RU2539968C1 - Differential-range method of determining coordinates of radio-frequency source - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: single calculation of cross-correlation functions for estimating time delay during propagation of radio-frequency source signals is realised through preliminary processing of radio-frequency source signals after relay thereof.

EFFECT: fewer calculations in procedure for calculating coordinates of radio-frequency source signals.

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Description

The invention relates to radio engineering and can be used in multi-position radio systems for determining the coordinates of radio emission sources (IRI).

Known:

1. Difference-range measuring method for determining the coordinates of a source of radio emission and its device [1].

2. A method for determining the location of the transmitter by measuring the difference in delay times [2].

3. Difference-range multi-position radio engineering systems [3, p. 246 ... 248].

The above methods for determining the coordinates / location can be used in multi-position wide-base radio systems in which analog communication lines (channels) are used to relay the signal from the radio source from the receiving point to the processing point (analog relaying takes place).

Closest to the claimed method according to the totality of the matching essential features is one of the methods [3, p.14-25], which is selected as a prototype.

This method consists in receiving a signal from a radio emission source, peripheral receiving points (SPPs) spaced apart in space, connected to the central reception and processing center (CPPO) by command communication lines and analogue signal relay lines, moreover, tuning commands are transmitted via command lines of communication with the CPPO to the SPT the frequency of the signal source of radio emissions, and along the lines of analogue relay received in IFR signals IRI are transmitted to the CPPO, where the measurement of the differences in the time of reception of these signals in the IFP and CPU Software as an argument for maximizing the modules of the inter-correlation functions of the IRI signals after their relay, and the coordinates of the IRI are calculated.

The structural diagram of a device that implements this method, containing three peripheral points of the reception of the signal of the source of radio emission (RFP) and one central point of reception and processing (CPPO), shown in figure 1.

Each peripheral point of reception of an IRI signal (IFPi), representing a set of devices emitting radio signals from an IRI against a background of interference, as well as devices organizing analogue relay lines, includes:

- antenna and radio receiver (RPrUi) devices for receiving an IRI signal;

- radio transmitting (RPdUi) and antenna devices for relaying the IRI signal,

where i = 1, 2, 3.

The central point of reception and processing, representing a set of devices emitting radio signals from the IRI against the background of interference, as well as devices designed to highlight useful information about the parameters of the IRI by joint processing of radio signals, includes:

- antenna and radio receivers (RPrU) for receiving relayed signals of IRI;

- antenna and radio receiving (RPrUo) devices for receiving IRI signals;

- central processing point (CPO).

In the CPO, the magnitude of the mutual delays of the IRI signal at the receiving points is estimated by calculating the maximization argument of the module of the inter-correlation functions R _{i, k} [τ] of the IRI signals after their relay [4, p.103 ... 104]:

Where

, $$x_k^{\ast }\left(t\right)$$

- сигналы, комплексно сопряженные с сигналами x_i(t), x_k(t).i, k = 0, 1, 2, ... N are the numbers of the RFP (i, k> 0) and the CPPO (i, k = 0), i ≠ k; N is the number of IFR; | · | - module of a complex number; x _i (t), x _k (t) - IRI signal received at the i, kth point; t is the time; $$x_i^{\ast }\left(t\right)$$

, $$x_k^{\ast }\left(t\right)$$

- signals complex conjugate with signals x _i (t), x _k (t).

And finally, the position of the IRI is calculated in the CPO, which is determined by the intersection points of the rotation hyperboloids with the foci at the locations of the receiving positions, constructed taking into account the measured differences in the propagation time of the IRI signal τ _{i, k} [5, p. 318].

However, in practice, when measuring the mutual propagation delays of the signals, errors are possible due to the frequency mismatch in the relay, which is due to two factors.

Firstly, if the carrier of the IRI is a rapidly moving object, such as an airplane, the carrier frequencies of the relayed signals can be shifted by the value of the Doppler shift proportional to the radial speed of the IRI relative to the receiving point.

Secondly, in multiposition radio engineering systems, when relaying an IRI signal from the IFR to the CPPO, the signal frequency f _{c is} preliminarily transferred to the relay frequency f _p . The transfer from the signal frequency f _c to the relay frequency f _{p is} usually carried out sequentially in several frequency converters, each of which contains a local oscillator, a mixer and an output band-pass filter. To ensure equal frequencies during relaying, it is proposed in [6, pp. 40 ... 41, Fig. 2.5] to use common local oscillators for all SPPs. However, the technical implementation of this method with a large territorial separation of the SPT is difficult, because it requires the inclusion of additional lines of relay signals of local oscillators in the equipment. Maintaining the same frequency of different local oscillators in the frequency converters on all IFs is also quite a challenge and requires both constant monitoring of the nominal frequency and the use of highly stable reference generators with compensation for external destabilizing factors (temperature, aging of the element base, instability of the supply voltage, etc. .).

Thus, the frequencies of the relayed signals of the radio source, which are received at the DSP (Fig. 1), may differ in nominal value due to Doppler bias and (or) due to the mismatch of the local oscillator frequencies at the receiving points.

To evaluate the influence of the frequency mismatch of the relayed signals of the IRI x _i (t) and x _k (t) on the magnitude of the shift of the maximum of the inter-correlation function (2), which leads to errors in measuring the differences in the propagation time of the IRI signal τ _{i, k} , the time-frequency mismatch function is used [4, p.105]. We obtain the formula of such a function as applied to the problem under consideration.

For this purpose, we write in a complex form the signal received at the input of the central processing center from the i-th receiving point:

where A (tt _i ), φ (tt _i ), t _i and µ _i are, respectively, the actual amplitude and phase of the IRI signal, as well as the delay and attenuation of the signal during propagation from the IRI to the CPU; ω _i is the carrier frequency of the signal after relaying; j is the imaginary unit; t is time.

Then, taking into account (3), the inter-correlation function of the i-th and k-th signals can be represented in the following form:

; $$P_k={\displaystyle \underset{-\infty }{\overset{\infty }{\int }}{x}_k\left(t\right)\cdot x_k^{\ast }\left(t\right)dt}$$

.where Δω _{i, k} = ω _i -ω _k ; Ф _{i, k} = -ω _i · t _i + ω _k · t _k -ω _k · τ; $$P_i={\displaystyle \underset{-\infty }{\overset{\infty }{\int }}{x}_i\left(t\right)\cdot x_i^{\ast }\left(t\right)dt}$$

; $$P_k={\displaystyle \underset{-\infty }{\overset{\infty }{\int }}{x}_k\left(t\right)\cdot x_k^{\ast }\left(t\right)dt}$$

.

Carrying out the change of variables under the integral sign in (4) - s = tt _i , and also taking into account that Ф _{i, k} does not depend on the integration variable, we obtain the expression:

where X _i (s), X _k (s) are the complex amplitudes of the relayed signals:

It is easy to notice that expression (5) coincides with the well-known formula for calculating the time-frequency mismatch function (VChFR) [4, p.105, f-la (9.12)].

Since the position of the RFID maximum (5) depends on both the time shift and the frequency mismatch of the relayed signals, in practice, the search for the propagation time delays of the signals in a differential-range measuring system is carried out in a multi-channel correlation-filter device as a maximum maximum for all possible values of time and frequency shifts [4, p. 106, fig. 9.2].

Thus, the main disadvantage of the prototype is that when evaluating the time delays of the IRI signals received at the IFR in the CPO, it is necessary to implement multiple calculation of the correlation functions for all possible values of the frequency shifts.

The purpose of the invention is to reduce the number of calculations when evaluating the time delays of the received IRI signals in the procedure for calculating the coordinates of the IRI realized by the central processing point.

This goal is achieved by the fact that in the proposed method changes the sequence of actions preceding the procedure for calculating the coordinates of the IRI. The essence of these changes is that before calculating the cross-correlation function, the IRI signals relayed to the CPO are subjected to additional processing:

where T is a fixed time shift, T≤1 / (2 · F); F is the width of the spectrum of the IRI signal, and the estimate of the signal delay is determined as an argument for maximizing the module of the inter-correlation function of the signals y _i (t) and y _k (t):

We show that (9) is equivalent to (1). To do this, we use the Cauchy-Bunyakovsky-Schwartz inequality [7]:

Moreover, equality in (10) is achieved when f (r) and g (r) are equal up to a constant factor.

In relation to signals (8), inequality (10) can be represented as follows:

Given the previously adopted notation (3) and (8), we obtain the formulas included in the numerator and denominator (11) of the expressions:

where E _i {t} = A (tt _i ) · A (tt _i + T); E _k {t} = A (tt _k + τ) · A (tt _k + T + τ); Θ _i {t} = φ (tt _i ) -φ (tt _i + T); Θ _k {t} = φ (tt _k + τ) -φ (tt _k + T + τ);

In view of (12) - (14), we obtain the inequality equivalent to (11)

Based on the properties of the Cauchy-Bunyakovsky-Schwartz inequality [7], it can be argued that if Θ _i {t} -Θ _k {t} ≠ 0, that is, when τ ≠ t _k -t _i , the module of the correlation function of signals y _i ( t) and y _k (t) (the left side of inequality (15)), will be less than unity. If τ = t _{k -} t _i , then inequality (15) is transformed into the equality:

Based on (16), it can be argued that the argument for maximizing the module of the inter-correlation function of the signals y _i (t) and y _k (t) (9), as well as the argument for maximizing the module of the inter-correlation function of the signals of ideal x _i (t) and x _k ( t) without frequency shifts (1), it will be equal to the difference in the propagation times of the IRI signals between the i-th and k-th IFRs: τ = t _k -t _i . In addition, from the previous calculations it follows that when calculating the differences in the propagation times of the signals, it is not necessary to repeatedly calculate the inter-correlation functions for all possible values of the frequency shifts.

Therefore, when determining the coordinates of the IRI using the differential-ranging method, the proposed approach allows us to calculate the difference in the propagation times of the IRI signals for a smaller number of operations than is required in the prototype.

A comparative analysis of the proposed technical solution with the prototype shows that the proposed method differs from the known one in that before calculating the IRI coordinates, the time delays of the received signals are estimated after additional processing of the IRI signals relayed to the CPO. Thus, the claimed method meets the criterion of "novelty."

Information sources

1. Patent RU: No. 2309420, publ. 10/27/2007

2. GDR patent No. 274102.

3. Kondratiev B.C. and other multi-position radio systems. / Edited by prof. V.V. Tsvetnova - M.: Radio and Communications, 1986. - 264 p.

4. Shirman Y.D., Manzhos VN, Theory and technique of processing radar information against a background of interference. - M.: Radio and Communications, 1981, 416 p.

5. Chernyak V.S. Multiposition radar. - M .: Radio and communications, 1993 .-- 415 p.

6. Kupriyanov A.I., Sakharov A.V. Radio-electronic systems in the information conflict. - M.: University Book, 2003 .-- 528 p.

7. Cauchy-Bunyakovsky inequality: [Electronic resource] // Wikipedia. URL: http://ru.wikipedia.org/wiki/Koshi_- Bunyakovsky Inequality (Date of treatment: December 16, 2013).

Claims (1)

A method for determining the coordinates of a radio emission source (IRI), based on the reception of its signal by spaced-apart peripheral reception points (PPP) associated with a central reception and processing center (CPPO) command lines of communication and analogue relay lines of the signal, moreover, through command lines of communication with the CPPO commands for tuning to the frequency of the signal source of radio emissions are transmitted to the RFP, and IRI signals received in the RFP are transmitted along the analogue relay lines to the CPPO, where the time differences of receiving these signals are measured in RFP and TSPPO and computes the coordinates of IRI, characterized in that the time difference of reception signals relayed radio source τ _{i, k} are defined as argument maximization module interrelation functions:

where i, k = 0, 1, 2, ..., N are the numbers of the RFP (i, k> 0) and the CPPO (i, k = 0); N is the number of IFR,
in which, before its calculation, the signals y _i (t) and y _k (t) are converted from the initial IRI signals x _i (t) and x _k (t) received at the i, kth point, respectively (t is time), by their multiplication by the same signals subjected to complex conjugation and time shift by the interval T:

(•) ^* - sign of complex conjugation;
T≤1 (2 · F);
F is the width of the spectrum of the IRI signal.