RU2196342C2 - Procedure determining coordinates of objects in process of passive bistatic radiolocation - Google Patents

Abstract

FIELD: radio engineering, radio engineering monitoring means, monopulse radars fixing positions of air targets. SUBSTANCE: procedure determining coordinates of objects in process of passive bistatic radiolocation includes monopulse measurement of angle of arrival of signals of airborne responders of air targets from reception center when range from reception center to interrogator and bearing on it are known, measurement of moments of reception of signals of airborne responders at reception center, extraction of series of signals of airborne responders and computation of difference of elliptical lines of positions of two air targets, difference of angular positions of two air targets from position of interrogator, direction of arrival of signal of airborne responders from reception center, range from reception center to air target. EFFECT: determination of coordinates of air target in process of passive bistatic radiolocation under conditions of lack of signals of interrogator. 2 dwg

Description

 The method for determining the coordinates of objects with passive bistatic radar refers to radio engineering and can be used in radio monitoring tools, as well as in remote radar stations to determine the location of air and surface objects.

 A known method for determining the coordinates of objects [1], based on measuring the difference in the time of arrival at the receiving point (PP) of two signals emitted by a radar transmitter located at a distance b from the PP and reflected from the object, and determining the direction to the object. In passive bistatic radar, the signals of a radar recognition system are used to measure the time difference: a ground radar interrogator (RLZ) and an airborne transponder (BO) of an airborne object. At the same time, the location of the airborne object (AO) is defined as the intersection point of two position lines (PL): an elliptical L and a line of a constant bearing β IN from the radar position (relative to the radar - PP direction).

The expression for the elliptic position line (L - const) has the form
L = R + rb,
where L is the path difference of the rays RLZ - VO - PP and RLZ - PP, a constant value;
R is the distance from the radar to the HE;
r is the distance from the PP to the HE.

Существенным недостатком этого способа является необходимость непрерывного приема сигналов РЛЗ для определения местоположения ВО в круговом секторе обзора, или экстраполяция моментов их прихода на интервалах времени между приемами двух очередных серий, расчет значения β по разности времени приема серий сигналов, поступающих от РЛЗ и БО.The distance from the PP to the VO is determined by the formula

A significant drawback of this method is the need for continuous reception of radar signals to determine the location of HE in the circular sector of the review, or extrapolation of the moments of their arrival at time intervals between receptions of two successive series, the calculation of the value of β according to the difference in the reception time of a series of signals from radar and BO.

 Closely in its technical essence to the claimed invention is a method for determining the coordinates of VO for radar and PP spaced apart by distance b [1], based on the use of an elliptical PL and the line of the constant bearing of the VO with PP - α (relative to the PP - Radar direction).

Угол α измеряется в ПП обычными моноимпульсными методами: фазовым, амплитудно-фазовым или амплитудным.The distance from the PP to the VO is determined by the formula

The angle α is measured in the PP by conventional single-pulse methods: phase, amplitude-phase or amplitude.

 The main disadvantage of this method is the need for continuous reception of radar signals to determine the location of HE in the circular sector of the review or extrapolation of the moments of their arrival at time intervals between receptions of two successive series.

 The aim of the invention is to determine the coordinates of VO with passive bistatic radar in the absence of reception of radar signals.

где (t_2,n-t_1,n) - время задержки между сигналами БО двух ВО (ВO₂, BO₁), отвечающих на n-й сигнал РЛЗ;
N - количество общих ответов на сигналы РЛЗ;
с - скорость распространения радиоволн;
- разности угловых положений двух ВО Δβ относительно позиции РЛЗ

где t_2c-t_1c - время задержки между срединами серий сигналов БО двух ВО (ВО₂ и BO₁), одновременно облучаемых РЛЗ;
t_m,c, t_(m-1),c - моменты времени приема средин серий сигналов БО одного ВО на m и (m-1)-м оборотах антенны РЛЗ;
- направлений приходов сигналов БО α_j в ПП по формуле

где α_ji - угол прихода i-го сигнала БO j-гo ВО;
N_S - количество импульсов в серии j-го ВО;
- расстояний r₁ и r₂ от ПП до ВО по формулам

где

β₂ = β₁+Δβ;

Сопоставительный анализ со способом, выбранным в качестве прототипа, показывает, что заявляемый способ отличается новыми операциями измерения в ПП моментов приема сигналов БО, выделения серий сигналов БО и новыми расчетами разностей эллиптических ЛП двух ВО, разностей направлений между двумя ВО относительно позиции РЛЗ, направлений на ВО и дальностей до них с ПП.The goal is achieved by the fact that in the known method, including a single-pulse measurement of the angles of arrival of the BO signals α _{i of} airborne objects with PP at a known distance b from the BF to the radar and direction to it, according to the invention, measurements of the moments of reception of BO signals, the allocation of series of BO signals by condition : | Δα _i | <Δα _max and T _min <Δt _j ≤3T _max and N _s > 3, where Δα _i is the spread between the values of α _i , Δα _max is the maximum direction finding error, T _min , T _max are the minimum and maximum possible RIL signal repetition intervals, Δt _j - signal BW repetition intervals, N _s - Included Quantity TVO pulses in the series and calculation:
- differences of elliptic position lines - ΔL of two VO

where (t _{2, n} -t _{1, n} ) is the delay time between the BO signals of two VO (VO ₂ , BO ₁ ), corresponding to the nth radar signal;
N is the number of general responses to radar signals;
C is the propagation velocity of radio waves;
- the difference in the angular positions of two HE Δβ relative to the position of the radar

where t _2c -t _1c is the delay time between the middle of the series of BO signals of two VO (VO ₂ and BO ₁ ), simultaneously irradiated by radar;
t _{m, c} , t _{(m-1), c} - moments of time of reception of the middle of series of BO signals of one HE at m and (m-1) -m revolutions of the radar antenna;
- directions of arrival of signals BO α _j in PP according to the formula

where α _ji is the angle of arrival of the i-th signal BO j-th BO;
N _S is the number of pulses in the series of the j-th VO;
- the distances r ₁ and r ₂ from PP to VO according to the formulas

Where

β ₂ = β ₁ + Δβ;

Comparative analysis with the method selected as a prototype shows that the claimed method is distinguished by new measuring steps in the receiver for receiving BO signals, extracting a series of BO signals and new calculations of the differences between the elliptical PLs of two HEs, the differences of directions between two HEs relative to the radar position, directions to In and ranges to them with PP.

 Thus, the claimed method meets the criteria of the invention of "novelty."

 The invention has an "inventive step", because it does not explicitly follow from the prior art for a specialist.

 The invention can be used to determine the location of air and surface objects and meets the criterion of "industrial applicability".

In FIG. 1 is a drawing explaining the location of the positions of PP, RLZ and VO, as well as drugs used to implement the proposed method;
figure 2 - algorithm for implementing the proposed method.

The proposed method is based on single-pulse measurements in PP of the angles of arrival of the BO signals of airborne objects α _i at a known distance from the BF to the radar detector b and direction to it, moments of reception of BO signals, selection of series of BO signals according to the condition: | Δα _i | <Δα _max and T _min <Δt _j ≤3T _max and N _s > 3, where Δα _i is the spread between the values of α _i , Δα _max is the maximum direction finding error, T _min , T _max are the minimum and maximum possible intervals of the radar signals, Δt _j are the intervals BO signals, N _s - the number of pulses in the series, and the calculations of the difference between the elliptic lines p the position of two HE ΔL; the difference Δβ of the angular positions of two HE relative to the position of the radar detector (Fig. 1), the directions of arrival of the BO signals of two HE α ₁ and α ₂ in the SP and ranges from the PP to the HE.

 The method is implemented as follows (figure 2).

In the PP, signals are received by the BO of the radar recognition system of the HE. BO signals are generated according to the “one request - one response” rule and are emitted by the BO VO antenna in a circular sector of space. These signals are received in the PP series, the duration of which depends on the width of the radiation pattern of the radar antenna and the remoteness of the HE from the radar. For each i-th signal, the moment of arrival t _i and the angular position of the HE α _i relative to the direction to the radar are fixed (block 2).

Next, a series of BO signals are highlighted (block 3). Moreover, it is assumed that the signals belong to a series of BO VO _j signals, if the spread Δα _j between α does not exceed the maximum direction finding error Δα _max (3), the intervals of these signals Δt _j and their number N _s correspond to condition (4)
| Δα _j | <Δα _max and T _min <Δt _j ≤3T _max and N _s > 3, (4)
where T _min and 3T _max - the minimum and maximum possible intervals of the radar signals.

Next, the difference between the elliptical PLs ΔL BO ₁ and BO ₂ , simultaneously irradiated by the radar detector (block 4), is calculated. For this, two VOs are selected (BO ₁ and VO ₂ ), the location of which can be determined by the proposed method. For this, it is necessary that condition (5) of the superposition of a series of signals of their BO
t _js > t _{(j + 1) 1} (5)
where t _js , t _{(j + 1) 1} is the last signal of the jth and first signal of the (j + 1) th series, respectively.

где (t_2,n-t_1,n) - время задержки между сигналами БО двух ВО, отвечающих на n-й сигнал РЛЗ;
N - количество общих ответов на сигналы РЛЗ;
с = 3•10⁸ м/с - скорость распространения радиоволн.According to the delay time Δt between the BO signals responding to the same nth request, ΔL is calculated
ΔL = cΔt, (6)
Where

where (t _{2, n} -t _{1, n} ) is the delay time between the BO signals of two VOs responding to the nth radar signal;
N is the number of general responses to radar signals;
s = 3 • 10 ⁸ m / s - the propagation velocity of radio waves.

где t_1c, t_2c - моменты времени, соответствующие срединам серий сигналов БO ВO₁ и ВО₂;
t_mc-t_(m-1)c - период вращения антенны РЛЗ, который определяется как интервал времени между срединами серий сигналов БО t_m,c и t_(m-1),c одного ВО на двух очередных m и (m-1)-м оборотах антенны РЛЗ.According to the delay time of the middle of the series of BO signals of two HE simultaneously irradiated by the radar detector, in block 5, the difference between the angles of arrival of the signals relative to the position of the radar detector Δβ is calculated: the average value of the angle of arrival of the signals of BO BO ₁ and VO ₂ relative to the direction to the radar

where t _1c , t _2c - time instants corresponding to the midpoints of the series of signals BO VO ₁ and VO ₂ ;
t _mc -t _{(m-1) c} is the radar antenna rotation period, which is defined as the time interval between the midpoints of a series of BO signals t _{m, c} and t _{(m-1), c of} one HE in two successive m and (m-1 ) th revolutions of the radar antenna.

где α_ji - угол прихода i-го сигнала БО j-го ВО,
N_S - количество сигналов в j-й серии;
- расчет расстояний с ПП до BO₁ и ВО₂ (блок 7) производится по формулам

где

Для получения расчетных формул (9-11) представим линии постоянного пеленга функциями y= f(x) для чего совместим ПП с началом декартовой системы координат, как показано на фиг.1

Значения координат точек пересечения BO₁ ВО₂ прямых y₁ и y₃, y₂ и y₄ равны

Расстояния до ВО r₁, r₂, R₁, R₂, выраженные через координаты (13, 14) имеют вид

Разность эллиптических ЛП ΔL равна
ΔL = (r₂-r₁)+(R₂-R₁), (17)
После подстановки выражений (13-16) в (17) и проведения тригонометрических преобразований выражение (17) приводится к виду

Откуда tg(β₁/2) находится как корень квадратного уравнения вида
a[tg(β₁/2)]²+dtg(β₁/2)+c = 0,
где a, d, с описываются выражениями (11).In block 6, the direction of arrival of the BO signals in the PP α _{j is} calculated based on averaging over a series of pulse-measured values

where α _ji is the angle of arrival of the i-th signal of BO j-th HE,
N _S is the number of signals in the j-th series;
- the calculation of distances from PP to BO ₁ and VO ₂ (block 7) is performed according to the formulas

Where

To obtain the calculation formulas (9-11), we represent the lines of the constant bearing by the functions y = f (x) for which we will combine the PP with the beginning of the Cartesian coordinate system, as shown in Fig. 1

The values of the coordinates of the points of intersection BO ₁ IN ₂ lines y ₁ and y ₃ , y ₂ and y ₄ equal

The distances to VO r ₁ , r ₂ , R ₁ , R ₂ expressed in terms of coordinates (13, 14) have the form

The difference of the elliptic LP ΔL is
ΔL = (r ₂ -r ₁ ) + (R ₂ -R ₁ ), (17)
After substituting expressions (13-16) in (17) and carrying out trigonometric transformations, expression (17) is reduced to

Whence tg (β _1/2 ) is found as the root of a quadratic equation of the form
a [tg (β _1/2 )] ² + dtg (β _1/2 ) + c = 0,
where a, d, c are described by expressions (11).

The expression for β ₁ has the form (10).

When calculating the distances r ₁ , r _{2, the} physical meaning has one of the values β ₁ at which r ₁ > 0 and r ₂ > 0.

The method is implemented based on the use of:
- omnidirectional direction finder [2] for receiving and monopulse determination of the direction of arrival of the BO signals in the PP;
- a time sensor for determining the moments of arrival of BO signals; constructed according to a typical build-up scheme [3] of pulse counters of the master oscillator on integrated circuits of the types IE11, IE13, IE18, AG1, AG3 of series 530, 533;
- A personal computer for isolating a series of BO signals, calculating directions and ranges to a VO.

To assess the accuracy of determining the coordinates of the targets of the proposed method, a simulation was carried out on a PC of 45,000 VO positions and the calculation of their coordinates. At the same time, it was taken into account that modern radio engineering tools allow measuring the parameters of drugs with the following standard errors (RMS):
σ _α - (0.2-0.5) ^° ; σ _Δβ -0.5 ^° , σ _ΔL = 0.15 km.
The standard deviation for determining the coordinates of the HE by the proposed method did not exceed 7 km.

Sources of information
1. V.E. Averyanov. Diversity radar stations and systems. Minsk, Science and Technology, 1978, pp. 27-29 (analog), p. 31 (prototype).

 2. Omnidirectional direction finder. Patent RU 2126978 C1, cl. G 01 S 3/54.

 3. M. I. Abramovich and others. Digital integrated circuits, reference book. Minsk, Belarus, 1991, pp. 118-122, 145, 146.

Claims (1)

A method for determining the coordinates of objects with passive bistatic radar, including monopulse measurement of the angles of arrival of the signals of the on-board transponders of the airborne objects of the receiving point at a known distance from the receiving point to the radar interrogator and the direction to it, characterized in that the moments of receiving signals of the on-board transponders are measured at the receiving point, series of signals from airborne transponders count
the difference between the elliptical positions ΔL of two air objects

where (t _{2, n} -t _{1, n} ) is the delay time between the signals of two airborne transponders VO ₂ and VO ₁ , responding to the nth signal of the radar interrogator;
N is the number of general responses to the signals of the radar interrogator;
C is the propagation velocity of radio waves,
the difference in the angular positions of two air objects Δβ from the position of the radar interrogator

where (t _2c -t _1c ) is the delay time between the middle of the series of signals of the airborne transponders of two airborne objects VO ₂ and VO ₁ ;
t _{m, c} , t _{(m-1), s} are the times of receiving the midpoints of the series of signals of the airborne transponder of one air object at the mth and (m-1) -m revolutions of the antenna of the radar interrogator;
the direction of arrival of the signals of the airborne transponders from the reception point α _j

where α _ji is the monopulse measured value of the angle of arrival of the i-th signal of the on-board transponder of the j-th air object;
N _s is the number of pulses in the series;
the distance from the receiving point to airborne objects r ₁ , r ₂ according to the formulas

Where

β ₂ = β ₁ + Δβ;
β ₁ , β ₂ - angle of arrival at the signal receiving station of the on-board transponder of the airborne object BO ₁ and BO _2, respectively;
a, d, c - variables defined by expressions

b is the distance from the receiving point to the radar interrogator.

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