RU2071080C1 - Amplitude direction finder - Google Patents

Abstract

FIELD: radio navigation systems. SUBSTANCE: antenna of direction finder has adjustable angular separation of two radiation patterns with input and two outputs controlling angular separation. Each of them is connected through logarithmic receiver to subtracter. Each output of antenna is connected through proper linear receiver to input of correlator which output is coupled through logarithm-taking unit to first input of first multiplier. Second input of this multiplier is connected to first input of second multiplier and through first squarer to terminal of input of width of radiation pattern. Output of first multiplier is linked to input of adder second input is connected through first squarer and delay unit connected in series to output of second divider and to antenna input angular separation. Output of delay unit is connected to second inputs of second and third multipliers. Terminal of input of stabilized value of direction finding is connected to first input of third multiplier which output is coupled to second input of second divider. Output of adder and output of second multiplier are connected to inputs of first divider which output is linked to first inputs of second and third dividers. Output of subtracter is connected to second input of third divider which output is connected to indicator. Operation of amplitude direction finder provides firstly for reduced shift of bearing evaluation thanks to elimination of prior indeterminacy in direction finding sensitivity and secondly for equal precision of measurements due to stabilization of direction finding sensitivity by means of adaptive change of angular separation of radiation pattern under alternating conditions of propagation of radio waves over paths with scattering. EFFECT: increased operational precision. 1 dwg

Description

 The invention relates to the field of radio engineering and can be used in beacon navigation systems.

 Known amplitude direction finders contain an antenna with two angularly spaced radiation patterns and two logarithmic receivers connected to the subtractor.

 The closest to the direction finder under consideration can be considered the direction finder [1] containing an antenna with two equally spaced along the angle of the beam and with two outputs, each of which is connected through a logarithmic receiver to the input of the subtractor. Bearing assessment in such a direction finder with non-tracking direction-finding is based on the measured value of the differential amplitude at the output of the subtractor and its a priori known dependence on the bearing of the HR direction finding, which is assumed to be linear in some direction-finding sector. The steepness of the HRP, which determines the direction-finding sensitivity of the IF of such a direction finder, is inversely proportional to the square of the width of its DN.

 The presence of a scattering medium violates the coherence of the field at the receiving site and causes a known expansion of the antenna patterns (for example, [2]). The degree of such expansion can reach one and a half two times, which is the reason for a threefold or more decrease in the IF compared to its value in a coherent field. The use of the IF value fair for a coherent field under these conditions to determine the bearing leads to the appearance of additional errors in the known direction finder to bias the bearing estimates and their unevenness. The considered amplitude direction finder makes it possible to increase the accuracy of direction finding of radiation sources in scattering media.

 To this end, in a known amplitude direction finder containing an antenna with two angularly spaced radiation patterns and with two outputs, each of which is connected to a subtractor through a logarithmic receiver, the antenna is made with an adjustable angular diversity of radiation patterns and with a control angular diversity input, and also introduced : two receivers, a correlator, a logarithm, three multipliers, an adder, two quadrators, a delay device, three dividers, a terminal for inputting the width of radiation patterns, a terminal input stabilized value of direction finding sensitivity and indicator. Moreover, each output of the antenna through a corresponding receiver is connected to the input of the correlator, the output of which through the logarithm is connected to the first input of the first multiplier, the second input of the first multiplier is connected to the first input of the second multiplier and through the second quadrator is connected to the input terminal of the beam width. The output of the first multiplier is connected to the input of the adder, the second input of which is connected in series through the first quadrator and the delay device to the output of the second divider and the antenna input that controls the angular diversity. The output of the delay device is connected to the second inputs of the second and third multipliers. The input terminal of the stabilized value of the direction-finding sensitivity is connected to the first input of the third multiplier, the output of which is connected to the second input of the second divider. The output of the adder and the output of the second multiplier are connected to the inputs of the first divider, the output of which is connected to the first inputs of the second and third dividers. The output of the subtractor is connected to the second input of the third divider, the output of which is connected to the indicator.

 The structural electrical circuit of the amplitude direction finder is shown in the drawing.

 The amplitude direction finder contains an antenna 1 with adjustable angular diversity of radiation patterns, with two outputs and a control of angular diversity input, logarithmic receivers 2 and 3, receivers 4 and 5, correlator 6, logarithm 7, first multiplier 8, adder 9, first 10 and second 11 quadrators, second multiplier 12, delay device 13, first 14 and second 15 dividers, indicator 16, third divider 17, third multiplier 18, subtractor 19, radiation pattern width input terminal K1 and stabilized value input terminal K2 elengatsionnoy sensitivity.

 In practice, the adjustment of the angular diversity of the beams can be implemented, for example, in a known manner by changing the distance between the irradiators located in the focal plane of the mirror antenna.

где U₁, U₂ амплитуды на выходах антенны;
a_p величина углового разнесения ДН;
θ ширина ДН антенны на уровне 3-х дБ от максимума;

ПЧ пеленгатора в когерентном поле, дБ/град.The direction-finding characteristic of the amplitude direction finder is analytically presented in the form of the dependence of the difference amplitude ΔU expressed in decibels on the bearing α, measured from the RSN:

where U ₁ , U _{2 the} amplitude at the outputs of the antenna;
a _{p the} magnitude of the angular spacing DN;
θ antenna beam width at the level of 3 dB from the maximum;

IF of the direction finder in a coherent field, dB / deg.

Для частично когерентного поля в месте приема, выражение для ПЧ логично представить в виде

4
где θ_э эффективная ширина ДН пеленгатора.From 1 and 2 follows the commonly used direction finding algorithm:

For a partially coherent field at the receiving location, the expression for the IF is logical to represent in the form

4
where θ _{e is the} effective beam width of the direction finder.

В рассеивающих средах, в общем случае θ_э больше θ и только в когерентных условиях эти величины совпадают. Это говорит о том, что крутизна m в общем случае меньше крутизны m_o, а оценка пеленга произведенная на трассах с рассеянием по алгоритму 3, оказывается смещенной, причем в сторону ее приближения к РСН.Similar to 3, bearing

In scattering media, in the general case, θ _{e is} greater than θ and only under coherent conditions do these quantities coincide. This suggests that the steepness m is generally less than the steepness m _o , and the bearing estimation made on the paths with scattering according to Algorithm 3 is biased, and toward its proximity to the RSN.

В результате, после использования 6 в 4 и 5, пеленгационная чувствительность

алгоритм оценки пеленга:

Алгоритм 8 позволяет устранить смещение оценки пеленга посредством исключения априорной неопределенности в ПЧ. Однако, это, как уже отмечалось, не устраняет нестабильности ПЧ при изменении условий распространения радиоволн, что, например, приводит к неравноточности измерений.The determination of θ _e to obtain from 5 algorithm an unbiased bearing estimate was possible by establishing and using the connection θ _e with the correlation value of the amplitudes r at the outputs of the direction finder antenna:

As a result, after using 6 in 4 and 5, direction-finding sensitivity

bearing estimation algorithm:

Algorithm 8 eliminates the offset of the bearing estimate by eliminating a priori uncertainty in the IF. However, this, as already noted, does not eliminate the instability of the IF when changing the propagation conditions of the radio waves, which, for example, leads to the imbalance of the measurements.

From 4 it follows that stabilization of the IF can be achieved by changing the angular spacing of the direction finder detector α _p , which is implemented in the direction finder under consideration.

где

требуемая для выполнения этого равенства величина углового разнесения.For the stabilized value of the inverter μ _st specified from various considerations, one can write:

Where

the angular diversity required to fulfill this equality.

Для получения из 10 алгоритма адаптивной перестройки углового разнесения ДН, необходимо определить неизвестную, существующую в данных условиях распространения, эффективную ширину ДН пеленгатора θ_э. Ее значение следует из 4:

где ПЧ μ определяется в рассматриваемом пеленгаторе по алгоритму 7.From 9 follows the necessary condition for stabilization:

In order to obtain from 10 algorithm for adaptive tuning of the angular diversity of DNs, it is necessary to determine the unknown effective direction finder width θ _e existing under the given propagation conditions. Its value follows from 4:

where the IF μ is determined in the direction finder under consideration according to algorithm 7.

где

является последующим (требуемым), а α_p настоящим, существующим (в момент оценки μ по алгоритму 7) значениями углового разнесения ДН.As a result, after using 11 to 10, the desired algorithm has the form of a recurrence expression describing the process of adaptive restructuring of the angular diversity of the direction finder detector:

Where

is the next (required), and α _{p is the} real, existing (at the time of estimating μ according to Algorithm 7) values of the angular diversity of MDs.

 Amplitude direction finder (drawing) works as follows.

 The oscillations from the outputs of the antenna 1 are amplified, logarithmized, detected in the logarithmic receivers 2, 3 and further, subtracted in the subtractor 19, forming at its output the difference amplitude DU expressed in dB.

The signals from the antenna outputs also go to linear receivers 4, 5, where they are amplified, detected and then fed to the correlator 6. The correlation coefficient r formed at the output of the correlator (hereinafter, the signal value is proportional to the parameter), is transmitted through the logarithmator 7 to the multiplier 8, where it is multiplied with a square of the width of the beam (θ ² ) formed at the output of the squad 11 according to the value of the width of the beam θ introduced to its input through terminal K1.

The value θ ² lnr from the output of the multiplier 8 is entered into the adder 9. At its second input, with the proportionality coefficient equal to ln2, the value of the square of the angular diversity (α $\genfrac{}{}{0ex}{}{\text{2}}{\text{p}}$ ) formed at the output of the quadrator 10 according to the value α _p received at its input available at the output of the delay device 13.

As a result, the sum θ ² lnr + α is formed at the output of the adder $\genfrac{}{}{0ex}{}{\text{2}}{\text{p}}$ ln2, which with a proportionality factor of 24, is input to the input of the divider 14. At its other input, the result is the multiplication in the multiplier 12 of a square of width θ ² coming from the square 11 and the angular separation a _p formed at the output of the delay device 13.

 After completing the division, at the output of the divider 14, in accordance with algorithm 7, the current direction-finding sensitivity value μ appears, which changes when the field coherence in the antenna aperture changes.

 As a result of dividing the difference amplitude DU in the subtractor 19 by the sensitivity value μ, in the divider 17, at its output, in accordance with algorithm 8, an unbiased bearing estimate is displayed on the indicator 16.

. Этот сигнал поступает на управляющий вход антенны, где и производится установка требуемого значения углового разнесения.To generate a signal for tuning the angular diversity of the DN, i.e. of the implementation of algorithm 12, in the multiplier 18, the product of the stabilized value of the direction-finding sensitivity m _st introduced at terminal K2 is formed by the currently existing value of the angular diversity α _p coming from the output of the delay device 13. Then this product is divided in the divider 15 by the existing value of the inverter μ, as a result, at the output of the divider according to algorithm 12, a control signal is generated corresponding to the required value of the angular diversity

. This signal is fed to the antenna control input, where the required value of angular diversity is set.

в качестве существующего в данный момент разнесения α_p, образуемого на его выходе. Величина задержки определяется временем необходимым для формирования нового сигнала управления. Это время ориентировочно складывается из времени перестройки углового разнесения в антенне и времени запаздывания сигналов (включая и время необходимое для оценки корреляции) от антенны до второго делителя 15.The delay device 13 provides a delay in the use of the subsequent value of the angular diversity arriving at its input

as the currently existing diversity α _p formed at its output. The amount of delay is determined by the time necessary to form a new control signal. This time is approximately the sum of the time of adjustment of the angular diversity in the antenna and the delay time of the signals (including the time necessary to estimate the correlation) from the antenna to the second divider 15.

 The use of an amplitude direction finder provides, firstly, a decrease in the bearing estimation bias due to elimination of a priori uncertainty in direction-finding sensitivity and secondly, the uniformity of measurements due to stabilization of direction-finding sensitivity by adaptive adjustment of the angular spacing of radiation patterns in changing propagation conditions of radio waves on scattered paths.

Information sources
1. Leonov A. I. Fomichev K.I. Monopulse radar. M. Radio and communications, 1984, p. 67 (prototype).

 2. Shifrin Ya. S. Questions of the statistical theory of antennas. M. Sov. Radio, 1970, p. 265 266.

Claims (1)

 An amplitude direction finder, comprising an antenna with two angularly spaced radiation patterns and with two outputs, each of which is connected to a subtractor through a logarithmic receiver, characterized in that the antenna is made with an adjustable angular diversity of radiation patterns and with a control angular diversity input, as well as two linear receiver, correlator, logarithm, three multipliers, adder, two quad, delay device, three dividers, input terminal for the width of the radiation patterns, cl a stabilizing value of the direction-finding sensitivity input and an indicator, each output of the antenna through a corresponding linear receiver connected to the input of the correlator, the output of which is connected through a logarithm to the first input of the first multiplier, the second input of the first multiplier is connected to the first input of the second multiplier and connected to the terminal input the width of the radiation patterns, the output of the first multiplier is connected to the input of the adder, the second input of which is connected in series through the first quadrator and the delay device are connected to the output of the second divider and the antenna input controlling the angular diversity, the output of the delay device is connected to the second inputs of the second and third multipliers, the stabilized value of the direction finding sensitivity input terminal is connected to the first input of the third multiplier, the output of which is connected to the second input of the second divider , the output of the adder and the output of the second multiplier are connected to the inputs of the first divider, the output of which is connected to the first inputs of the second and third divider her, the output of the subtractor is connected to the second input of the third divider, the output of which is connected to the indicator.