JP2908164B2 - Moving target detection radar device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar for detecting a moving target, and more particularly to an apparatus for detecting a moving target by extracting a reflected signal of the moving target from a Doppler shift frequency of a reflected signal from the moving target.

[0002]

2. Description of the Related Art Conventionally, this type of moving target detection radar system transmits a plurality of pulses and receives a reflected signal from a target as shown in, for example, US Pat. No. 4,730,189. The moving target is detected by taking out signals at intervals of a plurality of transmitted pulses from the received signals and performing synchronous integration.

[0003] First, an example of a conventional moving target detection radar system described in the aforementioned US Patent will be described with reference to FIGS. 6 and 7. FIG. 6 is a block diagram showing a synchronous integration processing system of a received signal of a conventional moving target detection radar. Analog-to-digital converters (hereinafter referred to as A / D converters) 51 and 52 convert the I and Q analog video signals of the demodulator 58 into digital signals. The synchronous integrator 53
The output signals of the A / D converters 51 and 52 are vector-added. The threshold circuit 54 extracts a signal having a predetermined amplitude or more from the output signal of the synchronous integrator 53. The indicator 55 displays an output signal of the threshold circuit 54. The transmitter 56 generates a transmission signal. The transmission / reception switch 57 sends the output signal of the transmitter 56 to the antenna, and sends the signal received by the antenna to the demodulator 58 side. Demodulator 58 converts the received signal into I and Q analog video signals. The synchronizing signal oscillator 59 generates a synchronizing signal necessary for generating a transmission signal and generating I and Q analog video signals. FIG. 7 shows a specific example of the synchronous integrator 53 of FIG. In the figure, shift registers 61, 62,
Reference numerals 63 and 64 denote shift registers that match the pulse interval of the transmission signal. Multipliers 65, 66, 67, 68 multiply input or output signals of shift registers 61, 62, 63, 64 by Doppler shift frequency coefficients. The adder 69
The outputs of the multipliers 65, 66, 67, 68 are added.

Next, the operation of FIG. 6 will be described. A signal generated by the transmitter 56 based on the synchronization signal of the synchronization signal oscillator 59 is radiated from the antenna to the air through the transmission / reception switch 57. The radiated signal is reflected by the target and received by the antenna. This received signal is applied to a demodulator 58 through a transmission / reception switch 57. The demodulator 58 performs reception processing of the received signal, and converts the received signal into I and Q analog video signals based on the synchronization signal of the synchronization signal oscillator 59. The I and Q analog video signals are supplied to an A / D converter 51,
Each is converted into a digital signal by 52. This digital signal is vector-added by the synchronous integrator 53 for each of a plurality of Doppler shift frequencies, and a threshold circuit 5
A signal having an amplitude equal to or larger than the amplitude determined by step 4 is taken out and displayed on the indicator 55.

Further, the operation of FIG. 7 will be described below. FIG.
Indicates the signal as a complex number for simplicity. Therefore, the input signal is also a complex signal. The input signal is
The contents of the shift registers, which are shifted by the shift registers 61, 62, 63, 64 and are equal to a plurality of transmission pulse intervals, are added to multipliers 65, 66, 67, 68,
It is multiplied by the complex number e ^{i · w0 · n · PRT} . ω ₀ represents an example of a plurality of Doppler shift frequencies, and n · PRT represents a time corresponding to a transmission pulse interval. The output of the multiplier is added by the adder 69.

[0006]

In the conventional moving target detection radar system, received signals of a plurality of transmission pulses are stored in a shift register or the like, and synchronous integration of the received signals is performed at intervals of the plurality of transmission pulses. Had to do. Therefore, a multiplication circuit of at least the number of transmission pulses is required for one synchronous integration process, and a complicated synchronous integration process and many multiplication circuits are required.

An object of the present invention is to provide a moving target detection radar device which can detect a moving target using a Doppler shift frequency of a reflected signal from the moving target with a simple circuit and a small number of multiplication circuits.

[0008]

According to the present invention, a predetermined
Transmits a signal modulated with the modulation code of
Receives the reflected signal, and from the received signal, the reflected signal due to the moving target
Moving target detection radar device that extracts
In the received signal in the range where you want to extract the reflected signal from
Multiple docks assumed for the moving target to be detected
Multiplication that multiplies the coefficients of the plastic shift frequency components in parallel
The circuit performs a correlation process between the received signal and the modulation code.
And a correlation processing circuit.
Receive the multiplied results, and
Multiple tap outputs with a delay relationship corresponding to the key code
Number of shift registers and data from multiple shift registers.
And a plurality of adders for adding the
Corresponding to multiple Doppler shift frequency components
And extracting the moving target detection signal. Further
If the modulation code contains signal components with different polarities,
Receive the tap output from the shift register and change the polarity of the signal.
A signal polarity controller that aligns the shift register and adder
It is characterized by being provided between them.

[0009]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG. 1, a modulation code generator 101 generates a modulation code based on a signal of a synchronization signal generator 110 and inputs the generated modulation code to a transmitter. The transmitter 102 generates a transmission frequency signal modulated by the modulation code from the modulation code generator 101. The transmission / reception switch 103 is connected to the transmitter 1
02 is sent to the antenna 104 and the antenna 10
The signal received at step 4 is sent to the receiver 105. The antenna 104 radiates a transmission signal into space and receives a reflection signal from a target of the transmission signal or the ground. Receiver 105
Converts an input signal into a video signal. Multiplier 1
06 multiplies the output signal of the receiver 105 by the Doppler coefficient generated by the Doppler coefficient generator 107.
The correlator 108 correlates the output signal of the multiplier 106 with the modulation code generated by the modulation code generator 101.
Here, when the modulation code information is stored in advance, the correlator 108 modulates the modulation code generator 1 of FIG.
01 and the correlator 108 need not be connected. The synchronization signal generator 110 generates a synchronization signal required for the operation of the radar device shown in FIG. Doppler coefficient generator 10
7 generates a Doppler coefficient and inputs it to the multiplier 106. The target determiner 109 extracts a target from the output signal of the correlator 108 based on a predetermined determination criterion. The receiver 105 suppresses clutter as necessary.

Next, the radar operation of FIG. 1 will be described. The modulation code generated by the modulation code generator 101 with reference to the signal generated by the synchronization signal generator 110 is transmitted to the transmitter 102.
Is added to The transmitter 102 generates a transmission signal using the added modulation code, and transmits the generated transmission signal to the antenna 104 through the transmission / reception switch 103. The antenna 104 radiates a transmission signal to space. Antenna 10
The signal radiated at 4 is reflected by the target or the ground, and a part is received by the antenna 104. The signal received by the antenna 104 is transmitted to the receiver 10 through the transmission / reception switch 103.
5 is input. The receiver 105 processes the input signal, suppresses clutter if necessary, and converts the signal into a video signal. The video signal is multiplied by a coefficient of a Doppler shift frequency component assumed for a moving target to be detected generated by a Doppler coefficient generator 107 by a multiplier 106, and correlated with a modulation code by a correlator 108. Can be
The output signal of the correlator 108 is input to the target determiner 109. The target determiner 109 extracts a moving target signal from the output signal of the correlator 108 based on a predetermined standard. The synchronization signal generator 110 generates a synchronization signal required for the radar.

FIG. 2 shows an embodiment of the rising timing of the n elements constituting the modulation code generated by the modulation code generator 101. (A) shows that the interval of the rising timing is larger than the rising interval of Nos. 1 and 2,
This is an example in which the rising interval is larger as the number is larger, such as the rising interval of No. 3 is larger and the rising interval of Nos. 3 and 4 is larger than the rising interval of Nos. 2 and 3. (B) is an example including those in which the rising intervals are all equal but the rising polarity is inverted. (C) is an example in which the rising interval is an arbitrary value. (D) is an example in which the rising intervals are equal. (E) is an example opposite to (a), in which the rising interval decreases as the rising timing number increases. The transmitter 102 generates a transmission signal by temporally switching one or a plurality of types of modulation codes of the modulation codes as shown in FIGS. The transmission signal is shown in FIG.
(A) to (e) shown in (a) to (e) of FIG. Transmitter 10
2 repeatedly generates 1, 2, 3,... N transmission pulse trains. The transmission signal generated by the modulation code shown in FIG. 2B is a pulse generated at the timing of 1, 2, 3,... N, and the timings 1, 3, 4,. At timings 2, 5,..., N, the phases of the transmission frequencies are 180 degrees different from each other, and the pulse width is arbitrarily determined, but the maximum width is each timing interval.

FIG. 3 is a diagram illustrating the multiplier 106, the Doppler coefficient generator 107, and the correlator 108. In FIG. 3, the input signal f (t) is transmitted from the antenna 104 to the receiver 10.
5 is a signal that has been input and received. f (t) is m
Coefficients e ^-jw1t , e generated by the Doppler coefficient generator 107 after being branched into channels and added to the multiplier 106
^-jw2t , ... e ^-jwmt is multiplied as shown in the figure. The output of the multiplier 106 is f (t) e ^-jw1t , f (t)
e ^-jw2t ,... f (t) e ^-jwmt and are applied to the correlator 108. The main configuration of the correlator 108 is the shift register 30
4, 305, 306 and adders 307, 308, 309. The output signal of the multiplier 106 is added to the shift register. The numbers 1, 2, 3,... N assigned to the outputs of the shift registers 304, 305, 306 are shown in FIG.
1, 2, 3,... Of the modulation code timing shown in FIG.
n is equal to n time intervals. Adder 30
7, 308 and 309 are shift registers 304, 305,
The outputs of 306 are added. To explain the multiplier 301, the input signal f (t) is multiplied by e ^−jw1t in the multiplier 301, and the output is f (t) · e ^−jw1t . This f
(T) · e ^−jw1t is added to the shift register 304. The outputs 1, 2,... N of the shift register 304 are added to an adder 307, where they are added and the result becomes an output signal 1. This operation is represented by Equation 1 below.

[0013]

[0014] Formula 1 _{t 1, t 2, ... t} n , the output timing and second shift register 304, equal to the ... n, t
₁ is 1, t ₂ is 2,..., T _n is equal to n. The value of Equation 1 is the maximum signal f (t) has a omega ₁ of the angular velocity. Therefore, processing is performed on each of a plurality of angular velocities ω ₁ , ω ₂ ,..., Ω _m necessary for detecting a moving target, and output signals 1, 2, 3,.

FIG. 4 is a block diagram of a radar using a transmission signal generated by the modulation code of FIG.
An embodiment will be described in which after receiving signals having different phases are controlled by the output of the shift register 310 so as to have the same phase by the signal polarity controller 312, the signals are added to the adder 313 to obtain an output signal.

FIG. 5 shows a multiplier 3 having a complex number shown in FIG.
An example of the operation of 01, the shift register 304 and the adder 307 will be described. The input signal f (t) is converted into I and Q video signals and processed separately. f (t) _I represents an I video signal, and f (t) _Q represents a Q video signal. The processing of f (t) _I will be described. The input signal f (t) _I is the multiplier 4
01 Kcosω ₁ is multiplied by. K is an arbitrary real number. The input signal f (t) _I is input to the multiplier 402 by Ksin ω ₁
multiplied by t. The outputs 1, 2,... N of the shift registers 405, 406 have timings equal to the rising timings 1, 2,.
Adders 409 and 410 are shift registers 405 and 406
Are added. The output signals of the adders 409 and 410 are converted by the vector synthesizer 413 into the following equation (2).
Is calculated, but the calculation by the vector synthesizer 413 is not limited to Expression 1, and may be an approximate expression of Expression 2 below.

[0017]

For the input signal f (t) _Q , the above f
(T) The same processing as in _I is performed. Vector synthesizer 41
Reference numeral 5 individually squares the signals from the vector synthesizers 413 and 414, adds the squares, and takes the square root to generate an output signal 1. The calculation by the vector synthesizer 415 may be an approximate calculation.

[0019]

As described above, the moving target detecting radar apparatus according to the present invention continuously multiplies the output signal of the radar receiver by the Doppler shift frequency component assumed for the moving target to be detected. By storing the result and performing correlation processing between the stored content and the modulation code used to generate the transmission signal, the moving target can be determined with a simple circuit having less multiplication circuits than the conventional synchronous integration processing. Can be detected.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a modulation code timing diagram of the modulation code generator of the block diagram shown in FIG. 1;

FIG. 3 is a block diagram showing a multiplier and a correlator in FIG. 1;

FIG. 4 is a block diagram of another correlator applicable to the embodiment of FIG. 1;

FIG. 5 is a block diagram illustrating details of a multiplier and a correlator in FIG. 1;

FIG. 6 is a block diagram showing a conventional example.

FIG. 7 is a block diagram of a synchronous integrator in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Modulation code generator 102 Transmitter 103 Transmission / reception switch 104 Antenna 105 Receiver 106 Multiplier 107 Doppler coefficient generator 108 Correlator 109 Target decision unit 110 Synchronous signal generator

Continuation of the front page (72) Inventor Seiichi Maeda 1-9-2 Heimus Square, Fuji-cho, Hoya-shi, Tokyo (56) References JP-A-5-34444 (JP, A) JP-A-6-18651 (JP, A) JP-A-5-40171 (JP, A) JP-A-4-286980 (JP, A) JP-A-3-272486 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 7/00-7/42 G01S 13/00-13/95

Claims (2)

(57) [Claims] A signal modulated by a predetermined modulation code is transmitted.
To receive the reflected signal from the target and move from the received signal
A moving target detection radar device that extracts a reflected signal from a target.
In the reception of the range where the reflected signal from the moving target is to be extracted
In the signal, the expected
Multiplied by the coefficients of the Doppler shift frequency components
And a correlation process between the received signal and the modulation code.
And a correlation processing circuit for performing a plurality of multiplications output from the multiplication circuit.
Receiving the results of the respective modulation codes, the delay corresponding to the predetermined modulation code.
Multiple shift registers that output tap outputs with a delay relationship
And tap outputs from the plurality of shift registers
And a plurality of Doppler shifts from the plurality of adders, respectively.
A moving target detection radar device for extracting a moving target detection signal corresponding to a frequency component . 2. A method according to claim 1, wherein the modulation code includes signal components having different polarities, and a signal polarity controller for receiving a tap output from the shift register and aligning the signal polarities is provided between the shift register and the adder. Claim 1.
A moving target detection radar device according to claim 1.