RU2071079C1 - Adaptive radio direction finder - Google Patents

Abstract

FIELD: radio engineering. SUBSTANCE: invention may be used for determination of angular positions of radio beacons. Finder comprises antenna with two outputs , each connected to subtracter via logarithmic receiver and indicator. Antenna has controlling input. Radio direction finder is inserted with two linear receivers, correlator, logarithm-taking unit, two multipliers, adder, two squarers, three dividers, sensor of width of directivity pattern, square root computer and delay device. Each output of antenna is connected via linear receiver to input of correlator which output is connected to input of first multiplier via logarithm-taking unit. Second input of first multiplier is connected to input of second multiplier and via first squarer, to sensor of directivity pattern width. Output of first multiplier is coupled to first input of adder which second input is connected to output of third divider via second squarer, delay device and square root computer connected in series. Second input of third divider is connected to output of delay and second input of second multiplier which output and output of adder are connected to inputs of first divider. Input of indicator is coupled to output of second divider one of which inputs is connected to output of subtracter and other input is linked to output of first divider and to first input of third divider. Output of square root computer is connected to controlling input of antenna. Increase of direction finding precision with reduction of coherence of field at reception point is realized firstly thanks to elimination of a period interdeterminance in direction finding sensitivity and secondly by enhancement of direction finding sensitivity by means of adaptive change of angular separation of directivity patterns. EFFECT: increased precision of direction finding. 1 dwg

Description

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

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

 Closest to the invention is a direction finder 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 difference amplitude at the output of the subtractor and its a priori known dependence on the direction-finding characteristic (PX), which is assumed to be linear in some direction-finding sector. The steepness of the HR direction finder, which determines its direction-finding sensitivity (IF), is inversely proportional to the square of the width of its radiation patterns.

 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. 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 increase their fluctuations. The adaptive direction finder under consideration allows one 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 adjustable angular diversity of the beam and with a control value of the angular diversity input, and also introduced two receivers, a correlator, a logarithmator, two multipliers, an adder, two quadrators, three dividers, a sensor for the width of the beam, a square root calculator, a delay device, and an indicator. In this case, each output of the antenna through the receiver is connected to the input of the correlator, the output of which through the logarithm is connected to the 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 sensor of the width of the beam through the first quadrator, the output of the first multiplier is connected to the first input of the adder, the second input of which is connected through the second quadrator, the delay device and the square root calculator to the output of the third divider . The second input of the third divider is connected to the input of the delay device and the second input of the second multiplier, the output of which and the output of the adder are connected to the inputs of the first divider. The indicator is connected to the output of the second divider, one of the inputs of which is connected to the output of the subtracter, and the other input is connected to the output of the first divider and to the first input of the third divider, the output of the square root calculator is connected to the antenna input controlling the angular diversity.

 The drawing shows a structural electrical diagram of an adaptive direction finder.

 The direction finder comprises an antenna 1 with an adjustable angular diversity of two radiation patterns, with a control value of the angular diversity of the input and two outputs, two logarithmic receivers 2 and 3, two receivers 4 and 5, a correlator 6, a logarithm 7, a first multiplier 8, an adder 9, and a second a quadrator 10, a first quadrator 11, a second multiplier 12, a delay device 13, a radiation pattern width sensor 14, a first divider 15, a square root calculator 16, an indicator 17, a second divider 18, a third divider 19, and a subtractor 20.

 In practice, the adjustment of the angular diversity of radiation patterns can be implemented in one of the known ways, for example, by changing the distance between the irradiators located in the focal plane of the mirror antenna of the direction finder.

 To describe the operation of the adaptive direction finder, it is necessary to make some analytical explanations.

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

(2)
крутизна ПХ пеленгационная чувствительность пеленгатора, дБ/град.The direction-finding characteristic of a conventional amplitude direction finder is analytically represented in the form of the dependence of the difference amplitude ΔU expressed in decibels on bearing α, measured, as a rule, from the equal-signal direction (RSN)

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

(2)
the steepness of the HR direction finding sensitivity of the direction finder, dB / deg.

From (1) and (2) the commonly used direction finding algorithm follows
α = ΔU / μ _o = ΔUθ ² / 24α _p (3) (3)
For a partially coherent field at the receiving location, the direction-finding sensitivity can be logically written as
μ = 24α _p / θ $\genfrac{}{}{0ex}{}{\text{2}}{\text{eff}}$ , (4) (4)
where θ _{eff is the} effective beam width of the direction finder.

Similar to (3) bearing
α = ΔU / μ _o = ΔUθ ² / 24α _p (5) (5)
In the general case, θ _{eff is} greater than θ and only in the coherent case q _eff = θ. This suggests that the steepness μ is generally less than the steepness m _o , and the bearing estimation made (on scattered paths) according to algorithm (3) turns out to be biased, and toward its approximation 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, но не снижает в то же время возрастающую при уменьшении ПЧ флуктуационную составляющую ошибки пеленгования. Эту ошибку можно уменьшить, повысив ПЧ за счет увеличения углового разнесения α_p. Как известно, соотношение между величиной углового разнесения и шириной ДН амплитудных пеленгаторов при их проектировании выбирается вполне определенным удовлетворяющим, например, требованию компромисса между ПЧ (т. е. точностью пеленгования) и энергетикой в РСН [1, c. 82 84] Можно считать, что в диапазоне изменения условий распространения на трассе необходимо сохранение задаваемого из конкретных тактико-технических требований отношения

где

требуемое в данных конкретных условиях распространения радиоволн угловое разнесение ДН-пеленгатора. Поскольку

учитывая (4) и (6) требуемое значение углового разнесения должно определяться величиной

(11)
В этом рекуррентном соотношении, описывающем процесс адаптивной перестройки углового разнесения,

можно считать последующим, а α_p - настоящим, существующим в момент измерения корреляции r, значениями углового разнесения.The determination of θ _eff for obtaining from (5) the algorithm of an unbiased bearing estimate was possible by establishing a relationship of θ _eff with the magnitude of the correlation of amplitudes (r) at the antenna outputs:

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

bearing estimation algorithm

Algorithm (8) makes it possible to eliminate the shift in the bearing estimate by eliminating a priori uncertainty in the IF, but it does not at the same time reduce the fluctuation component of the direction finding error that increases with decreasing IF. This error can be reduced by increasing the IF by increasing the angular separation α _p . As is known, the ratio between the angular spacing and the width of the bottom beams of the amplitude direction finders during their design is selected to be quite satisfactory that satisfies, for example, the requirement of a compromise between the inverter (that is, the direction finding accuracy) and the energy in the DCS [1, p. 82 84] We can assume that in the range of changes in the propagation conditions on the highway, it is necessary to preserve the relation specified from specific tactical and technical requirements

Where

the angular diversity of the DN direction finder required in these specific propagation conditions of radio waves. Because the

taking into account (4) and (6), the required value of the angular separation should be determined by

(eleven)
In this recurrence relation describing the process of adaptive adjustment of angular diversity,

can be considered subsequent, and α _p - real, existing at the time of measuring the correlation r, values of angular diversity.

 Adaptive direction finder (drawing) works as follows.

 The oscillations from the outputs of antenna 1 are amplified, logarithmic, detected in the logarithmic receivers 2, 3 and then subtracted in the subtractor 20, forming at its output a difference amplitude ΔU expressed in dB.

 The signals from the outputs of the antenna also arrive at line receivers 4, 5, where they are amplified, detected and fed to the correlator 6.

The correlation coefficient r formed at the output of the correlator (hereinafter referred to as a signal proportional to the parameter) is fed through a logarithmator 7 to a multiplier 8, where it is multiplied with a square of the width of the beam θ ² formed at the output of the quadrator 11 by the signal from the sensor 14 of the width of the beam q.

The value θ ² lnr formed at the output of the multiplier 8 is entered into the adder 9. At the second input of the adder with a proportionality coefficient equal to ln2, the value α is entered $\genfrac{}{}{0ex}{}{\text{2}}{\text{p}}$ formed at the output of the quadrator 10 about the angular diversity value α _p received at its input formed 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 equal to 24 is input to the first input of the first divider 15. At its second input, the result is the multiplication in the multiplier 12 of the value of the square of the width θ ² formed at the output of the quadrator 11 and the value of the angular separation a _p coming from the output of the delay device 13.

 After performing the division at the output of the divider 15, the current direction finding sensitivity value μ (7) appears, which changes when the field coherence in the antenna aperture changes.

 As a result of dividing the difference amplitude DU formed in the subtractor 20 by the sensitivity value μ in the divider 18, at its output, in accordance with the algorithm (8), the bearing estimate is displayed on the indicator 17.

To generate the adaptive adjustment signal of the angular diversity, the inverter m current value is supplied to one input of the third divider 19 from the output of the first divider 15, the current angle value is received to the other input of the divider 19 with a proportionality factor equal to 24 from the output of the delay device 13 a _p .

. Это значение подается на устройство задержки 13 и на управляющий вход антенны, где осуществляется установка требуемого значения углового разнесения. Устройство задержки 13 обеспечивает задержку использования последующего значения углового разнесения

в качестве существующего в данный момент разнесения α_p. Величина задержки складывается из времени перестройки углового разнесения в антенне 1 и времени распространения сигналов от антенны до делителя 18, на выходе которого формируется оценка пеленга.From the output of the divider 19, the value 24α _p / μ is input into the square root calculator 16 and with the proportionality coefficient ν forms at the output 16 the required subsequent value of the angular diversity

. This value is supplied to the delay device 13 and to the control input of the antenna, where the required value of the angular diversity is set. Delay device 13 delays the use of subsequent angular diversity values

as the currently existing diversity α _p . The magnitude of the delay is the sum of the adjustment time of the angular diversity in the antenna 1 and the propagation time of the signals from the antenna to the divider 18, at the output of which a bearing estimate is formed.

 Thus, the implementation of algorithms (7), (8), and (11) in the form of an adaptive direction finder allows one to increase the accuracy of direction finding of radiation sources in scattering media, firstly, by overcoming a priori uncertainty in direction finding sensitivity and, secondly, by increasing direction-finding sensitivity (its maximization) through adaptive adjustment of the angular diversity of radiation patterns.

Claims (1)

 An adaptive 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, characterized in that the antenna is made with an adjustable angular diversity of radiation patterns and with a control value of the angular diversity of the input, as well as two linear receivers, a correlator, a logarithmator, two multipliers, an adder, two quadrators, three dividers, a radiation pattern width sensor, a square calculator of the root, a delay device and an indicator, with each output of the antenna through a linear receiver connected to the input of the correlator, the output of which through the logarithm is connected to the input of the first multiplier, the second input of the first multiplier is connected to the first input of the multiplier and through the first quadrator is connected to the sensor , the output of the first multiplier is connected to the first input of the adder, the second input of which is connected through a second quadrator, a delay device and a square root calculator I am connected to the output of the third divider, the second input of the third divider is connected to the output of the delay device and the second input of the second multiplier, the output of which and the output of the adder are connected to the inputs of the first divider, the indicator is connected to the output of the second divider, one of the inputs of which is connected to the output of the subtractor, and the other input is connected to the output of the first divider and to the first input of the third divider, the output of the square root calculator is connected to the antenna input controlling the angular diversity.