JP4834508B2 - Radar equipment - Google Patents

Description

  The present invention relates to a radar apparatus, and in particular, uses a one-dimensional DBF (Digital Beam Forming) array antenna to suppress unwanted waves on a time-frequency axis, improve angular resolution, and improve angular accuracy in a multipath environment. For technology.

  FIG. 7 is a block diagram showing a configuration of a radar apparatus using a conventional one-dimensional DBF array antenna. The radar apparatus includes a square aperture antenna 1, a beam combiner 2, and a signal processor 3.

  The square aperture antenna 1 includes a one-dimensional DBF array antenna in which n (n is a positive integer) subarrays are arranged in the EL (elevation) direction. Note that the n subarrays are divided into two openings, but are not shown. Each sub-array is well known and is not shown in the figure, but includes a plurality of antenna elements, a plurality of transmission / reception modules respectively corresponding to the plurality of antenna elements, and a single feeding circuit that performs power distribution and combination for the plurality of transmission / reception modules. It is configured.

  The n sub-arrays constituting the square aperture antenna 1 generate sum signals Σ1 to Σn and difference signals Δ1 to Δn obtained by monopulse synthesis, and send them to the beam combiner 2.

  The beam combiner 2 synthesizes the sum signals Σ1 to Σn and the difference signals Δ1 to Δn sent from the square-aperture antenna 1, and the Σ beam that is the sum signal, the ΔAZ beam that is the difference signal in the azimuth direction, and the elevation direction A monopulse beam including a ΔEL beam which is a difference signal of the signal is formed and sent to the signal processor 3.

  The signal processor 3 generates various signals by performing signal processing on the monopulse beam sent from the beam combiner 2 and sends it as post-processing data to subsequent devices.

As a technique related to the DBF method, Patent Document 1 discloses a radar apparatus in which the scale of the apparatus is reduced by using a phased array antenna (PAA) transmission system in common during reception. This radar apparatus forms a reception beam subjected to DBF processing from reception signals from all element antennas, and uses a common direction signal distributor that distributes transmission signals to receive signals from element antennas used for transmission. Are combined to form a reception beam that has been subjected to PA processing, thereby reducing the processing area of the reception signal that is subjected to DBF processing.
JP 11-258331 A

  As described above, in the conventional radar apparatus, in order to perform multidimensional signal processing on the antenna aperture plane, input signals in units of antenna elements or at least in subarray units are required, and a two-dimensional full DBF array antenna is required. A circuit for analog synthesis is required for each subarray whose phase center is shifted. As a result, there is a problem that the circuit scale becomes large.

  The present invention has been made to solve the above-described problems, and its problems are, for example, suppression of unnecessary waves, improvement of angular resolution, and improvement of angular accuracy in a multipath environment without increasing the circuit scale. An object of the present invention is to provide a radar apparatus that can achieve the above.

In order to solve the above problems, a first aspect of the present invention, arranged in one direction so as circular openings are formed, and unrealized plurality of the plurality of sub-arrays having an opening divided in a direction perpendicular to said one direction For a one-dimensional DBF (Digital Beam Forming) array antenna that generates a two-dimensional sub-array signal having a different phase center by the sub- array antenna and a sub-array signal before monopulse synthesis sent from a plurality of sub-arrays of the one-dimensional DBF array antenna And a signal processor for performing signal processing.

Further, a second aspect of the present invention, arranged in one direction so as circular openings are formed, and the phase center of the plurality of sub-arrays having an opening divided in a direction perpendicular to said one direction by unrealized plurality of subarray antenna 1-dimensional DBF (Digital Beam Forming) array antenna that generates 2-dimensional sub-array signals of different sizes and monopulse-combined signals sent from multiple sub-arrays of 1-dimensional DBF array antennas into sub-array signals before mono-pulse synthesis And a signal processor for performing signal processing on a subarray signal before monopulse synthesis sent from the subarray division processor.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the signal processor includes a small antenna arranged as a part of a circular opening, and the signal processor includes a plurality of subarrays of the one-dimensional DBF array antenna. Signal processing is performed on the sub-array signal before monopulse synthesis sent from, and the signal sent from the small antenna.

  According to a fourth aspect of the present invention, there is provided the method according to any one of the first to third aspects, wherein the signal processor comprises a STAP processor that performs a STAP (Space Time Adaptive Processing) process. Features.

  The invention according to claim 5 is the invention according to any one of claims 1 to 3, further comprising a MUSIC processor for performing MUSIC (Multiple Signal Classification) processing based on the subarray signal. To do.

The invention according to claim 6 is the invention according to any one of claims 1 to 3, wherein the beams having different phase centers in a circular aperture are formed using a two-dimensional subarray antenna comprising a plurality of subarray antennas. And an aperture diversity processor for measuring an angle by applying an aperture diversity process using a beam having the maximum level among the formed beams .

According to the first aspect of the invention, arranged in one direction so as circular openings are formed, and the phase center of the plurality of sub-arrays having an opening divided in a direction perpendicular to said one direction by unrealized plurality of subarray antenna Since the one-dimensional DBF array antenna that generates two-dimensional sub-array signals having different phases is configured, a plurality of sub-arrays having different phase centers can be configured without increasing the circuit scale. For example, a one-dimensional DBF array antenna can be divided into N sub-arrays in one direction, and the direction orthogonal thereto can be divided into N × N by using the output of the sub-array divided into two when the aperture is divided into two. The output of two subarrays with different phase centers can be obtained. Therefore, by performing multidimensional signal processing using N × 2 subarray signals having different phase centers before monopulse synthesis sent from a plurality of subarrays of the one-dimensional DBF array antenna, unnecessary waves can be generated. The suppression performance can be improved.

  According to the second aspect of the present invention, a signal obtained by monopulse synthesis from a plurality of sub-arrays having different phase centers of a one-dimensional DBF array antenna having the same configuration as that of the first aspect is a signal before monopulse synthesis. And the multi-dimensional signal processing is performed using the N × 2 sub-array signals having different phase centers before the monopulse synthesis, thereby improving the unnecessary wave suppression performance.

  According to the invention of claim 3, since a small antenna is added, the number of signals used for signal processing can be increased. As a result, unnecessary wave suppression performance can be further improved.

  According to the invention described in claim 4, since the signal processor is configured to perform the STAP process which is the time-space process, the clutter and the interference wave can be automatically suppressed by the space-frequency filter. Can do.

  According to the fifth aspect of the invention, since the MUSIC process is performed, the target can be observed with a high angular resolution while reducing the correlation between the targets by using the correlation matrix by the spatial averaging process. .

According to the sixth aspect of the present invention, a beam having a different phase center is formed using a two-dimensional subarray antenna including a plurality of subarray antennas , and the beam having the maximum level among the formed beams is used. Therefore, it is possible to suppress multipath fading and obtain high angle measurement accuracy even in a multipath environment.

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

  In the case of the one-dimensional DBF array antenna described in the background section, the EL plane can be divided into subarrays, but the AZ plane is only configured to output a monopulse signal, and the phase of the subarray The center is aligned with the center. Therefore, the degree of freedom in the AZ direction is “1”. As the degree of freedom increases in the EL plane and the AZ plane, it is desirable to increase the degree of freedom because the unnecessary wave suppression performance is improved. The radar apparatus according to the first embodiment of the present invention increases the degree of freedom of the EL plane and the AZ plane to improve unnecessary wave suppression performance.

  FIG. 1 is a diagram illustrating a configuration of a radar apparatus according to Embodiment 1 of the present invention. The radar apparatus includes a circular aperture antenna 4, a small antenna 5, and a STAP (Space Time Adaptive Processing) processor 6.

  The circular aperture antenna 4 is composed of a one-dimensional DBF array antenna. In the circular aperture antenna 4, the EL direction is one-dimensional DBF and the AZ direction is analog-synthesized. The AZ direction is originally divided into two apertures in order to create a monopulse beam, and the EL direction is divided and synthesized in units of N (N is a positive integer), so a subarray of N × 2 division units. Output (signal before monopulse synthesis).

  Since each subarray is arranged so that a circular opening is formed, the phase center of each subarray is different. Therefore, this circular aperture antenna 4 has N × 2 degrees of freedom. The output of the subarray of N × 2 division units constituting this circular aperture antenna 4 is sent to the STAP processor 6 as subarray signals L1 to LN and R1 to RN.

  Note that the small antenna 5 is an option and is additionally disposed as a part of the circular opening when the degree of freedom is insufficient. The position and number of the small antennas 5 are arbitrary. Signals S1 to SP (P is a positive integer) output from the small antenna 5 are sent to the STAP processor 6.

  The STAP processor 6 performs STAP processing, which is multidimensional signal processing, using subarray signals. In this case, an input signal input to the STAP processor 6 is shown in FIG. The input signal is a two-dimensional signal having different positions in the AZ direction and the EL direction in a space defined by a two-dimensional subarray, and is a signal for each range cell for each of a plurality of PRI units on the time axis. By using this signal, STAP processing which is multidimensional signal processing of space-time (frequency) can be performed.

  The details of the STAP processing are described in, for example, “Richard Klemm,“ SPACE-TIME ADAPTIVE PROCESSING ”, IEEE RADAR, SONAR, NAVIGATION AND AVIONICS 9, pp. 110-118 (1998)”.

The optimum weight Wopt of the STAP process can be expressed by the following equation in the case of the direct solution method. The details of the direct solution method (SMI method, etc.) are described in, for example, “Nobuyoshi Kikuma,“ Adaptive Signal Processing by Array Antenna ”Science and Technology Publication (1999) pp. 35-37, 98-99”.

here,
Rxx: Correlation matrix of input signal x S: Suaring vector

      The above is the case of a linear array.

θb: beam directing direction m: frequency bank number (m = 1 to M)
k: wave vector dn: position vector of phase center of subarray n (n = 1 to 2N)
H: Complex conjugate transposition j: Imaginary unit The STAP processor 6 includes a TDL (tapped delay line) with a delay τ and a weight W in PRI units or range cell units as shown in FIG. The TDL type adaptive array is described in, for example, “Nobuyoshi Kikuma,“ Adaptive Signal Processing by Array Antenna ”, Science and Technology Publication (1999) pp. 17-21”.

  As a weight calculation method, for example, another method such as MSN (Maximum Signal to Noise Ratio) method may be used. The MSN method is described in, for example, “Nobuyoshi Kikuma,“ Adaptive Signal Processing by Array Antenna ”, Science and Technology Publishing (1999) pp. 67-86”.

  In the radar apparatus according to the first embodiment described above, a one-dimensional DBF array antenna having a circular aperture is used as the circular aperture antenna 4. However, the aperture shape does not necessarily have to be a perfect circle, for example, an ellipse. There may be. In short, antennas having various aperture shapes can be used as long as the subarrays are arranged so that the phase centers of the plurality of subarrays are two-dimensionally arranged.

  FIG. 4 is a diagram illustrating a configuration of a radar apparatus according to Embodiment 2 of the present invention. This radar apparatus includes a circular aperture antenna 4, a small antenna 5, a STAP processor 6, and a subarray division processor 7.

The circular aperture antenna 4 is composed of a one-dimensional DBF array antenna. In the circular aperture antenna 4, the EL direction is one-dimensional DBF and the AZ direction is analog-synthesized. With respect to the AZ direction, a sum signal Σ and a difference signal Δ obtained by monopulse synthesis are obtained from a power supply circuit (not shown). From these sum signal Σ and difference signal Δ, a signal divided into two apertures is obtained by the following equation.

here,
Xl: One surface divided into two apertures Xr; Other surface divided into two apertures Σ; Sum signal Δ; AZ surface difference signal From the equation (2), the aperture divided signal can be calculated by the following equation.

  In addition, the AZ direction is originally divided into two apertures in order to create a monopulse beam, and the EL direction is divided into N divided units and synthesized. Therefore, the output of the subarray of N × 2 divided units (monopulse synthesis) Signal) is obtained. Since each subarray is arranged so that a circular opening is formed, the phase center of each subarray is different.

  Therefore, this circular aperture antenna 4 has N × 2 degrees of freedom. The output of the subarray of N × 2 division units constituting the circular aperture antenna 4 is sent to the subarray division processor 7 as subarray signals Σ1 to ΣN and Δ1 to ΔN.

  The subarray division processor 7 converts the subarray signals Σ1 to ΣN and Δ1 to ΔN that have been monopulse synthesized into subarray signals L1 to LN and R1 to RN before monopulse synthesis, and sends them to the STAP processor 6. The STAP processor 6 is the same as that of the radar apparatus according to the first embodiment described above.

  Note that the small antenna 5 is an option and is additionally disposed as a part of the circular opening when the degree of freedom is insufficient. The position and number of the small antennas 5 are arbitrary. Signals S1 to SP (P is a positive integer) output from the small antenna 5 are sent to the STAP processor 6 via the subarray division processor 7.

  The radar apparatus according to Example 3 of the present invention is configured to perform MUSIC processing using the subarray signal of the radar apparatus according to Example 1 or Example 2 to perform angle measurement. The MUSIC processing is described in, for example, “Nobuyoshi Kikuma,“ Adaptive Signal Processing by Array Antenna ”, Science and Technology Publication (1999) pp.194-199”.

  FIG. 5 is a diagram partially showing a configuration of a radar apparatus according to Embodiment 4 of the present invention, excluding the circular aperture antenna 4 and the small antenna 5. This radar apparatus is configured by replacing the STAP processor 6 of the radar apparatus according to the first embodiment with a beam forming signal processor 8, and further adding a MUSIC processor 9.

  The beam forming signal processor 8 performs signal processing for forming a beam based on the subarray signals X1 to X2N from the circular aperture antenna 4, and outputs the result of this signal processing as post-processing data.

The MUSIC processor 9 executes MUSIC processing based on the subarray signals X1 to X2N from the circular aperture antenna 4. The spectrum of this MUSIC process can be expressed by the following equation.

here,
En: Eigenvector of thermal noise of correlation matrix Rxx a: Direction vector

            The above is for a linear array.

θ: Direction of incoming wave j: Imaginary unit According to the radar apparatus according to the second embodiment, the angle measurement is performed by the MUSIC process, and thus the correlation between the targets is reduced using the correlation matrix by the spatial averaging process. In addition, the target can be observed with high angular resolution.

  The radar apparatus according to the fourth embodiment of the present invention performs aperture diversity processing using the subarray signal of the radar apparatus according to the first or second embodiment, and performs angle measurement by obtaining the effect of the aperture diversity. Is. The aperture diversity is described in Japanese Patent Application No. 2006-103482 filed earlier by the applicant of the present application, and should be referred to as necessary.

  FIG. 6 is a diagram partially showing a configuration of a radar apparatus according to Embodiment 4 of the present invention, excluding the circular aperture antenna 4 and the small antenna 5. This radar apparatus is configured by replacing the STAP processor 6 of the radar apparatus according to the first embodiment with a beam forming signal processor 8 and further adding an aperture diversity processor 10. The beam forming signal processor 8 is the same as that of the radar apparatus according to the third embodiment.

The aperture diversity processor 10 performs aperture diversity processing. Aperture diversity changes the phase relationship between the direct wave and the multipath wave by changing the phase center of the subarray in the same aperture for the multipath, and detects the beam Σr with the maximum level. The reference beam for angle measurement is used.

here,
max []; Maximum value bq; Beam signal with different phase center by subarray synthesis (q = 1 to Q)
This aperture diversity processing enables detection with a high level signal even in a multipath environment, thus preventing the occurrence of a situation where the level is lowered due to multipath fading and angle measurement becomes impossible. Can do.

  The present invention can be used for a radar apparatus that is required to suppress unwanted waves, improve angular resolution, and improve angular accuracy in a multipath environment.

It is a figure which shows the structure of the radar apparatus which concerns on Example 1 of this invention. It is a figure for demonstrating the multidimensional signal processing in the radar apparatus which concerns on Example 1 of this invention. It is a figure which shows the structure of the STAP processor used with the radar apparatus which concerns on Example 1 of this invention. It is a figure which shows the structure of the radar apparatus which concerns on Example 2 of this invention. It is a figure which shows partially the structure of the radar apparatus which concerns on Example 3 of this invention. It is a figure which shows partially the structure of the radar apparatus which concerns on Example 4 of this invention. It is a figure which shows the structure of the conventional radar apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Square aperture antenna 2 Beam combiner 3 Signal processor 4 Circular aperture antenna 5 Small antenna 6 STAP processor 7 Subarray division processor 8 Beamforming signal processor 9 MUSIC processor 10 Aperture diversity processor

Claims (6)

Place in one direction so as circular opening is formed, and generates a two-dimensional sub-array signals with different phase centers of a plurality of sub-arrays of unrealized plurality of subarray antenna which is open divided in a direction perpendicular to said one direction A one-dimensional DBF (Digital Beam Forming) array antenna;
A signal processor for performing signal processing on a subarray signal before monopulse synthesis sent from a plurality of subarrays of the one-dimensional DBF array antenna;
A radar apparatus comprising: Place in one direction so as circular opening is formed, and generates a two-dimensional sub-array signals with different phase centers of a plurality of sub-arrays of unrealized plurality of subarray antenna which is open divided in a direction perpendicular to said one direction A one-dimensional DBF (Digital Beam Forming) array antenna;
A subarray split processor for converting monopulse synthesized signals sent from a plurality of subarrays of the one-dimensional DBF array antenna into subarray signals before monopulse synthesis;
A signal processor that performs signal processing on a subarray signal before monopulse synthesis sent from the subarray division processor;
A radar apparatus comprising: Comprising a small antenna arranged as part of the circular opening;
The signal processor performs signal processing on a sub-array signal before monopulse synthesis sent from a plurality of sub-arrays of the one-dimensional DBF array antenna and a signal sent from the small antenna. Item 3. The radar device according to item 1 or item 2.   The radar apparatus according to any one of claims 1 to 3, wherein the signal processor includes a STAP processor that executes a Space Time Adaptive Processing (STAP) process.   The radar apparatus according to claim 1, further comprising a MUSIC processor that performs MUSIC (Multiple Signal Classification) processing based on the subarray signal. A two-dimensional subarray antenna comprising a plurality of subarray antennas is used to form a beam having a different phase center within a circular aperture, and measurement is performed by applying aperture diversity processing using a beam having the maximum level among the formed beams. The radar apparatus according to any one of claims 1 to 3, further comprising an aperture diversity processor that performs cornering .

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