JPH08271614A - Unwanted-wave suppression apparatus - Google Patents

Abstract

PURPOSE: To simultaneously remove interference waves and a clutter by a processing in a space which is composed of a spatial frequency axis and a Doppler frequency axis, in an unwanted-wave suppression apparatus by which the interference waves and the clutter are removed so as to extract only a target signal. CONSTITUTION: A plurality of antenna elements 1, a plurality of receivers 2, a plurality of A/D converters 3 and a first discrete Fourier transform device 4 which finds the spatial frequency from output signals of the plurality of A/D converters 3 are installed. In addition, a second discrete Fourier transform device 5 which computes the Doppler spectrum at every output signal, i.e., at every spatial frequency, of the discrete Fourier transform device 4 is provided, and a target-signal extraction means 6 which extracts a target signal in a space frequency-Doppler frequency space in which output signals of the second discrete Fourier transform device are arranged at every spatial frequency is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an unnecessary wave suppression device for removing clutter, interference waves and the like, which are reflected echoes other than a target signal, of signals received by a radar.

[0002]

2. Description of the Related Art A conventional spurious wave suppression device has a structure as shown in FIG. In the figure, 1-1 to 1-N are N element antennas, 2-1 to 2-N are N receivers provided in each element antenna 1, and 3-1 to 3-N are receivers. 2, N number of A / D converters respectively provided in 2, 30 is an interference wave suppressing means for receiving the output of the N number of A / D converters 3,
Reference numeral 31 is a clutter suppressing means for receiving the output of the interference wave suppressing means 30, and 32 is a target extracting means for receiving the output of the clutter suppressing means 31.

In the conventional unnecessary wave suppressing device, the interference wave suppressing means 30 can intentionally change the operation between the beams formed by the element antennas 1-1 to 1-N, that is, the gain of the antenna pattern. This eliminates the interference wave. Then, the clutter suppressing means 31 performs a filtering operation in the time domain, thereby removing the clutter. That is, the conventional unnecessary wave suppression device is
It has the function of suppressing clutter as well as the function of suppressing interference waves.

The conventional interference wave suppressing means and clutter suppressing means will be individually described below. First, as an interference wave suppressing means for removing an interference wave received by a radar, for example, B.WIDROW et al., “ADAPTIVE ANTENNA SYSTEM
S '', PROCEEDINGS OF THE IEEE VOL.55 NO.12 DEC.1967
Have been disclosed in.

FIG. 10 is a block diagram of a conventional interference wave suppressing means shown in the above document. In the figure, 1-1 to 1
-N is N antenna elements that receive incoming waves, 2-1 to 2-1
2-N are respectively connected to the antenna element 1, and N receivers for amplifying and phase-detecting the transferred signals, 3-1 to 3
-N is an A / D converter that is connected to the receiver 2 respectively and samples and quantizes the transferred analog signal, 40-1 to 40-1
40-N is the output signal x ₁ of the A / D converters 3-1 to 3-N
(N) to x _N (n) and a complex multiplier that multiplies the load value output from the load calculating means 41, respectively, and 44 represents the complex multiplier 4
A complex adder for calculating the sum of output signals of 0-1 to 40-N, 43 is a reference signal generator for generating a reference signal d (n) having a strong correlation with the target signal, and 42 is a reference signal d (n). A complex subtractor 41 for obtaining the difference from the output signal y (n) of the complex adder 44, 41 is outputs 3-1 to 3-1 of the N A / D converters
A load calculating means for obtaining a load by inputting 3-N and the output signal ε (n) of the complex subtractor 43.

Next, the operation of the conventional interference wave suppressing means will be described with reference to FIG. Each antenna element 1-1 to 1-
The signals received by N are the receivers 2-1 to 2-N, A / D
Received signal X (n) = [x via converters 3-1 to 3-N
₁ (n), x ₂ (n), ..., X _N (n)] ^T. Here, T indicates a transposition operation. Load is W (n) =
[W ₁ (n), w ₂ (n), ..., W _N (n)] ^T , y is obtained from the received signal X (n) by the equation (1).
(N) is calculated. y (n) = W (n) ^T X (n) (1)

This y (n) is taken out as an output of the interference wave suppressing means 30 and transferred to the complex subtractor 42. In the complex subtractor 42, the output y (n) of the complex adder 44 and the error signal ε (n) of the reference signal d (n) are calculated as in Expression (2). ε (n) = d (n) −y (n) (2)

In the load calculation means 41, the error signal ε (n)
The load W (n) is adjusted so that the average power of the above is minimized. Minimizing the average power of the error signal means minimizing the average power of the signal that is not correlated with the reference signal, that is, the interference wave. After all, as shown in the diagram on the right side of FIG. 12, the antenna gain in the arrival direction of the interference wave is significantly reduced, and the interference wave can be suppressed. The optimum load W _{OP at} this time is represented by the following equation
It is known to be obtained by the r-Hopf equation. W _OP = R ^-1 P (3)

Where R is the autocorrelation matrix of the received signal, P
Is a correlation vector between the received signal and the reference signal, which is generally expressed by the following equation. R = E [X (n) ^T X ^* (n)] (4) P = E [d (n) X ^* (n)] (5)

Here, * is a complex conjugate, and E [] is a time average. However, since it is difficult to obtain the inverse matrix of the correlation matrix R of the received signal in real time, R ^-1 is actually estimated by some method. For example, in the LMS algorithm, the load is sequentially estimated by the following formula. W (n + 1) = W (n) + 2με ^* (n) X (n) (6) μ in the above equation is a constant for adjusting the convergence speed and accuracy of the algorithm.

Next, the clutter suppressing means for removing the clutter which is the unnecessary echo received by the radar will be described. As this kind of clutter suppressing means, for example, the Institute of Electronics, Information and Communication Engineers, Journal B Vol. J70-BN
o. 4 pp. The one disclosed in "Adaptive clutter suppressing device using multiple segment MEM" by Hideaki Watanabe et al. In 515-523 (April 1987 issue) is known. FIG. 11 is a block diagram of a circuit showing the configuration of the clutter suppressing means. In the figure, 85 is a reflection coefficient calculating means, 80-1 and 80-2 are delay elements, 81-
1, 81-2 are complex multipliers, 83-1, 83-2, 84
-1, 84-2 are complex adders. Also, ε (n),
f ^m (n) and b ^m (n) (n = 1 to 3, m = 1 and 2) are vector expressions of signals represented by the following expressions, respectively, and P ^m is a reflection coefficient.

[0012] _{E (n) = [ε 1} (n), ε 2 (n), ···, ε k (n)] T (7a) f m (n) = [f 1 m (n), f ^{_{2 m (n), ···,}} f k m (n)] T (7b) b m (n) = [b 1 m (n), b 2 m (n), ···, b k m ( n)] ^T (7c) P ^m = diag [ρ ₁ ^m , ρ ₂ ^m , ..., ρ _k ^m ] (7d) where T represents transposition and diag [∼] represents a diagonal matrix.

In the radar, a series of received radio waves are phase-detected and converted into baseband reception signals, which are then sampled and quantized to be converted into digital signals.
This digital signal holds the phase of the received radio wave,
So-called I signal (In-phase), Q signal (qua)
It is a complex signal having a real-time part and an imaginary part, respectively. Signal sampling is performed at the same timing for all received signals. That is, after a certain time delay from the time when the transmission signal is transmitted, sampling is performed at a constant period, and ε ₁ (n), ε ₂ (n) ,.
..., a total of k digital signals represented by ε _k (n) are generated. Here, n is called a hit number, k is a sampling order, and hereinafter, this k is called a range bin number.

As described above, the digital signal E (n) obtained by the radar is transferred as the input signal of the clutter suppression device 31. Hereinafter, this signal is referred to as an input signal.
The numeral m represents the stage number of the lattice filter as shown in FIG.

Next, the operation of the conventional apparatus will be described with reference to FIG. The input signal transferred from the radar receiver is input to the stage 1 lattice filter. At this time, the input signal E (n) is the forward prediction error signal vector f ⁰ (n), as shown in equations (8a) and (8b).
It is used as the backward prediction error signal vector b ⁰ (n). f ⁰ (n) = E (n) (8a) b ⁰ (n) = E (n) (8b)

The lattice filter of the stage 1 (the part surrounded by the dotted line on the left side of FIG. 11) has a signal vector f ⁰ (n),
Signal vectors f ¹ (n) and b ¹ (n) are generated from b ⁰ (n) according to equations (9a) and (9b).

[0017]

[Equation 1]

However, in the operations of the expressions (9a) and (9b), multiplication is carried out by the complex multipliers 82a-1 and 82b-1, and addition is carried out by the complex adders 83-1 and 84-1. The unit delay is implemented by the delay element 80-1. At the same time, the reflection coefficient calculation means 85 causes f ⁰ (n), b ^0.
Using (n) as an input, the reflection coefficient vector P ¹ is calculated as shown in equations (10a) and (10b).

[0019]

[Equation 2]

The algorithm for calculating the reflection coefficient shown in the equation (10a) is an application of the well-known Burg method, which is a forward prediction error vector f ¹ (n) and a backward prediction error vector b ¹ (n). This is an algorithm that minimizes the average power sum of. Next, the lattice filter of the stage 2 (the part surrounded by the dotted line on the right side of FIG. 11) inputs the prediction error vectors f ¹ (n) and b ¹ (n), and the following equation (11
a) and (11b) based on the signal vector f ² (n),
b ² (n) is generated.

[0021]

(Equation 3)

The multiplications in the operations of equations (11a) and (11b) are carried out by the multipliers 82a-1 and 82b-1, the addition is carried out by the complex adders 83-2 and 84-2, and the signal vector b ¹ ( The unit delay given to n) is the delay operator 80-
It is carried out in 2. At the same time, the reflection coefficient calculation means 86
Is an equation (11) using f ¹ (n) and b ¹ (n) as inputs.
The reflection coefficient vector P ² required for a) and (11b) is generated based on the following equations (12a) and (12b).

[0023]

[Equation 4]

The algorithm for calculating the reflection coefficient P ² shown in the equations (12a) and (12b) is the equations (10a) and (10).
b) Similarly, it is based on the Burg method.

Finally, the prediction error signal vector f ² (3) of the stage 2 is taken out as an output signal of the clutter suppressing device 31. As described above, in the clutter suppression means 31, the sequential prediction error signal from the input signal E (n),
Also, the clutter contained in the input signal can be eliminated by minimizing the average power of the output signal while generating the backward prediction error. The filter amplitude characteristic 92 of the clutter suppressing means at this time is as shown in FIG.
An inverse filter will be formed for the Doppler spectrum 91 of the clutter.

In the above description, the conventional example in which the number of lattice filter stages is 2 has been described, but the clutter suppressing means of any number of stages can be configured by connecting the lattice filters in cascade.

[0027]

Since the conventional unnecessary wave suppressing device is constructed as described above, the clutter suppressing process and the interference wave suppressing process cannot be performed at the same time.
That is, since it is necessary to fix the received beam during the clutter suppression process, the antenna weight in the interference wave suppression process must be fixed, and the adaptive algorithm cannot be operated. Therefore, there is a problem that unnecessary waiting time occurs and the effect of the interference wave suppression processing is diminished.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an unnecessary wave suppressing device capable of simultaneously performing clutter suppressing processing and interference wave suppressing processing.

[0029]

An unnecessary wave suppressing device according to a first aspect of the present invention includes a plurality of antenna elements for receiving signals, a plurality of receivers for detecting output signals of the plurality of antenna elements, respectively. A plurality of spatial frequency calculating means for obtaining the spatial frequencies of the signals based on the outputs of the plurality of receivers, and a plurality of spatial frequency calculating means for outputting as a plurality of received signals, and a plurality of output signals of the spatial frequency calculating means for respectively obtaining a Doppler spectrum Of the Doppler spectrum calculation means and the output signals of the plurality of Doppler spectrum calculation means, based on the signal intensity data distributed on the plane consisting of the spatial frequency axis and the Doppler frequency axis, to extract the target signal included in the signal And target signal extraction means.

The unnecessary wave suppressing device according to claim 2 further receives a plurality of output signals of the spatial frequency calculating means, removes unnecessary waves contained in each output signal,
A plurality of adaptive filters for outputting to the plurality of Doppler spectrum calculating means are provided.

According to a third aspect of the present invention, in the unnecessary wave suppressing device, the target signal extracting means is set to have a width of a main beam formed by the plurality of antenna elements on a plane composed of the spatial frequency axis and the Doppler frequency axis. It is configured to extract the data of the corresponding range, obtain the signal indicating the peak of these extracted data, and to extract only the signal having no spread in the spatial frequency among these peak signals. is there.

According to a fourth aspect of the present invention, in the unnecessary wave suppressing device, the target signal extracting means is set to have a width of a main beam formed by the plurality of antenna elements on a plane composed of the spatial frequency axis and the Doppler frequency axis. It is configured to extract the data of the corresponding range, obtain the signal showing the peak of these extracted data, and extract only the signal that does not have a spread in the Doppler frequency among these peak signals. is there.

According to a fifth aspect of the present invention, in the unnecessary wave suppressing device, the target signal extracting means is set to have a width of a main beam formed by the plurality of antenna elements in a plane composed of the spatial frequency axis and the Doppler frequency axis. Data in the corresponding range is extracted and CFAR is applied to these extracted data.
The processing is performed and the target signal is extracted.

According to a sixth aspect of the present invention, in the unnecessary wave suppressing device, the target signal extracting means is arranged so that the width of the main beam formed by the plurality of antenna elements is in a plane consisting of the spatial frequency axis and the Doppler frequency axis. Extract the data in the corresponding range, determine the signal showing the peak of these extracted data, when the difference in frequency between adjacent peak signals of these peak signals is less than or equal to a predetermined value, The target signal is extracted by removing this signal.

In the unnecessary wave suppressor according to the seventh aspect, the spatial frequency calculating means is constituted by a bit shift discrete Fourier transformer.

An unnecessary wave suppressing device according to an eighth aspect of the present invention is such that the plurality of Doppler spectrum calculating means are constituted by a bit shift discrete Fourier transformer.

[0037]

According to the invention of claim 1, the plurality of antenna elements respectively receive the signals, the plurality of receivers detect the output signals of the plurality of antenna elements, respectively, and the spatial frequency calculating means includes the plurality of receivers. Obtaining the spatial frequency of the signal based on the output of, outputs as a plurality of received signals, a plurality of Doppler spectrum calculation means receives a plurality of output signals of the spatial frequency calculation means, respectively obtain the Doppler spectrum, the target signal The extraction means extracts the target signal included in the signal based on the signal intensity data distributed by the output signals of the plurality of Doppler spectrum calculation means on the plane consisting of the spatial frequency axis and the Doppler frequency axis.

According to a second aspect of the present invention, the plurality of adaptive filters receive the plurality of output signals of the spatial frequency calculating means, remove unnecessary waves contained in the respective output signals, and thereby obtain the plurality of Doppler spectra. It outputs to each calculation means.

In a third aspect of the present invention, the target signal extracting means has a range corresponding to a width of a main beam formed by the plurality of antenna elements on a plane formed by the spatial frequency axis and the Doppler frequency axis. Of the extracted data, a signal indicating a peak is obtained, and only the signal having no spatial frequency spread is extracted from the peak signals.

In a fourth aspect of the present invention, the target signal extracting means has a range corresponding to a width of a main beam formed by the plurality of antenna elements on a plane formed by the spatial frequency axis and the Doppler frequency axis. Of the extracted data, a signal indicating a peak is obtained, and only a signal having no spread in the Doppler frequency is extracted from the peak signals.

According to a fifth aspect of the present invention, the target signal extracting means has a range corresponding to a width of a main beam formed by the plurality of antenna elements on a plane formed by the spatial frequency axis and the Doppler frequency axis. Data is extracted, and CFAR processing is performed on these extracted data to extract the target signal.

In a sixth aspect of the present invention, the target signal extracting means has a range corresponding to a width of a main beam formed by the plurality of antenna elements on a plane composed of the spatial frequency axis and the Doppler frequency axis. Of the extracted data, the signal indicating the peak of the extracted data is obtained, and when the difference in frequency between adjacent peak signals of these peak signals is less than or equal to a predetermined value, this signal is output. The target signal is extracted by removing it.

In the seventh aspect of the invention, the bit shift discrete Fourier transformer calculates the spatial frequency at high speed.

In the eighth aspect of the invention, the bit shift discrete Fourier transformer calculates the Doppler spectrum at high speed.

[0045]

【Example】

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a signal processing block diagram showing an embodiment of the unnecessary wave suppressing device according to the first embodiment. In FIG. 1, 1
-1 to 1-M are M antenna elements, 2-1 to 2-M are M receivers that receive signals from the M antenna elements 2, and 3-1 to 3-M are M receivers. A / D converters 4 respectively receiving the signals of the optical system 3 and 4 receiving the outputs of the M A / D converters 3 and receiving M signals for each spatial frequency after beam forming at the spatial frequency. Discrete Fourier transformers 5-1 to 5-M receive M outputs of the discrete Fourier transformer 4 and obtain M Doppler spectra of signal components for each spatial frequency. , 6 receive the outputs of the M discrete Fourier transformers 5 and analyze the distribution of the signal intensity on the plane defined by the spatial frequency axis and the Doppler spectrum axis, thereby removing interference waves and clutter. , Target extraction means for extracting only the target signal . The discrete Fourier transformers 4 and 5 determine the signal intensity distribution in the spatial frequency-Doppler frequency plane as shown in FIG.

Next, the operation will be described. As shown in FIG. 1, it is assumed that the target signal, the interference wave, and the clutter are simultaneously incident on the antenna element 1. At this time, the received signal regarding the Nth antenna element 1-N, which is received by the antenna element 1, amplified and phase-detected by the receiver 2 and converted into a digital signal by the A / D converter 3, is represented by the following equation (13). ) Can be described by a mathematical model.

[0047]

(Equation 5)

For simplicity, the initial phase and the like are omitted here. The first, second, and third terms in the above equation are the target signal,
Interference signal, clutter is shown. Further, the antenna element interval was d, and the plane wave incident angle was θ. Letting B (θ, n) be the signal obtained by combining the received signals with the received beam, the following equations (14) and (15) are obtained.

[0049]

(Equation 6)

However, M is the number of antenna elements. Since the equation (14) is in the form of discrete Fourier transform,
It can be seen that beam forming can be performed by performing a discrete Fourier transform on the received signal. Further, since the equation (14) is obtained by performing the conversion of the equation (15), the equation (1
The left side of 5) is called the spatial frequency.

From the equation (14), the M output signals of the discrete Fourier transformer 4 become the reception signals after beam forming at the spatial frequency corresponding to the angle θ, and the arrival of radio waves such as interference waves and target signals. It takes a maximum value when the direction and the calculated spatial frequency are closest.

Further, the Doppler spectrum of the signal component of each spatial frequency can be obtained by performing the discrete Fourier transform on the M output signals by the M discrete Fourier transformers 5-1 to 5-M. Therefore, when the output signals of the M discrete Fourier transformers are arranged for each spatial frequency,
A three-dimensional diagram like is obtained. In FIG. 2, 20 is an interference wave component, 21 is a clutter component, and 22 is a target signal component. As shown in FIG. 2, the interference wave and the target signal are generally different from each other in frequency and arrival angle, and thus can be easily separated. On the other hand, the clutter exists in a wide range near the arrival direction of the target signal, that is, in a wide spatial frequency, and therefore cannot be separated by a simple method.

The target extracting means 6 extracts a target from the distribution of the signals of FIG. 2 from the M discrete Fourier transformers 5-1 to 5-M. The procedure for extracting the target will be described below with reference to the flowchart of FIG.

First, as shown in FIG. 3, data is cut out in the Doppler frequency direction in the spatial frequency range corresponding to the main beam width (step 50). The cutout range is given in advance. As a result, the interference wave is separated.

A peak is searched for each spatial frequency of the cut out data, and the spatial frequency giving the peak is stored in the memory (step 52). In the example of FIG. 3, the spatial frequency and the Doppler frequency of the clutter 21 are
The spatial frequency and the Doppler frequency of the target 22 are stored respectively.

Repeat until the spatial frequency range to be cut out is completed (steps 51 and 56). Then, the spatial frequency giving the peak is checked, and if the peak spreads in space, it is determined as clutter (step 54), and if not, it is determined as the target and extracted (step 53). In addition,
In step 53, target extraction may be performed by utilizing the fact that clutter spreads in the Doppler frequency direction.

As described above, according to the first embodiment, 2
The interfering wave and the target are separated by converting the received signal into the spatial frequency-Doppler frequency by using the discrete Fourier transformer of the stage, and further, by examining the spread of the signal on this plane, the clutter and the target are separated. And can be separated. That is, by converting the spatial frequency to the Doppler frequency, it is possible to simultaneously suppress the interference wave and remove the clutter. Thus, these two processes can be performed simultaneously. Therefore, there is no unnecessary waiting time, and the processing speed and efficiency are improved.

Embodiment 2 FIG. 5 is a flow chart showing the processing of the target extracting means 6 in the unnecessary wave suppressing apparatus of this Embodiment 2. In the second embodiment, instead of the method of the first embodiment in which the clutter and the target are separated by examining the spread of the signal, CFAR (Con
These are separated by stant False Alarm Ratio) processing.

Similar to the first embodiment, first, data is cut out from the three-dimensional drawing (step 60). Then the well-known CF
AR (Constant False Alarm Ratio) processing is performed for each spatial frequency in the Doppler frequency axis direction (step 61). This makes it possible to extract only the target signal having no spread in the Doppler frequency.

Embodiment 3 FIG. 6 is a flow chart showing the processing of the target extracting means 6 in the unwanted wave suppression apparatus of this Embodiment 3. Example 1
Similarly, the data is first cut out from the three-dimensional drawing (step 70). A peak search is performed for each spatial frequency on the cut out data, and the spatial frequency giving the peak is stored in the memory (step 73).

Repeat until the spatial frequency range to be cut out is completed (steps 71 and 76). At that time, the peak frequency search results before and after the spatial frequency being processed are checked, and if the difference between the peak frequencies is equal to or less than a preset constant δ (step 75), these are regarded as unnecessary signals and peak The value is set to zero and returned to the cut out data (step 76).

This processing is equivalent to removing clutter. Finally, a peak search is performed on the new cut-out data in which the data has been replaced (step 7
2) The extracted signal becomes the target signal.

Fourth Embodiment FIG. 7 is a signal processing block diagram showing an unnecessary wave suppressing device of the fourth embodiment. In the figure, 7-1 to 7-M are adaptive filters which respectively receive the M outputs of the discrete Fourier transformer 4. Element antennas 1-1 to 1-M, receivers 2-1 to 2-M, A / D converters 3-1 to 3-M, discrete Fourier transformer 4, discrete Fourier transformers 5-1 to 5-M ,
The target extracting means 6 is the same as that shown in FIG.
The difference between the fourth embodiment and the first embodiment is that an adaptive filter 7 is provided between the discrete Fourier transformer 4 and the discrete Fourier transformer 5.

By the way, as described in the explanation of the conventional example, the adaptive filter adjusts the weight so that the average power of the output signal is minimized. Therefore, the signal obtained for each spatial frequency is directly used. On the other hand, if the filtering process is performed, the target signal may be erroneously removed when the target signal exists alone.

Therefore, the adaptive filters 7-1 to 7-1 of this embodiment are
7-M assumes that clutter does not vary much spatially, and is not data of the spatial frequency to be actually processed, but data of a different spatial frequency (for example, spatial frequencies before and after the spatial frequency to be actually processed). Data) use the weight value of the adaptive filter. As a result, the target signal, which is an isolated signal, is not removed. Further, since the clutter has a spatial spread, it is possible to suppress the clutter even if the weight is adjusted with spatial frequency data different from the spatial frequency data to be actually processed.

Fifth Embodiment FIG. 8 is a signal processing block diagram showing an unnecessary wave suppressing device of the fifth embodiment. In the figure, 10 is M A / D
BS discrete Fourier transformers 11-1 to 11-M, which receive the outputs of the transformers 3-1 to 3-M and output M reception signals after beam forming at the spatial frequency, are BS discrete Fourier transforms. It is a BS discrete Fourier transformer that receives the M outputs of the device 10 and obtains the Doppler spectrum of the signal component for each spatial frequency. Element antennas 1-1 to 1-M,
Receivers 2-1 to 2-M, A / D converters 3-1 to 3-M,
The target extracting means 6 is the same as that shown in FIG.

The difference between the fifth embodiment and the first embodiment is that a BS (BitShift) Fourier transformer is provided instead of the discrete Fourier transformer. In the BS Fourier transform, the real part and the imaginary part of the twiddle factor of the FFT are quantized as in the following equations, and the multiplication is replaced with the sum or difference of bit shifts to speed up the process.

[0068]

(Equation 7)

In the above equation, NT is the number of terms in the expansion equation, and IB is the number of quantization bits. They are integers of NT ≧ 1 and IB ≧ 0, respectively. For example, if a certain function f (n, θ) is BS-FFT
When doing, it becomes like the following formula.

[0070]

(Equation 8)

Here, W _N ^kn is a quantized FFT twiddle factor and has the following relationship.

[0072]

[Equation 9]

As described above, the Fourier transform can be speeded up by using the BS discrete Fourier transformer.

[0074]

As described above, according to the inventions of claims 1 and 3 to 6, the plurality of antenna elements for respectively receiving signals and the output signals of the plurality of antenna elements are respectively provided. A plurality of receivers to be detected, the spatial frequency of the signal is obtained based on the outputs of the plurality of receivers, a spatial frequency calculating means for outputting as a plurality of received signals, and a plurality of output signals of the spatial frequency calculating means. Receiving, each of a plurality of Doppler spectrum calculating means for obtaining the Doppler spectrum, by the output signal of the plurality of Doppler spectrum calculating means, based on the signal intensity data distributed on the plane consisting of the spatial frequency axis and the Doppler frequency axis, Since the target signal extracting means for extracting the target signal included in the signal is provided, the interference wave suppressing process and the clutter suppressing process are simultaneously performed. It can, processing speed and efficiency is improved.

According to the invention of claim 2, further,
Unnecessary because it has a plurality of adaptive filters that receive a plurality of output signals of the spatial frequency calculation means, remove unnecessary waves included in each output signal, and output to the plurality of Doppler spectrum calculation means, respectively. By automatically suppressing the wave, the extraction accuracy of the target signal is improved.

Further, according to the inventions of claims 7 and 8, the spatial frequency calculating means and the plurality of Doppler spectrum calculating means are constituted by a bit shift discrete Fourier transformer, so that the processing can be speeded up.

[Brief description of drawings]

FIG. 1 is a functional block diagram of an unnecessary wave suppression device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the unnecessary wave suppression device according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining the operation of the unnecessary wave suppression device according to the first embodiment of the present invention.

FIG. 4 is a flowchart for explaining the operation of the target extraction device according to the first embodiment of the present invention.

FIG. 5 is a flow chart for explaining the operation of the target extraction device according to the second embodiment of the present invention.

FIG. 6 is a flow chart for explaining the operation of the target extraction device according to the third embodiment of the present invention.

FIG. 7 is a functional block diagram of an unnecessary wave suppressor according to a fourth embodiment of the present invention.

FIG. 8 is a functional block diagram of an unnecessary wave suppressor according to a fifth embodiment of the present invention.

FIG. 9 is a functional block diagram of a conventional unnecessary wave suppression device.

FIG. 10 is a functional block diagram of an interference wave suppressing unit of a conventional unnecessary wave suppressing device.

FIG. 11 is a functional block diagram of clutter suppressing means of a conventional unnecessary wave suppressing device.

FIG. 12 is a diagram for explaining the operation of a conventional unnecessary wave suppression device.

FIG. 13 is a diagram for explaining the operation of the conventional unnecessary wave suppression device.

[Explanation of Codes] 1 antenna element, 2 receiver, 3 A / D converter, 4
Discrete Fourier transformer, 5 discrete Fourier transformer, 6
Target extraction means, 7 adaptive filter, 10 BS discrete Fourier transformer, 11 BS discrete Fourier transformer.

Claims (8)

[Claims] 1. A plurality of antenna elements for respectively receiving signals, a plurality of receivers for detecting output signals of the plurality of antenna elements, and a spatial frequency of the signal based on outputs of the plurality of receivers. A plurality of Doppler spectrum calculation means for obtaining a Doppler spectrum, each of which receives a plurality of output signals of the spatial frequency calculation means and a plurality of output signals of the spatial frequency calculation means; An unnecessary wave suppression device comprising: a target signal extraction unit that extracts a target signal included in the signal based on signal intensity data distributed on a plane composed of a spatial frequency axis and a Doppler frequency axis, which is obtained from the output signal. 2. A plurality of adaptive filters for receiving a plurality of output signals of the spatial frequency calculating means, removing unnecessary waves contained in the respective output signals, and outputting to the plurality of Doppler spectrum calculating means, respectively. The unnecessary wave suppressing device according to claim 1, further comprising: 3. The target signal extraction means, in a plane consisting of the spatial frequency axis and the Doppler frequency axis,
Data of a range corresponding to the width of the main beam formed by the plurality of antenna elements is extracted, a signal showing a peak of the extracted data is obtained, and a spatial frequency of these peak signals has a spread. The unnecessary wave suppressing device according to claim 1 or 2, wherein only the non-existent signal is extracted as a target. 4. The target signal extracting means, in a plane composed of the spatial frequency axis and the Doppler frequency axis,
The data in the range corresponding to the width of the main beam formed by the plurality of antenna elements is extracted, and the signal showing the peak of these extracted data is obtained, and the Doppler frequency of these peak signals has a spread. The unnecessary wave suppressing device according to claim 1 or 2, wherein only the non-existent signal is extracted as a target. 5. The target signal extracting means is arranged on a plane composed of the spatial frequency axis and the Doppler frequency axis,
It is configured such that data in a range corresponding to the width of the main beam formed by the plurality of antenna elements is extracted, CFAR processing is performed on the extracted data, and a target signal is extracted. The unnecessary wave suppressing device according to claim 1 or 2. 6. The target signal extracting means is arranged on a plane composed of the spatial frequency axis and the Doppler frequency axis,
The data in the range corresponding to the width of the main beam formed by the plurality of antenna elements is extracted, and the signal indicating the peak of these extracted data is obtained, and between the peak signals adjacent to each other among these peak signals. 3. The spurious wave suppression device according to claim 1, wherein the target signal is extracted by removing this signal when the frequency difference is equal to or less than a predetermined value. 7. The unnecessary wave suppressing device according to claim 1, wherein the spatial frequency calculating means is constituted by a bit shift discrete Fourier transformer. 8. The spurious wave suppression device according to claim 1, wherein the plurality of Doppler spectrum calculation means are constituted by bit shift discrete Fourier transformers.