JP7086784B2 - Radar system and its radar signal processing method - Google Patents

Description

The present embodiment relates to a radar system and a radar signal processing method thereof.

In a conventional radar system, when a clutter and an unnecessary wave of interference waves are present in a complicated environment, in order to suppress the unnecessary wave, a large number of freedoms of the AZ / EL / Doppler axis are used. The degree of freedom is required, and the processing scale tends to increase.

STAP, Richard Klemm,'Applications of Space-Time Adaptive Processing', IEE Radar, Sonar and Navigation series 14, p.375-395 (2004) CFAR (Constant False Alarm Rate), Yoshida,'Revised Radar Technology', Institute of Electronics, Information and Communication Engineers, pp.87-89 (1996) MSN method, SMI method, RLS method, Kikuma,'Adaptive signal processing by array antenna', Science and Technology Publishing, pp.67-86 (2004) Expansion Array (KR Product Array), Wing-Kin Ma,'DOA Estimation of Quasi-Stationary Signals With Less Sensors Than Sources and Unknown Spatial Noise Covariance: A Khatri-Rao Subspace Approach', IEEE Trans. Signal Process., Vol.58 , no.4, pp.2168-2180, April (2010) Spatial averaging method, Kikuma,'Adaptive signal processing by array antenna', Science and Technology Publishing, pp.163-170 (1999)

As described above, in the conventional radar system, in a complicated environment where unnecessary waves of clutter and interference waves exist, in order to suppress the unnecessary waves, the AZ / EL / Doppler axis is used. A large number of degrees of freedom were required, and the processing scale tended to increase.
This embodiment has been made in view of the above problems, and is a radar capable of suppressing unnecessary waves with a relatively small processing scale even in a complicated environment where unnecessary waves of clutter and interference waves exist. It is an object of the present invention to provide a system and a method for processing its radar signal.

In order to solve the above problems, the radar system according to the present embodiment receives the reflected signal of the N-hit transmission pulse by using the array antenna in which the reception aperture is divided into M (M ≧ 1) subarrays. At least M reception beams are formed from the reception signals of each of the M sub-arrays, and at least N reception beams are formed from the M reception beams for each range cell using the slow-time axis of the CPI (Coherent Pulse Interval) signal. A Doppler axis signal is generated, at least N × M outputs are acquired for each range cell from the N Doppler axis signals and distributed to the main channel and auxiliary channels, and a predetermined beam is obtained from the Doppler axis signal in the main channel. The direction direction and the Doppler cell are calculated, and the signal from the maximum amplitude value to the Pth amplitude value is extracted from the Doppler axis signal in the auxiliary channel except for the main channel, and the auxiliary channel is added to the signal of the main channel. Signals are combined to suppress unnecessary waves.

The block diagram which shows the structure of the radar system which concerns on 1st Embodiment. The conceptual diagram which shows the sub-array configuration used for the receiving antenna in 1st Embodiment. In the first embodiment, the timing diagram showing the N hit pulse to be transmitted. In the first embodiment, a conceptual diagram showing a series of flow of unnecessary wave suppression processing of a receiving system. In the first embodiment, the received data is represented by a spatial axis (AZ / EL), a Doppler axis, and a range axis. In the first embodiment, the data of the AZ / EL / Doppler axis shown in FIG. 5 is viewed in cross section of the AZ / EL axis. In the first embodiment, the conceptual diagram in the case where the amplitude in the AZ / Doppler axis is viewed stereoscopically in order to make it easier to understand. The principle diagram for demonstrating the extended array processing of an angle axis in 1st Embodiment. The principle diagram for demonstrating the extended array processing of a slow-time axis in 1st Embodiment. In the first embodiment, the flowchart which shows the flow of the selection process of the main ch and the main ch. In the first embodiment, a conceptual diagram showing how to select AZ / EL / Dopplasel for auxiliary channels. In the first embodiment, a principle diagram for explaining the extended array processing of the fast-time axis. In the second embodiment, the flowchart which shows the flow of the selection process of the main ch and the auxiliary ch. In the second embodiment, a conceptual diagram showing how to select AZ / EL / Dopplasel for auxiliary channels. In the third embodiment, the flowchart which shows the flow of the selection process of the main ch and the auxiliary ch. In the third embodiment, a conceptual diagram showing how to select AZ / EL / Dopplasel for auxiliary channels. The block diagram which shows the structure of the radar system which concerns on 4th Embodiment. In the fourth embodiment, a timing diagram showing a state in which thinning sampling is performed in a received PRI column.

Hereinafter, embodiments will be described with reference to the drawings. The radar system is usually provided with a transmitting device and a receiving device, and is configured to share antenna transmission / reception. However, here, it is assumed that the transmitting device is arranged separately from the receiving device. Further, in the following description, the description of the transmission device constituting the radar system will be omitted unless there is a characteristic portion particularly related to the embodiment. Further, in each embodiment, the same parts are designated by the same reference numerals, and duplicate description will be omitted.

(First Embodiment)
The radar system according to the first embodiment will be described with reference to FIGS. 1 to 12.
FIG. 1 is a block diagram showing a configuration of a radar system according to the present embodiment. In FIG. 1, in the transmission system, the signal generator 111 generates the N-hit transmission pulse train shown in FIG. 3, the modulator 112 modulates the reference signal in the pulse, and the frequency converter 113 determines the frequency of the transmission pulse train. It is converted into an RF band, the pulse of the transmission pulse train is modulated by the pulse modulator 114, and the pulse is transmitted from the transmission antenna 115 in a predetermined direction.

On the other hand, the receiving system includes sub-arrays (including the case where the sub-array has one antenna element) 211 to 21M in which the receiving aperture of the receiving antenna by the array antenna is divided into M systems as shown in FIG. However, in FIG. 2, for the sake of simplicity, the case where the sub-array is arranged in one dimension is shown, but it can be expanded to a two-dimensional array.

The sub-arrays 211 to 21M receive the target target reflected wave of the radar wave transmitted from the transmission system side, respectively. The signals received by the sub-arrays 211 to 21M are frequency-converted to the baseband by the frequency converters 221 to 22M, converted into element (sub-array) digital signals by the AD converters 231 to 23M, and then processed by the angle axis expansion array. It is sent to the vessel 24.

The angle axis expansion array processor 24 virtually increases the degree of freedom of the element signal (sub-array signal) by subjecting the element digital signal to the expansion array processing (see Non-Patent Document 4) by the KR product on the angle axis, and increases the degree of freedom. Increase the resolution. The element digital signal processed by the extended array is formed with a specified number of beams by the multi-beam former 25, and the slow-time (Dopper axis) extended array processor 26 performs the extended array processing by the KR product of the Doppler axes and slows. -After being transformed into the Doppler axis by timeFFT (Fast Fourier Transform) 27, it is distributed to the main ch (channel) and the auxiliary ch (channel).

In the main ch, the cell of the AZ / EL / Doppler axis to be observed is selected for each range cell by the main ch selector 28a, converted to the range axis by the fast-time (range axis) FFT29a, and then fast-time expansion is performed. The array processor 30a performs extended array processing by the KR product of the range axes, and the fast-time IFFT (Inverse Fast Fourier Transform) 31a converts it into the Doppler axis to obtain the signal to be observed.

On the other hand, in the auxiliary ch, the cell of the AZ / EL / Doppler axis exceeding the predetermined amplitude threshold is selected from the maximum value by the auxiliary ch selector 28b, converted to the range axis by the fast-time (range axis) FFT29b, and then converted to the range axis. The fast-time extended array processor 30b performs extended array processing by the KR product of the range axis, and the fast-time IFFT31b converts it to the Doppler axis to obtain a signal that becomes an unnecessary wave.

The extended array outputs of the main channel and the auxiliary channel are sent to the unnecessary wave suppressor 32, the unnecessary wave component is suppressed from the signal to be observed by the correlation processing, the target signal is detected by the detector 33, and the output processor 34. Is converted to the specified format and output.
In the radar system having the above configuration, the unnecessary wave suppression processing of the receiving system will be described with reference to FIGS. 4 to 12.
FIG. 4 is a conceptual diagram showing a series of flow of unnecessary wave suppression processing of the receiving system. Further, FIG. 5 is a diagram in which received data is represented by a spatial axis (AZ / EL), a Doppler axis, and a range axis, and FIG. 6 is a cross section of the AZ / EL / Doppler axis data shown in FIG. 5 in a cross section of the AZ / EL axis. It is the figure seen in. FIG. 7 is a conceptual diagram when the amplitude in the AZ / Doppler axis is viewed stereoscopically in order to make it easier to understand. FIG. 8 is a principle diagram for explaining the extended array processing of the angle axis, and FIG. 9 is a principle diagram for explaining the extended array processing of the slow-time axis. FIG. 10 is a flowchart showing the flow of selection processing of the main ch and the auxiliary ch, FIG. 11 is a conceptual diagram showing how the AZ / EL / Doppler cell of the auxiliary ch is selected, and FIG. 12 explains the extended array processing of the fast-time axis. It is a principle diagram for doing.

Here, on the spatial axis, a beam is formed on the AZ / EL surface, and each range (fast-time axis) cell is subjected to FFT processing on the slow-time axis and converted into a Doppler axis, and then expressed as data. Using this data, it is possible to suppress unnecessary waves such as clutter and interference waves by adaptive processing using all the data. However, if the number of sub-arrays (number of beams) M × the number of hits N (number of doppler cells), the processing scale becomes large.

As a countermeasure, some L data are selected from the M × N data and used as auxiliary channels, and the main channel is selected as the signal forming the main lobe of the AZ / EL / Dopplasel to be observed. .. STAP (Space-time Adaptive Processing) processing (see Non-Patent Document 1) is performed using the main ch and the auxiliary ch.

That is, the signals received in each of the subarrays 211 to 21M are frequency-converted (221 to 22M) and converted into digital signals (231 to 23M). Next, if necessary, an extended array process (24) of the angle axis is performed (see Non-Patent Document 4). This is a process that virtually increases the degree of freedom of the element signal (sub-array signal). As a result, when selecting the auxiliary channel as described later, it becomes easy to separate the target and the unnecessary wave, and the effect of suppressing the unnecessary wave and extracting the target can be expected. This effect applies not only to the angular axis, but also to the extended arrays of the slow-time and fast-time axes.

The principle diagram is shown in FIG. As shown in FIG. 8A, in the case of one target, since there is a phase gradient with respect to the element position, the signal is expanded by the processing shown below.

以上より、仮想平面アレイの位相中心に入力される信号Xinとして、信号Xaは次式となる。

From the above, the signal Xa is given by the following equation as the signal Xin input to the phase center of the virtual plane array.

次に、この信号Xaを用いて、拡張アレイ処理としてＫＲ積アレイ処理を行う。

Next, using this signal Xa, KR product array processing is performed as extended array processing.

複数反射点がある場合には、ＫＲ積アレイ処理により偽目標が発生する場合があるため、図８（ｂ）に示すように、入力信号それぞれの素子位置でスライディングさせて部分ベクトルを抽出し、各々の部分相関行列を計算して平均化処理を行う（非特許文献５参照）。

When there are multiple reflection points, a false target may be generated by the KR product array processing. Therefore, as shown in FIG. 8 (b), a partial vector is extracted by sliding at the element position of each input signal. Each partial correlation matrix is calculated and averaged (see Non-Patent Document 5).

このRxxaveの左端と上端の要素をベクトル化すると、次式となる。

Vectorizing the left and top elements of this Rxxave yields the following equation.

このXkra拡張アレイの素子信号（Xa）として、マルチビーム形成（２５）すればよい。
次に必要に応じて、slow-time軸のＫＲ積による拡張アレイ処理を行う（２６）。図９にその原理図を示す。ＡＺ／ＥＬ軸の拡張アレイと同様に、図９（ａ）に示すようにslow-time軸で位相勾配を持つデータであり、slow-time軸のＫＲ積アレイ処理により、図９（ｂ）に示すようにslow-time軸を仮想的に延長することができる。ＫＲ積アレイ処理の原理と、複数反射点の場合の部分相関行列の平均化による無相関化処理については、角度軸と同様なので割愛する。

Multi-beam formation (25) may be performed as the element signal (Xa) of this Xkra expansion array.
Next, if necessary, extended array processing is performed by the KR product of the slow-time axis (26). FIG. 9 shows the principle diagram. Similar to the AZ / EL axis expansion array, the data has a phase gradient on the slow-time axis as shown in FIG. 9 (a), and is shown in FIG. 9 (b) by the KR product array processing on the slow-time axis. The slow-time axis can be virtually extended as shown. The principle of KR product array processing and the uncorrelated processing by averaging the partial correlation matrix in the case of multiple reflection points are the same as the angular axis, so they are omitted.

Next, the slow-time axis FFT process (27) is performed to convert to the Doppler axis. Next, the main ch selection (28a) and the auxiliary ch selection (28b) are performed by the above-mentioned method. There are various methods for selecting the main channel and the auxiliary channel. First, the case of LPRF (Low Pulse Repetition Frequency) or the like having a relatively large number of range cells will be described with reference to FIG. 10 showing the flow of the selection process.

First, as shown in FIG. 11, in the auxiliary channel, the amplitude threshold is set for each range cell for each of the AZ / EL / Doppler axes (step S11), and the amplitude threshold is set from the maximum value for the signal of the AZ / EL / Doppler axis. The AZ / EL / Doppler cell to be exceeded is selected (step S12), and this is performed for all range cells (steps S13 and S14). Next, in the main channel, the cell of the AZ / EL / Doppler axis to be observed is selected (step S15), the sidelobes canceller is made to function for the range axis by SLC (step S16), and this is performed for the entire range (step S16). Steps S17, S18).

Here, the steering vector for forming the main channel is for forming the main lobe on the space axis-time axis (slow-time) of STAP (Space Time Adaptive Processing: see Non-Patent Document 1), and the space axis is primary. In the case of the original array, it is given by the following equation.

以下、レンジ軸のデータを用いて、アダプテーションを行うが、その前に必要に応じてfast-time軸のＫＲ積による拡張アレイ処理（３０ａ，３０ｂ）を行う。この原理を図１２に示す。fast-time軸では、位相勾配のデータを得るために、fast-time軸のＦＦＴ処理（２９ａ，２９ｂ）を行って、fast-timeの周波数軸に変換する。このfast-timeの周波数軸では、図１２（ａ）に示すように、位相勾配を持つデータであり、ＫＲ積アレイ処理により、図１２（ｂ）に示すように、fast-timeの周波数軸を仮想的に延長することができる。ＫＲ積アレイ処理の原理と、複数反射点の場合の部分相関行列の平均化による無相関化処理については、角度軸と同様なので、ここではその説明を割愛する。次にfast-time軸の逆ＦＦＴ処理（３１ａ，３１ｂ）を行って時間軸に変換する。このように、fast-time軸の拡張アレイ処理を行うことにより、レンジ軸を高分解能化して、クラッタ中の目標を抽出しやすくする等の効果が得られる。

Hereinafter, the adaptation is performed using the data of the range axis, but before that, the extended array processing (30a, 30b) by the KR product of the fast-time axis is performed as necessary. This principle is shown in FIG. In the fast-time axis, in order to obtain the phase gradient data, the FFT process (29a, 29b) of the fast-time axis is performed and converted into the fast-time frequency axis. This fast-time frequency axis is data having a phase gradient as shown in FIG. 12 (a), and by KR product array processing, the fast-time frequency axis is set as shown in FIG. 12 (b). It can be extended virtually. Since the principle of KR product array processing and the uncorrelated processing by averaging the partial correlation matrix in the case of multiple reflection points are the same as the angular axis, the description thereof is omitted here. Next, the fast-time axis reverse FFT processing (31a, 31b) is performed to convert to the time axis. In this way, by performing the extended array processing of the fast-time axis, the effect of increasing the resolution of the range axis and facilitating the extraction of the target in the clutter can be obtained.

Next, unnecessary wave suppression processing is performed using the signals of the main ch (antenna) and the auxiliary ch (antenna) (32). In this unnecessary wave suppression process (32), the complex weights W1 to WL are calculated by the correlation process. For example, when the steepest descent method of MSN is used, the adaptive weight is given by the following equation (see Non-Patent Document 3).

本実施形態の定式化では、簡単のために１次元配列アンテナの場合としているが、２次元配列のアンテナの場合にも容易に拡張できるのは言うまでもない。
アダプテーション後の結果の処理については、ＣＦＡＲ（非特許文献２参照）等の検出処理をすれば、目標を検出することができる（３３，３４）。

In the formulation of the present embodiment, a one-dimensional array antenna is used for simplicity, but it goes without saying that the two-dimensional array antenna can be easily extended.
Regarding the processing of the result after adaptation, the target can be detected by performing detection processing such as CFAR (see Non-Patent Document 2) (33, 34).

As described above, in the radar system according to the present embodiment, in the array antenna for transmitting and receiving N pulses, the antenna aperture is divided into M (M ≧ 1) sub-arrays, and each sub-array signal is used as needed. Then, the expansion array processing of the angle axis is performed to form Mex (Mex ≧ M) beams as Mex (Mex> M) signals, and the CPI signal (Coherent Pulse Interval) slow-time axis is formed for each range cell. If necessary, the slow-time axis expansion array processing is performed to obtain a Nex (Nex> N) signal, and the slow-time axis FFT processing is performed using the signal, and fast is performed as necessary. After performing the extended array processing of the -time axis, the output of Nex × Mex is obtained for each range cell, the main ch is set to the predetermined beam directing direction and the Doppler cell, and the auxiliary ch is P from the maximum amplitude value except for the main ch. The signal up to the second is extracted, and the unnecessary wave is suppressed by this. That is, since the spatial axis (AZ / EL) / Doppler axis / range axis with improved resolution uses channels exceeding a predetermined amplitude threshold as auxiliary channels, the scale can be reduced and unnecessary waves can be suppressed.

(Second embodiment)
In the first embodiment, in the selection of the auxiliary channel, the case where the cell of the AZ / EL / Doppler axis is selected for each range cell has been described. In this embodiment, a method for reducing the selection processing scale will be described.
FIG. 13 is a flowchart showing the flow of the selection process of the main ch and the auxiliary ch, and FIG. 14 is a conceptual diagram showing how the AZ / EL / Dopplasel of the auxiliary ch is selected. The system diagram is omitted because the internal processing of the main ch selector 28a and the auxiliary ch selector 28b in FIG. 1 is different.

First, the range cell is divided (step S21), and the amplitude of the AZ / EL / Doppler axis signal is added for each range division unit (step S22). Next, AZ / EL / Dopplasels of auxiliary channels exceeding a predetermined amplitude threshold are selected from the maximum value of the result of amplitude addition (steps S23 and S24). This is performed for each range division unit (steps S25 and S26).

Next, in the main channel, the cells of the AZ / EL / Doppler axis to be observed are selected in the same manner as in the first embodiment (steps S15 to S18). Using the main ch and the auxiliary ch, the adaptive process is performed in the same manner as in the first embodiment. Since it is common to the first embodiment except for the selection of the main ch and the auxiliary ch, other processes will be omitted.

As described above, in the radar system according to the present embodiment, the range is divided in the LPRF, the amplitude of the AZ / EL / Doppler axis data is added in the division unit, the auxiliary channel is selected, and the range axis division unit is used. SLC processing is performed using the summed signals. In the case of LPRF (Low Pulse Repetition Frequency), the channel that exceeds the predetermined amplitude threshold is used as the auxiliary channel on the spatial axis (AZ / EL) / Doppler axis / range axis, so the processing scale is reduced and unnecessary waves are eliminated. Can be suppressed.

(Third embodiment)
In the second embodiment, the case of LPRF (Low Pulse Repetition Frequency) or the like in which there are relatively many range cells and adaptation is performed on the range axis has been described. Here, the case of HPRF (High Pulse Repetition Frequency) with few range cells will be described.

FIG. 15 is a flowchart showing the flow of the selection process of the main ch and the auxiliary ch, and FIG. 16 is a conceptual diagram showing how the AZ / EL / Dopplasel of the auxiliary ch is selected. The system diagram is omitted because the internal processing of the main ch selector 28a and the auxiliary ch selector 28b in FIG. 1 is different.

First, for each range cell, the AZ / EL axis data is amplitude-added in the Doppler axis direction (that is, the AZ / EL is added over the entire Doppler cell axis) (step S31). Next, AZ / EL cells of auxiliary channels exceeding a predetermined amplitude threshold are selected from the maximum value of the result of amplitude addition (steps S32 and S33). This is done for each range cell (steps S34, S35).

Next, in the main channel, the cells of the AZ / EL axis to be observed are selected in the same manner as in the first and second embodiments (steps S15 to S18). The steering vector for forming the main ch is for forming the main lobe on the spatial axis, and is given by the following equation when the spatial axis is a one-dimensional array.

本実施形態の定式化では、簡単のために１次元配列アンテナの場合としているが、２次元配列のアンテナの場合にも容易に拡張することができる。
次に、この信号を用いてアダプティブウェイトを算出する。通常は、時間軸の信号を用いてアダプテーションを行うが、本実施形態ではドップラ軸のデータを用いる。

In the formulation of the present embodiment, the case of a one-dimensional array antenna is used for simplicity, but it can be easily extended to the case of a two-dimensional array antenna.
Next, the adaptive weight is calculated using this signal. Normally, adaptation is performed using a signal on the time axis, but in this embodiment, data on the Doppler axis is used.

アダプテーション後の結果の処理については、ＣＦＡＲ（非特許文献２参照）等の検出処理を行えば、目標を検出することができる。
以上のように、第３の実施形態に係るレーダシステムでは、ＨＰＲＦにおいて、レンジセル毎に、ＡＺ／ＥＬ軸のデータをドップラ軸で振幅加算し、補助ｃｈを選定して、ＳＬＣ処理する。すなわち、ＨＰＲＦの場合において、空間軸（ＡＺ／ＥＬ）／ドップラ軸／レンジ軸で、所定の振幅スレショルドを超えるチャンネルを補助ｃｈとしているので、処理規模を削減して、不要波を抑圧することができる。

Regarding the processing of the result after the adaptation, the target can be detected by performing a detection process such as CFAR (see Non-Patent Document 2).
As described above, in the radar system according to the third embodiment, in the HPRF, the amplitude of the AZ / EL axis data is added by the Doppler axis for each range cell, the auxiliary channels are selected, and the SLC processing is performed. That is, in the case of HPRF, since the channel exceeding the predetermined amplitude threshold is used as the auxiliary channel on the spatial axis (AZ / EL) / Doppler axis / range axis, the processing scale can be reduced and unnecessary waves can be suppressed. can.

(Fourth Embodiment)
In the first to third embodiments, in order to select the auxiliary channel, a multi-beam is formed and selected in a wide range of observation space by using all sampling data. In this case, especially when a multi-beam is formed by using the total number of elements, a huge amount of data is processed, and the processing scale increases. For this measure, in this embodiment, a method of reducing the processing scale for selecting an auxiliary channel will be described.

FIG. 17 is a block diagram showing a configuration of a radar system according to a fourth embodiment, and FIG. 18 is a timing diagram showing a state in which thinning sampling is performed in a received PRI row. In FIG. 17, the same parts as those in FIG. 1 are designated by the same reference numerals, and different parts will be described here.

In FIG. 17, the differences from the configuration shown in FIG. 1 are the angle axis expansion array processor 24a and 24b, the sub-array multi-beam former 251,25M, the beam synthesizer 35, the thinning sampling processor 36, and the multi-beam former 37. It is equipped with a slow-time extended array processor 38, a slow-time FFT 39, and a beam selector 40.

In the sub-array, the point (241 to 24M) of processing the extended array of the angle axis as needed is the same as that of the first to third embodiments. First, the selection of auxiliary channels will be described. As shown in FIG. 18, in the received PRI columns (PRI1 to PRIN), full sampling was performed in the first to third embodiments. In this embodiment, thinning sampling (36) is performed. Using this data, a multi-beam covering the entire observation space is formed (37), and if necessary, an extended array process of the slow-time axis is performed (38), and a slow-time axis FFT is performed (39). From this result, as in the first to third embodiments, a beam containing a large amount of unnecessary signals can be selected (40), and sub-array multi-beam formation (251 to 25M) is performed so as to form a beam containing at least that beam. Beam control. As a result, it is not necessary to form a beam with full sampling data in the entire observation space, and the processing scale can be reduced.

Hereinafter, using the full sampling data, in the main ch selection (28a), the predetermined beam directing direction and the Doppler cell are set, and in the auxiliary ch selection (28b), the auxiliary channels are selected by the same method as in the first to third embodiments. You can select and suppress unnecessary waves.
According to this embodiment, transfer data can be reduced by transferring after processing of sub-array multi-beam formation (251, 25M) and thinning sampling (36) to reduce the number of formed beams of full sampling.

As described above, in the radar system according to the fourth embodiment, in the array antenna for transmitting and receiving N pulses, the antenna aperture is divided into M (M ≧ 1) sub-arrays, and the element signals in each sub-array are thinned out. Using the data sampled in the above, if necessary, it is transferred as Mex (Mex> M) signals by extended array processing of the angle axis to form Mex (Mex> M) beams, and for each range cell. CPI signal (Coherent Pulse Interval) slow-time axis is used, and if necessary, the slow-time axis is extended array processed to obtain a Nex (Nex> N) signal, which is used for slow-time. After performing FFT of the axis and performing extended array processing of the fast-time axis as necessary, the output of Nex × Mex is obtained for each range cell, and the main channel is set to the predetermined beam directing direction and Doppler cell, and is assisted. For ch, the signals from the maximum amplitude value to the Pth are extracted except for the main ch, and then, using the element signals processed by the expansion array of the angle axis of each subarray, Mex (Mex>) is used for each subarray. M) A beam is formed, and the CPI signal (Coherent Pulse Interval) slow-time axis is used for each range cell, and if necessary, the slow-time axis is extended array processed to Nex (Nex>. Using the signal of N), FFT of the slow-time axis is performed, and if necessary, the extended array processing of the fast-time axis is performed, and then the output of Nex × Mex is obtained for each range cell. Unnecessary waves are suppressed by using the main ch and the auxiliary ch.

That is, when the number of elements in the sub-array is large, a wide range of beams are formed and signals for selecting auxiliary channels are thinned out and sampled, so that the processing scale can be reduced and unnecessary waves can be suppressed. ..
As described above, the radar system of the present embodiment can reduce the processing scale and suppress unnecessary waves even in a complicated environment in which unwanted waves such as clutter and interference waves exist.

It should be noted that the present invention is not limited to the above embodiment as it is, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof. In addition, various inventions can be formed by an appropriate combination of the plurality of components disclosed in the above-described embodiment. For example, some components may be removed from all the components shown in the embodiments. Furthermore, components over different embodiments may be combined as appropriate.

111 ... signal generator, 112 ... modulator, 113 ... frequency converter, 114 ... pulse modulator, 115 ... transmit antenna,
211-21M ... Sub-array, 221-22M ... Frequency converter, 231-23M ... AD converter, 24, 24a, 24b ... Angle axis expansion array processor, 25, 251-25M ... Multi-beam former, 26 ... slow- time extended array processor, 27 ... slow-time FFT, 28a ... main ch selector, 28b ... auxiliary ch selector, 29a, 29b ... fast-time FFT, 30a, 30b ... fast-time extended array processor, 31a, 31b ... fast-timeIFFT, 32 ... unwanted wave suppressor, 33 ... detector, 34 ... output processor, 35 ... beam synthesizer, 36 ... thinning sampling processor, 37 ... multi-beam former, 38 ... slow-time extended array processing Instrument, 39 ... slow-time FFT, 40 ... beam selector.

Claims (8)

A transmission means for transmitting an N-hit transmission pulse, and
A receiving means for receiving the reflected signal of the transmission pulse using an array antenna in which the receiving aperture is divided into M (M ≧ 1) sub-arrays.
A reception beam forming means for forming at least M reception beams from the reception signals of each of the M sub-arrays, and
A Doppler axis signal generation means that generates at least N Doppler axis signals using the slow-time axis of the CPI (Coherent Pulse Interval) signal for each range cell from the M received beams.
A distribution means that acquires at least N × M outputs for each range cell from the N Doppler axis signals and distributes them to the main channel and auxiliary channels.
A predetermined beam direction and a Doppler cell are calculated from the Doppler axis signal in the main channel, and a signal from the maximum amplitude value to the Pth amplitude value is output from the Doppler axis signal in the auxiliary channel except for the main channel. A radar system including an unnecessary wave suppressing means that extracts and synthesizes a signal of the auxiliary channel with a signal of the main channel to suppress unnecessary waves. The radar system according to claim 1, wherein the received beam forming means further performs an extended array process of an angle axis to form a received beam of Mex (Mex> M). The radar system according to claim 1, wherein the Doppler axis signal generation means further executes an extended array process of the slow-time axis to generate Nex (Nex> N) Doppler axis signals. The receiving beam forming means further performs an extended array process of the angle axis to form a receiving beam of Mex (Mex> M).
The Doppler axis signal generation means further executes an extended array process of the slow-time axis to generate Nex (Nex> N) Doppler axis signals.
The radar system according to claim 1, wherein the distribution means further executes an extended array process of the fast-time axis to acquire an output according to Nex × Mex for each range cell. The unnecessary wave suppressing means executes a range division process in LPRF (Low Pulse Repetition Frequency), adds amplitudes to AZ / EL / Doppler axis data in division units, and is a channel exceeding a predetermined amplitude threshold as the auxiliary channel. The radar system according to claim 1, wherein SLC (Side Lobe Canceller) processing is performed using the signals obtained by selecting the above and adding up in the range axis division unit. In the HPRF (High Pulse Repetition Frequency), the unnecessary wave suppressing means adds amplitudes of AZ / EL axis data for each range cell on the Doppler axis, selects a channel exceeding a predetermined amplitude threshold as the auxiliary channel, and selects an SLC. (Side Lobe Canceller) The radar system according to claim 1, which performs processing. The radar system according to claim 1, wherein the receiving means thins out the antenna element output in the sub-array to obtain the received signal. The reflected signal of the N-hit transmission pulse is received by using the array antenna in which the reception aperture is divided into M (M ≧ 1) sub-arrays.
At least M received beams are formed from the received signals of each of the M subarrays.
At least N Doppler axis signals are generated from the M received beams for each range cell using the slow-time axis of the CPI (Coherent Pulse Interval) signal.
At least N × M outputs are acquired for each range cell from the N Doppler axis signals and distributed to the main channel and the auxiliary channel.
A predetermined beam directing direction and a Doppler cell are calculated from the Doppler axis signal in the main channel, and a signal from the maximum amplitude value to the Pth amplitude value is output from the Doppler axis signal in the auxiliary channel except for the main channel. A radar signal processing method of a radar system that extracts and synthesizes a signal of the auxiliary channel with a signal of the main channel to suppress unnecessary waves.

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