RU2206901C1 - Phase direction finder - Google Patents

Abstract

FIELD: radiolocation, radio navigation, determination of angular coordinate of radiation source of phase-keyed signal. SUBSTANCE: phase direction finder incorporates first 1 and second 2 receiving antennas, first 3 and second 4 receivers, first 5, second 6 and third 14 multipliers, first 7 and second 8 narrow-band filters, first 9 and second 21 90 degrees phase inverters, phase detector 10, first 11 and second 16 indicators, correlator 12, unit 13 of controlled delay, low-pass filter 15, extremity regulator 17, measuring device 18, first 19, second 20, third 22 and fourth 23 squarers, scaling multiplier 24, subtracter 25 and adder 26. EFFECT: increased operational sensitivity of direction finder while measuring small phase shifts determining direction to radiation source of phase-keyed signal. 3 dwg

Description

 The proposed direction finder relates to radar, radio navigation and can be used to determine the angular coordinate of the radiation source phase-shift keyed (PSK) signal.

 Known devices for direction finding of radiation sources of signals (ed. Certificate of the USSR 164326, 558584, 1555695, 1591664, 1591665, 1602203, 1679872, 1730924, 1746807, 1832947; RF patents 2006872, 2003131, 2012010, 2010258, 2165628. Space trajectory measurements. edited by P.A. Azhadzhanov et al. - M .: Sov. radio, 1969, pp. 244-245; Kinkulkin I.E. et al. Phase method for determining coordinates. - M .: Sov. radio, 1979 and others) .

 As the basic device selected "Phase direction finder" (RF patent 2165628, G 01 S 3/00, 2000).

 This direction finder provides a solution to the contradiction between the requirements for measurement accuracy and the uniqueness of reading the angular coordinate. This is achieved by using two measuring scales: a phase scale - accurate, but ambiguous, and a time scale - rough, but unambiguous. In this case, due to convolution of the spectrum of the received FMN signals, the sensitivity, noise immunity, and accuracy of measuring the phase difference between the signals that have passed two channels of the phase direction finder are increased. Moreover, phase jumps in the received FMN signals do not affect the results of direction finding.

 An object of the invention is to increase the sensitivity of the direction finder when measuring small phase shifts Δφ, which determine the direction of the FMN signal to the radiation source.

The problem is solved in that the phase direction finder containing the first receiving antenna in series, the first receiver, the first multiplier, the second input of which is also connected to the output of the first receiver, the first narrow-band filter and the first 90 ^o phase shifter, the second receiving antenna, the second receiver connected in series the second multiplier, the second input of which is also connected to the output of the second receiver, the second narrow-band filter, a phase detector, the second input of which is connected to the output of the first phase 90 ^° switch, and the first indicator, a variable delay unit connected to the output of the second receiver, a third multiplier, the input of which is connected to the output of the first receiver, a low-pass filter and a measuring device, the output of the low-pass filter through an extreme regulator is connected to the second input of the adjustable block delay, to the second output of which is connected a second indicator administered four quad, second phase shifter 90 ^o, a scaling multiplier, adder and subtractor, and to the output of the phase etektora series connected first squarer, a second squarer and an adder whose output is connected to a second input of the first indicator to the output of a phase detector connected in series with a second phase shifter 90 ^o, the third squarer, scaling multiplier, a second input coupled to an output of the first squarer and subtractor, the second input of which through the fourth quadrator is connected to the output of the third quadrator, and the output is connected to the second input of the adder.

 The structural diagram of the proposed phase direction finder is presented in figure 1. Direction finding characteristic is depicted in figure 2. The relative position of the receiving antennas and the radiation source of the FMN signal is shown in FIG. 3.

The phase direction finder comprises in series the first receiving antenna 1, the first receiver 3, the first multiplier 5, the second input of which is also connected to the output of the first receiver 3, the first narrow-band filter 7, the first phase shifter 9 by 90 ^° , the second receiving antenna 2, the second receiver connected in series 4, the second multiplier 6, a second input of which is also connected to the output of the second receiver 4, the second narrow-band filter 8, the phase detector 10, a second input coupled to an output of the first phase shifter 9, 90 ^o, and the first ind a cator 11, connected in series to the output of the second receiver 4, an adjustable delay unit 13, a third multiplier 14 (the second input of which is connected to the output of the first receiver 3), a low-pass filter 15 and a measuring device 18, the output of the low-pass filter 15 through an extreme controller 17 is connected to the second input of the adjustable delay unit 13 (to the second output of which a second indicator 16 is connected), the first quadrator 19, the second quadrator 20 and the adder 26 (the output of which is connected to the second input of the first indicator 11), connected in series to the output of the phase detector 10, a second phase shifter 21 by 90 ^° , a third quadrator 22, a scaling multiplier 24 (the second input of which is connected to the output of the first quadrator 19), and a subtractor 25, the second input of which is through the fourth quadrator 23 is connected to the output of the third quadrator 22, and the output is connected to the second input of the adder 26.

 Phase direction finder works as follows.

где V₁(t),V₂(t-τ),Wc,φ₁,φ₂,Tc - огибающие, несущая частота, начальные фазы и длительность сигналов,

- время запаздывания сигнала, приходящего на антенну 2 по отношению к сигналу, приходящему на антенну 1;
d - расстояние между приемными антеннами 1 и 2, расположенными на одной линии (измерительная база);
γ - угол прихода радиоволн;
c - скорость распространения света;
φ_к(t) = {0,π} - манипулируемая составляющая фазы, отображающая закон фазовой манипуляции в соответствии с модулирующей функцией (кодом) M(t), причем φк(t)=const при Kτ_э<t<(K+1)τ_э и может изменяться скачком при t = Kτ_э, т.е. на границах между элементарными посылками (К=1, 2,...N-1).Received FMN signals:
U ₁ (t) = V ₁ (t) • cos [Wc · t + φ _к (t) + φ ₁ ];

where V ₁ (t), V ₂ (t-τ), Wc, φ ₁ , φ ₂ , Tc are envelopes, carrier frequency, initial phases and signal duration,

- the delay time of the signal arriving at the antenna 2 with respect to the signal arriving at the antenna 1;
d is the distance between the receiving antennas 1 and 2 located on the same line (measuring base);
γ is the angle of arrival of radio waves;
c is the speed of light propagation;
φ _к (t) = {0, π} is the manipulated component of the phase that displays the law of phase manipulation in accordance with the modulating function (code) M (t), and φк (t) = const for Kτ _e <t <(K + 1 ) τ _e and can change abruptly at t = Kτ _e , i.e. on the boundaries between elementary premises (K = 1, 2, ... N-1).

где V₀ - порог ограничения.τ _e , N - the duration and number of chips that make up a signal of duration Tc (Tc = N • τ _e );
from the outputs of the receiving antennas 1 and 2 go to the inputs of the receivers 3 and 4, respectively, where they are amplified and limited in amplitude:
U ₃ (t) = V ₀ • cos [Wc • t + φ _к (t) + φ ₁ ],

where V ₀ is the limit threshold.

These signals in the multipliers 5 and 6 are multiplied by themselves. As a result of this, the following resulting voltages are formed at the outputs of multipliers 5 and 6:
U ₅ (t) = V ₁ • cos [2Wc • t + 2φ ₁ ],
U ₆ (t) = V ₁ • cos [2Wc (t-τ) + 2φ ₂ ], 0≤t≤Tc,
where V ₁ = 1 / 2K ₁ • V ₀ ² ;
K ₁ - transmission coefficient of the multipliers, which are the second harmonics of the channel voltage.

It should be noted that the width of the spectrum Δfc of the received FMN signals is determined by the duration τ _{e of} their elementary premises
Δfc = 1 / τ _e
while the width of the spectrum of the second harmonics is determined by the duration Tc of the signals:
Δf ₂ = 1 / Tc.

Therefore, when multiplying the FMN signals themselves, their spectrum collapses N times
Δfc / Δf ₂ = N.
This circumstance makes it possible to distinguish harmonic oscillations U ₅ (t) and U ₆ (t) using narrow-band filters 7 and 8, filtering out a significant part of noise and interference.

где V₂ = 1/2К₂•V₁ ²; Δφ = φ₂-φ₁;
К₂ - коэффициент передачи фазового детектора (фазового различителя).If harmonic oscillations U ₅ (t) and U ₆ (t) from the outputs of narrow-band filters 7 and 8 are directly fed to the phase discriminator 10, then at the output of the latter we obtain

where V ₂ = 1 / 2K ₂ • V ₁ ² ; Δφ = φ ₂ -φ ₁ ;
To ₂ - the transfer coefficient of the phase detector (phase discriminator).

It can be seen from the above relation that the voltage at the output of the discriminator depends on the angle γ, however, due to the fact that the cosine is an even function, the sign of the Uout (γ) does not depend on the sign of the angle γ, i.e. independent of side deviation. To eliminate this drawback, a phase shifter 9 is included in the first channel, changing the phase of the harmonic signal U ₅ (t) by 90 ^° . In this case, the mismatch voltage at the output of the phase discriminator 10 is determined by the expression
U _o (γ) = V ₂ • sin (2π • d / λsinγ) = V ₂ • sinΔφ.
The above dependence is usually called direction-finding characteristic (figure 2).

Таким образом, крутизна характеристики определяется величиной отношения d/λ. Увеличение базы d и уменьшение длины волны λ повышают крутизну K_γ, однако при этом возрастает неоднозначность отсчета угла γ.
Крутизна пеленгационной характеристики определяет величину зоны нечувствительности 2γ_min, при заданном значении шумов V_ш (фиг.2).The steepness of the characteristic in the region of small angles γ, where the characteristic is almost linear, is

Thus, the slope of the characteristic is determined by the value of the ratio d / λ. An increase in the base d and a decrease in the wavelength λ increase the steepness of K _γ , however, the ambiguity of the reading of the angle γ increases.
The steepness of the direction-finding characteristic determines the value of the deadband 2γ _min , for a given value of noise V _W (figure 2).

The number of ambiguity zones, i.e. areas where the phase difference Δφ changes by an amount equal to 2π, is determined by the relation
n = 2d / λ.
For a unique reference, it is necessary to choose n = 1, i.e. choose a measuring base d based on the condition
d <λ / 2.
This forms the phase scale for reading the angular coordinate γ, which is accurate but ambiguous. The measurement results are recorded by indicator 11.

Напряжения U₈(t)и U₁₃(t) поступают на два входа сумматора 26, на выходе которого формируется напряжение

Это напряжение фиксируется на втором входе первого индикатора 11.To increase the sensitivity of the direction finder when measuring small values of the phase shift Δφ, the principle of its "amplification" is used, which is based on the technical implementation of the algorithm
cos ⁴ Δφ-6cos ² Δφ • sin ² Δφ + sin ⁴ Δφ = cos ⁴ Δφ.
The voltage U _o (γ) = U ₂ • sinΔφ from the output of the phase detector 10 is supplied to the input of the first quadrator 19, the output of which is generated
U ₇ (t) = V $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ • sin ² Δφ.
This voltage is supplied to the input of the second quadrator 20, the output of which is formed voltage
U ₈ (t) = V $\genfrac{}{}{0ex}{}{\text{4}}{\text{2}}$ • sin ⁴ Δφ.
At the same time, the voltage U _o (γ) from the output of the phase detector 10 is supplied to the input of the phase shifter 21 by 90 ^o , the output of which is generated
U ₉ (t) = V ₂ • sin (Δφ + 90 ^° ) = U ₂ • cosΔφ,
which is fed to the input of the third quadrator 22. A voltage is generated at the output of the latter
U ₁₀ (t) = V $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ • cos ² Δφ.
This voltage is supplied to the input of the fourth quadrator 23, the output of which is formed voltage
U ₁₁ (t) = V $\genfrac{}{}{0ex}{}{\text{4}}{\text{2}}$ • cos ⁴ Δφ.
The voltages U ₇ (t) and U ₁₀ (t) from the outputs of the quadrants 19 and 22, respectively, are supplied to the two inputs of the scaling multiplier 24, at the output of which a voltage is formed
U ₁₂ (t) = 6 • U ₇ (t) • U ₁₀ (t) = 6V $\genfrac{}{}{0ex}{}{\text{4}}{\text{2}}$ • sin ² Δφ • cos ² Δφ.
Voltage U ₁₁ (t) and U ₁₂ (t) are fed to two inputs of the subtractor 25, the output of which is formed voltage

Voltages U ₈ (t) and U ₁₃ (t) are supplied to two inputs of the adder 26, at the output of which a voltage is formed

This voltage is fixed at the second input of the first indicator 11.

The voltages U ₃ (t) and U ₄ (t) from the outputs of the receivers 3 and 4 simultaneously arrive at two inputs of the correlator 12, which consists of an adjustable delay unit 13, a multiplier 14, and a low-pass filter 15. The correlation function R (τ) obtained at the output of the correlator 12, measured by the measuring device 18, has a maximum at the value of the introduced adjustable delay
τ ₀ = t ₂ -t ₁ ,
where t ₁ , t ₂ - the travel time of the signal distances R ₁ and R ₂ from the radiation source to the first 1 and second 2 receiving antennas.

где τ₀ - введенная во второй канал задержка сигнала, соответствующая максимуму корреляционной функции R(τ₀).
Значение угловой координаты γ фиксируется вторым индикатором 16.The maximum value of R (τ ₀ ) of the correlation function is supported by the extreme controller 17, acting on the second input of the adjustable delay unit 13. The scale of the block 13 adjustable delay (angle indicator) is graded directly in the values of the angular coordinate of the radiation source of the FMN signal

where τ ₀ is the signal delay introduced into the second channel corresponding to the maximum of the correlation function R (τ ₀ ).
The value of the angular coordinate γ is fixed by the second indicator 16.

 Thus, the time scale for counting the angular coordinate γ is formed rough, but unambiguous.

Essentially measuring scales measure the total phase difference
ΔF ₁ = m + Δφ,
where m is the number of complete cycles of the measured phase difference, determined by the time scale;
Δφ is the phase difference, as measured by the phase scale (0≤Δφφ≤2π).
Thus, the measured phase shift Δφ, which determines the direction of the FMN signal to the radiation source, is 4 times larger than the initial phase shift. Thus, in the proposed phase direction finder in comparison with the prototype and other known devices provides an increase in sensitivity when measuring small phase shifts corresponding to the direction of the radiation source of the FMN signals.

Claims (1)

A phase direction finder comprising a first receiving antenna, a first receiver, a first multiplier, the second input of which is also connected to the output of the first receiver, a first narrow-band filter and a first 90 ^o phase shifter, a second receiving antenna, a second receiver, a second multiplier, and a second input which is also connected to the output of the second receiver, the second narrow band filter, a phase detector, a second input coupled to an output of the first phase shifter 90 ^o, and the first indicator, pos continuously adjustable delay unit connected to the output of the second receiver, a third multiplier, the second input of which is connected to the output of the first receiver, a low-pass filter and a measuring device, the output of the low-pass filter through an extreme regulator is connected to the second input of the adjustable delay unit, the second output of which is connected to the second indicator, characterized in that it introduced four quadrator, the second phase shifter 90 ^o , scaling multiplier, subtractor and adder, and to the output of the phase det a first quadrator, a second quadrator and an adder, the output of which is connected to the second input of the first indicator, are connected in series to the output of the phase detector, a second 90 ^o phase shifter, a third quadrator, a scaling multiplier, the second input of which is connected to the output of the first quadrator, and a subtractor are connected in series the second input of which through the fourth quadrator is connected to the output of the third quadrator, and the output is connected to the second input of the adder.

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