RU2206903C2 - Radar for helicopter - Google Patents

Abstract

FIELD: radiolocation. SUBSTANCE: technical result of invention consists in raised probability of detection of small-sized ground and surface objects against background of reflections from underlying surface due to increase of angular resolution and to enhanced operational efficiency of radar under complex meteorological conditions. This result is achieved by insertion into mix of radar equipment of array based on two-wire line made of film foiled dielectric with radiators in the form of printed vibrators which is placed in helicopter propeller blade in area of its maximal length. Mass of array used as antenna does not exceed 0.3 kg which markedly diminishes mass of radar equipment and its cost. EFFECT: raised probability of detection of small-sized ground and surface objects. 6 dwg

Description

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

 Known radar stations (radar) of the survey of the earth and water surface, performing a survey by sector or circular motion of the antenna beam in the azimuthal plane. Most helicopter radars use a 3-centimeter wavelength range. Such radar stations are mainly used to detect marine objects.

 An analogue of such a radar can be radar company "Marconi" SEASPRAY-2000, which is used to detect marine objects. As a prototype, the Octopus-E radar station, used in the export version on Ka-28 helicopters, is considered. It is designed to detect marine targets in a circular sector of view.

The block diagram of the on-board radar station of the prototype is presented in figure 1, where:
1 - antenna post;
2 - transmitting device;
3 - circulator;
4 - receiving device;
5 - antenna engine;
6 - a device for primary information processing;
7 - information computing system;
8 - indicator;
9 - device control and stabilization of the antenna.

 As follows from the description, the prototype uses a parabolic antenna measuring (0.95 • 0.45) m in circular rotation with the help of an engine (5), designed to emit and receive microwave energy when viewing the sea surface. A magnetron transmitter is used to generate electromagnetic energy. This radar is incoherent and works according to the traditional principle. A synchronizer located in an information-computing system (7) generates pulses with a given duration and repetition rate and feeds them to the modulator of the transmitting device (2). From the transmitting device (2), microwave pulses through the circulator (3) are fed to the antenna post (1) and radiated into space. The energy reflected from sea objects (and the sea surface) enters the antenna post (1) and through the circulator (3) to the receiving device (4), then it enters the primary processing device (6), and then after the signal is accumulated on the indicator (8) . Using the control and stabilization device (9), the antenna is stabilized along the slope during helicopter evolutions.

 The main disadvantage of the given radar stations is the poor angular resolution of the antenna, which results in ineffective application for detecting small-sized ground and sea objects against reflections from the earth and sea surfaces due to the large reflection area overlapped by the diagram of such an antenna. The reason for the poor angular resolution of the radar is the limited size of the antenna aperture, which can be realized by placing the antenna only in the limited dimensions of the fuselage of the helicopter, as implemented in the prototype - Octopus-E radar. In addition, a disadvantage of the 3-cm range radar is also a decrease in the detection characteristics in bad weather conditions, especially in rain, due to reflections and attenuation characteristic of this wavelength range. A significant drawback of the used radar, and, in particular, the prototype, is the use of the antenna as a separate device with its own engine for rotation of the antenna mirror, which makes a significant contribution to the mass and cost of the radar equipment.

 The objective of the invention is to increase the resolution of the radar in the angle in the azimuthal plane and the probability of detecting small-sized ground and surface objects against the underlying surface in difficult weather conditions while reducing weight and size characteristics.

 This problem is solved by the fact that in the proposed radar, the antenna is made according to the structure of the antenna array in the L-wave range of waves from a film foil dielectric with emitters in the form of printed vibrators and placed in the helicopter blades in the region of the maximum size of its length, as well as the introduction of a digital processor signals, a digital data processor, a master oscillator and an angle sensor, which provide the radar in coherent and incoherent modes, synchronization and processing of received reflected signals.

 Figure 1 shows a block diagram of an on-board radar station of the prototype.

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

 In FIG. Figure 3 shows the electrical circuit of the antenna and its connection with the transceiver units of the radar using the feeder path.

 Figure 4 presents a detailed structural diagram of the proposed radar station.

 Figure 5 shows a sketch of the placement of the antenna array in the blades of the helicopter.

The proposed radar station includes:
1 - antenna array;
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;
Figure 4 presents a detailed structural diagram of the proposed radar station, where:
1 - antenna array;
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 - phase detector;
16 - phase detector;
17 - ADC;
18 - ADC;
19 is an analog-to-digital processor.

 The input-output of the antenna array (1) through the circulator (3) is connected to the first input of the receiving device (4), and the output of the transmitting device (2) is connected through the circulator (3) to the input-output of the antenna array (1), the first synchronizer output ( 7) connected to the first input of the transmitting device (2), the second output of the synchronizer (7) is connected to the second input of the transmitting device (2), the third output of the synchronizer (7) is connected to the second input of the receiving device (4), the fourth output of the synchronizer (7) connected to the third input of the receiving device (4), the fifth output with the synchronizer (7) is connected to the fourth input of the receiving device (4), the sixth output of the synchronizer (7) is connected to the second input of the digital signal processor (6), the seventh output of the synchronizer (7) is connected to the first input of the data processor (9), the second input of which connected to the output of the angle sensor (8), the output of the digital data processor (9) is connected to the third input of the digital signal processor (6), the first input of which is connected to the output of the receiver (4), and the output of the digital signal processor (6) with the indicator input (10).

 The antenna array (1) (see Fig. 3) is a two-wire line that is made of a foil-film dielectric (material of the type FDME-1-A-0.1 mm) with emitters (1i) in the form of printed vibrators and placed in the blades (20) a helicopter using its maximum length (see FIG. 5). The feeder path (1ph) is made on a coaxial cable of the type RK-50-4-46. A rotating coaxial transition (1B) is used to transfer (receive) energy from a transmitting (2) (receiving) device (3) mounted on the fixed part of the helicopter to the antenna array (1) mounted on the rotating blade (20) of the helicopter. A balancing device (1c) is used to coordinate a coaxial input with a wave impedance of 50 Ohms on a symmetrical two-wire line loaded on emitters (1i).

The placement of such an antenna array (1) in the blades (20) of the helicopter is shown in Fig.5. Here:
20 - helicopter blade;
21 - cargo centering;
22 - blade spar;
23 - fiberglass duct;
24 - the tail of the blade;
25 - placeholder;
26 - coaxial cable;
27 - high-frequency connector.

 As can be seen from the drawing (Fig. 5), the antenna array (1) with a balancing device (1c) is placed in the tail of the blade (20) along its entire length. The antenna array (1) is placed and glued to the fiberglass duct (23). The box with the enlarged lateral surface is then glued to the rear wall of the side member (22). The coaxial cable (26) of the antenna array power is also glued to the rear wall of the spar (22). Coaxial cable (26) ends with a high-frequency connector (27). The total mass of the antenna array does not exceed 0.3 kg. With this mass, the fiberglass duct (23) with the antenna array (1) is securely fixed to the side member (22), and the position of the center of gravity of the blade does not change much, and, if necessary, its displacement can be restored by increasing the weight of the centering load (21).

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 synchronizing the operation of the blocks, analog-digital transducer.

 The introduced synchronizer (7) in its structure corresponds to a frequency synthesizer necessary for a coherent mode of operation, as well as frequencies synchronizing the operation of blocks. All high-frequency signals necessary for the operation of the radar are generated in the synchronizer (7) by multiplying the frequency of the signal of the master oscillator (5), and low-frequency synchronizing signals are formed by dividing the frequency of the signal of the master oscillator (5).

The synchronizer (7) generates the following signal frequencies at the respective outputs:
- output 1 - radiation frequency f;
- output 2 - pulse repetition frequency F _p ;
- output 3 - the frequency of the local oscillator f _c ;
- output 4 - intermediate frequency f _pp ;
- output 5 - ADC sampling frequency f _sa ;
- output 6 - the synchronization frequency of the digital signal processor f _SP ;
- output 7 - the synchronization frequency of the digital data processor f _PD .

 To process the received reflected signals, a digital reprogrammable signal processor (6) was introduced in the radar, which provides compression, 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 (10). A digital data processor (9) has also been introduced into the radar, which provides the calculation of radar parameters in coherent and incoherent modes, as well as the generation of signals and commands for controlling radar units. One of the functions of the data processor in the proposed radar is to calculate the current coordinates of the radar information based on the values of the angle of rotation of the helicopter blade, taken from the angle sensor.

The radar operates as follows:
When the helicopter engine is in operation, the blade rotates with the antenna array (1) in the circular sector.

During the rotation of the antenna array (1), the power amplifier (11) amplifies the high-frequency pulses f coming from the synchronizer (7) and transfers them to the antenna array (1) through the circulator (3) and the feeder path (1ph). By the antenna array (1), these pulses are emitted into space and propagate in the direction determined by the antenna pattern. Signal coherence is determined by a highly stable master oscillator (5). The input of the modulator (12) from the synchronizer (7) receives trigger pulses (F _n ). The repetition frequency of the start pulses (F _p ) is formed in the synchronizer (7) by dividing the signal frequency f _{g of the} master oscillator (5). The pulse duration is also generated from the signal of the master oscillator by using the signal period. The modulator (12) modulates the high-frequency signal f and generates pulses entering the power amplifier (11) having a given duration (τ) and a repetition period (T _p ), determined by a unique range.

A high-frequency carrier frequency signal f is generated by the synchronizer (7). From the master oscillator (5), a signal with a frequency (f _g ) enters the synchronizer (7), multiplies to a higher frequency (f) and is used as the carrier frequency of the radar signal emitted by the antenna array. Also, during the rotation of the antenna array, the reflected signals from objects and the surface are received by the antenna array (1) and through the feeder path (1ph) and the circulator (3) enter the receiving device (4). In the microwave receiver (13), these signals in the receiver mixer are mixed with the synchronizer signal f _c , resulting in the formation of intermediate frequency signals f _pp . The intermediate frequency signals are fed to an analog-to-digital processor (19), where in the intermediate frequency amplifier the amplifier (14) is amplified and fed to phase detectors (15) and (16), to which a signal with a frequency equal to the intermediate signal is received from the synchronizer (7) frequency f _approx . Moreover, the signal f _pr enters one of the phase detectors with a shift by π / 2.

At the outputs of the phase detectors, in-phase I and quadrature Q signals are formed. Further, both signals I and Q by means of the ADC (17) and (18), controlled by the clock signal f _ca , are converted to digital form. From the outputs of the ADC (17) and (18), the signals of two quadratures enter the digital signal processor (6), synchronized by the signal f _cn from the sixth output of the synchronizer (7). In the digital signal processor (6), depending on the operating mode of the station, coherent or incoherent processing of the received signals is performed. After the threshold processing of radar signals, the digital signal processor (6) converts the coordinates of the incoming radar information from the polar coordinate system to a specified coordinate system.

For this, a digital data processor (9), synchronized by the signal f _pd , on the basis of the angle of rotation of the antenna array (1) (angle of rotation of the blade (20) of the helicopter) received from the angle sensor (8) (connection "a" (figure 2)) calculates the current coordinates of the radar information in a given system, transmits them to a digital signal processor (6) to convert the current coordinates of the radar information. From the digital signal processor, the radar information comes in the indicator (10).

 The effectiveness of the proposed radar compared with the prototype is to increase the angular resolution in the azimuthal plane.

где λ - длина волны излучения,
L - линейный размер антенны в азимутальной плоскости.As is known, the beam width θ _{l of the} radiation pattern at the power level P = 0.5

where λ is the radiation wavelength,
L is the linear size of the antenna in the azimuthal plane.

 In the prototype radar due to the limitation of the dimensions of the helicopter fuselage, the linear antenna size is 0.95 m.

 The maximum allocated size of the helicopter blade for placement of an antenna array in it is 6 m.

 It follows that when using the same wavelength λ, the angular resolution in the azimuthal plane in the inventive radar will be more than 6 times better than in the prototype.

Claims (1)

 A helicopter radar station, consisting of an antenna, a transmitting device, a circulator, a receiving device, a synchronizer and an indicator, while the antenna input-output through a circulator is connected to the first input of the receiving device, and the output of the transmitting device through a circulator is connected to the antenna input-output, the first the synchronizer output is connected to the first input of the transmitting device, the second synchronizer output is connected to the second input of the transmitting device, characterized in that the antenna is made according to the structure of the antenna ki in the L-range of wave radiation from a film foil dielectric with a radiator in the form of printed vibrators and placed in the helicopter blades in the region of the maximum size of its length, as well as a digital signal processor, a digital data processor, a master oscillator and an angle sensor, with the third output 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 digits Vågå signal processor, and the seventh output - to the first input of the digital data processor, a second input coupled to an output of the angle sensor; the output of the digital data processor is connected to the third 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 the indicator input.

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