RU2633380C1 - Passive location system for determining aircraft coordinates in near aerodrome area and at landing with reserve channel of determining distance - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: system contains three narrow-base subsystems, each of which includes N receiving antennas, the first and the second analog-to-digital converter, a central electronic computing machine, a low-noise amplifier, N inputs of which are connected to N receiving antennas, the first and the second multi-channel synchronous quadrature receivers, the inputs of which are connected respectively with the first and the second outputs of the low-noise amplifier, and the outputs - with the first inputs of the first and the second analog-to-digital converters, the first and the second information processing channels, the first inputs of which are connected to the outputs of the analog-to-digital converters, and the outputs are connected to the central electronic computing machine; the controller is connected at the input to the central computing machine, the first output of which is connected to the second input of the first multi-channel synchronous quadrature receiver, to the second input of the first analog-to-digital converter and to the second input of the first information processing channel, and the second output - to the second input of the second multi-channel synchronous quadrature receiver, to the second input of the second analog-to-digital converter and to the second input of the second information processing channel; the central processing point, which is composed of three input ports, each input of which is connected through a hybrid fibre-coaxial network to the central electronic computer of each narrow-base subsystem, a keyboard unit, a display unit, a unit for calculating the current speed of the aircraft, a unit for calculating the current flight altitude of the aircraft, a unit for calculating the distance to the, random access memory, a persistent storage device, the first additional output port, a microprocessor, interconnected by the address and data bus; a radio modem of decameter radio wave range, the input of which is connected to the output of the first additional output port, and the output is an overall output of the system providing radio communication with the aircraft.

EFFECT: controlling the aircraft at extremely low altitudes in the near zone of the aerodrome and the withdrawal of the aircraft to the landing point.

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Description

The invention relates to radio engineering, and in particular to methods and systems of passive radar, and can be used to determine the location in three-dimensional space of a source of radio emission (IRI) located on an aircraft (aircraft) (airplane, helicopter, etc.), due to reception and subsequent processing of electromagnetic waves generated by this IRI.

The invention is used to solve a technical problem, which consists in determining the coordinates of an aircraft in the near zone of an aerodrome and at the stage of its approach for landing in order to monitor it and control its movement by ground services, as well as for its navigation support. The technical result achieved is to increase the accuracy of estimating the coordinates of a moving object equipped with a source of radio emission.

On-board radio equipment of aircraft (LA) when performing tasks create active electromagnetic fields of artificial origin in the frequency range from 1 MHz to 40 GHz. In addition to the active fields of the aircraft, they create their own electromagnetic radiation. This emission spectrum can be used to solve the problem of detecting, direction finding and determining the coordinates of an aircraft.

When constructing a multi-position passive radar, the difference-ranging method is used, based on measuring the difference in the signal path from the target to the receiving antennas of the radar. This method allows you to work on pulsed and continuous signals, including noise and noise-like.

The principal features of the method are the synchronous method of receiving signals from a radiating source on spaced antennas. High accuracy of determining the coordinates of the aircraft is provided due to the correlation signal processing, in which the form of the received signal does not matter. The coordinates of the source are determined by the difference in the arrival of signals at each position, and the difference in the arrival of the signal at one position relative to another is determined from the position of the maximum cross-correlation function of the signals from these positions.

The closest technical solution that meets the requirements of passive detection and direction finding is the device described in the article “One-stage estimation of the location of a radio emission source by a passive system consisting of narrow-base subsystems” (Radio Engineering and Electronics, Volume 49, No. 2, 2004, p. . 156-170) is a prototype.

This device contains N receiving antennas, a first and second analog-to-digital converter (ADC), and a computer.

The purpose of the invention is the control of the aircraft at extremely low altitudes in the near zone of the aerodrome and the withdrawal of the aircraft to the approach point.

The result is achieved by centralized processing of signals obtained as a result of receiving electromagnetic oscillations at points whose placement in space is determined by the optimal grouping of weakly directed antenna elements inside structural blocks implemented by separate technical means of a distributed complex.

This goal is achieved by the fact that in the system containing three narrow-base subsystems (UE), each of which contains N receiving antennas, the first and second analog-to-digital converter (ADC), the central electronic computer (CE) additionally introduced a low-noise amplifier (LNA) ), N inputs of which are connected to N receiving antennas, the first and second multichannel synchronous quadrature receivers (MSCP), the inputs of which are connected respectively to the first and second outputs of the low-noise amplifier, and the outputs to the first inputs of the first and second analog-to-digital converters, the first and second information processing channels, the first inputs of which are connected to the outputs of the analog-to-digital converters, and the outputs are connected to a digital computer; a control controller connected at the input to the computer, the first output of which is connected to the second input of the first multi-channel synchronous quadrature receiver, to the second input of the first analog-to-digital converter and to the second input of the first information processing channel, and the second output to the second input of the second multi-channel synchronous quadrature a receiver, to the second input of the second analog-to-digital converter and to the second input of the second information processing channel; central processing center (CPO), which includes 3 ports for inputting information, each input of which is connected through a hybrid optical-coaxial network to the output of a computer of each narrow-base subsystem (UE), a keyboard block, an indication block, a block for calculating the current speed of the aircraft, a calculation block the current flight altitude of the aircraft, the unit for calculating the range to the aircraft, random access memory (RAM), read-only memory (ROM), the first additional output port, microprocessor, which are interconnected by an address and data bus, radio mode DKMV range, the input of which is connected to the output of the first additional output port, and the output is a common system output providing radio communication with the aircraft.

Comparison with the prototype shows that the inventive system is characterized by the presence of new blocks and their connections between them. Thus, the claimed system meets the criterion of "novelty."

A comparison of the proposed solutions with other technical solutions shows that the listed elements used in the blocks are known, however, their introduction in this connection with other elements leads to the expansion of the functionality of the device.

This confirms the conformity of the technical solution to the criterion of "significant differences".

In FIG. 1, 2 presents a general diagram of the proposed passive location system for determining the coordinates of the aircraft in the near zone of the aerodrome and during approach, in FIG. 3 shows the structure of a central processing center (CPO), FIG. 4 - structure of a narrow base subsystem (UP), in FIG. 5 shows the structure of an information processing channel; FIG. 6 - selection of a coordinate system, in FIG. 7 - explanations for obtaining corrective deviations (± ΔX, ± ΔY, ± ΔZ) of the reference values of the altitude Z and azimuth (X, Y) of the aircraft in the near zone of the aerodrome and during approach, in FIG. 8 is a flowchart of a correction deviation algorithm ΔX _T , ΔY _T , ΔZ _T.

The system includes (Fig. 2):

- 3 narrow-base subsystems (UP) II (Fig. 4), consisting of: antenna-feeder system (AFS) II-1, low-noise amplifier (LNA) II-2, multi-channel synchronous quadrature receiver (MSC) II-3.4; analog-to-digital converter (ADC) II-5.6; control controller II-9, computer II-10, information processing channel II-7.8, including filters 11, detector 12, direction finder 13, output driver 14,

- Central processing point (CPO) I (Fig. 3), consisting of: first, second, third input ports I-1,2,3; I-4 keyboard unit, I-5 display unit, I-6 recorder, I-7 microprocessor, I-8 first auxiliary output, I-9 aircraft current speed calculation unit, I-10 aircraft current altitude calculation unit, operational memory device (RAM) I-11, read-only memory device (ROM) I-12, address and data bus I-13, radio modem of the decameter band of radio waves (DKMV) I-14, unit for calculating the range to the aircraft I-15,

Hybrid Optical Coaxial Network III.

The system operates as follows.

, где Н_ЛА - высота полета ЛА.The task of obtaining the coordinates of the aircraft at low altitude using active radars and a short range radio navigation system (RSBN) is solved only at the line of sight. Moreover, for all radio bands except DKMV, the short-range navigation problem at heights of at least 500 m is solved at a range of 80-90 km, and at lower altitudes it is difficult to talk about any kind of navigation. Detection range can be calculated as

where N _LA - _aircraft altitude.

If we use a DKMV range direction finder, similar in principle to the existing landing system, the task is solved, except for obtaining sufficient direction finding accuracy (no better than 12 arc minutes in angular parameters).

In this case, the following system architecture can be considered: at low altitudes and large distances, a DKMV radio line operates, the radiation of which is detected by three or more ground-based direction finders with a phased array (PAR) (or one without the function of determining the range to the aircraft). The range to the aircraft is measured using the method of separating the functions of the receiving and transmitting antennas in the active type radar (or the range by triangulating three positions of the direction finder with the PAR). At the ground control point, the coordinates of the aircraft are calculated and transmitted via the DKMV radio link to the aircraft for navigation. In the case of the approach of the aircraft to the near zone of the aerodrome for direct visibility (the landing zone), the aircraft control is transferred to the VHF radio line and the contour of the landing equipment is turned on.

The accuracy of determining the angular coordinates of the DKMV radio range depends on the opening of the PAR on the ground, which is significantly limited by its linear dimensions. The acceptable dimensions of the HEADLIGHTS equipment in the direction finder have linear dimensions in the diameter of the annular lattice from 60 m to 200 m and the accuracy of determining the angular values to the radiation source (reradiation) is 12 angular minutes. An increase in the size of the headlamps requires large areas and is possible in principle, but from a practical point of view, the area of accommodation is not unlimited.

Based on this, we have a significant error in measuring the range to an aircraft with a radiation source.

To reduce the magnitude of the error, a radar method for measuring the range to the aircraft is proposed, but with significant changes in the principle of operation of the meter.

As you know, to determine the range to the aircraft by the radar method, one should measure the delay in the arrival time of the reflected wave from the radio contrast target. By the value of the delay time, the distance to the target is estimated. This is true if the receiver and transmitter are located on the same directional antenna and time synchronization is used.

In this case, we have an omnidirectional emitter (IRI) on board the aircraft and a high-precision direction finder of the angular parameters of the radio signal on the ground.

To ensure time synchronization of the operation of the receiving equipment of the direction finder and the omnidirectional emitter on board the aircraft, the time stamp of global satellite navigation Glonass-Navstar is used, that is, the start of the receiver and transmitter are synchronized in time with the accuracy of the time stamp of satellites.

To resolve the uncertainty of bearing removal to the radiation source, the direction finder uses a one-stage method for determining coordinates with a known time of the period of operation of the computer by angular coordinates.

In our case, the operating time of the algorithm for determining the position of the aircraft in azimuth and elevation takes a period of 20 to 75 ms.

Therefore, if the emitter signal is longer than 75 ms, then in any case it will be received and the angular parameters of the aircraft (target) will be calculated from it.

Further refinement of the azimuth and elevation angle from the direction finder to the range meter to the aircraft makes it possible to use a transmitter signal of the emitter and measure its delay relative to the start of the measurement channel synchronized from the satellite.

If you do not use satellite constellation for synchronization, then in the case of using a highly stable (10 ^{-10 (11)} ) generator on board the aircraft and in the synchronization system of the direction finder and range meter, the algorithm works similarly, except for the presence of the phase of establishing communication in the radio modem algorithm, which allows provide an individual communication session with the aircraft.

In practice, it is possible to control the IRI outside the radar monitoring zone, and in the radio communication zone to obtain accurate information about the location of the aircraft.

It is important that in this case, its coordinates measured by satellite navigation systems are not received or transmitted in the message from the aircraft. The task and goal of the system in question is to obtain the true coordinates of the IRI (LA) at the time of its transmission of messages. Thus, the system is not subject to the imposition of false information, the withdrawal of the satellite reference system from the anchor point and other things that can be done with the satellite signal.

The position of the meter cannot be calculated, since the system is passive, and the radiation of the radio line in the DKMV range has a maximum directivity only at the location of the aircraft.

The result of the problem being solved is achieved by the method of centralized processing of signals obtained as a result of receiving electromagnetic oscillations at points whose placement in space is determined by the optimal grouping of weakly directed antenna elements inside structural blocks implemented by separate technical means of a distributed passive radar complex, the structural diagram of which is shown in FIG. 1. The complex consists of several (two or more) narrow-base subsystems (UE) (2), which include separate points of reception (TP) (3), and a central processing point (CPO) (1) connected by wired or wireless communication lines (LAN) (5), providing high speed information transfer, network bandwidth of at least 100 Mbps.

The source of radio emission (IRI) (4) generates an electromagnetic signal, for the description of which a model of a Gaussian radio signal is used:

where K is the number of components taken into account,

ƒ ₀ - carrier frequency,

ƒ _k are the frequencies of the considered components in the spectrum of the complex envelope,

and _k and b _k are coefficients that are Gaussian mutually independent random variables.

Such a signal corresponds to the case of a stochastic model, the application of which ensures the operation of the system in conditions of the least available a priori information.

The narrow-base subsystem (UE) is a technically unified receiving station that implements multi-channel reception at individual receiving points (TP), the placement of which in the structure of the UE antenna system satisfies two conditions:

1. The distance between the TP of the same UE is much less than the distance between the UE and IRI. This condition provides a flat wave front.

2. The distance between the TPs of the same UE does not exceed half the wavelength λ0 = c / ƒ ₀ corresponding to the carrier or the center frequency of the received radio signal ƒ ₀ , and c means the propagation speed of the signal from the IRI to the UE equal to the speed of light.

The block diagram of the station implementing UP1-3 (II) is shown in FIG. 2. The unit consists of an antenna-feeder system (AFS) II-1, a low-noise amplifier unit (LNA) II-2, a multi-channel synchronous quadrature receiver (MSC) II-3, 4, a block of analog-to-digital converters (ADC) II-5 , 6, the first and second channels of information processing II-7, 8, the control controller II-9 and the computer II-10, connected by a communication line (LAN) 5 to the CPU (I). The LNA block carries out preliminary amplification of the signals before it is transmitted to the MSCP input. Blocks MSCP, ADC are program-controlled, the mode of operation of which is set by the control signals of the computer II-10. When receiving electromagnetic waves are converted into an analog electrical radio signal, which is fed to the input of the LNA, from the output of which the radio signal is fed to the input MSCP. As a result of synchronous detection, an analog video signal is generated at the output of the MSCP, which is supplied in the form of pairs of quadrature to the ADC input, at the output of which a digital signal is generated in the form of samples.

Distinctive characteristics of the MSCP are the central frequency, tunable over a wide range: from 20 MHz to 3 GHz, and a wide frequency band of the demodulated signal, amounting to 60 MHz, which defines the signal as broadband in the upper part of the center frequency range, and as ultrawideband in its lower parts. To achieve the required reception quality, independent digital gain control of each channel is carried out in 0.5 dB steps, and the synchronization of each channel pair of the quadrature receiver should provide a phase difference of the accuracy of the quadrature of no more than 2 degrees in absolute value. To obtain a technical result, a multi-channel 16-bit multi-channel ADC with a tunable sampling frequency is used, with a maximum frequency of 100 MHz, which, taking into account the protective intervals, is consistent with the maximum band of the received radio signal. The synchronization of sampling in various ADC channels should ensure the mismatch of time instances of not more than 0.05 of the used sampling period.

The II-10 computer is implemented on the basis of a high-performance multiprocessor workstation equipped with at least two multi-core universal Intel Xeon processors with an operating frequency of at least 1.8 GHz and a random access memory (RAM) of at least 8 GB. The TsEVM II-10 in the structure carries out the functions of controlling the operation of UP1-3 (II) by setting the functional modes of individual blocks. In addition, the II-10 digital computer performs preliminary digital processing of the received signals, as well as their compression before transmission over the communication line.

The antenna system UP1-3 (II) is located on a vertical mast, the height of which is from 1.5 to 18 m. In the upper part of the mast, over a section of length L, from one to nine annular antenna sublattices (CAD) are located. The minimum distance between planar CADs is 0.5 m, which is due to the technological features of the mount, and the maximum is limited by the length of the working section of the mast L.

The structural organization of the distributed receiving system of the passive radar system allows you to form the necessary spatial distribution of the electromagnetic field of the signal emitted by the IRI at the reception.

Let the IRI be located at a point in space whose coordinates are given by the vector r = (X, Y, Z) ^T. Then the signal received by the m-th TP consisting of the structure of the n-th CP is the sum of the delayed and weighted useful signal and additive noise:

where a _n is the amplitude of the signal at the inputs of the TP n-th UP;

- время прохождения сигнала от ИРИ до условного фазового центра (УФЦ) n-й УП;τ _nm = τ _n + χ _n + ς _nm ;

- the signal transit time from the IRI to the conditional phase center (UFC) of the nth unitary enterprise;

- координаты УФЦ n-й УП;

- coordinates of the UFC n-th unitary enterprise;

χ _n is the error of the signal binding in time;

ς _nm = (r _nm -r _n ) ^T with _α / s is the signal propagation time from UFC to TP (from TP to UFC if ς _nm <0);

- координаты m-й ТП n-й УП;

- coordinates of the m-th TP n-th UP;

α _n , β _n - azimuth and elevation angle of the beam directed from the n-th unitary enterprise to IRI;

c - signal propagation speed.

A distinctive condition for the effective use of this model is that the signal observation time at each position should be chosen much longer than the correlation times of the signal and the noise. Digital samples of all received signals are transmitted via high-speed communication lines to a data center located in the structure of the CPU. Digital signals received by individual TPs are considered together and form a multidimensional digital signal.

Coordinates are estimated using a combined goniometric and differential-ranging method of estimation, in which the entire distributed system is considered as a combined passive system (CPS), combining the common features of a wide-base passive system (SBPS) and a passive system consisting of narrow-base subsystems (PSUP) . The estimation method of such a system is based on a method for calculating the estimate of the difference in the arrival of signals based on the correlation reception by the maximum likelihood method, which is presented in two papers for two reception points [2].

The angular coordinates of the aircraft in azimuth and elevation relative to the point of the center of mass of the carrier are determined by the phase-difference direction finder.

The range to the aircraft is determined by computational methods according to known bearings and the law of displacement of the center of mass in a relative coordinate system.

Functionally, the device consists of a direction finder 13 with a digital antenna array II-1, a detector 12 of time-frequency characteristics of targets (classifier of targets), output shapers 14 matrices of coordinates of targets and calculators II-9, 10, in which algorithms for extrapolating the trajectories of the aircraft, control algorithms operate devices and network algorithms for data exchange and control from the radio complex.

The direction finder 13 with a digital antenna array II-1 consists of a fixed antenna array (receiving antennas 20 ... 18000 MHz) located at a spatially separated reception point.

Each of the antennas is connected to the input of the LNA II-2, which provides coordination of the impedances of the antenna element and the connecting cable. Each LNA II-2 output is connected to its receiving path, which is formed by one of the channels of the multichannel synchronous quadrature receiver (MSC) II-3, 4 and the analog-to-digital converter (ADC) II-5, 6. Thus, an individual digital channel is formed signal samples from one element of the array.

The ADC II-5.6 signal simultaneously samples a signal across multiple channels. The size of this set is determined by the number of elements of the antenna array II-1. For example, depending on the accuracy requirements for determining the coordinates, you can select 16, 26 or 32 channels. So, for a lattice of 16 elements, the potential accuracy of the device is about 6 arc minutes. As the number of elements increases, accuracy increases.

Coherent signal processing is performed in filters 11, detector 12 and direction finder 13 of information processing channel II-7, 8.

Due to the need to ensure the stability of the amplitude-frequency characteristics (AFC) of the direction-finding path, it provides measures for measuring the AFC before taking signal samples in the operating frequency band. Frequency response of the frequency response is associated with the stability of the electrical parameters of the channel and is controlled by the control algorithm of reference (known signal sources) during operation from the controller II-9.

The direction finder 13 provides the determination of the angular coordinates of the aircraft (sources of radio emission - IRI) from the phase portrait of the incoming signal. The direction finder determines the angles of arrival of signals to the antenna array from different directions on the same frequency and frequency band. The number of directions is set by the required accuracy of determining the angular coordinates. For an accuracy of 6 minutes, the instantaneous matrix of angles has a dimension of 3600 elements. The time it takes to obtain the bearing (the quantum of time for solving the problem) depends on the speed of the II-10 computer.

Information processing is carried out in the computer II-10.

The matrix (azimuth-elevation angle) is preliminarily filled in the frequency range, which is incomplete, without the range coordinate, which is obtained by the calculation method according to the trigonometric equations of aircraft flight. This coordinate is calculated and it complements the IRI coordinate base to a logical level.

Work dynamics

The multichannel synchronous quadrature receiver (MSCP) II-3, 4 operates in the direction finding mode of an aircraft at the same frequency with one of the available bands.

The signals from the output of the computer II-10 in digital form are received for processing and issued in the information complex.

With a certain pace of restructuring of MSCI II-3, 4 over the range, the IRI is monitored (located) and their coordinates are automatically determined, with reference to the time of detection.

Time binding is performed for the differential-range measuring method for updating coordinates and solving special algorithms for the synthesis of space-time separation.

Thus, the considered system of passive detection of radio emission sources increases the accuracy of determining the coordinates of the aircraft in the near zone of the aerodrome and at the stage of its approach to landing for the purpose of its navigation support.

Bibliography

1. Aviation radio navigation. Handbook Ed. Sosnovsky A.A., Moscow: Transport, 1990.

2. Knapp S.N., Carter G.C., The Generalized Correlation Method for Estimation of Time Delay // IEEE Transactions on Acoustic, Speech and Signal Processing, 1976, vol. 24, no. 4, pp. 320-327.

Claims (1)

A passive location system for determining the coordinates of the aircraft in the near zone of the aerodrome and at the approach stage, containing three narrow-base subsystems, each of which contains N receiving antennas, the first and second analog-to-digital converters, and a central electronic computer, characterized in that in each narrow-base subsystem, a low-noise amplifier is additionally introduced, N inputs of which are connected to N receiving antennas, the first and second multi-channel synchronous quadrature receivers, whose inputs s are connected respectively to the first and second outputs of the low-noise amplifier, and the outputs are connected to the first inputs of the first and second analog-to-digital converters, the first and second information processing channels, the first inputs of which are connected to the outputs of the analog-to-digital converters, and the outputs are connected to the central electronic a computer; a control controller connected at the input to the central electronic computer, the first output of which is connected to the second input of the first multi-channel synchronous quadrature receiver, to the second input of the first analog-to-digital converter and to the second input of the first information processing channel, and the second output to the second input a second multi-channel synchronous quadrature receiver, to the second input of the second analog-to-digital converter and to the second input of the second information processing channel; a central processing center, which includes three information input ports, each input of which is connected through a hybrid optical-coaxial network to the output of the central electronic computer of each narrow-base subsystem, a keyboard unit, an indication unit, a unit for calculating the current speed of the aircraft, a unit for calculating the current altitude of the aircraft, unit for calculating the distance to the aircraft, random access memory, read-only memory, the first additional O port, a microprocessor, interconnected by address bus and data; a radio modem of the decameter range of radio waves, the input of which is connected to the output of the first additional output port, and the output is the general output of the system, providing radio communication with the aircraft.

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