KR101770098B1 - Doppler beam sharpening apparatus using range cell migration compensation and method therefore - Google Patents

Abstract

The present invention relates to a radar altimeter and, more specifically, relates to a Doppler beam reduction apparatus and method to reduce a Doppler beam of a radar altimeter by compensating for range cell migration. The Doppler beam reduction apparatus using range cell migration compensation of a radar comprises: a transmission antenna; a transmission unit which transmits a Doppler beam to a target in a pulse signal form by using the transmission antenna; a plurality of reception antennas which receive a target reflection signal reflected from the target; a reception unit which generates a deramping signal by deramping of the target reflection signal; and a signal processing unit which immediately performs fast Fourier transform (FFT) of the deramping signal in a directly downward direction, calculates FFT in an along-track direction, compensates for a range cell, and performs inverse fast Fourier transform (IFFT) in an along-track direction, to reduce a Doppler beam.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a Doppler beam shrinking apparatus and a method for compensating a Doppler beam using distance cell movement compensation,

The present invention relates to radar altimeter technology, and more particularly, to a Doppler beam reduction apparatus and method for reducing a Doppler beam of a radar altimeter by compensating for distance cell movement.

The existing Delay-Doppler Altimeter (DDA) is used in Synthetic Aperture Radar (SAR) to reduce beam foot print in the along-track direction of the aircraft. The Doppler beam is reduced by using the point where the Doppler is zero rather than the compression method, which is the direct downward position of the altimeter.

This is advantageous because it uses a noncoherent method for each compression, and has a disadvantage in that the resolution is lower than that of a coherent method.

On the other hand, the existing SAR compression method improves the resolution but increases the calculation amount, which makes it difficult to apply directly to the radar altimeter which requires high-speed processing.

1. Korean Registered Patent No. 10-0749336 (Registration date 2007.08.08) 2. Korean Patent Publication No. 10-2015-0058682 3. Korean Patent Publication No. 10-2011-0076008

1. Research on Synthetic Aperture Radar (SAR) Shaking Compensation Technique, Journal of the Institute of Electronics Engineers of Korea, 50 (3), pp. 424 (March, 2013) pp. .221-229

The present invention has been proposed in order to solve the problem according to the above background art, and it is an object of the present invention to compensate a distance cell movement in order to reduce a disadvantage that a Doppler beam reduction resolution of a general DDA (Delay-Doppler Altimeter) is lower than a coherent scheme And it is an object of the present invention to provide a Doppler beam reduction apparatus and method for reducing a Doppler beam of a radar altimeter.

In order to achieve the above object, the present invention provides a Doppler beam shrinking apparatus for shrinking a Doppler beam of a radar altimeter by compensating a distance cell movement.

The Doppler beam reduction apparatus is a Doppler beam reduction apparatus using distance cell movement compensation of a radar,

radiator;

A transmitter for transmitting a Doppler beam to a target in the form of a pulse signal using the transmission antenna;

A plurality of receive antennas for receiving a target reflected signal reflected from the target;

A receiving unit for deraming the target reflection signal to generate a demodulation processing signal; And

The fast Fourier transform (FFT) operation is performed on the demodulation processing signal directly in the downward direction, the FFT operation is performed in the along-track direction, the distance cells are compensated, and then the IFFT operation is performed in the along- (Inverse Fast Fourier Transform) operation to reduce the Doppler beam.

(여기서,

는 얼롱트랙(along-track) 방향의 주파수,

는 고도계로부터 직하방으로의 거리주파수,

는 스케일링 함수, λ는 파장을 나타낸다) 를 이용하여 이루어지는 것을 특징으로 할 수 있다. Also,

(here,

The frequency in the along-track direction,

Is the distance frequency from the altimeter to the direct room,

Is a scaling function, and lambda is a wavelength).

(여기서, V는 고도계가 탑재된 비행체의 비행속도를 나타낸다)으로 정의되는 것을 특징으로 할 수 있다.In addition, the scaling function may be expressed by a formula (

(Where V represents the flight speed of the aircraft on which the altimeter is mounted).

Wherein the pulse signal type and the target reflection signal are LFM (Linear Frequency Modulated) signals.

Wherein the radar is a synthetic aperture radar (SAR).

On the other hand, another embodiment of the present invention provides a method of transmitting a Doppler beam, the method comprising: (a) transmitting a Doppler beam to a target using a transmit antenna in the form of a pulse signal; (b) receiving a target reflected signal from a plurality of receive antennas reflected from the target; (c) receiving a target reflection signal by deriving a target reflection signal to generate a demodulation processing signal; (d) the signal processing unit performs a fast Fourier transform (FFT) operation on the demodulation processing signal directly in a downward direction; (e) compensating the distance cell after the signal processing unit performs an FFT operation in a direction along-track; And (f) reducing the Doppler beam by performing Inverse Fast Fourier Transform (IFFT) on the signal processing unit in a follow-track direction. Method can be provided.

 According to the present invention, there is an advantage of improving the Doppler beam reduction resolution by performing each compression in the along-track direction in a coherent manner, as compared to the already known noncoherent approach. .

As another effect of the present invention, the problem of the increase in the amount of calculation that can occur in the SAR angle compression is that the characteristics of the interferometer radar altimeter, that is, the distance cell movement in the direct downward direction occurs in the distance cell, And can be overcome by applying a high-speed processing method using a compensation function.

Further, as another effect of the present invention, when applied to an interferometer radar altimeter, since the Doppler beam resolution is improved, it is possible to improve the information quality in the along-track direction and to rely on the comparison point selection in the along- The effect of improving the information quality in the cross-range direction can be expected.

1 is a conceptual diagram showing the operation principle of a general radar altimeter.
2 is a block diagram of a configuration of a Doppler beam reduction apparatus 200 according to an embodiment of the present invention.
3 is a flowchart illustrating a Doppler beam reduction process according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Like reference numerals are used for similar elements in describing each drawing.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. The term "and / or" includes any combination of a plurality of related listed items or any of a plurality of related listed items.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Should not.

Hereinafter, an apparatus and method for reducing a Doppler beam using distance cell movement compensation according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a conceptual diagram showing the operation principle of a general radar altimeter. In particular, FIG. 1 is a conceptual diagram showing the operation principle of the interferometer radar altimeter 100. Referring to FIG. 1, the interferometer radar altimeter 100 may include a linear frequency modulated (LFM) signal (i.e., a Doppler beam) in pulse form for distance resolution enhancement and / Sending and receiving.

The DDA (Delay-Doppler Altimeter) takes a Fast Fourier Transform (FFT) in the along-track direction and maps the Doppler beam 110 in a manner of mapping the Doppler position (the point where the Doppler is zero is directly below the altimeter) Reduce.

However, in the case of the present invention, the Doppler beam is reduced by compensating for the delayed phase, i.e., the distance cell movement, and taking an IFFT (Inverse FFT).

2 is a block diagram of a configuration of a Doppler beam reduction apparatus 200 according to an embodiment of the present invention. 2, the Doppler beam reduction apparatus 200 includes a transmitter 210 for transmitting a linear frequency modulated (LFM) signal to a target (not shown) in the form of a pulse signal using a transmission antenna 210 and a transmission antenna 210 A plurality of reception antennas 220 for receiving a target reflection signal reflected from a target (not shown), a receiver 240 for deriving a target reflection signal to generate a dimming processing signal, A signal processing unit 260 for reducing the Doppler beam by compensating the movement of the distance cell through a ramping process signal and a control unit 25 for controlling the transmitting unit 230, the receiving unit 240 and the signal processing unit 260, And the like.

The signal processing unit 260 performs an FFT operation on the de-ramping processing signal directly in the downward direction in consideration of the fact that the distance cell movement compensation to the direct downward direction is unnecessary, and then performs a Fast Fourier Transform (FFT) operation in the along- Compensates for the distance cell, and then performs inverse Fast Fourier Transform (IFFT) operation in the along-track direction to reduce the Doppler beam.

3 is a flowchart illustrating a Doppler beam reduction process according to an embodiment of the present invention. 3, when a plurality of reception antennas 220 receives a target reflection signal reflected from a target (not shown), the reception unit 240 performs a deramping processing on the target reflection signal to generate a de- (Step S310). At this time, the target reflection signal may be a reception LFM (Linear Frequency Modulated) signal.

The signal processing unit 260 generates a de-ramping process signal using the following equation.

는 고도계로부터 최근 지점까지의 시간,

는 진행방향으로의 시간,

는 표적으로 식별된 최근 지점에서의 진행방향으로의 시간,

는 LFM 신호의 기울기(처프(chirp) 변조율), C는 광속, λ는 고도계의 반송주파수 파장,

는 표적과 안테나 간 거리를 나타낸다.here,

The time from the altimeter to the last point,

Is the time in the direction of travel,

Is the time in the direction of travel at the most recent point identified as the target,

(Chirp modulation rate) of the LFM signal, C is the speed of light,? Is the carrier frequency of the altimeter,

Represents the distance between the target and the antenna.

Generally, in order to compress the above signals, a conventional Synthetic Aperture Radar (SAR) algorithm, a Range-Doppler Algorithm, a Chirp Scaling Algorithm, a Delay Sum algorithm Algorithm) can be used.

However, since a process of oversampling and encoding an LFM (Linear Frequency Modulated) signal is required, the signal processing speed is slow.

Referring to FIG. 3, according to an embodiment of the present invention, distance cell movement compensation is unnecessary in the direct downward direction of the interferometer radar altimeter, and signal processing can be performed for each pulse section, (Step S320, S330, S340) by compensating for the distance cell movement in the along-track direction by using the fact that the Doppler beam can be represented by a compensation function usable for the Doppler beam. (Shrink Doppler beam

를 나타내었으며, 수학식 3에 보상 함수

를, 수학식 4에 최종 수신신호를 나타내었다.In Equation (2) below, a scaling function

And Equation (3) represents the compensation function

And the final received signal is shown in Equation (4).

는 얼롱트랙(along-track) 방향의 주파수,

는 고도계로부터 직하방으로의 거리주파수,

는 신호처리후 남은 복소 상수,

는 직하방으로의 시간 대역폭,

는 얼롱트랙(along-track) 방향의 주파수 대역폭을 나타내며,

는 표적까지의 최단(closest) 거리를 나타낸다. Where V is the flight speed of the altimeter-

The frequency in the along-track direction,

Is the distance frequency from the altimeter to the direct room,

Is the complex constant remaining after signal processing,

The time bandwidth to the direct down room,

Represents the frequency bandwidth in the along-track direction,

Represents the closest distance to the target.

The remaining variables are the same as in Equation 1 above.

When the distance cell movement compensation using the compensation function is performed, the IFFT operation in the erroneous track direction is performed (step S350).

의

는

의

로 변환되는데, 수학식 4의 sinc 함수에서

인 지점이 직하방으로의 표적거리로 산출된다. 그런 다음 수학식 1의 지수함수는 얼롱트랙 방향으로 FFT 후 S340의 보상함수 보상을 거치게 되고 다시 IFFT 연산을 수행하게 되는데, 수학식 4의 sinc 함수에서

인 지점이 얼롱트랙 방향의 표적거리로 산출된다. 따라서 제안하는 발명을 통해 표적지점으로의 도플러 빔 축소가 가능하게 된다.As described above, after the FFT operation to the direct downward direction

of

The

of

In the sinc function of Equation 4,

The target point is calculated as the target distance to the direct downward direction. Then, the exponential function of Equation (1) is subjected to the compensation function compensation of S340 after the FFT in the erroneous track direction, and then the IFFT operation is performed again. In the sinc function of Equation

Is calculated as the target distance in the erroneous track direction. Therefore, it is possible to reduce the Doppler beam to the target point through the proposed invention.

으로 계산할 수 있다.As a result, the distance to the most recent point

.

200: Doppler beam reduction device
210: transmitting antenna
220: receiving antenna
230:
240: Receiver
250:
260: Signal processor

Claims (6)

A Doppler beam shrinking apparatus using distance cell movement compensation of a radar,
radiator;
A transmitter for transmitting a Doppler beam to a target in the form of a pulse signal using the transmission antenna;
A plurality of receive antennas for receiving a target reflected signal reflected from the target;
A receiving unit for deraming the target reflection signal to generate a demodulation processing signal; And
The fast Fourier transform (FFT) operation is performed on the demodulation processing signal directly in the downward direction, the FFT operation is performed in the along-track direction, the distance cells are compensated, and then the IFFT processing is performed in the along- A signal processor for performing an Inverse Fast Fourier Transform (FFT) operation to reduce the Doppler beam;
Wherein the Doppler beam is compensated for by the distance cell movement compensation.
The method according to claim 1,
The compensation includes a compensation function

(here,

The frequency in the along-track direction,

Is the distance frequency from the altimeter to the direct room,

Is a scaling function, and lambda is a wavelength). ≪ / RTI >
3. The method of claim 2,
The scaling function can be used in close proximity to compensate for the phase delay in the along-track direction,

(Where V represents the flight speed of the aircraft on which the altimeter is mounted).
The method according to claim 1,
Wherein the pulse signal type and the target reflection signal are LFM (Linear Frequency Modulated) signals.
The method according to claim 1,
Wherein the radar is a Synthetic Aperture Radar (SAR).
A method for reducing a Doppler beam using a distance cell movement compensation of a radar,
(a) transmitting a Doppler beam to a target in the form of a pulse signal using a transmitting antenna;
(b) receiving a target reflected signal from a plurality of receive antennas reflected from the target;
(c) receiving a target reflection signal by deriving a target reflection signal to generate a demodulation processing signal;
(d) the signal processing unit performs a fast Fourier transform (FFT) operation on the demodulation processing signal directly in a downward direction;
(e) compensating the distance cell after the signal processing unit performs an FFT operation in a direction along-track; And
(f) reducing the Doppler beam by performing an Inverse Fast Fourier Transform (IFFT) operation on the signal processing unit in an erroneous track direction;
And compensating for the Doppler beam using the distance cell motion compensation.

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