RU2296344C2 - Helicopter ground obstacles detection radar - Google Patents

Abstract

FIELD: the invention refers to the field of radiolocation and may be used by helicopters.

SUBSTANCE: the helicopter ground obstacles detection radar has an antenna system, the first and the second separation filters, a rotating junction, a transmitting arrangement, a driving generator, a digital signal processor including an arrangement for processing of a summarily-differential diagram, a synchronizer, an angular sensor, a digital data processor and an indicator. At that the digital processor has an arrangement for narrowing the summary diagram.

EFFECT: narrowing the summary directional diagram.

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Description

The invention relates to the field of radar and can be used in helicopters.

Known airborne radar radar station, providing detection of ground obstacles in front of a flying helicopter. These radars can be both multifunctional and specialized. The antennas of most radars are located in the bow of the helicopter and provide an overview of the space in the front hemisphere. As an analogue of radar detection of ground obstacles, you can bring APG-78 (V) radar Longbow [1], the antenna of which is located above the sleeve of the helical part of the helicopter. All radars receive the necessary information to ensure low-altitude flight when operating in the millimeter-wave range of radio waves. Known stations, including the above analogue, have the following main disadvantages:

- the presence of an antenna, which makes a significant contribution to the mass of radar equipment;

- a significant reduction in range due to attenuation of energy in bad weather conditions and almost inoperability in the rain.

The results of work carried out by domestic and foreign researchers to assess the absorption of electromagnetic energy in the atmosphere show that the decimeter range of radio waves is the best range of electromagnetic waves to work in bad weather conditions, as well as in rain, for use in onboard radar.

However, information on airborne radars that use the decimeter wave band to solve the problem of detecting obstacles is not available in domestic and foreign publications.

In this regard, it seems appropriate to consider as a prototype a helicopter radar operating in the "L" range of radio waves, designed to detect ground and air targets (Application No. 2004106248/09 IPC: G 01 S 13/04, G 01 S 13 / 90 dated 04.03.2004, positive decision dated 02.10.2005).

In this radar, helicopter blades with linear antenna arrays “L” of the wave range placed in them are used as scanning antennas.

A block diagram of the radar of the prototype is presented in figure 1.

The radar station includes:

1 - antenna system consisting of a first antenna array 20

and a second antenna array 21;

2 - transmitting device;

3 - circulator;

4 - receiving device;

5 - master oscillator;

6 - digital signal processor;

7 - synchronizer;

8 - angle sensor;

9 - digital data processor;

10- indicator.

11 - power amplifier;

12 - modulator;

13 - microwave receiver;

14 - intermediate frequency amplifier;

15 is a first phase detector;

16 - second phase detector;

17 - the first ADC;

18 - second ADC;

elements 14 ÷ 18 form an analog-to-digital processor 19;

analog-digital processor 19 and the microwave receiver form a receiving device 4.

The radar operates in both coherent and incoherent mode.

In the air target detection mode, the radar station operates in a coherent mode using two antenna arrays 20 and 21 to increase the accuracy of the angular coordinate in the elevation plane. For this, the antenna arrays 20 and 21 work sequentially through the rotation rotation of the blade. In this case, also through a revolution, the radiation frequency switches from f ₁ to f ₂ . Through the separation filter 24, the radiation frequency f ₁ passes into the first antenna array and through the separation filter 25 the frequency f ₂ into the second antenna array.

When the radar is in operation, the signals reflected from the target, received by the first and second antenna arrays, having undergone primary processing in the analog-to-digital processor 19, enter the digital signal processor 6, where a fast Fourier transform, finding the module in two quadratures, and threshold processing are performed. The signals that passed through the threshold during the turnaround time of each of the antenna arrays are accumulated in the memory of the digital signal processor 6 for a time corresponding to a time of at least two revolutions. After the accumulation in memory of the signals received by the second antenna array 20 in a subsequent revolution after the rotation of the first antenna array 21, the signals in the cells of the same name in range and azimuth are summed in the digital signal processor 6, and thus a total antenna pattern is formed. The same signals are subtracted and thus the difference antenna radiation pattern in the elevation plane is found.

The disadvantage of this radar is the large angle "θ _lβ " of the total radiation pattern (BH) of the scanning antenna array in the elevation plane (θ _{lΔβ ≥60} °). A wide radiation pattern in the elevation plane does not allow selection of signals reflected from ground obstacles from signals reflected from the earth's surface (ground background) falling into the same range element and does not allow one to estimate the height of obstacles.

The objective of the invention is the detection of ground obstacles, the height of which corresponds to or above the height of the flight plane (plane of rotation of the blades), and by eliminating the influence of reflection signals from the surface of the earth and other objects located at heights below the plane of flight.

This problem is solved by narrowing the total radiation pattern at the reception, providing the required angular selection of such objects (or the background of the earth). The use of total and difference radiation patterns allows the total beam to be narrowed for reception in the elevation plane and to provide the required selection. To do this, the signal processor uses devices that sum the signals of the same name in range and azimuth, received by the radiation pattern of each antenna array, and subtract them, providing a total-difference radiation patterns. Also introduced are devices for narrowing the overall radiation pattern.

The total diagram is admitted to reception by subtraction from the signals of the difference diagram from the signals of the same diagram from the signals of the same diagram by the formula

| U _∑ | -k | U _Δ | = U _∑ob ,

where k is the gain of the signals of the difference diagram.

The magnitude of the angle of the total diagram at the reception with such a shoe is determined by the gain "k".

The coefficient "k" is taken as a compromise between the value of the narrowed angle and the allowable loss of signal power. An additional aggravation of the overall radiation pattern and a decrease in the level of side lobes is provided by multiplying the amplitude of the signals of the same total range and azimuth of the primary total diagram by the amplitude of the signals of the narrowed total diagram

| U _∑ | · | U _∑ob | = | U ^* _∑ob |

As a result of such actions, during the rotation of the antenna arrays at the output of the processing system, reflection signals from obstacles are generated and selected in the range-azimuth coordinates, which are received by the antenna system only by a narrowed total radiation pattern. The received signals from the processor go to the indicator.

Figure 1 shows a block diagram of an airborne radar station - a prototype.

Figure 2 presents a block diagram of the proposed radar station.

Figure 3 shows a detailed structural diagram of the proposed station.

Figure 4 shows a detailed structural diagram of a digital processor.

The proposed radar station (figure 2 and 3) includes:

1 - antenna system, consisting of: the first antenna array 20

second antenna array 21

2 - transmitting device;

3 - circulator;

4 - receiving device;

5 - master oscillator;

6 is a digital signal processor, consisting of:

- signal processing devices of the total difference diagram 60,

- fencing device diagram 67;

7 - synchronizer;

8 - angle sensor;

9 - digital data processor;

10 - indicator;

11 - power amplifier;

12 - modulator;

13 - microwave receiver;

14 - intermediate frequency amplifier;

15 - phase detector;

16 - phase detector;

17 - ADC;

18 - ADC;

elements 14 ÷ 18 form an analog-to-digital processor 19;

the analog-digital processor 19 and the microwave receiver 13 form a receiving device 4;

24 - the first separation filter;

25 - the second separation filter;

26 - rotating transition;

27 - emitters.

The detailed structural diagram of a digital signal processor 6 (figure 4) includes:

60 - a device for processing signals of the total difference diagram of the antenna, consisting of:

61 - module devices;

62 - switch;

63 - the first memory device;

64 - a second memory device;

65 - devices of the sum;

66 - the first difference device;

67 is a device for narrowing the total antenna diagram, consisting of:

68 - second difference device;

69 - the first multiplication device;

70 is a second multiplication device.

A helicopter radar station for detecting ground obstacles consists of a first scanning antenna array 20 and a second scanning antenna array 21 located in the first and second blades of the helicopter, as well as a transmitting device 2, a circulator 3, a receiving device 4, a driving generator 5, a digital signal processor 6, a synchronizer 7, an angle sensor 8, a digital data processor 9, a rotating transition 26, a first separation filter 24, a second separation filter 25 and an indicator 10. Moreover, for transmitting x pulses arrays circulator first input connected to the output 3 of the transmitting device 2.

To receive signals from the antenna arrays, the first output of the circulator 3 is connected to the input of the receiving device 4, and to transmit the transmitted and receiving reflected signals, the second output of the circulator 3 is connected to the input-output of the rotating transition 26. To start the transmitting device by the frequency signal F _{p the} first output of the synchronizer 7 is connected to the first input of the transmission device 2, and for the formation of the emitted microwave signal of frequency f _1, f ₂ of the second synchronizer output 7 is connected to the second input of the transmitting apparatus 2. for the formation of interm exact frequency of the received signal f _ave third output signal by synchronizer 7 heterodyne frequency f _c1 or f _c2 is connected to the second input of the receiving device 4. For the offset frequency signal to the Doppler frequency f _d fourth synchronizer output signal 7 to the intermediate frequency f is connected to a third _straight the input of the receiving device 4. To generate the sampling frequency of the analog-to-digital converter (ADC), the fifth output of the synchronizer 7 is connected to the fourth input of the receiving device 4 by the signal of the reference frequency f _ca , and for the synchronization of the digital signal processor, the sixth output on a clock signal f _sp connected to the second input of a digital signal processor 6.

To synchronize the operation of the data processor 9, the seventh output of the synchronizer 7 is connected to the first input of the digital data processor 9 by a pulse signal f _{pd ≈} 2 kHz, the second input of which is connected to the output of the angle sensor 8. To control the operating modes of the synchronizer 7, the first output of the digital data processor is connected to the second input of the synchronizer 7.

To control the digital signal processor 6 in the mode of framing the total radiation pattern by the signal "n revolution", the second output of the data processor 9 is connected to the third input of the digital signal processor. To control the operating modes and output the initial parameters, the third output of the digital data processor 9 is connected to the fourth input of the digital signal processor 6 (signals are transmitted via a standard interface).

To receive and process radar information, the first input of the signal processor 6 is connected to the output of the receiving device 4, the output of the digital signal processor 6 is connected to the input of the indicator 10.

For the operation of the antenna arrays at different carrier frequencies f ₁ or f ₂ , the first and second separation filters 24 and 25 are introduced, while the input-output of the first antenna array 20 is connected to the input-output of the rotary transition 26 through the first separation filter 24, and the input-output the second antenna array 21 is connected through a second separation filter 25 to the input-output of the rotating transition 26.

To switch the carrier frequencies through the review period when two antenna arrays 20 and 21 are in operation, the second input of the synchronizer 7 is connected to the first output of the data processor 9 by control commands. In order to ensure angle reflection selection to narrow the overall radiation pattern in the signal processor 6, the following is used: a signal processing device of a sum-difference diagram 60, including: a module device 61, a switch 62, a first memory device 63, a second memory device 64, a sum device 65, a first difference device and 66. In addition, a shrink device 67 is introduced into the signal processor 6, consisting of a second difference device 68, a first multiplier device 69, and a second multiplier device 70. In this case, to obtain a reflected signal module, the output of the receiving device 4 by quadrature signals U _I and U _{Q is} connected to the device of module 61 in the digital signal processor 6 (via a 2 × 16-bit line). Signals are accumulated in the first 63 or second 64 memory devices through a switch 62, to the input of which signals from the device of the module 61 are supplied. To ensure switching, signals (“n” turns) are sent to the second input of the switch 62.

The switch according to the "n revolution" signal is controlled from the data processor 9, for which the second output of the data processor 9 is connected to the third input of the signal processor 6. To form the total and difference radiation patterns of the antenna, the output of the first memory device 63 is connected to the first input of the sum device 65 and the first the input of the difference device 66, and the output of the second memory device 64 is connected to the second input of the device of the sum 65 and the second input of the difference device. Directly framing the total radiation pattern produces the firing device 67, in which the signals of the total diagram from the output of the sum device 65 of the processing device 60 of the total difference diagram are supplied to the firing device 67, to the first input of the second difference device 68 and to the second input of the multiplying device 69, and the output the first difference device 66 is supplied to the input of the first multiplication device 69.

To obtain a narrowed total diagram, the signals of the difference diagram after multiplying by the coefficient “k” from the output of the first multiplication device 69 are supplied to the second difference device 68. Then, from the output of the second difference device 68, the signals of the narrowed radiation pattern are fed to the input of the second multiplication device 70, where they are multiplied by signals of the initial (unbroken) summary chart. From the output of the second multiplication device, the signals are sent to indicator 10

The radar operates in both coherent and incoherent mode.

The radar in coherent mode provides a highly stable master oscillator 5, the frequency of which f _g is the base and is used in the synchronizer 7 to generate the radiation signal of the carrier frequency of the L-band, as well as heterodyne and other signals that synchronize the operation of the blocks of the analog-to-digital Converter.

All high-frequency signals necessary for the operation of the radar are generated in the synchronizer 7 by multiplying the frequency of the master oscillator 5, and low-frequency synchronizing signals are formed by dividing the frequency of the signal of the master oscillator 5. Processing of the received reflected signals in the radar is performed in a digital signal processor 6, which provides compression, accumulation, filtering, threshold processing of signals, assignment and transformation of coordinates, as well as the formation of an array of radar information to display it on The lamp 10.

In radar, a digital data processor 9 provides the calculation of radar parameters in coherent and incoherent modes, as well as the generation of signals and commands for controlling radar units.

Digital data processor 9 calculates the current coordinates of the radar information using the values of the angle of rotation of the helicopter blade, taken from the angle sensor 8.

To assign the coordinates of the radar information, the fourth output of the digital data processor 9 is connected to the fifth input of the digital signal processor 6.

In the detection mode of ground obstacles, the radar operates as follows. During operation of the helicopter engine, the blades rotate with antenna arrays 20 and 21 in the circular sector.

During the rotation of the antenna arrays 20 and 21, the power amplifier 11 amplifies the high-frequency pulses of the carrier frequency f ₁ or f ₂ coming from the synchronizer 7, and through the circulator 3, the feeder path and the rotary transition 26 transmit them to this or that antenna array 20 or 21.

Depending on the emitted frequency f ₁ or f _2, the radiation signal enters the first antenna array 20 or the second 21. This is determined by the separation filters 24 and 25. The antenna arrays 20, 21 are emitted into space and propagate in the direction determined by the antenna radiation pattern . Switching the radiation frequency to f ₁ or f _{2 is} carried out in the synchronizer 7 according to the commands issued from the data processor 9 and generated according to the data of the angle of rotation of the blade. The radiation of frequencies f ₁ or f ₂ alternates in time corresponding to one revolution of the blade. The input of the modulator 12 from the synchronizer 7 receives the start pulses F _p . The repetition frequency of the start pulses F _p is generated in the synchronizer 7 by dividing the frequency of the signal f _{g of the} master oscillator 5. The pulse duration is also formed from the signal of the master oscillator by using the period of this signal. The modulator 12 modulates the high-frequency signal f ₁ , f ₂ and generates pulses entering the power amplifier 11 having a given duration τ and a repetition period T _p defined by a unique range. The high-frequency signal of the carrier frequency f ₁ or f ₂ is generated by the synchronizer 7.

From the master oscillator 5, a signal with a frequency f _g enters the synchronizer 7, is multiplied to a higher frequency and is used as the carrier frequency f ₁ or f ₂ (where f ₂ = f ₁ + Δf, and Δf is the frequency spacing of the emitted signals by the antenna arrays) radar signal emitted by antenna arrays. Also, during the rotation of the antenna arrays, the reflected signals from ground obstacles are received by the antenna array 20 or 21 and through the separation filters 24 or 25, the rotating transition 26, the feeder path and the circulator 3 are received in the receiving device 4.

The reflected signals in the mixer of the microwave receiver 13 are mixed with the synchronizer signals "f _c1 " or "f _c2 ", differing in the intermediate frequency (where f _c1 = f ₁ + f _pr ; f _c2 = f ₂ + f _pr ), as a result of which signals of intermediate frequency f _ave

The intermediate frequency signals are fed to an analog-to-digital processor 19, where in the intermediate frequency amplifier UPCH 14 are amplified and fed to phase detectors 15 and 16, to which a signal with a frequency equal to the intermediate frequency f _{pr is} supplied from the synchronizer 7, and to one of the phase detectors the signal f _pr comes with a shift π / 2. At the outputs of the phase detectors, in-phase I and quadrature Q signals are generated. Next, both signals U ₁ and U _Q in the ADC 17 and 18, triggered by the clock signal f _ca , are converted to digital form.

From the outputs of the ADCs 17 and 18, the signals of two quadrature U _I and U _Q are fed to a digital signal processor 6, synchronized by a clock signal f _sp from the sixth output of the synchronizer 7 (a 2 × 16-bit line is used to transmit signals from the ADC to the digital signal processor 6 , to transfer signals from the digital data processor to the digital signal processor and vice versa, the standard trunk parallel interface MPI GOST 26765.51-86 is used).

In the digital signal processor 6 (Fig. 4), the signals of two quadratures U _I and U _Q from the receiving device are sent to the device of the module 61 of the signal processing device of the sum-difference diagram of the antenna 60, after which the signals are sent to the switch 62.

Depending on the rotation number of the antenna array, the output of the switch is connected to the first memory device 63 or second 64. In this case, with “n” rotation, the radar information enters the first memory device 63, and with a rotation of “n + 1” - into the second memory device 64, where, respectively, the signals received by the first and second antenna array (20 and 21) are accumulated. After the accumulation of reflection signals from ground-based obstacles in both memory devices 63 and 64, the signals are sent to a sum device 65, where a sum chart is formed from the signals of the same range and azimuth, and to the first difference device 66, where a difference chart is formed.

From the outputs of the devices of the sum 65 and the difference 66, the signals are fed to the fencing device 67, which consists of the second difference device 68, the first multiplier device 69 and the second multiplier device 70. The signals from the first difference device 66 are fed to the first multiplier device 69, where the signals of the difference diagram multiplied by the coefficient "k", which determines the magnitude of the angle of obuzhenie total radiation pattern in the elevation plane. From the first multiplication device 69, the signals enter the second difference device 68, where the signals of the difference diagram amplified by the coefficient “k” are subtracted from the signals of the total diagram. At the output of the second difference device 68, a narrowed total radiation pattern is formed in the elevation plane. To further aggravate the overall radiation pattern and reduce the level of the side lobes, the signals from the output of the second difference device 68 are supplied to the second multiplication device 70, where the same signals in range and azimuth of the primary total diagram are multiplied by the corresponding signals of the narrowed total diagram. From the output of the second multiplication device 70, the signals are fed to the indicator 10 to display them.

The technical result of the proposal is to narrow the overall antenna pattern.

может быть более 10. Обужение суммарной диаграммы на прием за счет угловой селекции обеспечивает возможность обнаружения наземных препятствий в требуемой угловой зоне по углу места относительно плоскости вращения антенных решеток (лопастей).Moreover, the size of

may be more than 10. The narrowing of the total reception pattern due to angular selection makes it possible to detect ground-based obstacles in the required angular zone by the elevation angle relative to the plane of rotation of the antenna arrays (blades).

Claims (1)

A helicopter radar station for detecting ground-based obstacles consists of an antenna system consisting of a first scanning antenna array and a second scanning antenna array located in the first blade of the helicopter and the second blade of the helicopter, as well as the first and second separation filters, with the input-output of the first antenna array through the first separation filter is connected to the input-output of the rotating transition, the input-output of the second antenna array is connected through the second separation filter to the input-output of the rotation a transition, a transmitting device, a circulator, a receiving device, a master oscillator, a digital signal processor, including a sum-difference diagram processing device, consisting of a device for finding a module by two reflected signal quadratures, a switch, a first memory device, a second memory device, a sum device, and the first difference device, synchronizer, angle sensor, digital data processor and indicator, while the input of the circulator is connected to the output of the transmitting device, the first the output of the circulator is connected to the first input of the receiving device, the second output of the circulator is connected to the input-output of the rotating transition, the first output of the synchronizer is connected to the first input of the transmitting device, the second output of the synchronizer is connected to the second input of the transmitting device, the third output of the synchronizer is connected to the second input of the receiving device , the fourth output of the synchronizer is with the third input of the receiving device, the fifth output is with the fourth input of the receiving device, the sixth output is with the second input of the digital percent an essor of signals, and the seventh output is with the first input of the digital data processor, the second input of which is connected to the output of the angle sensor, the second output of the digital data processor is connected to the third input of the digital signal processor, and the third output of the digital data processor is connected to the fourth input of the digital signal processor, the fourth output of the digital data processor is connected to the fifth input of the digital signal processor, the first input of which is connected to the output of the receiving device, and the output of the digital signal processor is connected to indicator house, characterized in that a digital beam processor is introduced into the digital signal processor, consisting of a second difference device, a first multiplication device and a second multiplication device, while the first input of the second difference device is connected to the output of the sum device, and the output of the second difference device connected to the first input of the second multiplication device, the second input of which is connected to the output of the sum device, the input of the first multiplication device is connected to the output of the first device difference, and the output of the first multiplier is connected to the second input of the second difference device, the output of the second multiplier is connected to the indicator input, the second synchronizer input is connected to the first output of the digital data processor, while the digital data processor calculates the station parameters in coherent and incoherent modes and calculates the current coordinates of the radar information using the angles of rotation of the helicopter blade, taken from the angle sensor, and the digital signal processor provides compression, n accumulation, filtering, threshold signal processing, assignment and transformation of coordinates, as well as the formation of an array of radar information for displaying it on the indicator screen.

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