SU1663572A1 - Method of determining phase shift - Google Patents

Abstract

The invention relates to radio engineering and can be used to measure the phase shift between narrowband signals. The aim of the invention is to improve the accuracy when measuring signals with an unknown structure and carrier frequency. A device that implements the method contains four phase detectors 1, 2, 3, 4, a reference signal generator 5 and a phase shifter 6 at 90 °, four low-pass filters (LPF) 7, 8, 9 and 10, four multipliers 11, 12, 13 and 14, four integrators 15, 16, 17 and 18, a subtractor unit 19, an adder 20, a division unit 21 and an arc tangent calculation unit 22. A feature of the invention is the allocation of low-frequency signals 7, 8, 9, 10 at the output. The determination of the desired phase is made according to the mathematical formula provided in the description of the invention. 1 il.

Description

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The invention relates to the field of radio engineering and can be used to measure the phase shift between narrowband signals with a priori uncertain structure and an unknown carrier frequency.

The aim of the invention is to improve the accuracy in measuring signals with an unknown structure and carrier frequency. The drawing shows a structural electrical circuit of a device for measuring the phase shift between narrowband signals, implementing a method for measuring the phase shift.

The device for determining the phase shift contains the first to fourth phase detectors (PD) 1–4, the generator 5 of the reference signal, the phase shifter 6 by 90 °, the first to fourth filters 7–10 low frequency (LPF), the first to fourth multipliers 11–14 , first-fourth integrators 15-18, subtraction unit 19, adder 20, division block 21, arc-tang calculation unit 22

The device inputs are respectively connected to the first (signal) inputs of the first 1 and second 2, as well as the third 3 and fourth 4 phase detectors, in pairs, the second inputs of which are connected to the reference signal generator 5 directly (PD 1 and PD 4) and through a phase shifter 6 ( PD 2 and PD 3).

The output of PD 1 through serially connected low-pass filter 7, multiplier 11 and integrator 15 is connected to the first input of block 19. Output FD2 via serially connected low-pass filter 8, multiplier 12 and integrator 16 is connected to the second input of block 19, the output of which is connected to the first input of block 21 division, the output of PD 3 through serially connected low-pass filters 9, multiplier 13 and integrator 17 is connected to the first input of adder 20, the output of PD 4 through serially connected low-pass filters 10, multiplier 14 and integrator 18 connected to the second input of adder 20, output th connected to the second input of the dividing block 21, whose output is connected to the unit 22 for calculating arctangent

The output of the low-pass filter 7 is additionally connected to the second input of the multiplier 14, the output of the FICH 8 is additionally connected to the second input of the multiplier 13, the output of the low-pass filter 9 is additionally connected to the second input of the multiplier 11, and the output (the low-pass filter 10 is additionally connected to the second input of the intermediate 12.

The device for measuring the phase shift works as follows.

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Input Signals xi (t) Uc (t) t +

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X2 (t) Uc (t) sin t + f (t) +. Ay, where Uc (t) is the envelope of the measured narrow-band signal; (tk is the carrier frequency of the signal; - / X (t) is the current phase angle; the measured phase shift is transmitted to the PDD-PD4 phase detectors, where they are multiplied with the reference signal of the generator 5

UroHi UoSin t directly (on FD1 and FD4) and with a reference signal shifted by 90i, Hijacking Uocos Shot t (on FD2 and FDZ), where Sho is the frequency of the reference signal, generally not coincident with the carrier

° frequency of the measured signal. As a result, low-frequency components are extracted at the outputs of the low-pass filter 7-low pass filter 10, which, in accordance with the multiplication rules

The trigonometric functions and the phenomena of suppression of the high-frequency components of the multiplication in the low-pass filter are as follows: Ai (t) KiUc (t) U0cos (bc - Sho) t + p (

5 Bi (t) KiUc (t) UoSinl (bc - b0} + p (tjj:

Aa (t) K2Uc (t) UoCOSJ We - Sho) t + f (t) + A (

B2 (t) K2Uc (t) U0Sin (ftjc - (Do) t + p (t) + A p

where Ki and K2 are the transfer coefficients of the corresponding channels to the low-pass filter outputs 7-10.

After pairwise multiplying these signals in multipliers 11-14 and integrating the results of this multiplication in integrators 15-18 at the outputs of the latter, by analogy with the result obtained above, the signals have the following form:

Ai (t) -B2 (t) KiK2Uc (t) UoSln Ai (t) A2 (t) KiK2UJ (cos Ap; A2 (t) Bjt) -KiK2Uc (t) -UJsln A (p; Bi (t) .B2 (t) KiKrUi (t) u2 cos.

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where Uc (t) is the signal energy during the measurement.

After appropriate subtraction and summation of the results obtained in block 19 and adder 20, as well as division in block 21 at the input of the arc tangent calculator, the signal has the following form:

AI ((t) -tatsh

Ai (t) .Az (t) + Bi ((t)

 2 Kl K2 J0 ssin A "a d"

2 Ki K2TjF (t) -lJ§cosA

After calculating the arc tangent function in block 22, we have the desired result, i.e. measured phase shift ar.

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Another embodiment of the proposed method is the use of computer technology. To do this, in the described device, at the outputs of the low-pass filter 7-10, with the help of an ADC, a set of signal samples in a digital code is generated, which is fed into the computer and then the phase shift value is calculated using the appropriate program. In this case, the formula for calculating the phase shift is converted as follows:

Nn

2) A1 | B2 | - 2) A2I-B1J

Ap arctgl

Aii A2i +2, BirB2i

where Ac, Bi, A2k B2i are samples from Ai (t), Bi (t), A2 (t), 82 (1), respectively, taken at the 1st time instant; N is the number of samples taken from the outputs of each low-pass filter during the measurement time.

From the above description, it can be seen that the measurement result of the phase shift does not depend on the signal structure, i.e. on the form of the function Uc (t) and p (t), or on whether the carrier frequency of the measured signals coincides with the frequency of the reference oscillator 5 or not.

These functions, which determine the fine structure of the signal, are excluded from the processing and do not participate in the formation of the final result of measuring the relative phase shift.

Claims (1)

Invention Formula The method of determining the phase shift, which consists in multiplying each of the signals under study with a reference signal and with a reference signal shifted by 90 °, with the corresponding signals ai (t), b (t) n a2 (t), 02 (1), multiply and integrate the multiplied signals a second time, calculate the desired parameter from the integration results, different by the fact that, in order to increase the accuracy in measuring signals with an unknown structure and carrier frequency, their low-frequency signals are additionally extracted from the signals obtained as a result of the first multiplication of signals the components Ai (t), Bi (t) and A2 (t), B2 (t), respectively, upon repeated multiplication, respectively, multiply the signals Ai (t) "B2 (t); Ai (t) A2 (t); A2 (t) -Bi (t); Bi (t) -B2 (t), and the phase shift between the studied signals is determined by the formula p arctgACO-B2 (0-Ai (t) Bi (tI, Ai (t) -Az (t) + Bi (t). B2 (t) where Ai (t) .B2 (t). Ai (t). A2 (t), A2 (t). Bi (t). B1 (t) .62 (t) are time averaged signals.