RU2526533C2 - Phase-based direction-finder - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: invention relates to radio engineering and can be used for detection and direction-finding of signal sources. The phase-based direction-finder comprises two antennae, two receivers, a phase meter, four frequency converters, four high-frequency band-pass filters, four intermediate frequency filters, two rejection filters at a second intermediate frequency, two filter banks, a phase meter unit, six radio-frequency amplifiers and a computing device, connected to each other in a certain manner, wherein the computing device calculates angular coordinates of the radiation source.

EFFECT: high noise-immunity, broader functional capabilities and increased sensitivity of the direction-finder.

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Description

The invention relates to radio engineering and can be used for detection and direction finding of radiation sources of signals.

A device for direction finding of radiation sources of signals [1], containing the first and second receiving antennas, the first and second receivers, the first, second and third multipliers, the first and second narrow-band filters, 90 ° phase shifter, phase detector, first and second indicators, correlator , adjustable delay unit, low-pass filter, extreme regulator and measuring device.

The disadvantage of the analog device is the impossibility of simultaneous direction finding of several radiation sources, as well as low sensitivity and noise immunity.

As a prototype device, a phase direction finder was selected, in which two antennas, two receiving devices, and a phase meter are used [2].

The specified direction finder uses the phase direction finding principle when a radio wave with a flat front forms coherent signals at the outputs of the antennas, the phase difference Δφ between which depends on the direction a to the direction finding radiation source:

where d is the distance between the antennas (base), λ is the wavelength.

The disadvantages of this construction are low noise immunity and limited functionality.

The objective of the invention is to increase noise immunity, expanding functionality and increasing the sensitivity of the direction finder.

The problem is solved in that in the phase direction finder containing two antennas and two receiving devices, according to the invention, four frequency converters, four high-pass bandpass filters, four intermediate frequency filters, two notch filters at the second intermediate frequency, two filter units, a unit are additionally introduced according to the invention phase meters, six radio frequency amplifiers and a computing device, wherein the first high-pass filter is serially connected, the first receiving device, representing e is a low-noise radio frequency amplifier, and a second high-pass filter, form a first high-frequency amplifier, a third high-pass filter, connected in series, a second receiver, also a low-noise radio frequency amplifier, and a fourth high-pass filter, form a second high-frequency amplifier, in series connected by a first intermediate-frequency bandpass filter, a first radio frequency amplifier and a second intermediate-frequency bandpass filter the first intermediate frequency amplifier is connected, the third intermediate frequency bandpass filter is connected in series, the second radio frequency amplifier and the fourth intermediate frequency bandpass filter form the second intermediate frequency amplifier, the first notch filter of the second intermediate frequency is connected in series, the third radio frequency amplifier form the third second intermediate frequency amplifier, connected in series second notch filter of the second intermediate frequency, fourth amplifier for the sake of the frequencies form the fourth amplifier of the second intermediate frequency, with the input of the first high-frequency amplifier connected to the first antenna, and the output to the first input of the first frequency converter, the second input of which is connected to the local oscillator output, the input of the second high-frequency amplifier connected to the second antenna, and the output - with the first input of the second frequency converter, the second input of which is connected to the output of the phase shifter, the input of which is connected to the local oscillator output, the input of the first intermediate frequency amplifier is connected to the output the house of the second frequency converter, and the output is with the first input of the third frequency converter, the input of the second intermediate frequency amplifier is connected to the output of the first frequency converter, and the output is with the first input of the fourth frequency converter, the input of the fifth radio frequency amplifier is connected to the output of the first high-frequency amplifier, and the output is with the second input of the third frequency converter, the input of the sixth radio frequency amplifier is connected to the output of the second high-frequency amplifier, and the output is with the second input of the fourth converter frequency converter, the input of the third amplifier of the second intermediate frequency is connected to the output of the third frequency converter, and the output is connected to the input of the first filter block, the input of the fourth amplifier of the second intermediate frequency is connected to the output of the fourth frequency converter, and the output is to the input of the second filter block, the output of each filter the first filter block is connected to the first inputs of the phase meters of the phase meter block, and the output of each filter of the second filter block is connected to the second inputs of the corresponding phase meters of the phase meter block, and the outputs the azometers of the phasemeter block are connected to a computing device that calculates the angular coordinates of the radiation source.

Achievable technical result of the invention is to increase the sensitivity, increase the frequency resolution while receiving radio signals from several sources of radio emission, increase the reliability and accuracy of bearing detection on signal sources.

The claimed phase direction finder contains two antennas, two receiving devices, four frequency converters, four high-pass bandpass filters, four intermediate frequency filters, two notch filters at the second intermediate frequency, two filter units, a phase meter unit, six radio frequency amplifiers and a computing device, in a specific way interconnected. A distinctive feature of the direction finder construction is that phase information is used about the angular coordinates of the sources at individual Raman frequencies at the intermediate frequency, and not at the substitution frequency, since it is the substitution frequency that the signals of all sources are superimposed, which leads to a false bearing. Therefore, in the proposed scheme, it is precisely the signals at the substitution frequency that are rejected, and the signals at the Raman frequencies are extracted.

The combinational components arising from the interaction on non-linear elements of signals received at spaced antennas from the same radiation source are defined as intrinsic combinational components. The combinational components formed by the interaction on non-linear elements of signals from various emitters, we define as mutual combinational components.

To provide an instant frequency overview, it is proposed to implement a phase direction finder with substitution of the local oscillator frequency. In the conventional approach, the use of such a scheme, which reduces all signals from the span to the substitution frequency, prevents the provision of resolution conditions. That is, the requirements of an instant review of a wide frequency band and signal resolution are, in principle, contradictory. The task becomes especially difficult when you consider that when applying the substitution of the local oscillator frequency, the number of combination frequencies at the output of the multiplying phase discriminator increases in proportion to the fourth power of the number of direction finding sources. The combinational frequencies contain all combinations of the initial phases of the signals that produce them, and therefore the resulting direction-finding characteristic can be significantly deformed. In this case, the task of determining the angular coordinates of each radiation source in a multipurpose situation becomes even more difficult to solve [3, 4].

The solution is assumed based on the consideration of the phase structure of the signal at the outputs of the phase channels. The new approach involves a review of the mutual Raman frequencies at an intermediate frequency. The band boundary is determined by the maximum value of the combination frequencies. The simplest option, providing an instant overview of the intermediate frequency, is based on the filter method, in which informative combinational components are saved and the rest are rejected. In this case, the introduction of additional high-intensity interference increases the sensitivity of the phase direction finder, while in conventional radio receivers the presence of powerful interference leads to large distortions and even loss of useful information.

Figure 1 shows the direction finder circuitry containing the first 1 and second 2 antenna inputs, the first 3, second 4, third 7 and fourth 8 input high-pass bandpass filters, the first 5 and second 6 receiving devices, local oscillator 11, phase shifter 12, first 9 , second 10, third 19 and fourth 20 frequency converters, first 13, second 17, third 14 and fourth 18 intermediate frequency filters, first 15, second 16, third 25, fourth 26, fifth 21 and sixth 22 radio frequency amplifiers, the first 23 and second 24 notch filters of the second intermediate frequency, the first 27 and second 28 filter units, phase meter unit 29, and computing device 30.

Let us explain the operation of the device. The signals received by antennas 1 and 2, amplified by UHF1 and UHF2 and supplied to the inputs of frequency converters 9 and 10, are defined respectively in the form:

,

,

,

,

, $$U_{m\nu }^a$$

- амплитуда сигнала, принятого от ν-го источника на антенну 1, $$U_{m\nu }^b$$

- амплитуда сигнала, принятого от ν-го источника на антенну 2, ω_ν - частота v-того источника излучения, $${\psi }_{\nu }^a$$

и $${\psi }_{\nu }^b$$

- начальные фазы для v-того сигнала, принятого разнесенными антеннами 1 и 2 фазового радиопеленгатора.Where $$F_{\nu }^{a,b}(t)={\omega }_{\nu }t+{\psi }_{\nu }^{a,b}$$

, $$U_{m\nu }^a$$

- the amplitude of the signal received from the νth source to the antenna 1, $$U_{m\nu }^b$$

- the amplitude of the signal received from the νth source to the antenna 2, ω _ν is the frequency of the vth radiation source, $${\psi }_{\nu }^a$$

and $${\psi }_{\nu }^b$$

- initial phases for the v-th signal received by the diversity antennas 1 and 2 of the phase direction finder.

We write the signal of the local oscillator 11

U _Г (t) = U _mГ sin [Ф _Г (t)],

where Ф _Г (t) = ω _Г t + ψ _Г.

The phase difference for the νth source is determined by the expression

.

.

The signal allocated by the first intermediate frequency amplifier, when multiplying the signals U _A1 and U _G in the frequency Converter 9 is defined as

.

.

To the frequency converter 10, the signal U _Г from the local oscillator 11 enters through the phase shifter 12, which shifts the phase of the signal by π / 2 and, therefore, for the signal at the output of the phase shifter 12 write:

U _Ф (t) = U _mГ cos [Ф _Г (t)].

The signal allocated by the second intermediate frequency amplifier, when multiplying the signals U _A2 and U _G in the frequency converter 10 is defined as

.

.

The signal at the output of the third frequency converter 19 when multiplying the signals U _A2 and U _{2 is} defined as

.

.

The signal at the output of the fourth frequency converter 20 when multiplying the signals U _A2 and U _{1 is} defined as

.

.

на одной частоте - частоте гетеродина, что вызовет существенные искажения пеленгационной характеристики. Поэтому целесообразно осуществлять режектирование смеси сигналов на частоте гетеродина. Остальные n²-n слагаемых, которые являются взаимными комбинационными составляющими, содержат фазы в виде $$({\omega }_{Г}+{\Omega }_{\nu \lambda })t+{\psi }_{\nu }^a-{\psi }_{\nu }^b+{\psi }_{Г}$$

для U_k1 и $$({\omega }_{Г}+{\Omega }_{\nu \lambda })t+{\psi }_{\nu }^b-{\psi }_{\nu }^a+{\psi }_{Г}$$

для U_k2, $$\nu ,\lambda =\overline{\mathrm{1,}n}$$

, ν≠λ.From the form of the signals U _k1 and U _k2 it _can be seen that n components of the double sum when the indices λ = ν coincide (proper combination components) contain the initial phases Δφ _ν + ψ _Г , $$\nu =\overline{\mathrm{one,}n}$$

at one frequency - the frequency of the local oscillator, which will cause significant distortion of the direction-finding characteristic. Therefore, it is advisable to carry out the notch of a mixture of signals at the local oscillator frequency. The remaining n ² -n terms, which are reciprocal combinational components, contain phases in the form $$({\omega }_G+{\Omega }_{\nu \lambda })t+{\psi }_{\nu }^a-{\psi }_{\nu }^b+{\psi }_G$$

for U _k1 and $$({\omega }_G+{\Omega }_{\nu \lambda })t+{\psi }_{\nu }^b-{\psi }_{\nu }^a+{\psi }_G$$

for U _k2 , $$\nu ,\lambda =\overline{\mathrm{one,}n}$$

, ν ≠ λ.

Isolation of mutual combination components at frequencies Ω _νλ using filter units 27 and 28 for both phase channels and measurement for each pair of phase differences at each combination frequency using phase block unit 29 gives Δφ _νλ = Δφ _ν + Δφ _λ . Moreover, Δφ _νλ = Δφ _λν . Therefore, to uniquely resolve the resulting system of equations, it is sufficient to use half of all possible combination components lying either above or below the local oscillator frequency. In this case, the number of equations will be n (n-1) / 2, and the number of unknowns will be n. Thus, for n≥3, the resulting system of linear equations has a unique solution, which allows one to obtain a separate bearing for each radiation source.

Let us now consider the effect of transformations in the scheme of the proposed phase direction finder on the relative levels of combinational components in order to evaluate the increased sensitivity of the proposed phase direction finder circuit. Suppose that U _m1 > U _m2 . The relative levels of mutual Raman components at the outputs of the phase channels for n = 2 are shown in FIG. 2, from which it follows that at the substitution frequency ω _G we have levels for signals of the 1st and 2nd emitters equal to 1 and k ^2, respectively, where k = U _m2 / U _m1 . Here, the 1st number indicates the source of a stronger signal, relative to the level of which normalization is performed (in this case, the ratio of signal levels of various sources at the direction finder input is k, where k <1). Since at the frequency ω _G we have signal levels 1 and k ² , the weak signal at the input of the phase channel is weakened even more after transformations in the measuring path, “strong presses weak”). Accordingly, the relative level of the weak signal at the output of the phase discriminator will be k ⁴ relative to unity for the level of the strong signal. Thus, after conversion in the phase discriminator, the weak signal will be attenuated even more. The relative level of mutual Raman components at the outputs of the phase channels is equal to k, and the corresponding components at the output of the phase discriminator have a relative level of k ² against a level equal to one for a strong (normalizing) signal and against a level for a weak signal. An important conclusion can be drawn from this: the level of the mutual Raman component at the output of the phase channel is 1 / k times less than the strong signal and 1 / k times more than the weak signal; in accordance with this, and at the output of the phase discriminator, we have mutual combinational components (used for separate measurement of phase differences), the level of which is 1 / k ² times less than the level of a strong signal and 1 / k ² times more than the level of a weak signal. Therefore, when using reciprocal combinational components to measure the phase differences between the signals of each of the emitters compared to the operation of the phase direction finder in single-purpose mode with its own combinational components, the level of the strong signal is attenuated 1 / k ² times at the output of the phase discriminator, and the level of the weak signal increases by as many times. In this case, the levels of mutual Raman components are equalized for signals of different radiation sources (for n = 2, both mutual Raman components for strong and weak signals are equal). Thus, the use of a phase direction finder with frequency substitution due to the use of mutual combination components for direction finding not only solves the problem of simultaneously viewing a wide frequency band of the radar range with instant resolution of signals, but also improves the measurement conditions for weak signals compared to a single-purpose phase direction finder, working on an equivalent source with a lower relative signal level.

The above reasoning can be extended to the case when the number of radiation sources is n> 2. In this case, the relative level of the input signals can be determined by the formula k _νλ = U _mλ / U _mν , where the source is selected as the _νth source, from which the signal received by the phase-direction finder radio receiver is the most intense.

Therefore, in the case of a multipurpose situation (n> 2), the relative intensities measured by the levels of the reciprocal combinational components are smoothed relative to the levels of the own combinational components for the same sources, which determine the meter mode in a single-purpose situation.

Thus, as the above discussion has shown, the operation of the phase direction finder with respect to the reciprocal combinational components does not worsen, but even, on the contrary, improves the energy of the radio line relative to the more difficult case of weak signals. By introducing high-intensity interference, an increase in the level of a weak signal is achieved, and, consequently, an increase in the sensitivity of the phase direction finder.

Information sources

1. RF patent 2165628, G01S 3/00, G01S 3/46, publ. 04/20/2001.

2. Denisov V.P., Dubinin D.V. Phase direction finders. Tomsk, 2002, p. 8.

3. Zolotarev I.D., Berezovsky V.A. Phase direction finder with a local oscillator frequency substitution circuit when working for multiple targets, Omsk: Omsk State Technical University, Omsk Scientific Bulletin, 2009, No. 3 (83) - S.260-264.

4. Zolotarev I.D., Berezovskiy V.A., Privalov D.D. Signal Analysis at the Phase Discriminator Output of the Phase Direction Finder Circuit with the Frequency Substitution. - International Conference on Actual Problems of Electronic instrument Engineering Proceedings, APEIE-2010. - Novosibirsk: NSTU, September 22-24, 2010, V.1. - P.18-22.

Claims (1)

Phase direction finder containing two antennas and two receiving devices, characterized in that four frequency converters, four high-pass bandpass filters, four intermediate-frequency filters, two notch filters at the second intermediate frequency, two filter units, a phase meter unit, six radio frequency amplifiers are additionally introduced and a computing device, wherein the first high-pass filter is serially connected, the first receiving device, which is a low-noise radio clock amplifier and the second high-pass filter form a first high-frequency amplifier, connected in series with a third high-pass filter, a second receiver, also a low-noise radio frequency amplifier, and a fourth high-pass filter form a second high-frequency amplifier, connected in series with a first intermediate frequency, the first radio frequency amplifier and the second intermediate frequency bandpass filter form the first intermediate frequency amplifier Astotas connected in series to a third intermediate-frequency bandpass filter, a second radio frequency amplifier and a fourth intermediate-frequency bandpass filter form a second intermediate-frequency amplifier, a first intermediate frequency notch filter connected in series, a third radio-frequency amplifier to form a third intermediate-frequency amplifier, second second notch filter connected in series intermediate frequency, the fourth radio frequency amplifier form the fourth amplifier intermediate frequency, the input of the first high-frequency amplifier connected to the first antenna, and the output to the first input of the first frequency converter, the second input of which is connected to the local oscillator output, the input of the second high-frequency amplifier connected to the second antenna, and the output to the first input the second frequency converter, the second input of which is connected to the output of the phase shifter, the input of which is connected to the local oscillator output, the input of the first intermediate frequency amplifier is connected to the output of the second frequency converter, and the output is with the first input of the third frequency converter, the input of the second intermediate frequency amplifier is connected to the output of the first frequency converter, and the output is with the first input of the fourth frequency converter, the input of the fifth radio frequency amplifier is connected with the output of the first high-frequency amplifier, and the output is with the second input of the third frequency converter, the input of the sixth radio frequency amplifier is connected to the output of the second high-frequency amplifier, and the output is connected to the second input of the fourth frequency converter, the input of the third amplifier the second intermediate frequency is connected to the output of the third frequency converter, and the output is connected to the input of the first filter block, the input of the fourth amplifier of the second intermediate frequency is connected to the output of the fourth frequency converter, and the output is connected to the input of the second filter block, the output of each filter of the first filter block is connected to the first the inputs of the phase meters of the phase meter block, and the output of each filter of the second filter block with the second inputs of the corresponding phase meters of the phase meter block, and the outputs of the phase meters of the phase meter block are connected to a computing device that calculates the angular coordinates of the radiation source.

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