RU2126978C1 - Omnidirectional radio direction finder - Google Patents

Abstract

FIELD: radio engineering, monopulse radars determining azimuths of air, surface and ground objects. SUBSTANCE: omnidirectional radio direction finder has three antennas 1-3, three commutators 4-6, three receivers 7-9 with common local oscillator 10, generator 11 of signals of constant frequency, frequency converter 12, three voltage limiters 13-15, gate forming unit 16, three phase inverters 17-19, nine phase detectors 20-28, nine analog-to-digital converters 29-37, digital computer 38. Gate forming unit 16 includes three voltage comparator 39-41, AND gate 42, univibrator 43. Novelty of invention lies in addition to radio direction finder of two commutators, one receiver with local oscillator common for all receivers, generator of signals of constant frequency, frequency converter, voltage limiter, three 90 deg phase inverters, eight phase detectors, nine analog-to-digital converters, digital computer and gate forming unit 16. Usage of proposed circuit design of radio direction finder makes it feasible to enhance speed of action, to take azimuths to radiation sources of single radio pulses within sector 0-360 deg, to increase accuracy of direction finding thanks to employment of processing algorithm invariant to angle of coming of signals in angle of elevation plane and to their carrier frequency. EFFECT: increased speed of action and accuracy of direction finding to air objects in azimuthal plane. 1 cl, 4 dwg, 1 tbl

Description

 The invention relates to radio engineering and can be used in radio monitoring tools, as well as in monopulse radar stations to determine the azimuth of air and surface (ground) objects.

 Known direction finders, providing a measurement of the direction of arrival of signals in the circular azimuthal sector by a phase method using at least three antennas as angular sensors [1, 2].

 The known direction finder [1] contains a grating of "n" omnidirectional antennas located at the vertices of a regular "n" - third-sided polygon and directed perpendicular to the plane of the polygon, with amplifiers with electronic gain control connected to them via transmission lines, the outputs of the amplifiers are connected to the summation circuit. The amplification of the amplifiers is carried out by supplying control signals from the shaper of control signals separately to each amplifier.

 This direction finder has a low speed, since the amplitude of the signals is limited by adjusting the amplification of the amplifiers; insufficient noise immunity, since the phase difference of the signals received by the antennas is measured in the entire frequency range; low azimuth direction finding accuracy in the absence of a priori data on the position of the radiation source in the elevation plane and its radiation frequency.

 Of the known devices, the closest in technical essence to the claimed invention is a radio direction finder [2] selected as a prototype, comprising several antennas that are mounted around the circumference at predetermined intervals from each other, a switch, a series switching antenna, two receivers that are connected to the outputs of the switch , two limiters, a phase detector that determines the phase difference of the output signals of the limiters. In addition, the prototype contains a generator that generates sine and cosine signals, two circuits for multiplying the detector output signal by a sine and cosine signal, respectively, two filters for eliminating the components of the rotational speed of the switch, a low-frequency signal generator for indicating, two circuits for multiplying the generator output signal by filter output signals, radio wave arrival azimuth indicator.

 This direction finder has the following disadvantages: sequentially paired switching antennas, which eliminates the work on a single pulse signals; the measured values of the bearing contain errors due to fluctuations in the frequencies of the signals of the received radiation sources and the direction of their arrival in the elevation plane.

These shortcomings do not allow the use of the prototype for direction finding of radiation sources in the azimuthal sector 0 - 360 ^o single pulses, as well as to eliminate direction finding errors due to elevation of sources and fluctuations in their carrier frequency.

 Measurement and accounting of errors due to the elevation angle of the radiation source, involves the use of antennas with directional patterns in the azimuthal and elevation planes as angular sensors, leading to a more complicated direction finder structure [3].

The technical task of the proposed omnidirectional direction finder is to increase speed, ensure direction finding of sources using single pulse signals and increase the accuracy of measuring the direction of arrival of signals in the azimuth sector 0 - 360 ^o through the use of three omnidirectional antennas connected to superheterodyne radio receivers whose output signals of intermediate frequency are measured the phase difference of the signals received by each two adjacent antennas, as well as phase deviations, copulating fluctuations signal frequencies within the bandwidth of the transmission path of each radio receiving and applying digital measurement processing algorithm is invariant to direction of arrival of the signals in the elevation plane and their carrier frequency.

This task is achieved by the fact that in the known device containing three antennas installed around the circumference at an equal distance from each other, a switch, two receivers, connected to them voltage limiters, a phase detector connected to the outputs of the voltage limiters according to the invention introduced the second and third switches, the first inputs of each of the three switches are connected to antennas, a third receiver having a common local oscillator with the first two, a constant frequency signal generator, a frequency converter, output One of which is connected to the combined second outputs of the switches, the first input with a local oscillator and heterodyne inputs of the receivers, and the second with a constant-frequency signal generator, the input of each receiver is connected to the output of one of the three switches, respectively, the third voltage limiter connected to the output of the intermediate path the third receiver frequency, a strobe forming unit, three 90 ^o phase shifters, eight phase detectors, nine analog-to-digital converters, the inputs of which are connected to the outputs and corresponding phase detectors, and the control inputs of the ADC are interconnected and connected to the output of the strobe forming unit, the first, second and third inputs of which are connected to the video outputs of the respective receivers, the input of the first phase shifter is connected to the output of the first voltage limiter, the first input of the third and second inputs seventh and eighth phase detectors, and the output with the first input of the second and second input of the third phase detectors, the input of the second phase shifter is connected to the output of the second connector I voltage, the first inputs of the fourth and sixth and second input of the second phase detectors, and the output is from the first input of the fifth and second input of the sixth phase detectors, the input of the third phase shifter is connected to the output of the third voltage limiter, the first inputs of the seventh and ninth and the second inputs of the fourth and fifth phase detectors, and the output with the first input of the eighth and second input of the ninth phase detectors, a digital computing device, each of the nine inputs of which are connected to the outputs of analog-to-digital converters ers, the control input - with a joint between the control inputs of switches and one control input, the output of the digital computing device is the output of the omnidirectional finder.

 In the omnidirectional direction finder, the strobe forming unit contains three voltage comparators, the inputs of which are the unit inputs, series elements And and a one-shot, each of the three inputs of the element And is connected to the output of the corresponding voltage comparator, and the output of the one-shot is the output of the block.

 A comparative analysis with the prototype shows that the claimed device is distinguished by the presence of new elements with appropriate connections and is not known from the prior art. Thus, the invention meets the criterion of "Novelty."

Analysis of known technical solutions (analogues) in the studied and related fields allows us to conclude that the introduced functional units are known. However, their introduction into an omnidirectional direction finder with the indicated connections gives this device new properties. The introduced functional units interact in such a way that after tuning the omnidirectional direction finder to the required frequency, the azimuth of all sources whose radiation frequency is within the receiver bandwidth is determined pulse by pulse. In this case, immediately after tuning the device to the reception frequency, by applying a pulse signal to its control input, the calibration mode is set in it. At the inputs of the receivers through the switches from the built-in signal generator of constant frequency, in-phase signals begin to arrive, which are upset in frequency relative to the center of the bandwidth of the receivers f _och by a certain value Δf. _{Using the} known values of Δf and f, the _mismatch is determined in digital form for the mismatch between signals of the sinX, cosX type generated using phase shifters in each receiving channel of the device. The measured values are stored in a digital computing device. After a time equal to the duration of the control pulse, the omnidirectional direction finder is put into operation. From the measured phase differences of the signals received by the antennas and the magnitude of the phase mismatch between signals of the sinX, cosX type, taking into account the values obtained in the calibration mode, the azimuth of the radiation sources is determined on a pulse-by-pulse basis. For the calculation, the algorithm is invariant to the frequency and elevation of the direction finding sources.

Thus, the invention meets the criterion of "Inventive step"
The invention can be used in various sectors of the economy and meets the criterion of "Industrial applicability".

 In FIG. 1 is a structural electrical diagram of an omnidirectional direction finder; in FIG. 2 is a drawing explaining the dependence of the bearing values on the direction of arrival of signals in space; in FIG. 3 is a drawing of the dependences of the phase differences of the signals at the outputs of two adjacent antennas on the directions of their arrival in the azimuthal plane; in FIG. 4 is a timing diagram of the operation of the strobe forming unit.

The device of FIG. 1 contains three omnidirectional antennas 1 to 3 installed around the circle at an equal distance from each other, three switches 4 to 6, three receivers 7 to 9 with a shared local oscillator 10, a constant frequency signal generator 11, a frequency converter 12, the first inputs of each of the switches 4 to 6 are connected to antennas 1 to 3, respectively, the second inputs are interconnected and connected to the output of the frequency converter 12, the first input of which is connected to the local oscillator 10, and the heterodyne inputs of the receivers, and the second to the output of the signal generator via toyannoy frequency 11, three voltage limiter 13 - 15 whose inputs are connected to outputs of the intermediate frequency signal receivers 7 - 9, respectively, block the formation of gate 16, three phase shifter 90 ^o 17 - 19, nine phase detectors 20 - 28, nine analog-to-digital converters 29 - 37, the inputs of which are connected to the outputs of the phase detectors 20 - 28, respectively, and the control inputs are interconnected and connected to the output of the strobe forming unit 16, the first, second and third inputs of which are connected to the outputs of the video signals of the receivers 7 - 9, respectively, the voltage limiting output 13 is connected to the first inputs of the first 20 and third 22 and second inputs of the eighth 26 and ninth 27 phase detector inputs of the phase shifter 17, the output of which is connected to the first input of the second 21 and second input of the third 22 phase detectors, the output of the second voltage limiter 14 is connected to the first inputs of the fourth 23 and sixth 25 and the second inputs of the first 20 and second 21 phase detectors, the input of the second phase shifter 18, the output of which is connected to the first input of the fifth 24 and the second input of the sixth 25 phase of the third detector, the output of the third voltage limiter 15 is connected to the first input of the seventh 26 and ninth 28 and the second input of the fourth 23 and fifth 24 phase detectors, the input of the third phase shifter 19, the output of which is connected to the first input of the eighth 27 and the second input of the ninth 28 phase detectors, digital computing device 38, each of the nine inputs of which is connected to the outputs of analog-to-digital converters 29 - 37, respectively, the control input is connected to each other by the control inputs of the switches 4 - 6 and the control input present device 38 is an output of an omni-directional finder.

 The strobe forming unit (Fig. 1) contains three voltage comparators 39 - 41, the inputs of which are the block inputs, series elements And 42 and a single-shot 43, each of the three inputs of the element And is connected to the outputs of the voltage comparators 39 - 41, respectively, and the output of a single-vibrator 43 is the output of the strobe forming unit.

As antennas can be used quarter-wave or half-wave vibrators, designed for a maximum frequency of reception f _max [4]. Electronically-controlled switches are keys made on diodes 2A516, 2A530 and others (see, for example, [5]). The receivers are known devices and can be designed and manufactured according to the recommendations [6], their high-frequency part is expediently performed on gallium arsenide field-effect transistors. As a local oscillator and a frequency converter, devices can be used according to [7, 8]. Voltage limiters and a constant frequency signal generator can be performed on integrated circuits 171UV3, δ KO 347, 198-04TU and 174GF2 δ KO, 374, 175-14TU, respectively. As phase shifters, RC chains are used. Phase detectors are run on voltage multipliers - integrated circuits 525 PS3, 525 PS4, analog-to-digital converters - on elements 1107-PV1, 1107 PV2, according to the recommendations [9]; voltage comparators - on integrated circuits 521 CA1-CA3 [9], the element And - on the chip LI6 series 530, 533; one-shot - on the AG1 chip of series 155, 530; digital computing device - on programmable logic elements such as 573 RF4 and others or on elements of microprocessor technology of the 1810 series. Recommendations on the use of logical integrated circuits and elements of microprocessor technology are given in [10, 11].

 Omnidirectional direction finder operates as follows.

где β - угол между перпендикуляром, восстановленным к базе антенн 1 и 2 и направлением прихода сигналов в горизонтальной плоскости;
λ - длина волны принимаемых сигналов,
Значение d, входящее в выражение 1, задается из условия d ≤ 0,5λ_min.
После преобразования сигналов по частоте в приемниках 7 - 9, нормировки по амплитуде элементами 13 - 15 и смещении по фазе на 90^o элементами 22, 25, 28 они перемножаются в фазовых детекторах 20 - 28. При этом на выходе фазовых детекторов формируются низкочастотные напряжения вида:

где U₁, U₂, U₃ - амплитуда напряжений с выходов ограничителей напряжений 13 - 15 соответственно;
K₁, K₂ - коэффициенты пропорциональности, имеющие размерность 1/β;
ΔФ₁₂,ΔФ₂₃,ΔФ₃₁ - разность набегов фаз сигналов с выходов ограничителей 13 - 14, 14 - 15, 15 - 13 соответственно;
Ф_s1, Ф_s2, Ф_s3 - фазовые ошибки, возникающие на выходах фазовращателей 17 - 19 за счет расстройки частоты принимаемого сигнала относительно середины полосы пропускания радиоприемных трактов.The direction of arrival of signals is determined in the frequency range from f _min to f _max = 3f _min in the azimuthal plane and sector 0 - 360 ^o from the measured phase differences of the signals received by antennas 1 - 3. By changing the frequency of the local oscillator 10, the receivers 7 - 9 are tuned to the desired frequency. Next, direction-finding sources whose radiation frequency is within the bandwidth of the amplifiers of the intermediate frequency of the receivers. The phase difference φ _{ij of the} signals arriving at the inputs of the receivers 7 - 9 depends in the general case on the azimuth β and the elevation angle γ of the radiation source, the geometry of the antenna location and the distance d between them (Fig. 2). The phase difference of the signals received by the antennas φ ₁₂ , φ ₂₃ , φ ₃₁ , taking into account the values of their carrier frequency, can be written as:

where β is the angle between the perpendicular restored to the base of antennas 1 and 2 and the direction of arrival of the signals in the horizontal plane;
λ is the wavelength of the received signals,
The value of d included in expression 1 is set from the condition d ≤ 0.5λ _min .
After the frequency signals are converted in receivers 7–9, the amplitudes are normalized by elements 13–15, and the phase shift is 90 ^{° by} elements 22, 25, 28, they are multiplied in phase detectors 20–28. In this case, low-frequency voltages of the form are formed at the output of phase detectors :

where U ₁ , U ₂ , U ₃ - the amplitude of the voltages from the outputs of the voltage limiters 13 - 15, respectively;
K ₁ , K ₂ - proportionality coefficients having a dimension of 1 / β;
Δ Ф ₁₂ , Δ Ф ₂₃ , Δ Ф ₃₁ - the difference of the phase incursions of the signals from the outputs of the limiters 13 - 14, 14 - 15, 15 - 13, respectively;
Ф _s1 , Ф _s2 , Ф _s3 - phase errors that occur at the outputs of the phase shifters 17 - 19 due to the detuning of the frequency of the received signal relative to the middle of the passband of the radio channels.

Значения φ_uij не будут зависеть от значений U_i, K_i (см. выражения 2), однако сохраняются ошибки, обусловленные составляющими ΔФ_ij, Ф_s1 - Ф_s3. Чтобы учесть их значения, во всенаправленном радиопеленгаторе предусмотрен режим калибровки.In analog-to-digital converters 29 - 37, the voltages are converted to binary codes and recorded at time points specified by the negative edge of the sampling pulse coming from the forming unit 16. From the measured values of U ₂₀ - U ₂₆ , the phase difference φ _ij can be calculated using the expressions

The values of φ _uij will not depend on the values of U _i , K _i (see expression 2), however, errors due to the components ΔФ _ij , Ф _s1 - Ф _s3 remain. To take into account their values, the omnidirectional direction finder provides a calibration mode.

The calibration mode is set after setting omnidirectional radio bearer to the carrier frequency, which switches to control inputs 4 - 6 is energized U _exercise on which switches through to the inputs of receivers receives signals output from the in-phase 12 the frequency value f _{to the} inverter frequency which is equal to
f _k = f ₂ + f _G
where f ₂ is the frequency of the local oscillator 10;
f _G - the value of the frequency of the generator 11, equal to
f _G = f _oph + Δf
where f _opch is the central frequency of tuning the paths of the intermediate frequency of the receivers;
Δf - is the frequency of _{mismatch of the} calibration signal relative to f _opch .

Значения фазовых ошибок Ф_s1k - Ф_s3k не зависят от частоты настройки пеленгатора и линейно зависят от величины Δf

где K_si - коэффициент пропорциональности.The voltage values U _20k - U _27k in the calibration mode (taking into account expression 2) can be written as:

The values of phase errors Ф _s1k - Ф _s3k do not depend on the frequency of the direction finder settings and linearly depend on the value Δf

where K _si is the coefficient of proportionality.

где Δf_пч - ширина полосы пропускания трактов промежуточной частоты приемников.When choosing Δf, the conditions
Δf <0.1f _oph ,

where Δf _pch is the bandwidth of the paths of the intermediate frequency of the receivers.

По известным значениям Δf, f_опч и измеренным напряжениям U_20k - U_28k в цифровом вычислительном устройстве производится:
1) расчет нормировочных коэффициентов L₁, L₂, L₃

2. Расчет фразовых ошибок ΔФ_12к,ΔФ_23к,ΔФ_31к

Выражение (5) получены путем решения уравнений

Поскольку фазочастотная характеристика радиоприемных трактатов в пределах полосы пропускания линейна, то можно считать
ΔФ_12к≈ ΔФ₁₂; ΔФ_23к≈ ΔФ₂₃; ΔФ_31к≈ ΔФ₃₁.
3. Расчет разностей фаз φ_ij с учетом составляющих ΔФ₁₂, ΔФ₂₃, ΔФ₃₁,Ф_s1-Ф_s3

Зависимость значений φ_ij от β для

γ = 0 представлены на фиг.3.Moreover, the expressions U _22k , U _25k , U _28k can be written as

According to the known values of Δf, f _oph and the measured voltages U _20k - U _28k in a digital computing device,
1) calculation of normalization coefficients L ₁ , L ₂ , L ₃

2. Calculation of phrasal error ΔF _{12K, 23K} ΔF, ΔF _31K

Expression (5) is obtained by solving the equations

Since the phase-frequency characteristic of the radio receiving tracts within the bandwidth is linear, we can assume
ΔF ΔF _12k ≈ _12; ΔF ΔF _23K ≈ _23; ΔF ΔF _31K ≈ _31.
3. Calculation of phase differences φ _ij taking into account the components ΔF ₁₂ , ΔF ₂₃ , ΔF ₃₁ , F _s1 -F _s3

The dependence of the values of φ _ij from β for

γ = 0 are presented in figure 3.

4. The calculation of the values of β from the values of φ _ij in the following order:
two values are selected out of three, belonging to the dependencies having the greatest steepness in the selected measurement sub-range D (the conditions for choosing the sub-range and the calculated expressions are presented in the table).

The calculation of the values of β with respect to two values of φ _ij belonging to the dependences having the maximum steepness in the measurement area provides, in comparison with known devices of this type, high measurement accuracy with weak signals (no worse than 0.7 ^o with a signal-to-noise ratio of 13 - 14 dB )

 It does not require data on the values of the carrier frequency of the signals and the position of the radiation sources in the elevation plane (see expressions 1).

 Block formation of the gate 16 operates as follows. According to the video pulses arriving at its inputs (Fig. 4a - 4c), the comparators 39 - 41 form pulses of a duration equal to the pulse duration counted relative to the threshold of operation of the comparators (Figs. 4g - 4e).

 The response threshold of the comparators is selected so that a sufficient signal-to-noise ratio (13 dB or more) is provided at the time of measurement. For this, an And element forms an impulse when all three comparators work (Fig. 4g). According to the negative voltage drop, which is formed at the time when the transient processes in the radio paths of the omnidirectional direction finder are completed, the one-shot 43 stores the code values in the elements 29 - 37 of the device (Fig. 4h).

 Thus, the formulated task of increasing the speed of an omnidirectional direction finder, ensuring direction finding of sources of single pulse signals and improving the accuracy of determining the azimuth of radiation sources is solved using the proposed device.

Sources of information
1. The direction finder, patent N 4551 727, class. G 01 S 3/54, USA, publ. 5.11.85, t. 1060 N 1.

 2. Direction finder, application N 3-15991, MKI G 01 S 3/54, Japan, publ. 4.03.91, N 6-400.

 3. A.I. Leonov, K.I. Fomichev. Monopulse radar, M., radio and communication, 1984, p. 77 - 78.

 4. V.V. Ovsyannikov. Vibrating reactive antenna. M., Radio and Communications, 1985, p. 29 - 41.

 5. Two-channel microwave switch, a. with. N 12220031 A, MKI H 01 P 1/15, publ. 03/23/86, bull. N 11.

 6. Radio receivers, under. ed. A.G. Barulina. M., Radio and Communications, 1984, p. 26 - 23, 36 - 44.

 7. Highly stable frequency tunable microwave generator. A.c. N 42663, MKI 4 H 03 B 9/14, 7/14, 5/18, publ. 01/15/88, N 1.

 8. Balanced mixer, a. with. N 964967, MKI H 03 D 7/14, publ. 10/01/08, bull. N 37.

 9. B. G. Fedorkov et al. Microelectronic digital-to-analog and analog-to-digital converters. M., Radio and Communications, 1984, p. 15 - 17, 77 - 83.

 10. M.I. Bogdanovich et al. Digital integrated circuits, reference book. Minsk, Belarus, 1991. 47, 118 - 121.

 11. B.A. Kalabekov. Microprocesses and their application in signal transmission and processing systems. Textbook for high schools. M., Radio and Communications, 1988, p. 71 - 74, 175 - 181.

Claims (2)

1. An omnidirectional direction finder, comprising three antennas installed around a circle at an equal distance from each other, a first switch, two receivers with voltage limiters connected to them, characterized in that the second and third switches are inserted into it, the first inputs of each of the three switches are connected with corresponding antennas, a third receiver having a common local oscillator with the first two, a constant frequency signal generator, a frequency converter, the output of which is connected to the second inputs connected together dams of switches, the first input with a local oscillator and heterodyne inputs of the receivers, and the second with a constant-frequency signal generator, the input of each receiver is connected to the output of the corresponding of the three switches, the third voltage limiter connected to the output of the intermediate frequency path of the third receiver, the strobe block, three phase shifter 90 ^o, eight phase detectors, nine analog-digital converters (ADC), whose inputs are connected to outputs of the respective phase detectors, and control inputs AC combined with each other and are connected to the output of forming the gate, the first, second and third inputs connected to the outputs of video signals corresponding receivers input of the first phase shifter 90 ^o connected to the output of the first voltage limiter, the first input of the third and second inputs of the seventh and eighth phase detector, and the output is with the first input of the second and second input of the third phase detectors, the input of the second phase shifter 90 ^{o is} connected to the output of the second voltage limiter, the first inputs of the fourth and sixth o and the second input of the second phase detectors, and the output with the first input of the fifth and second input of the sixth phase detectors, the input of the third phase shifter 90 ^{o is} connected to the output of the third voltage limiter, the first inputs of the seventh and ninth and second inputs of the fourth and fifth phase detectors, and output - with the first input of the eighth and second input of the ninth phase detectors, a digital computing device for calculating normalization coefficients, phase errors, phase differences, azimuth, each of the nine inputs to torogo connected to the input of the corresponding analog-to-digital converter, the control input - with a joint between the control inputs and the control device switches the input, output of the digital computing device for computing the normalization factors of the phase error, phase difference, azimuth is the output device.  2. The device according to claim 1, characterized in that the strobe forming unit contains three voltage comparators, the inputs of which are the unit inputs, a series element And a one-shot connected in series, each of the three inputs of the element And is connected to the output of a corresponding voltage comparator, and the output of a single-shot block output.

Images