement of the local oscillator signal, and can test the relative phase of the complex signal with many multi-tone components and relatively wide frequency. Moreover, in the down-conversion process of the present invention, a broadband signal is used as a frequency-mixing signal, and in the subsequent calculation process, calculation errors are reduced by using a statistical average point of view.

Contents of the invention

The purpose of the present invention is to provide a method for testing relative phase information of multi-tone signals, which can indirectly test the relative phase of signals with wide frequency distribution and many multi-tone components.

The technical solution of the present invention is: a method for testing the relative phase of a multi-tone signal, which consists of two parts: building a test platform and solving the relative phase; Two broadband signals with the same baseband spectrum information are mixed, and the intermediate frequency components after mixing are collected by a sampling instrument, and the relative phase of the signal to be measured is obtained by calculation.

Thereby the present invention a kind of method for testing the relative phase of multi-tone signal, this method comprises:

Step 1: Divide the signal to be tested into two paths, one path is connected to the local oscillator port of the mixer after passing through the first gain control unit, and the other path is connected to the trigger signal generator;

Step 2: The trigger signal generator counts the cycle of the signal to be tested according to the input signal to be tested, and generates a trigger signal every N cycles, and the value of N is determined according to the ADC sampling length and the cycle of the multi-tone signal; The trigger signal is divided into two channels, which are respectively sent to the detection signal generator and the ADC sampling device;

Step 3: Send the trigger signal to the detection signal generator, control the detection signal generator to repeatedly generate a broadband signal, adjust the carrier frequency of the broadband signal so that it corresponds to the frequency of one of the single tone components of the signal to be tested, and then speak the The broadband signal is connected to the RF port of the mixer after passing through the second gain control unit;

Step 4: After the intermediate frequency signal generated by the mixer is filtered by a low-pass filter, it is sent to the ADC sampler; through another trigger signal sent to the ADC sampling device, the time node at which the ADC sampling device records the sampling data is controlled; whenever the ADC Each time the sampling device receives a trigger signal, it records a certain length of sampling data;

Step 5: The sampling sequence value corresponding to the i-th monotone component is recorded as y _i [n], and the Fourier transform is performed on y _i [n] to obtain Y _i (f), and the a-th monotone component is selected arbitrarily The corresponding sampling sequence is used as a reference standard, set to y _a [n], perform Fourier transform on it to get Y _a (f), and perform the operation of formula 1

Where θ is the phase difference between the i-th monotone component and the a-th monotone component.

Here, the test method proposed in this patent is described by taking the test of the Fourier coefficient of the local oscillator signal of the compressed sensing receiver based on the MWC framework as an example. The local oscillator signal of the compressive sensing receiver based on the MWC framework is a high-speed pseudo-random series, and the pseudo-random sequence appears repeatedly in M bits. Therefore, it appears as an equally spaced multi-tone signal in the frequency domain. In practical applications, its coverage range is very wide, ranging from hundreds of MHz to more than ten GHz. Due to the existence of non-ideal factors such as channels and frequency mixing, the Fourier coefficients are distorted, so the Fourier coefficients cannot be obtained through calculation. It needs to be tested to recover the signal accurately. However, it is difficult to directly test the Fourier coefficients in such a wide frequency range with the current test method by sampling once, and it is also difficult to generate a multi-tone signal with known phase for mixing test. But this patent mentions that the indirect test method can solve this problem, and obtain the relative value of each Fourier coefficient. In the experiment, we tested the Fourier coefficients of multi-tone signals (pseudo-random sequence of compressive sensing receiver) in the frequency range of 1800MHz-2000MHz with equal intervals of 40MHz. In this frequency range, there are six spectrums of 1800MHz, 1840MHz, 1880MHz, 1920MHz, 1960MHz and 2000MHz. Taking 1880MHz as a reference, set the amplitude of its Fourier coefficient to 1 and the phase to 0. After testing, the relative amplitudes of the other spectra are shown in Figure 5, and the relative phases are shown in Figure 6. Each frequency point was tested 20 times. According to the test results, the fluctuation of each test result is very small, which shows that the test is stable and repeatable, and also proves the reliability of the test results.

Description of drawings

Fig. 1 is a multi-tone signal relative phase test system block diagram of the present invention;

Fig. 2 is the frequency domain characteristic of multi-tone signal to be measured;

Fig. 3 is the frequency domain characteristic of test signal;

Fig. 4 is the signal IF_1 after the low-pass filter;

Fig. 5 multi-tone signal Fourier coefficient relative amplitude;

Figure 6 Relative phase of the Fourier coefficients of the multi-tone signal.

Detailed ways

The present invention is further described in conjunction with accompanying drawing; The instrument device used in the present invention comprises test signal generator, trigger signal generator, gain control unit (broadband linear), mixer, low-pass filter, ADC sampling device and data processing calculation tools. Its system block diagram like chart 1 shows.

A kind of concrete steps of the method for testing the relative phase of multi-tone signal are:

1. According to the system block diagram 1, build a measurement platform.

2. The signal to be tested defaults to the relative phase of the multi-tone signal. If multiple single-tone signals need to be measured, a coupler is used to couple multiple single-tone signals into a multi-tone signal.

3. Synchronize the clocks of the signal generator, trigger signal generator, and ADC sampling device in the test platform.

4. Divide the multi-tone signal into two paths, one path is connected to the local oscillator port of the mixer after passing through the gain control unit, and the other path is connected to the trigger signal generator.

5. The trigger signal generator counts the period of the multi-tone signal according to the incoming multi-tone signal, and generates a trigger signal every N cycles. The value of N is determined according to the ADC sampling length and the period of the multi-tone signal. The trigger signal is divided into two paths, which are respectively sent to the signal generator and the ADC sampling device.

6. Send the trigger signal to the signal generator to control the signal generator to repeatedly generate broadband signals, that is, every time the signal generator receives the trigger signal, it will regenerate a broadband signal with exactly the same baseband information, and adjust the carrier frequency of this broadband signal. Corresponding to the frequency of one of the single-tone components of the multi-tone signal to be tested, the intermediate-frequency component can pass through the low-pass filter after mixing, and the intermediate-frequency component contains the phase information of the single-tone signal.

7. After the broadband signal generated by the signal generator passes through the gain control unit, it is sent to the RF port of the mixer, and mixed with the signal of this card, and the intermediate frequency signal generated by the mixing is filtered by a low-pass filter, and then sent to the Analog Input for ADC Sampling Device.

8. Send another trigger signal to the ADC sampling device to control the time node when the ADC sampling device records the sampling data. That is to say, whenever the ADC sampling device receives a trigger signal, it records a certain length of sampling data.

9. Repeat steps 5-7, and change the carrier frequency of the broadband signal in step 5 each time, corresponding to a single-tone component of the multi-tone signal to be tested, until all single-tone components are correspondingly measured.

10. Calculate the relative phase of the multi-tone signal by using the correlation calculation tool through the recorded multiple sets of sampling data. The specific calculation process is: the sampling sequence value corresponding to the i-th monotone component is recorded as y _i [n], and the Fourier transform is performed on y _i [n] to obtain Y _i (f), and the a-th monotone is selected arbitrarily The sampling sequence corresponding to the sound component is used as a reference standard, set to y _a [n], perform Fourier transform on it to get Y _a (f), and perform the operation of formula 1

Where θ is the phase difference between the i-th monotone component and the a-th monotone component (reference value).

The principle is as follows. The signal SS to be tested is a multi-tone signal. If it is necessary to measure multiple single-tone signals, a coupler can be used to couple first to obtain a multi-tone signal. The characteristic of the multi-tone signal to be tested is that each single-tone component is relatively stable, and the overall signal presents obvious periodicity. for

In formula (2), A _i , i=1, 2,...n are real numbers, representing the magnitude of the Fourier coefficients after the Fourier transform of the signal, θ _i , i=1, 2,...n represent Fourier The phases of the Lie coefficients, f _i , i=1, 2, . . . n respectively represent the carrier frequency of each single tone component in the signal. The purpose of the present invention is to obtain the relative value between each θ.

The expression form of the signal SS in the frequency domain is shown by the arrow in Fig. 2 of the schematic diagram.

In system block diagram 1, in order to ensure the synchronization of the whole system, we synchronize the signal source, trigger signal generator, and ADC sampling device with clock. First, the signal SS to be tested is divided into two paths, one path is passed through a gain control unit composed of a low-noise amplifier and an attenuator, and its amplitude is adjusted to an appropriate range to obtain SS1=G ₁ *ss, where G ₁ is the gain coefficient. Connect SS1 to the LO input of the mixer. Since the signal to be tested is a multi-tone signal, SS is a periodic signal. The other branch of the SS is connected to the trigger signal generator. The trigger signal generator records the number of cycles of the SS signal, and sends out a trigger signal every N cycles. The value of N is determined according to the ADC sampling length and the cycle of the multi-tone signal. . The trigger signal is fed into the signal source and the ADC sampling device. The detection signal is a broadband modulated signal with a signal bandwidth of B. Every time the signal source receives a trigger signal, it always generates a detection signal with exactly the same baseband information, and its carrier frequency can be adjusted and changed. First adjust the carrier frequency of the detection signal to f ₁ -f _a , the expression of the detection signal is:

Among them, B/2<f _a <f _p -B/2, f _p is the cut-off frequency of the low-pass filter. At this time, the expression form of RF1 in the frequency domain is shown as the trapezoid in FIG. 3 . RF1 adjusts its power to an appropriate range through a gain control unit composed of a low noise amplifier and an attenuator, and the adjusted signal RF1_a=G ₂ *RF1, where G ₂ is the gain coefficient. Send RF1_a to the RF port of the mixer. After passing through the mixer, the phase information of the monotone component of the signal to be tested at frequency f ₁ is included in the spectrum at the intermediate frequency f _a . After passing through the low-pass filter, it will be The spectrum at f _a is taken out, as shown in Figure 4, assuming that the mixing gain is assuming that G ₃ is the mixing gain, the expression of the filtered signal IF_1 is as follows:

Due to the clock synchronization and trigger synchronization of the system and the periodicity of the local oscillator signal, the state of the local oscillator involved in frequency mixing in each test sample is exactly the same, and the carrier frequency of the test signal generated by the adjusted signal is f ₂ -f _a , Corresponding to a monotone component f ₂ of the signal to be tested, the expression of the test signal is:

Through the gain control unit, frequency mixing, and filtering, the expression form of the intermediate frequency in the frequency domain can be obtained as shown in Figure 4, and its expression is:

Adjust the carrier frequency of the test signal, and repeat the above operations until all the single tone components of the signal to be tested are measured.

Here only the ratio of the positive spectrum of IF_1 and IF_2 can be obtained:

Thus we find the relative phase θ ₁ −θ ₂ of the monotone components at frequencies f ₁ and f ₂ . It should be pointed out that better anti-noise performance can be obtained by using the complex ratio method expressed in formula (8), and the relative phase is still θ ₁ -θ ₂ .

Claims (1)

1. a kind of method of test multi-tone signal relative phase, this method include：

Step 1：Measured signal is divided into two-way, all the way by accessing frequency mixer local oscillator port after the first gain control unit, separately Trigger signal generator is accessed all the way；

Step 2：Trigger signal generator counts the period of this measured signal according to the measured signal of feeding, every N number of period A trigger signal is generated, the value of N is determined according to the period of ADC sampling lengths and multi-tone signal；Trigger signal is divided into two Road is respectively fed to detection signal generator and ADC sampler part；

Step 3：It is sent into the trigger signal of detection signal generator, control detection signal generator is repeated to generate broadband signal, be adjusted The carrier frequency of this whole broadband signal keeps the frequency of one of itself and measured signal tone components corresponding, then by the width Band signal is by accessing frequency mixer prevention at radio-frequency port after the second gain control unit；

Step 4：After the intermediate-freuqncy signal that frequency mixer generates is filtered by low-pass filter, it is sent into ADC sampler；By being sent into ADC The another way trigger signal of Sampling device, the timing node of control ADC sampler part record sampled data；Whenever ADC sampler As soon as part often receives a trigger signal, the sampled data of certain length is recorded；

Step 5：The corresponding sample sequence value of i-th of tone components is denoted as y_i[n], to y_i[n] does Fourier transformation, obtains Y_i (f), it arbitrarily chooses the corresponding sample sequence of wherein a-th of tone components to be used as the standard of referring to, is set as y_a[n], is in Fu it Leaf transformation obtains Y_a(f), 1 operation of formula is done

Wherein θ is the phase difference of i-th of tone components and a-th of tone components.