RU2740790C1 - Method of evaluating phases of multi-frequency periodic signals in conditions of presence of interference using compensation for conversion noise - Google Patents

Abstract

FIELD: radio equipment.SUBSTANCE: for an initial signal specified by counts of instantaneous values at moments of time for a signal frequency sequence, a signal is determined - a result of multiplying the input signal by a sine of the reference frequency. Reference frequencies are set equal to the frequencies of the input multifrequency signal. Each reference sinusoidal signal is repeatedly shifted by discrete phase values. Signals generated after multiplying the input signal by reference signals are processed identically in the respective lines - each of the signals is branched into two identical components. First component is filtered by a low-pass filter (LPF), while the second component is filtered by a band-pass filter (BF). Selection of filters is carried out with phase-frequency and amplitude-frequency characteristics identical to each other. Signals counts are formed and sums of signals counts are found. Values of differences of obtained sums are calculated. Values of phases are stored.EFFECT: high accuracy of estimating phases of multi-frequency periodic signals in conditions of interference.1 cl, 2 dwg, 1 tbl

Description

The invention relates to the field of evaluating the values of signal parameters and can find application in the field of radio engineering, in particular in communication devices, in measuring technology, in devices for spectral analysis of electrical signals.

Known digital method and device for determining the instantaneous phase of the adopted implementation of a harmonic or quasi-harmonic signal (RF patent No. 2463701, H3D 3/00).

The disadvantage of this method and device is their insufficiently high efficiency in the presence of interference.

A known method for assessing the signal delay time (phase), described in the tutorial "Fundamentals of the theory of radio engineering systems". Tutorial. // IN AND. Borisov, V.M. Zinchuk, A.E. Limarev, N.P. Mukhin. Ed. IN AND. Borisov. Voronezh Scientific Research Institute of Communications, 2004 ", pp. 123-124.

The disadvantage of this method is insufficiently high efficiency in the presence of interference.

The known method and device for energy detection of a signal with compensation of the combination components of interference and signal and interference (RF patent No. 2683021, Н04В 1/10), the disadvantage of which is the inability to assess the value of the phase of periodic signals.

There is a known method of spectral analysis of signals (RF patent No. 2127888, G01R 25/16), in which, when sampling and quantizing a signal, a sequence of discrete signal values with different sampling rates in each of them is created. In this case, the discrete values of these sequences are filtered using digital band-pass filters and digital low-pass filters. Signals from the outputs of digital bandpass filters are subjected to processing associated with the determination of the amplitude values, and on their basis, and the rest of the informative parameters of the bandpass signals.

The disadvantage of this method is its insufficiently high noise immunity.

A known method of spectral analysis of signals (RF patent No. 2229725, G01R 23/16), in which a reference sinusoidal signal is formed, which is repeatedly phase shifted relative to the analyzed periodic multifrequency signal. Both signals are represented by counts of instantaneous values for the same moments of time t _j = t ₁ , t ₂ , ..., t _N , where N is the number of partitions in the period T. Next, the points of the joint solution a (b ₀ ) are found at different angular frequencies the reference signal and the phases of the reference signal, build current-voltage characteristics and determine their area F _{B4X min} , and the conclusion about the presence of a harmonic component with a certain angular frequency and phase in the analyzed signal a (t _j ) is made based on the condition F _BAX = 0,

The disadvantage of this method is insufficiently high efficiency in the presence of interference.

The closest analogue in technical essence to the proposed one is a method of spectral analysis of multifrequency periodic signals represented by digital readings (Functional control and diagnostics of electrical systems and devices by digital readings of instantaneous current and voltage values, / edited by E.I. Goldstein - Tomsk: Izd . "Printing Manufactory", 2003, pp. 92-94), taken as a prototype.

The prototype method consists in the fact that for the initial signal a (t _i ), given by the counts of instantaneous values at times

t ₁ , t ₂ ,…, t _j ,…, t _N ;

t ₂ -t ₁ = t ₃ -t ₂ = t _N -t _N-1 =… = Δt;

Δt = T / N,

where Δt is the sampling step;

N is the number of points during T.

for a sequence of frequencies ω ₁ , ω ₂ ,…, ω _j ,…, ω _n , the instantaneous spectral density (MRP) is determined by the expressions:

where S ₁ (ω _j ) and S ₂ (ω _j ) are the sine and cosine components of the instantaneous spectral density.

where f _k - frequency, Hz,

contained in the original signal a (t _i ) corresponds to the extremum of the function S (ω _j ). Thus, the sequence of frequencies ω ₁ , ω ₂ ,…, ω _j ,…, ω _n , contained in the signal, is found. Find the phase ϕ _{k of the} frequency component ω _k by the formula:

The disadvantage of the prototia method is insufficiently high efficiency in the presence of interference.

The objective of the proposed method is to improve the accuracy of determining the phase value of an arbitrary series of harmonic signals in the presence of interference.

To solve the problem in the method for estimating the phase of multifrequency periodic signals in the presence of interference with compensation for conversion noise, which consists in the fact that for the initial signal a (ts), given by the samples of instantaneous values at times

t ₁ , t ₂ ,…, t _j ,…, tN; t ₂ -t ₁ = t ₃ -t ₂ = t _N -t _N-1 =…. = Δt; Δt-T / N,

where Δt is the sampling step; N is the number of points in time T,

for a sequence of signal frequencies ω ₁ , ω ₂ , ..., ω _i , ..., ω _n , the signal is determined - the result of multiplying the input signal by the sine of the reference frequency: S (ω _j t _j ) = α (t _j ) Sin (ω _j t _j ), according to the invention, the values of the reference frequencies are set equal to the values of the frequencies of the input multifrequency signal, the discrete values of the phases, ϕ ₁ , ϕ ₂ ,…, ϕ _j …, ϕ _m , are determined, so that: ϕ ₂ -ϕ ₁ = ∆ϕ; ϕ ₃ -ϕ ₂ = ∆ϕ; ...; ϕ _m -ϕ _(m-1) = ∆ϕ, ∆ϕ = 2π / m,

where Δϕ is the phase sampling step; m is the number of phase values used in its sampling; each reference sinusoidal signal is repeatedly phase-shifted; the processing of signals that are formed after multiplying the input signal by the reference signals is carried out in the same way in the corresponding lines: each of the received signals is split into two identical components, the first component is filtered with a low-pass filter (LPF), the band of which is matched to the signal band, while the second component is filtered a bandpass filter, the passband of which is selected so that the upper frequency of the bandpass filter corresponds to the upper frequency of the signal band, the lower frequency of the bandpass filter is set as close as possible to zero; the choice of the low-pass filter and the band-pass filter is carried out with phase-frequency characteristics identical to the maximum extent and so that the amplitude-frequency characteristic (AFC) of the band-pass filter in the frequency region close to zero has the maximum possible slope in the frequency region, starting from the value for which the difference in values The frequency response of the low-pass filter and the band-pass filter becomes less than a predetermined value, ensuring their frequency response is identical to the maximum; for each reference signal and for each phase value of each reference signal, samples of the signals passed to the output of the low-pass filter and the band-pass filter are generated; summarize the samples of the signals of the passed low-pass filter and summarize the samples of the signals that have passed the bandpass filter; calculate the values of the differences of the amounts obtained; for each reference signal from the obtained differences of the sums corresponding to the result obtained when changing the phases of the reference signal in the entire possible range, find the difference with the maximum value, store the phase values for which the values of the differences have the maximum value.

The proposed method is as follows.

The values of the reference frequencies ω ₁ , ω ₂ , ..., ω _i , ... ω _n are set equal to the values of the frequencies of the multifrequency periodic signal.

The discrete values of the phases, ϕ ₁ , ϕ ₂ ,…, ϕj…, ϕ _m , are determined in such a way that:

where Δϕ is the phase sampling step;

m is the number of phase values used in its sampling, each reference sinusoidal signal is repeatedly phase shifted.

The additive mixture of signals with different frequencies and interference is multiplied in multiplication units, which can be performed, for example, in the form of mixers, by reference signals.

The phases of the reference signals are changed after a predetermined time so that they take all possible discrete values.

Further processing is carried out using the method of compensation for conversion noise - difference frequency harmonics (combination components), described in RF patent No. 2683021, as follows.

The results of the signal multiplication and interference by the corresponding reference signals are treated in the same way.

They are split into two identical components, the first component is filtered with a low-pass filter (LPF), the band of which is matched to the signal bandwidth, while the second component is filtered with a bandpass filter, the bandwidth of which is selected so that the upper frequency of the bandpass filter corresponds to the upper frequency of the signal band, the lower frequency of the bandpass the filter is set as close as possible to zero.

The choice of the low-pass filter and the band-pass filter is carried out with phase-frequency characteristics identical to the maximum extent and so that the frequency response of the band-pass filter in the frequency region close to zero has the maximum possible slope, in the frequency region, starting from the value for which the difference in the frequency response of the low-pass filter and the band-pass filter becomes less than a certain predetermined value, ensure the identity of their frequency response to the maximum extent (an illustrative example is shown in Fig. 1).

For each reference signal and for each phase value of each reference signal, samples of the signals passed to the output of the low-pass filter and passed to the output of the band-pass filter in the corresponding analog-to-digital converters (ADC) are formed. In the computing device, the samples of the signals that have passed the LPF are summed up and the samples of the signals that have passed the bandpass filter are summed.

Calculate the values of the differences of the received sums corresponding to some reference signal and the phase values of each reference signal

U _ij ,

where i is the number of the reference frequency;

j is the number of the discrete phase value.

For each reference signal, from the obtained differences of the sums corresponding to the result obtained when the phase of the reference signal changes over the entire possible range, the difference with the maximum value is found. The phase values for which the difference values have the maximum value are stored.

Below are the results of modeling the process of estimating the phase of multifrequency periodic signals in the presence of interference with compensation for conversion noise.

The sum of the interference harmonics in modeling is presented as a set of harmonic oscillations with random values of amplitudes (U _si ) and phases (ϕ _si ), which are distributed according to the normal (amplitude) and uniform (phase) laws, respectively

where: ω _si ϕ _si U _si - frequency, phase, amplitude of the i-th harmonic signal;

Ns is the number of harmonic signals.

The simulation was carried out using the following representations of signal and interference parameters:

- the amplitudes, frequencies and phases of signals are presented as random variables, the values of amplitudes, phases and frequencies of harmonics are distributed according to a uniform law.

Simulation was carried out for the following parameter values:

- number of realizations - 500;

- the number of signal harmonics - 5;

- the number of interference harmonics - 30;

- the number of time steps - 800;

- the number of phase values used in its sampling - 72;

- coefficient that determines the sampling rate - 48000;

- range of signal amplitudes change - from 1 to 2;

- signal frequency values - from 300 to 3400 in conventional units;

- the value of the frequency band of the bandpass filter, where the slope of its frequency response has a maximum value of 200 in arbitrary units.

Results of modeling the process of evaluating the phase of multifrequency

periodic signals in the presence of interference with compensation for conversion noise are given in the table.

Based on the results of the analysis of the data shown in the table, it can be concluded that the average value of the phase determination error does not exceed 0.39 radians for the signal-to-noise ratio values of at least 0.5.

A block diagram of a device that implements the proposed method is shown in Fig. 2, where indicated;

1.1-1.n - from the first to the n-th multiplication blocks;

2.1-2.n - from the first to the n-th low-pass filters (LPF);

3.1.1, 3.2.1 - the first and second analog-to-digital converters (ADC) of the first line;

3.1.2, 3.2.2 - the first and second ADCs of the second line;

3.1.n, 3.2.n - the first and second ADCs of the n-th line;

4.1-4.n - from the first to the n-th reference voltage generators (GON);

5.1-5.n - from the first to the n-th band pass filters:

6 - computing device (VU).

The device contains n parallel lines, each of which consists of the corresponding series-connected multiplication unit 1, LPF 2, and the first ADC 3.1, while the bandpass filter 5 is connected between the output of the multiplication unit 1 and the second ADC 3.2, while the GON 4 output is connected to the second the input of the multiplication unit 1. In addition, the first inputs of the multiplication units 1.1-1.n of each line are interconnected and are the input of the device. The outputs of the first 3.1.1-3.1.n and the second 3.2.1-3.2.n ADCs of each line are connected to the corresponding inputs of the computing device 6, the output of which is the output of the device.

The device works as follows.

The values of the reference frequencies ω ₁ , ω ₂ , ..., ω _i , ..., ω _n are set equal to the values of the frequencies of the multifrequency periodic signal. Discrete phase values are determined.

Each reference sinusoidal signal is repeatedly phase-shifted. The phase change of the reference signals can be provided, for example, by performing the GON 4.1-4.n in the form of a series-connected generator and a phase-shifting device, made, for example, in the form of a delay line. Or, for example, by performing GON 4.1-4.n in the form of a series-connected programmable logic integrated circuit (FPGA) and a digital-to-analog converter (DAC) (not shown in Fig. 2). At the same time, a reference signal of a given frequency is formed in the FPGA in digital form, which is phase-shifted at predetermined time intervals, and a digital signal is converted into an analog form in the DAC.

The additive mixture of interference and signaling with different frequencies is multiplied by reference signals in multiplication units 1.1-1.n, which can be made, for example, in the form of mixers.

The phases of the reference signals are changed after a predetermined time so that they take all possible discrete values.

Further processing is carried out using the method of compensation for conversion noise - difference frequency harmonics (combination components), described in RF patent No. 2683021, as follows.

The results of the signal multiplication and interference by the corresponding reference signals are treated in the same way. They are branched into two identical components, the first component is filtered by LPF 2.1-2.n, while the second component is filtered by bandpass filters 5.1-5.n.

For each reference signal and for each phase value of each reference signal, samples of signals are generated that passed to the output of the low-pass filter 2.1-2.n in the corresponding ADCs 3.1.1-3.1.n and passed to the output of the band-pass filters 5.1-5.n in the corresponding 3.2 .1-3.2.n. The samples are fed to the computing device 6, where for each line the samples of the signals of the passed LPF 2.1-2.n for each of them are summed, and the samples of the signals that have passed the bandpass filters 5.1-5.n for each of them are summed. Calculate the values of the differences of the received sums corresponding to a certain reference signal and the phase values of each reference signal.

For each reference signal, from the obtained differences of the sums corresponding to the result obtained when the phase of the reference signal changes over the entire possible range, the difference with the maximum value is found. The phase values for which the difference values have the maximum value are stored.

The results of modeling the phase estimation of multifrequency periodic signals in the presence of interference with compensation for conversion noise are given above.

Multiplication blocks 1.1-1.n can be performed, for example, in the form of a frequency converter (mixer), see, for example, the tutorial "Fundamentals of the theory of radio engineering systems". Tutorial. // IN AND. Borisov, V.M. Zinchuk, A.E. Limarev, N.P. Mukhin. Ed. IN AND. Borisov, Voronezh Scientific Research Institute of Communications, 2004 ", pp. 186-189.

ADCs 3.1.1-3.1.n and 3.2.1-3.2.n can be performed, for example, on the AD7495BR microcircuit from Analog Devices.

Computing device 6 can be implemented as a single microprocessor device with appropriate software, for example, a TMS320VC5416 processor from Texas Instruments, or as a programmable logic integrated circuit (FPGA) with appropriate software, for example, XCV400 FPGA from Xilinx.

Thus, the inventive method can be implemented by the described device.

Claims (6)

A method for estimating the phase of multifrequency periodic signals in the presence of interference with compensation for conversion noise, which consists in the fact that for the initial signal a (t _i ), given by the samples of instantaneous values at times t ₁ , t ₂ ,…, t _j ,…, t _N ; t ₂ -t ₁ = t ₃ -t ₂ = t _N -t _N-1 =… = Δt; Δt = T / N, where Δt is the sampling step; N is the number of points in time T, for a sequence of signal frequencies ω ₁ , ω ₂ , ..., ω _i , ..., ω _n , the signal is determined - the result of multiplying the input signal by the sine of the reference frequency: S (ω _j t _j ) = α (t _j ) Sin (ω _j t _j ), characterized in that the values of the reference frequencies are set equal to the frequencies of the input multifrequency signal, discrete phase values are determined, ϕ ₁ , ϕ ₂ , ..., ϕ _j …, ϕ _m , so that: ϕ ₂ -ϕ ₁ = ∆ϕ; ϕ ₃ -ϕ ₂ = ∆ϕ; ...; ϕ _m -ϕ _(m-1) = ∆ϕ, ∆ϕ = 2π / m, where Δϕ is the phase sampling step; m is the number of phase values used in its sampling; each reference sinusoidal signal is repeatedly phase-shifted; the processing of signals that are formed after multiplying the input signal by the reference signals is carried out in the same way in the corresponding lines: each of the received signals is split into two identical components, the first component is filtered with a low-pass filter (LPF), the band of which is matched to the signal band, while the second component is filtered a bandpass filter, the passband of which is selected so that the upper frequency of the bandpass filter corresponds to the upper frequency of the signal band, the lower frequency of the bandpass filter is set as close as possible to zero; the choice of the low-pass filter and the band-pass filter is carried out with phase-frequency characteristics identical to the maximum extent and so that the amplitude-frequency characteristic (AFC) of the band-pass filter in the frequency region close to zero has the maximum possible slope in the frequency region, starting from the value for which the difference in the AFC values of the low-pass filter and the bandpass filter becomes less than a predetermined value, ensure that their frequency response is identical to the maximum extent; for each reference signal and for each phase value of each reference signal, samples of the signals passed to the output of the low-pass filter and the band-pass filter are generated; summarize the samples of the signals of the passed low-pass filter and summarize the samples of the signals that have passed the bandpass filter; the values of the differences of the obtained sums for each reference signal are calculated from the obtained differences of the sums corresponding to the result obtained when the phases of the reference signal are changed in the entire possible range, the difference with the maximum value is found, the phase values for which the values of the differences have the maximum value are stored.

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