JP5161474B2 - Unwanted wave suppression device - Google Patents

Description

  The present invention relates to an unnecessary wave suppressing device that is applied to a radar device or a receiving device to suppress unnecessary waves, and more particularly to a technique for performing adaptive processing or STAP (Space Time Adaptive Processing) processing on a rotating antenna.

  Conventionally, in an unnecessary wave suppressing device applied to a radar device or a receiving device, adaptive processing or STAP processing is performed to reduce the antenna gain in the arrival direction of the interference wave to form a null point and suppress the interference wave. The technology of adaptive null steering is known. Details of adaptive processing and STAP processing are described in Non-Patent Documents 1 to 4 and Non-Patent Document 5, for example.

  FIG. 11 is a diagram for explaining a side lobe canceller (SLC), which is an adaptive null steering system, as an example of such an unnecessary wave suppressing device.

  As shown in FIG. 11A, the SLC processing unit processes the signal from the main antenna and the signal from the auxiliary antenna to reduce the antenna gain in the arrival direction of the interference wave and suppress the interference wave.

Specifically, as shown in FIG. 11B, the weight is changed so that the side lobe of the main antenna and the level of the auxiliary antenna are matched by the feedback loop of the SLC process, as shown in FIG. 11C. In addition, a null point is formed in the main antenna pattern. Thereby, the sensitivity with respect to the arrival direction of the jamming wave is reduced, and the jamming wave is suppressed.
Nobuyoshi Kikuma, “Adaptive signal processing by array antenna”, Science and Technology Publishing (1999) pp.35-37, 98-99 Nobuyoshi Kikuma, “Adaptive signal processing by array antenna”, Science and Technology Publishing (1999) pp.67-86 Nobuyoshi Kikuma, “Adaptive signal processing by array antenna”, Science and Technology Publishing (1999) pp.17-21 Nobuyoshi Kikuma, “Adaptive signal processing by array antenna”, Science and Technology Publishing (1999) pp.43-46, 76-78 Richard Klemm, “SPACE-TIME ADAPTIVE PROCESSING”, IEE RADAR, SONAR, NAVIGATION AND AVIONICS 9, pp.110-118 (1998)

  By the way, in a radar device or a receiving device having a rotating antenna, adaptive processing or STAP processing is performed to calculate a weight that forms a null point in the arrival direction of the interference wave as shown in FIG. If the antenna is rotated while the weight is fixed, the null point with respect to the arrival direction of the disturbing wave is shifted as shown in FIG.

  In order to avoid such a state, it is necessary to update the weights in units of range cells or in units of several range cells. However, if the weight calculation is performed every time the antenna rotates, the scale of the operation increases, and processing is performed within a specified time. There is a problem that it becomes difficult. Further, there is a problem that the main lobe is disturbed by adaptive processing, and the main lobe is further broken by the target signal when the antenna rotates.

  The present invention has been made to solve the above-mentioned problems, and the problem is that even when a rotating antenna is provided, unnecessary waves are suppressed with a small calculation scale, and disturbance of the main lobe is reduced. An object of the present invention is to provide an unnecessary wave suppression device that can perform the above-described operation.

In order to solve the above-mentioned problem, the invention described in claim 1 is an unnecessary wave suppression device that performs an element or subarray type adaptive process, and based on the rotation angle information of the rotating antenna to direct null in the direction of the unnecessary wave. A correction phase weight calculation unit for calculating a correction phase weight for directing the beam in a direction opposite to the rotation direction of the first phase, and an adaptive weight calculated by the first PRI (Pulse Repetition Interval) as an initial weight, and a correction phase weight calculation unit for the initial weight by multiplying the correction phase weight from calculating a corrected weight, and a processing unit that performs adaptive processing on the basis of the corrected weights wherein the processing unit, while repeating the corrected weights Ri by the recursive method sequentially calculating, prior Symbol gives a limit on the number of iterations representing the number of times to calculate the corrected weights of the main lobe It is characterized by suppressing disturbance.

According to the first aspect of the present invention, the adaptive weight calculated in the first PRI is used as the initial weight, and this is multiplied by the correction phase weight corresponding to the rotation angle of the antenna to obtain a weight (corrected weight). It is possible to easily calculate the weight when the is rotated. As a result, even when a rotating antenna is provided, unnecessary waves can be suppressed with a small amount of computation, and disturbance of the main lobe can be reduced. In addition, by limiting the number of iterations of the recursive method, disturbance of the main lobe due to adaptive processing can be suppressed, and only the phase weight is changed after setting the corrected weight. Can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram for explaining the principle of the present invention. Now, when the antenna rotates from the state shown in FIG. 1 (a) to the state shown in FIG. 1 (b), the arrival direction of the disturbing wave changes. Therefore, in the present invention, in order to direct null to the arrival direction of the disturbing wave, The entire beam is scanned in a direction opposite to the direction of rotation of the antenna. That is, a back scan is performed using a phase weight, and a null point is held.

  Taking this as an example of an unnecessary wave suppression device applied to a radar device, it is expressed in time series as shown in FIG. First, as shown in FIG. 2A, weight calculation is performed at the first PRI (Pulse Repetition Interval) of CPI (Coherent Processing Interval), and adaptive weight (initial weight) is calculated. Is done. The adaptive weight calculation is performed in the second half of the PRI corresponding to the farther possible distance with less clutter because the adaptive processing for suppressing the interference signal cannot calculate a weight with a high degree of suppression if clutter is included.

  When time management has a margin, as shown in FIG. 3A, a reception period is provided before the first transmission pulse, and an adaptive weight is calculated in the absence of clutter. You can also

  The adaptive weight calculated in this way is stored in the memory, and is set as the initial weight in the first PRI of the CPI as shown in FIG. The initial weight is multiplied by a correction phase weight for back scanning every range cell or every several range cells (thinned range cells) according to the rotation angle of the antenna, and the multiplication result is set as a corrected weight.

The calculation of adaptive weight and the corrected weight are formulated as follows. First, when the adaptive weight Wopt is calculated by the SMI method (refer to Non-Patent Document 1 for details), the following equation is obtained.

here,
Wopt: Adaptive weight (column vector)
Y: Adaptive output X: Input signal Rxx: Correlation matrix of input signal X S: Steering vector t: Transposition The steering vector S is expressed by the following equation.

θb: beam directing direction k: wave vector 2π / λ
λ: wavelength dn: position vector (n = 1 to N) of phase center of input (element or subarray) n
j: Imaginary unit Weight is generally expressed using a tapped delay line (refer to Non-Patent Document 3 for details), but for simplicity, it is expressed as a complex weight. In consideration of the rotation angle Δφ with respect to this adaptive weight Wopt, the following correction phase weight is required.

here,
ΔW: Correction phase weight Δφ: Rotation amount The corrected weight Wc can be calculated by the following equation using this correction phase weight.

  FIG. 4 is a block diagram illustrating a configuration of the unwanted wave suppressing device (element or subarray type adaptive) according to the first embodiment of the present invention. The processing described above is realized by this unnecessary wave suppressing device. The unnecessary wave suppressing device includes a plurality of input signals X1 to XN (N is a positive integer) sent from an antenna element (not shown) or a subarray in which a plurality of antenna elements are arranged. TDL (Taped Delay Line) 2 and the output of TDL2 are added, adder 3 is output as adaptive output Y, and adaptive processing is performed to calculate the weight to be multiplied by the signal output from each tap of TDL2. And a correction phase weight calculation unit 5 that calculates correction phase weights based on rotation angle information sent from an angle detection unit (not shown) of the antenna.

  The details of the TDL type adaptive array and the STAP process are described in Non-Patent Document 3 and Non-Patent Document 5.

  Next, the operation of the unwanted wave suppressing apparatus according to the first embodiment will be described with reference to the flowchart shown in FIG. First, an adaptive weight is calculated (step S1). That is, an adaptive weight is calculated in the first PRI of CPI. The calculated adaptive weight is used as an initial weight. Next, PRI is incremented (+1) (step S2). The initial value of PRI is “0”.

  Next, an initial weight is set (step S3). That is, the initial weight calculated in step S1 is set. Next, a corrected weight corresponding to the rotation angle is calculated (step S4). That is, the correction phase weight calculator 5 calculates a correction phase weight that directs the beam in the direction opposite to the rotation direction of the antenna based on the rotation angle information from the rotating antenna (not shown).

  Next, a corrected weight is set (step S5). That is, the corrected weight calculated in step S4 is set inside the adaptive processing unit 4 and used for adaptive processing. In this case, the corrected weight is set for each range cell or for several range cells (thinned range cells).

  Next, it is checked whether or not the processing for one CPI has been completed (step S6). If it is determined in step S6 that the processing for one CPI has not ended, the process returns to step S2 and the above-described processing is repeated. On the other hand, when it is determined that the processing for one CPI is completed, the processing proceeds to the processing for the next CPI.

  Note that the interval for calculating the adaptive weight (initial weight) can be determined in CPI units or several PRI units according to the rotational speed of the antenna, PRI, and the like.

  As the weight calculation method, other methods such as a recursive algorithm MSN (Maximum Signal to Noise Ratio) method (for details, refer to Non-Patent Document 2) can be used.

  FIG. 6 is a block diagram showing the configuration of the unwanted wave suppressing device (SLC type adaptive) according to the second embodiment of the present invention, and FIG. 7 is a diagram showing the configuration of the arithmetic cell used in this unwanted wave suppressing device. It is. In addition, since the structure of SLC type adaptive is well-known, below, it demonstrates focusing on the part directly related to this invention.

  In this unnecessary wave suppressing device, signals transmitted and received by a plurality of antenna elements constituting the main antenna 6 are sent to the beam combining circuit 7 as main channel (hereinafter, abbreviated as “main CH”) signals.

  A plurality of subarrays can be used instead of the plurality of antenna elements. The beam combining circuit 7 performs the beam calculation using the correction phase weight for the main CH sent from the auxiliary phase weight calculation unit 10, then combines the beam, and sends it to the cancel processing circuit 12.

  A part or all of a plurality of antenna elements or subarrays constituting the main antenna 6 is shared as an auxiliary antenna. An auxiliary channel (hereinafter abbreviated as “auxiliary CH”) signal obtained by the auxiliary antenna is sent to the TDL 8.

In combination with the SLC processing unit 9, the TDL 8 suppresses unnecessary waves by performing adaptive processing using a signal in units of range cells of the auxiliary CH signal from the auxiliary antenna. When an SMI (Direct Solution: Sampled Matrix Inversion) algorithm operation (see Non-Patent Document 1) is used as the optimal weight Wopt for adaptive processing, the following equation is obtained.

here,
Wopt: Adaptive weight (column vector)
Y: adaptive output Xm: main CH signal Xa: auxiliary CH signal Rxx: correlation matrix of input signal Xa rxd: correlation coefficient of auxiliary CH signal Xa and SLC output Y Sm: weight for main CH (steering vector)

θb: beam directing direction dn: position vector of phase center of input (element or subarray) of main CH (n = 1 to N)
When the rotation angle Δφ is taken into consideration for this weight Wopt, the following correction phase weight is required.

here,
ΔS: correction phase weight Δφ: rotation amount N: number of elements of main CH (n = 1 to N)
Similarly, the auxiliary CH is represented by the following formula.

here,
Na: number of elements of auxiliary CH dna: position vector of phase center of auxiliary CH input (element or subarray) (na = 1 to Na)
Using this corrected phase weight, the corrected weight can be calculated by the following equation.

here,
Sc: Weight after correction of main CH Wc: Weight after correction of auxiliary CH The above processing can be realized by the processing in the unnecessary wave suppressing apparatus according to the first embodiment shown in the flowchart of FIG. The corrected weight is set for each range cell or for several range cells (thinned range cells). Further, the interval for calculating the adaptive weight (initial weight) can be determined in CPI units or several PRI units according to the rotational speed of the antenna, PRI, and the like.

  In the unwanted wave suppressing device according to the first and second embodiments described above, the signal processing is performed on the space axis. However, when the time axis (frequency axis) is further added, the space-time (frequency) axis is increased. Multidimensional STAP processing (see, for example, Non-Patent Document 5) becomes possible. FIG. 8 is a block diagram showing the configuration of the unwanted wave suppressing device (element or subarray type STAP) according to the third embodiment of the present invention. Since the configuration of the element or the sub-array type STAP is well known, the following description will focus on the portion directly related to the present invention.

The optimum weight Wopt of the STAP process performed by the unnecessary wave suppression device can be expressed by the following equation in the case of the direct solution (see Non-Patent Document 4).

here,
Wopt: Adaptive weight (column vector)
Y: STAP output X: Input signal (N × M, N: number of auxiliary antennas, M: number of taps)
X = [X11..., XNM] ^t
Rxx: correlation matrix of input signal X S: steering vector

        The above is the case of a linear array.

θb: beam directing direction p: frequency bank number (p = 1 to P)
m: Tap number (m = 1 to M)
In consideration of the rotation angle Δφ for the weight Wopt, the correction phase of the following equation can be calculated.

here,
ΔW: correction phase weight Δφ: rotation amount The corrected weight Wc can be calculated by the following equation using this correction phase weight.

  The above process can be realized by the process in the unnecessary wave suppressing apparatus according to the first embodiment shown in the flowchart of FIG. The corrected weight is set for each range cell or for several range cells (thinned range cells). Further, the interval for calculating the adaptive weight (initial weight) can be determined in CPI units or several PRI units according to the rotational speed of the antenna, PRI, and the like.

  When calculating the initial weight, in the case of the STAP process, as shown in FIG. 9, the weight calculation is performed based on the range cell data of each PRI of the CPI.

  The unnecessary wave suppression device according to the third embodiment described above is configured to perform element or subarray type STAP processing, but can be configured to perform SLC type STAP processing. FIG. 10 is a block diagram illustrating a configuration of the unwanted wave suppressing device (SLC type STAP) according to the fourth embodiment of the present invention. Since the configuration of the SLC type STAP is well known, the following description will focus on the part directly related to the present invention.

In this unnecessary wave suppressing device, the main CH signal from the main antenna 6 is combined by the beam combining circuit 7 and then beam-formed in time and space by the Fourier transform circuit 12. When the SMI (Direct Solution: Sampled Matrix Inversion) algorithm operation is used as the optimum weight Wopt for the STAP process, the following equation is obtained.

here,
Wopt: Adaptive weight (column vector)
Y: Adaptive output Xm: Main CH signal Xa: Auxiliary CH signal
(N x M, N: number of auxiliary antennas, M: number of taps)
Xa = [X11..., XNM] ^t
Rxx: Correlation matrix of input signal Xa rxd: Correlation coefficient between auxiliary CHXa and SLC output Y Sm: Weight for main CH (steering vector)

p: frequency bank number (p = 1 to P)
m: Tap number (m = 1 to M)
dn: position vector (n = 1 to N) of the phase center of the input (element or subarray) of the main CH
This optimal weight is set in the adaptive processing computation cell, the auxiliary CH signal is added, and the cancellation processing computation cell is subtracted from the main CH signal.

When the rotation angle Δφ is taken into consideration for this weight Wopt, the following correction phase weight is required.

Similarly, the auxiliary CH is represented by the following formula.

here,
Na: number of auxiliary CH elements dna: position vector of phase center of auxiliary CH input (element or subarray) (na = 1 to Na)
Using this corrected phase weight, the corrected weight can be calculated by the following equation.

here,
Sc: Weight after correction of main CH Wc: Weight after correction of auxiliary CH The above processing can be realized by the processing in the unnecessary wave suppressing apparatus according to the first embodiment shown in the flowchart of FIG. The corrected weight is set for each range cell or for several range cells (thinned range cells). Further, the interval for calculating the adaptive weight (initial weight) can be determined in CPI units or several PRI units according to the rotational speed of the antenna, PRI, and the like.

  When calculating the initial weight, in the case of STAP, as shown in FIG. 9, the weight calculation is performed by the range cell data of each PRI of CPI.

  The unnecessary wave suppressing apparatus according to the fifth embodiment suppresses disturbance of the main lobe by limiting the number of iterations when the processing unit calculates the corrected weight by the recursive method.

  The unnecessary wave suppression apparatus according to the fifth embodiment is configured such that weights are sequentially calculated while being repeated in the recursive method, but the number of repetitions is limited and the weight calculation is stopped when the limit number is exceeded. It is a thing.

  Thereby, although unnecessary wave suppression performance slightly deteriorates, it is possible to calculate weights in a range that does not affect the main lobe. As the recursive method, various methods such as the MSN method (see Non-Patent Document 2) and the RLS method (see Non-Patent Document 4) can be used.

  Note that the method of suppressing the main lobe disturbance by limiting the number of iterations can be applied to the case where the number of iterations is fixed to zero.

  The present invention is applicable to a radar device or a receiving device provided with a rotating antenna.

It is a figure for demonstrating the principle of this invention. It is a figure for demonstrating the operation | movement which determines an initial weight with a transmission timing in the unnecessary wave suppression apparatus which concerns on Example 1 of this invention. FIG. 6 is a diagram for explaining another operation for determining an initial weight at transmission timing in the unnecessary wave suppressing apparatus according to Embodiment 1 of the present invention. It is a block diagram which shows the structure of the unnecessary wave suppression apparatus which concerns on Example 1 of this invention. It is a flowchart which shows operation | movement of the unnecessary wave suppression apparatus which concerns on Example 1 of this invention. It is a block diagram which shows the structure of the unnecessary wave suppression apparatus which concerns on Example 2 of this invention. It is a figure which shows the structure of the calculation cell used with the unnecessary wave suppression apparatus which concerns on Example 2 of this invention. It is a block diagram which shows the structure of the unnecessary wave suppression apparatus which concerns on Example 3 of this invention. It is a figure for demonstrating the operation | movement which determines an initial weight with a transmission timing in the unnecessary wave suppression apparatus which concerns on Example 3 of this invention. It is a block diagram which shows the structure of the unnecessary wave suppression apparatus which concerns on Example 4 of this invention. It is a figure for demonstrating the principle of SLC which is an adaptive null steering system as an example of the conventional unnecessary wave suppression apparatus. It is a figure for demonstrating the problem of the conventional unnecessary wave suppression apparatus.

Explanation of symbols

2 TDL (range cell unit)
2a TDL (PRI unit)
3 Adder 4 Adaptive processing unit 4a STAP processing unit 5, 5a Corrected phase weight calculation unit 6 Main antenna 7 Beam combining circuit 8 TDL (range cell unit)
8a TDL (PRI unit)
9 SLC processing unit 9a STAP processing unit 10, 10a Correction phase weight calculation unit 11, 11a Cancel processing circuit 12 Fourier transform circuit

Claims (1)

In an unnecessary wave suppression device that performs element or subarray type adaptive processing,
A correction phase weight calculator for calculating a correction phase weight for directing the beam in the direction opposite to the rotation direction of the antenna based on the rotation angle information of the rotating antenna in order to direct the null in the unnecessary wave direction;
The adaptive weight calculated by the first PRI (Pulse Repetition Interval) is used as the initial weight, and the corrected weight is calculated by multiplying the initial weight by the corrected phase weight from the corrected phase weight calculation unit. Based on the corrected weight A processing unit for performing adaptive processing;
With
Wherein the processing unit, characterized in that the sequentially calculated while repeating the by Ri before Symbol corrected weights recursive method, before Symbol gives a limit on the number of iterations representing the number of times to calculate the corrected weight, suppress the disturbance of the main lobe An unnecessary wave suppression device.

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