RU2774864C1 - Method for increasing the energy potential of a single-position radar station - Google Patents

Abstract

FIELD: radar technology.

SUBSTANCE: invention relates to radar technology. This result is achieved by independently setting the amplitude distribution of the field along the antenna opening to receive and transmit signals, respectively, as well as by pre-amplifying the signals received by individual spatial elements, the totality of which forms the antenna aperture when receiving signals.

EFFECT: an increase in the energy potential of a single-position radar station (RS) without increasing the radiation power and maintaining the overall dimensions of the antenna and the shape of its resulting (for transmitting and receiving signals) directional pattern (DP).

1 cl, 3 dwg

Description

SUBSTANCE: invention relates to radar technology and can be used in radar, where narrowly directional antennas with a low level of side lobes of the radiation pattern are used, including in radars with a synthesized antenna aperture.

A known method of increasing the energy potential of the radar by increasing the power of the emitted signal. The essence of the method obviously follows from the radar range equation [1]. The disadvantages of the method include an increase in the cost of implementing the radar, since the cost of the radiation signal generator (radar transmitter) is a significant fraction of the cost of the entire radar, especially with a solid-state version of the transmitter. It should also be noted that in the case of a solid-state version of the transmitter, increasing the power of the emitted signal above a certain limit is a complex technical problem, which in some cases cannot be solved at this stage in the development of microelectronics.

There is a known method (chosen by the authors for the prototype) to increase the energy potential of the radar by increasing the gain of the transmit-receive antenna with an uneven field distribution along the opening, providing the required level of side lobes (hereinafter UBL) resulting (for transmission and reception) DN. The essence of the method also obviously follows from the radar range equation [1]. The disadvantages of the method include the need to either increase the overall dimensions of the antenna, since in this case it is possible to increase its gain by increasing the opening area, or to reduce the uneven distribution of the field over the antenna aperture, which also increases its gain, but causes an increase in the level of side lobes resulting DN.

The main technical problem solved by the claimed invention is to increase the energy potential of the radar while maintaining the radiation power, antenna opening area and side lobes (SL) of the resulting (for transmitting and receiving signals) DN. In this case, the resulting RP is defined as the multiplication of the radiation RP by the RP of the radar electromagnetic signal reception.

распределения амплитуды сигналов, излучаемых отдельными пространственными элементами апертуры L, обеспечивающая необходимый пользователю РЛС уровень БЛ диаграммы направленности излучения, при приеме каждый из сигналов, принятых отдельным пространственным элементом апертуры L, предварительно усиливается, а функция распределения

амплитуд усиленных сигналов по апертуре L выбирается исходя из требования необходимого пользователю РЛС уровня БЛ результирующей диаграммы направленности РЛС. При этом выигрыш в энергетическом потенциале достигается тогда, когда коэффициент использования апертуры антенны на излучение больше коэффициента использования апертуры антенны при приеме сигналов.The solution of the problem is achieved by the fact that in the method of increasing the energy potential of the radar, including the directional signal emission by the spatial in-phase aperture L and the directional reception of the reflected signal by the spatial common-mode aperture L, while the received and emitted signals are formed, respectively, as the sum of the signals emitted and received by separate spatial elements (SE), the totality of which forms the aperture L, and the resulting radiation pattern for the emission and reception of signals provides the level of BL required for the radar user, when emitting, the function

distribution of the amplitude of the signals emitted by individual spatial elements of the aperture L, which provides the level of BL of the radiation pattern necessary for the radar user, when receiving each of the signals received by a separate spatial element of the aperture L, it is preliminarily amplified, and the distribution function

the amplitudes of the amplified signals over the aperture L is selected based on the requirement for the BL level required by the radar user of the resulting radar radiation pattern. In this case, the gain in the energy potential is achieved when the utilization factor of the antenna aperture for radiation is greater than the utilization factor of the antenna aperture when receiving signals.

The essence of the proposed method is as follows:

распределения амплитуды сигналов излучения ПЭ, образующих синфазный раскрыв L передающей антенны, при этом функция

обеспечивает необходимый пользователю РЛС уровень БЛ диаграммы направленности излучения;1) when a probing signal is emitted, the function is set in the radar antenna

distribution of the amplitude of the radiation signals of the PE, forming an in-phase opening L of the transmitting antenna, while the function

provides the level of BL of the radiation pattern required by the user of the radar;

2) when receiving the reflected field, an independent in-phase amplification of the signals received by individual PEs is carried out, the totality of which forms the aperture L of the receiving antenna;

, выбранной исходя из необходимого пользователю РЛС уровня БЛ результирующей на прием и передачу сигнала ДН приемо-передающей антенной системы РЛС, при этом результирующая ДН определяется произведением диаграмм направленности при излучении и при приеме сигнала, соответственно;3) the amplitude weighting of the amplified signals received by individual PE is performed in accordance with the function

, selected on the basis of the BL level required by the user of the radar station, resulting in the reception and transmission of a signal of the RP of the radar receiving and transmitting antenna system, while the resulting RP is determined by the product of the radiation patterns during radiation and when receiving a signal, respectively;

4) the output signal of the receiving antenna is formed by in-phase summation of the weighted signals.

The gain in the energy potential of the radar when using the proposed method is due to two factors:

распределения сигнала по излучающей апертуре может быть задана более равномерной, чем распределение

амплитуды принимаемого поля по приемной апертуре. При этом по сравнению с прототипом, где коэффициенты использования апертуры на излучение и прием, соответственно, равны, повышается коэффициент использования излучающей апертуры и, следовательно, повышается плотность потока мощности в главном лепестке ДН излучения сигнала, а коэффициент использования приемной апертуры снижается для сохранения уровня БЛ результирующей ДН, равного уровню БЛ результирующей ДН антенной системы прототипа.1. The narrowing of the main lobe of the DN radar for radiation, because, unlike the prototype, the function

signal distribution over the emitting aperture can be set more uniform than the distribution

the amplitude of the received field over the receiving aperture. At the same time, in comparison with the prototype, where the coefficients of use of the aperture for radiation and reception, respectively, are equal, the coefficient of utilization of the emitting aperture increases and, consequently, the power flux density in the main lobe of the radiation pattern of the signal increases, and the utilization coefficient of the receiving aperture decreases to maintain the level of BL resulting DN equal to the level of BL of the resulting DN of the antenna system of the prototype.

2. Reducing the noise figure of the receiving antenna compared to the prototype by weighing the thermal noise of the output feeders of the spatial elements, the totality of which forms the aperture of the receiving antenna, since the output signals of the PE are pre-amplified, and only then are weighted to ensure the required level of the BL of the resulting DN.

The first assertion is based on the fact that the resulting RP is determined by the product of the radiation patterns during radiation and during signal reception. The legitimacy of the second statement follows from the following comparative analysis of the noise figure of passive and active receiving antenna arrays (AR), the aperture L of which is formed by a set of N independent spatial elements (elementary receiving antennas).

The main difference between active receiving arrays and passive ones is that the amplitude distribution of the field over the opening of the active array is set after pre-amplification of the output signals of the antenna elements of the array. In this case, both the useful signal and the thermal noise reduced to the input of each of the LNA are weighted.

, ниже получены количественные оценки коэффициента шума активной и пассивной АР.To estimate the quantitative energy gain when using active arrays with non-spatial summation, a comparative analysis of the noise properties of passive and active receiving arrays, whose directivity characteristics are identical, is carried out below. On the example of the analysis of an N-element linear array, in which the field distribution over the opening is given by the coefficients a _i , which determine the relative coefficients of signal transmission in amplitude from the i -th antenna element to the adder, while

, below we obtain quantitative estimates of the noise figure of the active and passive antenna array.

, формирующие дискретный раскрыв АР, есть отсчеты

непрерывной функции

, определяющей в аналитической форме вид распределения поля по раскрыву АР единичной длины. Функция

нормирована к ее максимуму на интервале определения x

(-1/2; 1/2). Площадь под кривой, заданной функцией

, всегда меньше единицы и величина

определяет потери коэффициента усиления антенны при отличии распределения поля по раскрыву от равномерного, для которого

и, следовательно, А = 1. Очевидно, чтоNote that the coefficients

, forming a discrete opening AR, there are readings

continuous function

, which determines in analytical form the type of field distribution over the opening of an AR of unit length. Function

normalized to its maximum on the interval of definition x

(-1/2; 1/2). Area under the curve given by the function

, is always less than unity and the value

determines the loss of the antenna gain when the field distribution along the aperture differs from the uniform one, for which

and, consequently, A = 1. It is obvious that

(1)

(one)

where the value C is called "total radiated (received) power" [2].

Passive AR. For an N-element passive array (Fig. 1), in which there are no losses during signal transmission from antenna elements to the antenna output, and the coefficientsa _i are equal to unity (uniform in-phase distribution of the field amplitude over the AR opening),

, отношения «принимаемый сигнал/шум» на ее выходе, имеет видexpression for quantity

, the "received signal/noise" ratio at its output has the form

, (2)

, (2)

- полная мощность плоской электромагнитной волны (э.м.в.) принимаемого сигнала, падающей на раскрыв АР, волновой вектор которой перпендикулярен плоскости раскрыва;where:

is the total power of a plane electromagnetic wave (EMW) of the received signal incident on the aperture of the AR, the wave vector of which is perpendicular to the plane of the aperture;

- мощность э.м.в. волны, принимаемая отдельным антенным элементом;

- em.m. power waves received by a separate antenna element;

- мощность тепловых шумов МШУ, усиливающего выходной сигнал пассивной АР, приведенная к его входу,

is the thermal noise power of the LNA, which amplifies the output signal of the passive antenna array, reduced to its input,

- мощность тепловых шумов в пассивной линии (фидере) передачи сигналов антенных элементов,

- power of thermal noise in the passive line (feeder) of signal transmission of antenna elements,

- полная мощность шумов на входе МШУ.

is the total noise power at the LNA input.

. Собственный шум пассивного сумматора на его выходе не зависит от величины коэффициентов а _i .It should be noted that to simplify the analysis, we assume that both the inputs of the passive adder and its output have the same active impedance (for example, 50 ohms, often used in microwave technology), which determines the thermal noise power

. The intrinsic noise of the passive adder at its output does not depend on the value of the coefficients a _i .

1, отношение сигнал/шум будет хуже. Отметим также, что для а _i = 1 (равномерное распределение) ДН АР имеет максимально узкий главный лепесток и, следовательно, максимальный коэффициент усиления.Expression (2) determines the maximum possible value of the signal-to-noise ratio at the AA output. For all other coefficient ratios, when a _i

1, the signal-to-noise ratio will be worse. Note also that for a _i = 1 (uniform distribution) the AP AP has the narrowest main lobe and, consequently, the maximum gain.

In the general case, for arbitrary values of a _i , the value of the signal-to-noise ratio (in terms of power) at the output of the passive array (Fig. 1) is determined by the expression

, (3)

, (3)

- мощность сигнала на выходе синфазного сумматора (синфазное «весовое» суммирование N взаимно когерентных сигналов с выходов антенных элементов [3].where

- signal power at the output of the in-phase adder (in-phase "weighted" summation of N mutually coherent signals from the outputs of antenna elements [3].

и при любых а _i справедливо неравенство

.It is easy to make sure that for a _i = 1 expression (3) is identical to expression (2), the value

and for any a _i the inequality

.

и

определяет коэффициент шума

пассивной АР с произвольным распределением коэффициентов а _i относительно антенны с равномерным (а _i =1) распределением этих коэффициентов. Учитывая выражение (1) можем записать соотношениеValue ratio

and

determines the noise figure

passive AR with an arbitrary distribution of the coefficients a _i relative to the antenna with a uniform ( a _i =1) distribution of these coefficients. Taking into account expression (1), we can write the relation

. (4)

. (four)

where A is the magnitude of the antenna gain loss (in amplitude) [2]. Thus, the noise figure (4) determines the magnitude of the gain loss in times of the power of the passive antenna array when its pattern changes relative to the pattern of the antenna array with a uniform distribution of the coefficients a _i .

. Выражение для величины отношения сигнал/шум

на выходе сумматора активной АР имеет вид active AR. For an active array (Fig. 2), the output signals of the antenna elements are pre-amplified by the LNA with a gain (in terms of power)

. Expression for the signal-to-noise ratio

at the output of the active AA adder has the form

, (5)

, (5)

- мощность принятого и усиленного сигнала на выходе сумматора активной АР,where:

is the power of the received and amplified signal at the output of the adder of the active array,

- мощность шумов на выходе сумматора, обусловленная совокупностью

взаимно некоррелированных выходных шумов МШУ и тепловых шумов

выходного фидера пассивного сумматора.

- noise power at the output of the adder, due to the combination

mutually uncorrelated LNA output noise and thermal noise

output feeder of the passive adder.

получаемAs noted above, the noise of the output feeder of a passive adder does not depend on the values of the coefficients a _i and is always present at its output. By choosing a large enough LNA gain, the effect of noise from the output feeder of the passive combiner can be neglected, so the output noise will be determined only by the output noise of the LNA. When the inequality

we get

, (6)

, (6)

and expression (5) is simplified and takes the form

. (7)

. (7)

For the case а _i = 1 (uniform distribution of values а _i , A=C=1) we have the equality

,

,

and the active array is equivalent in terms of noise properties to the passive array with a uniform field distribution over the aperture.

In the general case, for arbitrary values of a _i , the noise figure of the active array is equal to

. (8)

. (eight)

1), можно записать неравенствоComparing the noise figure (4) of the passive AA and the noise figure (8) of the active AA (considering that C

1), we can write the inequality

, (9)

, (9)

).from which it follows that the noise figure of an active array, in which the weighting of signals from individual antenna elements is performed after their amplification, is always less than the noise figure of a passive array with the same RP and is compared with it only in the limiting case of a uniform distribution of weighting coefficients (

).

It follows from expression (9) that the gain in the noise figure of the active array compared to the passive array is

. (10)

. (ten)

.The limiting transition to a continuous opening AR in expressions (3), (4), (7), (8), (10) allows you to calculate the required values directly from the values \u200b\u200bof A and C known for a number of distributions (see expression (1) ), without making a preliminary calculation of the coefficients

.

задано широко применяемой в антеннах активной радиолокации функцией «cos на пьедестале», имеющей видThe gain in the noise properties of the active array is the greater, the stronger the difference between the distribution of the coefficients a _i from the uniform one. For example, for a 33-element ( N =33) active receive AP, when the distribution

is given by the “cos on a pedestal ” function widely used in active radar antennas, which has the form

, (11)

, (eleven)

the level of the first sidelobe of the RP is ~ -22 dB, and the others are below -30 dB, and the value C = 0.559 (see [2], p. 269). The gain in noise figure compared to a passive 33-element antenna array with a similar pattern is equal to

. (12)

. (12)

задано широко применяемой в антеннах активной радиолокации функцией Хемминга, имеющей видFor a 33-element ( N =33) active receive AP, when the distribution

is given by the Hamming function widely used in active radar antennas, which has the form

, (13)

, (13)

the level of the first sidelobe of the RP is ~ -43 dB, and the others are below -45 dB), and the value of C = 0.394. The gain in noise figure compared to a passive 33-element antenna array with a similar pattern is equal to

. (14)

. (fourteen)

Active AR in a single position radar. Using the results of the above analysis, we will obtain a quantitative estimate of the gain relative to a radar with a passive array in the energy potential of the radar when using an active array with independent formation of field distributions over the antenna aperture for radiation and reception of signals, respectively. In this case, the resulting DN of the "passive" and "active" radar should be identical.

, суммарные потери усиления

относительно приемо-передающей АР с равномерным распределением поля по апертуре определяются квадратом величины

(см. (4)):For a single-position radar with a passive N-element array having identical patterns for emitting and receiving signals, given by the distribution

, total gain loss

relative to the transmitting and receiving array with a uniform field distribution over the aperture are determined by the square of the value

(see (4)):

(15)

(fifteen)

, а на прием сигналов распределение

, суммарные потери усиления

определяются произведением величин

(потери усиления при излучении, обусловленные отличием распределения

от равномерного) и

(коэффициента шума приемной активной антенны с распределением поля

, см. выражение (8)):For a radar with an active N-element array having a radiation field distribution along the opening

, and for signal reception the distribution

, total gain loss

are determined by the product of quantities

(gain loss during radiation, due to the difference in the distribution

from uniform) and

(noise figure of the receiving active antenna with field distribution

, see expression (8)):

(16)

(16)

есть потери усиления, обусловленные распределением

, величина

- полная мощность приема для распределения

:Value

there are gain losses due to the distribution

, value

- total receiving power for distribution

:

Thus, the ratio of the energy potentials of the radar with active and passive radar, all other things being equal, is the value

. (17)

. (17)

в соответствии с выражением (11), суммарные потери усиления

на передачу и прием сигналов (по сравнению с приемо-передающей АР с равномерным распределением поля по апертуре) определяются квадратом величины

(см. (4)), и, учитывая, что для данного распределения

(см. [2], стр. 269), суммарные потери, выраженные в децибелах, равныFor a single-position radar with a passive 128-element array having identical patterns for emitting and receiving signals, given by the distribution

in accordance with expression (11), the total gain loss

for the transmission and reception of signals (compared to a transmit-receive antenna array with a uniform field distribution over the aperture) are determined by the square of the value

(see (4)), and taking into account that for the given distribution

(see [2], p. 269), the total losses, expressed in decibels, are

.

.

In this case, the UBL (for the first lobe) of the resulting RP, determined by the product of the RP for the reception and transmission of the signal, is ~ -46 dB, and the UBL for the remaining lobes of the RP lies below -60 dB (see Fig. 3, blue curve).

, а на прием распределение

, заданное окном Хемминга [2],For a radar with an active 128-element array having a uniform radiation distribution

, and at the reception distribution

, given by the Hamming window [2],

, (18)

, (eighteen)

, определяются только коэффициентом шума

(см. (8)) приемной АР (поскольку потери усиления при излучении отсутствуют в силу равномерного распределения

). Для распределения (18) С = 0,394, А = 0,536 (см. [2], стр. 271) и суммарные потери равныtotal gain loss

, are determined only by the noise factor

(see (8)) of the receiving antenna array (since there are no gain losses during radiation due to the uniform distribution

). For distribution (18) C = 0.394, A = 0.536 (see [2], p. 271) and the total losses are

. (19)

. (19)

Thus, in this case, the gain in the energy potential of a radar with an active array compared to a passive array (all other things being equal) is a significant amount

(20)

(twenty)

This gain is physically due to two factors:

1) narrowing the radar pattern for radiation, since a uniform distribution of the field over the aperture of the emitting antenna is set, while compared to a passive antenna by 3.18 dB (see expression (11)) the power flux density in the main lobe of the radiation pattern increases;

2) by reducing the thermal noise of the receiving active antenna (compared to the passive one) by weighing the thermal noise of the output feeders of the antenna elements (AE), since the AE output signals are preliminarily amplified and only then weighed (to ensure the necessary UBL).

The resulting DN of the "active" radar (see Fig. 3, red curve) has UBL (for the first lobe) - 26 dB and UBL for the remaining lobes below - 60 dB. Moreover, the first lobe falls off very quickly, and in the angular direction of the maximum of the first lobe of the resulting RP of the passive array (Fig. 3, blue curve), its level is -46 dB, which allows us to talk about almost the same angular resolution of the radar when using passive and active array , respectively.

(излучение и прием в «пассивной» РЛС),

(излучение в «активной» РЛС),

(прием в «активной» РЛС), при этомThe above analysis (see expression (17)) allows us to conclude that the gain in the energy potential of an “active” radar compared to a “passive” radar will always be when the antenna aperture utilization factor for radiation is greater than the antenna aperture utilization factor for reception. signals, provided that the resulting DN "active" radar and "passive" radar are close in shape (see Fig. 3). The quantitative value of the gain can be calculated by formula (17) for specific distributions

(radiation and reception in a "passive" radar),

(radiation in the "active" radar),

(reception in the "active" radar), while

The presented results are consistent with the known data of the theory and practice of antennas [2-7], and were obtained using the basic provisions of microwave radio engineering.

The resulting gain of 5 dB for the “active” radar option considered above can be large in practice, since the losses in the feeders of a radar with a passive antenna, as a rule, are greater than the corresponding losses in active radars, since in active arrays, signal amplifiers are located in close proximity to the antenna elements and the losses for transmitting and receiving signals are minimal. An additional gain in the energy potential can be up to 1.5-2.5 dB (losses in the inlet feeder of the passive antenna), and the total gain is up to 7.5 dB, which reduces the requirement for the power of the emitted signal by more than 4 times (ceteris paribus conditions) and, consequently, qualitatively reduces the cost of implementing solid-state radar radiation signal generators.

The results of a comparative analysis of the noise properties of active and passive linear arrays are also valid for two-dimensional arrays, including conformal ones. In them, as well as in linear arrays, the weighting of the signals received by the antenna elements is carried out after their amplification.

Thus, it has been proven that the independent setting (for radiation and reception) of the field distribution in the radar antenna aperture and the preliminary independent amplification of the signals received by individual elements of the receiving antenna aperture (in accordance with the proposed method) makes it possible to increase the energy potential of the radar without increasing the radiation power and maintaining the overall dimensions of the antenna and the shape of its resulting (for transmitting and receiving signals) radiation pattern (hereinafter referred to as DN).

The specific gain in the energy potential of the radar depends on the specific requirements for the BL level of the radiation pattern and for the BL level of the resulting (receiving and transmitting) radiation pattern of the radar antenna system. As shown above, the total gain relative to passive radars with the parameters of the resulting RP and the design of passive radar antenna feeders often used in practice can reach 5-7.5 dB.

Literature

[1] Handbook of radar. Ed. M. Skolnik. New York, 1970. Per. from English. (in four volumes) floor of the general ed. K. N. Trofimova. Volume 1. Fundamentals of radar. Ed. Ya. S. Yitzchoki. M., "Owls. Radio”, 1976, 456 p.

[2] Barton D., Ward G. Handbook of radar measurements. Per. from English. under the editorship of M. M. Weisbein.- M.: “Owls. radio”, 1976, 392 p. from ill.

[3] Active phased antenna arrays. Under. ed. DI. Voskresensky and A.I. Kanashchenkov. - M.: "Radio engineering", 2004, 488 p. from ill.

[4] R.V. Gatti, M. Dionigi, R. Sorrentino. "Computation of Gain, Noise Figure, and Third-Order Intercept of Active Array Antennas", IEEE Transactions on Antennas and Propagation Vol. 52, Issue 11, pp. 3139-3143.

[5] E. L. Holzman and A. K. Agrawal, “A comparison of active phasedarray, corporate beamforming architectures,” in Proc. IEEE Int. Symp. Phased Array Systems and Technology, Oct. 15-18, 1996, pp. 429-434.

[6] J. J. Lee, “G/T and noise figure of active array antennas,” IEEE Trans. Antennas Propagat., vol. 41, pp. 241-244, Feb. 1993.

[7] E. L. Holzman, “Intercept points of active phasedarray antennas,” in Proc. IEEE MTT-S Int. Microwave Symp., 1996, pp. 999-1002.

Claims (1)

A method for increasing the energy potential of a radar, including directional radiation and directional signal reception by a spatial in-phase aperture L, while the emitted and received signals are formed, respectively, as the sum of weighted signals emitted and received by individual spatial elements, the combination of which forms the aperture L, and the resulting radiation pattern , which determines the spatial selectivity of the radar, is defined as the product of radiation patterns for radiation and reception of signals with aperture L, characterized in that upon reception, each of the signals received by a separate spatial element of aperture L is preliminarily amplified, and the function

distribution over the aperture L of the amplitudes of the signals emitted by individual spatial elements, and the function

the distributions over the aperture L of the amplitudes of the received amplified signals are chosen so that the aperture utilization factor L when the signal is emitted is greater than the aperture utilization factor L when the signal is received.

Images