WO2011027969A9

WO2011027969A9 - Missile warning radar system

Info

Publication number: WO2011027969A9
Application number: PCT/KR2010/004254
Authority: WO
Inventors: Gyu Churl Park; Jong Soo Ha; Jeong Soo Lee; Jin Ho Yoo; Jong Min Lee; Youn Sik Kang
Original assignee: Agency For Defense Development
Priority date: 2009-09-07
Filing date: 2010-06-30
Publication date: 2012-02-16
Also published as: WO2011027969A1; TR201201854T1; KR101007892B1

Abstract

Disclosed is a missile warning radar system comprising a first oscillator for generating a RF frequency(f₃), a second oscillator for generating a IF(f₂), a waveform generator for generating a pulse of a first IF(f₁), and outputting a composite frequency (f₁+f₂), a transmitter receiving the pulse output and performing preprocessing of the frequency, a first mixer performing up conversion, a RF power amplifier, a LNA, a second mixer, a IF amplifier, a third mixer, and a DSP.

Description

MISSILE WARNING RADAR SYSTEM

The present invention relates to a missile warning radar system, and more particularly, to a missile warning radar system wherein the system determines whether the target is directed to the radar system based on the detected information of the radar.

Recent development in the weapons against a tank such as anti-tank missile, rocket and cannon has made it possible to increase the penetrating power of the weapons. Especially, anti-tank missiles have been rapidly developed with greatly increased penetrating power, and the guiding method tends to change from conventional visible light guiding method to the fire-and-forget method with the help of equipped detector.

Missile detecting radars generally detect missiles attacking ships or airplanes but few radar systems can detect missiles attacking ground weapon system.

In the target detection by the ground weapon system radar, the target signal is very low compared to the ground clutter which is comparatively high, and the angle of direction rapidly changes making it difficult to build an algorithm for determining whether the target is directed to the corresponding ground weapon system or directed to adjacent weapon system. Also, the target signal is lower than the noise level of 20-30dB, requiring various methods for overcoming the problems.

The present invention has been designed to solve the problem of the prior arts and aims to provide a missile warning radar system by which determination can be made whether the target is directed to the radar system based on the detected information of the radar, and warning of threat can be issued based on the determination.

To achieve the object of the present invention, the missile warning radar system of the present invention comprises: a first oscillator for generating a RF(radio frequency)(f₃) for up conversion of transmitted signal and down conversion of received signal;

a second oscillator for generating a IF(intermediate frequency)(f₂) for up conversion of transmitted signal and down conversion of received signal; a waveform generator for generating a pulse of a first IF(f₁) for the transmitted signal, and outputting a composite frequency (f₁+f₂) by compositing the second IF(f₂) generated by the second oscillator and the first IF(f₁);

a transmitter receiving the pulse output from the waveform generator 103, and performing preprocessing for shaping the pulse and up conversion of the frequency; a first mixer performing up conversion to a signal of RF(f₁+f₂+f₃) by adding the frequency (f₁+f₂) of the pulse that went through the transmitter 104 and the RF(f₃) generated by the first oscillator; a RF power amplifier amplifying the pulse signal of RF that went through the first mixer to a high output, and transmitting the signal to the transmitting antenna;

a LNA(low noise amplifier) performing low noise amplification of the mixed signal of RF (f₁+f₂+f₃+f_d) received by the receiving antenna; a second mixer performing a down conversion of the signal that went through the LNA by subtracting the RF(f₃) related to the up conversion of the transmission signal from the RF(f₁+f₂+f₃+f_d) of the signal that went through the LNA; a IF amplifier amplifying the IF(f₁+f₂+f_d) signal that went through the second mixer; a third mixer performing a down conversion of the signal that went through the IF amplifier by subtracting the second IF(f₂) related to the up conversion of the transmission signal from the IF(f₁+f₂+f_d) of the signal that went through the IF amplifier; a signal converter conversion the analog IF signal that went through the third mixer to a digital IF signal; and a DSP(digital signal processor) receiving input of the digital signal converted by the signal converter, and determining on the threat of the target by performing a threat decision algorithm.

The signal converter can include a ADC(analog-to-digital converter) which converts the analog IF signal to a digital IF signal, and a DDC(digital down converter) which converts the digital IF signal converted by the ADC to a digital baseband signal.

The signal processing algorithm performed by the DSP comprises a windowing module receiving input of digital baseband signal that went through the DDC and multiplying a weighting value to the baseband signal to reduce the effect of the signals like clutter, thereby producing 5 bursts of data (1024 data), a DFB(Doppler filter bank) processing module calculating power level of range cells and Doppler(velocity) cells by performing FFT(fast Fourier transform) on the 5 bursts produced by the windowing module, a CA-CA-CFAR(cell averaging constant false alarm rate) module detecting among the signals input through the DFB processing module the signals higher than a threshold level which is determined to become a constant false alarm rate from the noise level, a post-detection module receiving input of signals that went through the CA-CFAR module 114c, and recognizing a target when 3 or more bursts of the 5 bursts produced by the windowing module pass the CA-CFAR level;

a module for estimating an angle of direction estimating an angle of direction on the signals higher than the CA-CFAR level of the CA-CFAR module by using a number of channel (channel 1, channel 2), and a module for deciding threat which determines on the threat of the target that passes the post-detecting module by using the angle of direction calculated by the module for estimating an angle of direction, the velocity and range in the Doppler cell and range cell of the DFB processing module, and the TTI (time to impact) calculated by the velocity and range.

The post-detecting module transmits the velocity data of signals of 3 or more bursts of the 5 bursts higher than the CA-CFAR level directly to the module for deciding threat by the internal 3/5 mutual relation unit, and transmits the range data to the module for deciding threat after performing range interpolation (search for optimum range value) at the interpolation.

The module for estimating an angle of direction acquires the angle of direction by calculating electric power ratio of the signal of

channels

1 and 2 which is calculated at the DFB processing module, performs poly fitting of the angle of direction by using the angle of directions from the first detected data to the currently detected data, and transmits the data obtained by averaging recent 3 angles of direction to the module for deciding threat.

The module for deciding threat calculates TTI by using the velocity and range, calculates threat by using the angle of direction, and determines on the threat by using the TTI calculation and the calculated data of threat.

The transmitting antenna and receiving antenna are preferably placed so that two receiving antennas are placed at the right and left side of the transmitting antenna located at the center with angle of 45°.

According to the missile warning radar system of the present invention, the system determines whether the target is directed to the radar system (the existence of threat) based on the acquired information of the radar, making it possible to issue an early warning and to respond quickly to the threats.

Fig. 1 shows the construction of the missile warning radar system of the present invention.

Fig. 2 shows the frame construction window in the DFB processing module of the missile warning radar system of the present invention.

Fig. 3 shows the structure of the frame of the post-detecting module of the missile warning radar system of the present invention.

Fig. 4 illustrates the orientation structure of the transmitting antenna and receiving antenna of the missile warning radar system of the present invention.

Fig. 5 illustrates the missile warning radar system of the present invention having the structure comprising 4 units.

Fig. 6 illustrates the process of signal processing at the signal processing unit of the missile warning radar system of the present invention.

101: a first oscillator 102: a second oscillator

103: waveform generator 104: transmitter

105: a first mixer 106: RF power amplifier

107: transmitting antenna 108: receiving antenna

109: LNA(low noise amplifier) 110: a second mixer

111: IF amplifier 112: a third mixer

113: signal converter 114: DSP(digital signal processor)

113a: ADC(analog-to-digital converter) 113b: DDC(digital down converter)

114a: windowing module 114b: DFB(Doppler filter bank) processing module

114c: CA-CFAR(cell averaging-constant false alarm rate) module 114d: post-detecting module

114e: module for estimating an angle of direction 114f: module for deciding threat

The invention will now be described with reference to the drawings attached.

Referring to Fig. 1, the missile warning radar system of the present invention comprises a first oscillator 101, a second oscillator 102, a waveform generator 103, a transmitter 104, a first mixer 105, a RF power amplifier 106, a transmitting antenna 107, a receiving antenna 108, a LNA 109, a second mixer 110, a IF amplifier 111, a third mixer 112, a signal converter 113 and a DSP 114.

The first oscillator 101 generates a RF (f₃) for up conversion of transmitted signal and down conversion of received signal.

The second oscillator 102 generates a IF (f₂) for up conversion of transmitted signal and down conversion of received signal.

The waveform generator 103 generates a pulse of a first IF (f₁) for a transmitted signal, and outputs composite frequency (f₁+f₂) by compositing the second IF (f₂) generated by the second oscillator 102 and the first IF (f₁).

The transmitter 104 receives the pulse output from the waveform generator 103, and performs preprocessing for shaping the pulse and up conversion of the frequency.

The first mixer 105 performs up conversion to a signal of RF (f₁+f₂+f₃) by adding the frequency (f₁+f₂) of the pulse that went through the transmitter 104 and the RF (f₃) generated by the first oscillator 101.

The RF power amplifier 106 amplifies the pulse signal of RF that went through the first mixer 105 to a high output, and transmits the signal to the transmitting antenna 107.

A SSPA (solid state power amplifier) can be used as the RF power amplifier 106. The LNA (109) performs low noise amplification of the mixed signal of RF (f₁+f₂+f₃+f_d) received by the receiving antenna 108. At this step, the frequency f_d means the frequency of the signal reflected from the target.

The second mixer 110 performs a down conversion of the signal that went through the LNA 109 by subtracting the RF (f₃) related to the up conversion of the transmitted signal from the frequency (f₁+f₂+f₃+f_d) of the signal that went through the LNA 109.

The IF amplifier 111 amplifies the IF (f₁+f₂+f_d) signal that went through the second mixer.

The third mixer 112 performs a down conversion of the signal that went through the IF amplifier 111 by subtracting the second IF (f2) related to the up conversion of the transmitted signal from the frequency (f₁+f₂+f_d) of the signal that went through the IF amplifier 111.

The signal converter 113 converts the analog IF signal that went through the third mixer 112 to a digital IF signal.

The DSP 114 receives input of the digital signal converted by the signal converter 113, and determines on the threat of the target by performing a threat decision algorithm.

The signal converter 113 can include a ADC 113a which converts the analog IF signal to a digital IF signal, and a DDC 113b which converts the digital IF signal converted by the ADC 113a to a digital baseband signal.

Also, the signal processing algorithm performed by the DSP 114 comprises a plurality of modules 114a-114f each of which is a software program performing specific function.

Windowing module 114a receives input of digital baseband signal that went through the DDC 113b, and multiplies a weight value to the baseband signal to reduce the effect of the signals like clutter, producing 5 bursts of data (1024 data) as shown in Figs. 2 and 3.

DFB processing module 114b calculates power level of range cells and Doppler (velocity) cells by performing FFT on the 5 bursts produced by the windowing module 114a.

CA-CFAR module 114c detects among the signals input through the DFB processing module the signals higher than a threshold level which is determined to become a constant error warning rate from the noise level.

Post-detection module 114d receives input of signals that went through the CA-CFAR module 114c, and recognizes a target when 3 or more bursts of the 5 bursts produced by the windowing module 114a pass the CA-CFAR level.

Module for estimating an angle of direction 114e estimates an angle of direction on the signals higher than the CA-CFAR level of the CA-CFAR module 114c by using a plurality of channel (channel 1, channel 2; see Fig. 6).

Module for deciding threat 114f determines on the threat of the target that passes the post-detecting module 114d by using the angle of direction calculated by the module for estimating an angle of direction 114e, the velocity and range in the Doppler cell and range cell of the DFB processing module 114b, and the TTI (time to impact) calculated by the velocity and range.

Also, preferably, the transmitting antenna 107 and the receiving antenna 108, as shown in Fig. 4, has the structure in which a transmitting antenna 107 is placed at the center portion, and a receiving antenna 108 is placed at the right and left side of the transmitting antenna 107 with angle of 45° to the transmitting antenna 107.

Fig. 5 illustrates the missile warning radar system of the present invention having the above described structure, wherein the structure comprises 4 units.

Referring to Fig. 5, the missile warning radar system of the present invention comprises 4 LRUs(Line Replacement Unit) in order to increase efficiency of the space and to repair the disorder of the equipment more easily. In other words, the system comprises 2

AUs(antenna units) 510, 520, a TSPU(transceiver/signal processing unit) 530 and a power supply 540.

The AU 510,520 comprises an antenna assembly and a receiver front end unit 511,521. The length of a cable between the receiver front end unit 511,521 and the receiver rear end unit 535 is about 3m providing the possibility of increased noise index due to a cable loss. Therefore, in order to reduce the noise index of the receiver as small as possible, the receiver front end unit 511,521 is placed at the AU 510,520.

The construction of the AU 510,520 is, as described above (see Fig. 4), comprises one transmitting antenna 107 and two receiving antennas 108, with the receiving antenna 108 oriented with 45° at the right and left side of the transmitting antenna 107, and the receiving antennas 108 having angle of 90° each other. Therefore, the SPDT(single pole double throw) 532 can cover the area of left 90° from the front when connected to the left AU 510, and can cover the area of right 90° from the front when connected to the right AU 520, providing coverage of front 180°.

The transceiver unit in the TSPU 530 performs high output amplification of the up converted radar transmitting signal in the L-band frequency range and transmits through the transmitting antenna 107, and applies down conversion and super-heterodyne method of demodulation to the signal received through the receiving antenna 108, and transmits the signal to the signal processing unit 536. The transceiver unit comprises a transmitter 104, frequency synthesizer 534 (corresponds to an assembly of a first oscillator 101, a second oscillator 102, a waveform generator 103 in Fig. 1), a receiver front end unit 511,521, a receiver rear end unit 535, individual module of a RF power amplifier 106. The SPDT 532 is a switch having one input and two outputs, connecting the left AU and right AU through signals.

The signal received by the receiving antenna 108 passes through the Limiter of the receiver front end 511,521, and is amplified through the LNA 109 (see Fig. 1), and transmitted to the receiver rear end 535. The signal which is amplified by the LNA 109 is down-converted to IF signal, and then the analog signal is converted to digital signal by the ADC 113a. Then, the converted signal is modulated to I/Q signal by the DDC 113b.

The frequency synthesizer 534 uses the frequency generated by OCXO(Oven-Controlled Crystal Oscillator) to multiply and divide the frequencies. To synchronize the whole radar system frequency of 40MHz is used with reference clock 10MHz, and the second oscillator 102 uses frequency of 5MHz.

The signal processing unit 536 (corresponds to the signal converter 113 and the digital signal processor 114 in Fig. 1) converts the IF signal of 5MHz from the receiver unit to a digital signal through the ADC 113a with sampling rate of 20MHz, and this digital signal is down-converted at DDC 113b to a baseband signal, and the target is detected through the signal processing algorithm and threat of the target is determined.

The process will be further described in detail with reference to Fig. 6.

Fig. 6 illustrates the process of signal processing in the signal processing unit of the missile warning radar system of the present invention.

Referring to Fig. 6, the ADC 113a of the signal converter 113 converts analog IF signal to digital IF signal, and the DDC 113b down-converts the digital IF signal to digital baseband signal, thereby modulating to I/Q signal.

Then, the windowing module 114a multiplies a weight value to the input baseband signal in order to reduce the effect of very large signal such as clutter, and produces 1024 data of 5 bursts as shown in Figs. 2 and 3.

Then, the DFB processing module 114b performs FFT on the 5 bursts thereby calculating power values per 5 range cells and Doppler (velocity) cells. In other words, the complex FFT 601 of the DFB processing module 114b calculates the baseband signal as range cells and Doppler (velocity) cells, and the magnitude calculator 602 calculates the size of signals over the whole cells.

The CA-CFAR module 114c receives the output signal from the DFB processing module 114b, and detects the signals higher than the threshold level (Vth) which is set to become a constant false alarm rate from the noise level. In other words, the CA-CFAR module 114c determines a threshold level, calculates the threshold level (Vth) by multiplying k to the determined threshold level, compares the threshold level (Vth) with the current level (V) of the cell, detects the signal with the current level (V) of the cell higher than the threshold level (Vth), and transmits these signals to the post-detecting module 114d.

The post-detecting module 114d recognizes an object as a target when 3 or more bursts of the 5 bursts pass the CA-CFAR level. In other words, the post-detecting module 114d transmits the velocity data of signals of 3 or more bursts of the 5 bursts which passed the CA-CFAR level directly to the module for deciding threat 114f by the internal 3/5 mutual relation unit 603, and the range data is transmitted to the module for deciding threat 114f after performing range interpolation (search for optimum range value) at the interpolation unit.

Meanwhile, the module for estimating an angle of direction 114e calculates the angle of direction of the signals higher than the CA-CFAR level by using the values of channel 1 and channel 2. In other words, module for estimating an angle of direction 114e acquires the angle of direction by calculating electric power ratio of the signal of

channels

1 and 2 which is calculated at the DFB processing module 114b, performs poly fitting of the angle of direction by using the angle of directions from the first detected data to the currently detected data, and transmits the data obtained by averaging recent 3 angles of direction to the module for deciding threat 114f.

The module for deciding threat 114f determines tracing and threat of the target of the target which passed the post-detecting module 114d by using the angle of direction of the module for estimating an angle of direction 114e, the velocity in Doppler cell, the range in the range cell, the TTI (time to impact) calculated by the velocity and range. At this step, the module for deciding threat 114f calculates TTI by using the velocity and range, calculates threat by using the angle of direction, and determines the threat by using the TTI calculation and the calculated data of threat.

Then, the target information obtained by the above processes (range, velocity, angle of direction, TTI, threat) is transmitted to the control system (not shown), and displayed on the display.

As described above, the missile warning radar system of the present invention determines whether the target is directed to the radar system (the existence of threat) based on the aquired information of the radar, making it possible to issue an early warning and to respond quickly to the threats.

The present invention has been described in detail with reference to a preferable example. The invention, however, is not limited by the example, and it is obvious that the example can be variously modified by those skilled in the art within the scope of the present invention. Accordingly, the scope of the invention should be interpreted by the claims attached, and all technical ideas which are equivalent to the present invention should be regarded as belonging to the scope of the present invention.

Claims

A missile warning radar system comprising:

a first oscillator for generating a RF(radio frequency)(f₃) for up conversion of transmitted signal and down conversion of received signal;

a second oscillator for generating a IF(intermediate frequency)(f₂) for up conversion of transmitted signal and down conversion of received signal;

a waveform generator for generating a pulse of a first IF(f₁) for the transmitted signal, and outputting a composite frequency (f₁+f₂) by compositing the second IF(f₂) generated by the second oscillator and the first IF(f₁);

a transmitter receiving the pulse output from the waveform generator 103, and performing preprocessing for shaping the pulse and up conversion of the frequency;

a first mixer performing up conversion to a signal of RF (f₁+f₂+f₃) by adding the frequency (f₁+f₂) of the pulse that went through the transmitter 104 and the frequency (f₃) generated by the first oscillator;

a RF power amplifier amplifying the pulse signal of RF that went through the first mixer to a high output, and transmitting the signal to the transmitting antenna;

a LNA(low noise amplifier) performing low noise amplification of the mixed signal of RF (f₁+f₂+f₃+f_d) received by the receiving antenna;

a second mixer performing a down conversion of the signal that went through the LNA by subtracting the RF(f₃) related to the up conversion of the transmitted signal from the frequency (f₁+f₂+f₃+f_d) of the signal that went through the LNA;

a IF amplifier amplifying the IF (f₁+f₂+f_d) signal that went through the second mixer;

a third mixer performing a down conversion of the signal that went through the IF amplifier by subtracting the second IF (f₂) related to the up conversion of the transmitted signal from the frequency (f₁+f₂+f_d) of the signal that went through the IF amplifier;

a signal converter conversion the analog IF signal that went through the third mixer to a digital IF signal; and

a DSP(digital signal processor) receiving input of the digital signal converted by the signal converter, and determining on the threat of the target by performing a threat decision algorithm.
The missile warning radar system of claim 1, wherein the signal converter includes a ADC(analog-to-digital converter) which converts the analog IF signal to a digital IF signal, and a DDC(digital down converter) which converts the digital IF signal converted by the ADC to a digital baseband signal.
The missile warning radar system of claim 1, wherein the signal converter includes a ADC(analog-to-digital converter) which converts the analog IF signal to a digital IF signal, and a DDC(digital down converter) which converts the digital IF signal converted by the ADC to a digital baseband signal.
The missile warning radar system of claim 3, wherein the post-detecting module transmits the velocity data of signals of 3 or more bursts of the 5 bursts which passed the CA-CFAR level directly to the module for deciding threat by the internal 3/5 mutual relation unit, and transmits the range data to the module for deciding threat after performing range interpolation (search for optimum range value) at the interpolation.
The missile warning radar system of claim 3, wherein the module for estimating an angle of direction acquires the angle of direction by calculating power ratio of the signal of channels 1 and 2 which is calculated at the DFB processing module, performs poly fitting of the angle of direction by using the angle of directions from the first detected data to the currently detected data, and transmits the data obtained by averaging recent 3 angles of direction to the module for deciding threat.
The missile warning radar system of claim 3, wherein the module for deciding threat calculates TTI by using the velocity and range, calculates threat by using the angle of direction, and determines on the threat by using the TTI calculation and the calculated data of threat.
The missile warning radar system of claim 1, wherein the transmitting antenna and receiving antenna are placed so that two receiving antennas are placed at the right and left side of the transmitting antenna located at the center with angle of 45°.