JP2020041969A - Radar device - Google Patents

Abstract

To prevent the expansion of a device scale irrespective of the number of targets to track.SOLUTION: According to an embodiment, a radar device comprises an antenna unit and a signal processing unit. The antenna unit captures a wireless band signal in which an echo signal from a regular target and a response signal from a transponder coexist. The signal processing unit processes a received signal based on the wireless band signal in a digital domain. The antenna unit includes a local oscillator, a converter for frequency-converting the wireless band signal with the local frequency of the local oscillator, and a plurality of digital computation circuits. Each of the digital computation circuits digitally converts the output of the converter and outputs digital data based on frequency shift indicated by the echo signal and response signal. The signal processing unit includes a beam formation processing unit and a detection processing unit. The beam formation processing unit forms received beams corresponding to the regular target and the transponder on the basis of the digital data. The detection processing unit detects the regular target and the transponder from the formed received beams.SELECTED DRAWING: Figure 2

Description

  Embodiments of the present invention relate to a radar device.

  2. Description of the Related Art There is known a radar apparatus capable of following a test flying target and searching, detecting, and following another target (normal target) at a time. This type of radar device is used, for example, for airspace safety monitoring (anti-aircraft security monitoring radar device).

  In order to follow the flying target, a transponder is mounted on the flying target. For this reason, the radar apparatus is required to have a performance capable of processing the transmission / reception frequency for the target search and the transmission / reception frequency for the transponder, and has a great impact in terms of cost.

  Also, as the number of test flying targets increases, the number of transponders also increases. In order to prevent interference of responses from each transponder, it is necessary to increase the reception band on the radar device side. For this reason, it is necessary to provide a plurality of local oscillators for frequency conversion and take measures such as switching with a switch, thereby further increasing the cost.

Supervised by Takashi Yoshida "Revised radar technology" IEICE, October 1, 1996 (first edition)

  As described above, when a radar device that searches for and follows a target also attempts to follow a flying target equipped with a transponder, the transmission and reception frequency for the normal target and the transmission and reception frequency for the transponder are changed. It was necessary to switch in a time-sharing manner. As a result, there is a risk of competing for time resources, resulting in a decrease in performance. Also, as the number of flying objects to follow increased, the scale of the radar device had to be expanded, and a solution was required.

  Therefore, an object of the present invention is to provide a radar apparatus capable of preventing an increase in apparatus scale regardless of the number of targets to be followed.

  According to the embodiment, the radar device includes an antenna unit and a signal processing unit. The antenna unit normally captures a radio band signal in which an echo signal from a target and a response signal from a transponder are mixed. The signal processing unit processes a received signal based on a wireless band signal in a digital domain. The antenna unit includes a local oscillator for generating a local frequency, a converter for frequency-converting a radio band signal at the local frequency, and a plurality of digital operation circuits. The digital operation circuit digitally converts the output of the converter and outputs digital data based on the frequency shift indicated by the echo signal and the response signal. The signal processing unit includes a beam forming processing unit and a detection processing unit. The beam forming unit forms a reception beam corresponding to the normal target and the transponder based on the digital data. The detection processing unit detects a normal target and a transponder from the formed reception beam.

FIG. 1 is a diagram illustrating an example of transmission / reception frequencies related to the radar device according to the embodiment. FIG. 2 is a functional block diagram illustrating an example of the radar device according to the first embodiment. FIG. 3 is a functional block diagram showing an example of the receiver 8 shown in FIG. FIG. 4 is a functional block diagram showing an example of the signal processor 10 shown in FIG. FIG. 5 is a functional block diagram showing an example of the transponder mounted on the flying target shown in FIG. FIG. 6 is a functional block diagram illustrating an example of a radar device according to the second embodiment. FIG. 7 is a functional block diagram showing an example of the signal processor 19 shown in FIG.

  FIG. 1 is a diagram illustrating an example of transmission / reception frequencies related to the radar device according to the embodiment. In FIG. 1, the flying target (my target) on which the transponder is mounted is indicated by a white circle, and the normal target (his target) is indicated by a black circle. FIG. 1 shows a relationship between a radar transmission frequency of a radar apparatus, reflection frequencies (echo frequencies) from a plurality of normal targets, and response frequencies from a transponder of a plurality of flying targets. That is, in the environment of FIG. 1, the echo signal from the normal target and the response signal from the transponder are mixed. The radar antenna 100 captures a radio band signal in which these signals are mixed.

  The radar device searches a space by radiating a chirp signal of one transmission frequency while changing the directivity angle of the radar antenna 100 regularly. On the other hand, the transponder can receive a radar transmission wave if it is within the directional angle of the radar device, and transmits a response signal to the radar transmission wave to the radar device. That is, each transponder shifts the received radar transmission wave at a frequency corresponding to its own transponder identification information, and gives a delay to avoid a radar transmission period (transmission blind) to generate a response signal.

When a radar transmission wave and F _0, the frequency of the signal received by the radar device is, for example, as shown below.
From the plurality of normal target, signal frequency F ₀ is reached.
From the transponder 1, a signal of the frequency F ₁ (F ₀ + Δf1) is returned.
From the transponder 2, a signal of the frequency F ₂ (F ₀ + Δf2) is returned.
,,,
From the transponder N, a signal of the frequency F _N (F ₀ + ΔfM) is returned.

  The radar apparatus receives and demodulates the delayed and frequency-shifted response signal. At that time, the transponder can be identified based on the frequency shift amount. On the other hand, since the signal from the target detected by the normal search has no frequency shift, it can be identified and detected as the normal target.

  Here, the frequency shift amount may be set to, for example, 5 MHz for each transponder. For example, when identifying five transponders, each shift frequency can be set as follows. That is, Δf1 = 5 MHz, Δf2 = 10 MHz, Δf3 = 15 MHz, Δf4 = 20 MHz, and Δf5 = 25 MHz. The delay amount may be any value as long as the value is long enough to avoid radar blinds, and may be undefined.

[First Embodiment]
In the first embodiment, a description will be given of a phased array type radar apparatus in which a radar antenna has separate apertures for transmission and reception, and a DBF (Digital Beam Forming) method is applied to reception.
FIG. 2 is a functional block diagram illustrating an example of the radar device according to the first embodiment. In FIG. 2, the radar apparatus includes an antenna unit 101 and a signal processing unit 102 that processes a received signal based on a radio band signal captured by the antenna unit 101 in a digital domain.

  In FIG. 2, the radar controller 1 of the signal processing unit 102 gives the antenna control data to the antenna controller 2 of the antenna unit 101. In response to this, the antenna controller 2 gives the transmission beam direction to the transmission scanning controller 3 and the transmission timing to the transmitter 4. Further, the antenna controller 2 gives a reception beam pointing instruction to the reception scanning controller 7.

  The transmission scanning controller 3 transmits the element phase shift data to the transmission antenna 5. The transmitter 4 supplies a transmission chirp signal to the transmission antenna 5. The transmission antenna 5 has a plurality of antenna elements 51, a plurality of transmission units 52 for controlling the gain and phase of a transmission wave, and a transmission distribution circuit 53. Then, the transmitting antenna 5 radiates a chirp signal in the designated direction.

  The receiving antenna includes a plurality of (# 1 to #N) sub-arrays 6. Each sub-array 6 includes a plurality of antenna elements 61, a plurality of receiving units 62 for controlling the gain and phase of a received wave, and a receiving combining circuit 63. Have. Then, the received signals are captured in the sub-arrays 6 from # 1 to #N, and are respectively sub-array synthesized. The generated high-frequency signal is input to a plurality of receivers 8 (# 1 to #N) connected to each sub-array 6 (# 1 to #N). Here, the receiving beam directing direction is in accordance with the element phase shift data from the receiving scanning controller 7 controlled by the antenna controller 2.

  The receiver 8 inputs the frequency-converted and digital-converted received digital signal to the signal processor 10 of the signal processing unit 102 via the signal transmission interface 9. The signal processor 10 sends target detection data to the tracking controller 11. The tracking controller 11 calculates target position data, outputs the target position data to the display unit 12, and displays the target symbol on the display unit 12.

FIG. 3 is a functional block diagram showing an example of the receiver 8 shown in FIG. The receiver 8 includes an analog down converter 301 and a digital down converter 302.
The analog down-converter 301 frequency-converts the sub-array received signal into an intermediate frequency (IF) signal using the first image suppression filter 80, the first mixer 81, and the first local oscillator 85. Further, the second image suppression filter 82, the second mixer 83, and the second local oscillator 86 frequency-convert the IF signal into a video signal. The video signal has its alias removed by an anti-aliasing filter 84 and is input to the digital down converter 302. The anti-aliasing filter 84 is provided to perform analog / digital (A / D) conversion on the premise of undersampling in the digital down converter 302.

  The digital down-converter 302 inputs the digital reception signal digitally converted by the A / D converter 87 to a plurality of digital operation circuits 91. The digital operation circuit 91 multiplies a digital frequency signal generated by an NCO (Numerically Controlled Oscillator module) 90 and a digital reception signal by a digital multiplier 88 to shift the frequency of the digital reception signal. Thereafter, when the image signal generated by the digital multiplication is suppressed by the digital filter 89, desired frequency components of the I channel and the Q channel are extracted.

  The digital operation circuit 91 is provided according to the number of flying targets, that is, the number of transponders. In the embodiment, an M-system digital operation circuit 91 is provided, and the generated digital frequency of the NCO 90 is set to ω0 to ωM. The following is a series of digital operations.

  Assuming that the input signal is S, the input signal S can be expressed by the following equation (1), and the NCO signal can be expressed by the following equation (2).

  The I signal is represented by the following equation (3), and the Q signal is represented by the following equation (4).

  The image is represented by the following equation (5).

  When this image is suppressed by a digital filter, the frequency components of the I channel and the Q channel are extracted as shown in the following equation (6).

  The frequency shift amount is set according to the identification number of the transponder. For example, a total of six digital operation circuits 91 are provided, five systems for five transponders and one system for a normal target.

Δf1 = 5MHz, Δf2 = 10MHz, Δf3 = 15MHz, Δf4 = 20MHz, and Δf5 = 25MHz, when the antenna reception frequency _{F 0,} for example, a first local oscillator frequency _{F L1} at a second local oscillator frequency _{F L2,} A / D The IF frequency before conversion is frequency-converted to 60 MHz.

If the A / D conversion clock is selected to be 90 MHz, the digital signal frequency after digital conversion is 30 MHz. In this case, the NCO generation frequency is set as follows, for example.
ω ₀ = 2 × π × 30 MHz: normal target ω ₁ = 2 × π × 35 MHz (30 MHz + 5 MHz): transponder 1
ω ₂ = 2 × π × 40 MHz (30 MHz + 10 MHz): transponder 2
ω ₃ = 2 × π × 45 MHz (30 MHz + 15 MHz): transponder 3
ω ₄ = 2 × π × 50 MHz (30 MHz + 20 MHz): transponder 4
ω ₅ = 2 × π × 55 MHz (30 MHz + 25 MHz): transponder 5
From such a frequency setting and a series of calculations, a response signal and a normal target echo from each transponder can be separated for each digital calculation circuit 91. The digital operation circuit 91 can be realized by, for example, an FPGA (field-programmable gate array). In addition, it can be implemented by an ASIC (application specific integrated circuit).

  FIG. 4 is a functional block diagram showing an example of the signal processor 10 shown in FIG. In the signal processor 10, the received data, which is the output of the receiver 8 corresponding to each of the sorted sub-arrays, is input to the plurality of DBF formation processing units 401. The DBF formation processing unit 401 is a process realized by, for example, an arithmetic function of a processor, and is normally activated by the number of targets and the number of transponders 1 to M. In the embodiment, the DBF formation processing units 401 of the transponders 1 to 5 are activated. The output from each DBF formation processing unit 401 is divided into a normal target system and a transponder system and subjected to different signal detection processes.

  The normal target system detects a normal target via the pulse compression processing unit 402, the MTI processing unit 403, the CFAR processing unit 404, the detection processing unit 405, and the angle measurement processing unit 406. On the other hand, in the transponder system, the transponders 1 to M are detected via the pulse compression processing unit 402, the transponder detection processing unit 405, and the angle measurement processing unit 406.

  FIG. 5 is a functional block diagram showing an example of the transponder mounted on the flying target shown in FIG. The transponder receives a radar transmission wave in the RF band radiated from the transmission antenna 5 of the radar device, and removes an unnecessary wave component with the image suppression filter 501. Then, the local oscillator 503 and the mixer 502 convert the RF signal into an IF signal. This IF signal is input to the high-speed A / D converter 505 via the bandpass filter 504, converted into digital data, and stored in the memory 506.

  The data of the transmission wave stored in the memory 506 is read out under the control of the clock generation / control circuit 507 according to a preset delay amount, and is input to the digital I / Q filter 509.

  The digital I / Q filter 509 performs I / Q detection on the digital data and separates the digital data into an I signal and a Q signal. On the other hand, the NCO 508 generates a COS wave and a SIN wave corresponding to a preset frequency shift amount. The COS signal is multiplied by the multiplier 510 with the I signal output from the digital I / Q filter 509. Similarly, the SIN signal is multiplied by the Q signal in multiplier 510. The outputs of the multipliers 510 are added by the digital adder 511, thereby generating a response signal having a delay and a frequency shift.

  The generated response signal is converted into an analog signal by the high-speed D / A converter 512, an unnecessary wave component is removed by the image suppression filter 513, and then up-converted into an RF band by the local oscillator 503 and the mixer 514. After that, the signal is radiated to the space as a transponder response signal via the bandpass filter 515.

  Here, a system in which a high-speed A / D converter, a memory, and a high-speed D / A converter are combined and a received RF signal is stored in a memory and output with a delay is known as a digital RF memory.

  A series of digital operations is shown below. The I signal and the Q signal output from the digital I / Q filter 509 are represented by Expression (7), and the output signal of the NCO 508 is represented by Expression (8).

  Then, the I multiplied signal input to the digital adder 511 can be expressed by Expression (9), and the Q multiplied signal can be expressed by Expression (10).

  The addition signal input to the high-speed D / A converter 512 is represented by Expression (11).

In Expression (11), the ω _NCO frequency is a shift amount corresponding to the identification frequency.

The features of the radar device according to the first embodiment will be described below.
[1] The radar antenna 100 of the radar device is a phased array antenna having separate apertures for transmission and reception.
[2] A radar transmission wave from a phased array antenna is used as a fan beam, and a radio wave is radiated over a wide area in a short time.
[3] In the radar wave reception phase, a plurality of pencil beams are simultaneously formed by the DBF method.
[4] The reception band of the receiver of the radar device is set to several times to several tens times the transmission band according to the target number of flight.
[5] The transponder gives the received signal a frequency shift corresponding to the identification frequency of each flying target and a delay for avoiding transmission blind, and transmits the radar transmission wave after returning the frequency shift. Specifically, a digital RF memory and an NCO are used.
[6] The radar device receives a return signal from the transponder, and performs a digital operation circuit that performs frequency shift by a digital I / Q circuit after A / D conversion according to the number of normal targets and flying targets. Implement as many as you want.
[7] In the signal processing in the radar device, the transponder tracking and the skin track tracking are simultaneously performed by identifying the signal shifted in frequency for each target.

  According to the above configuration, in the first embodiment, the number of transmission waves from the radar device may be only one, and the frequency identification is performed while simultaneously receiving a plurality of reception frequencies, so that the normal target and the flying target are obtained. Can be distinguished. In other words, the search and tracking of the normal target and the tracking of the flying target by the transponder can both be achieved by the common transmission frequency.

  In the existing technology, when there are a plurality of flight targets (transponders) in addition to the normal targets, a plurality of local oscillators are provided and transmitted and received in a time-division manner with a switch in order to broaden the reception band on the radar side. Needed.

On the other hand, according to the first embodiment, it is possible to search, detect, and follow a target flying to the monitoring area, and at the same time, to follow a plurality of test flying targets by the transponder, a narrow band receiving system is required. It becomes possible by using That is, a single local oscillator provided in the radar apparatus can cope with target search, target tracking, and multiple transponder tracking. Furthermore, it is possible to reduce the number of high-frequency components related to transmission and reception, and to narrow the response reception band from each transponder.
Furthermore, in the first embodiment, the beamforming is performed by the DBF method for the transponder, so that the observation time can be reduced.

  Therefore, according to the first embodiment, it is possible to follow up while identifying a plurality of normal targets and a plurality of flying targets (transponder responses), and it is possible to shorten the search resources (time) and the following resources (time). Become like From these facts, according to the first embodiment, it is possible to provide a radar apparatus capable of preventing an increase in apparatus scale regardless of the number of targets to be followed.

[Second embodiment]
In the second embodiment, a description will be given of a phased array type radar apparatus in which a radar antenna has a common aperture for transmission and reception, and reception is performed by analog synthesis. As the transponder, a type using a so-called digital RF memory shown in FIG. 5 can be used.

  FIG. 6 is a functional block diagram illustrating an example of a radar device according to the second embodiment. In FIG. 6, parts that are common to FIG. 2 are given the same reference numerals, and only different parts will be described here. Also in the second embodiment, the environment shown in FIG. 1 is assumed.

  FIG. 6 is a functional block diagram illustrating an example of a radar device according to the second embodiment. In this radar apparatus, the transmission aperture and the reception aperture of the radar antenna 100 are shared, and a transmission pencil beam and a reception pencil beam are formed by analog synthesis. 6, the radar device includes an antenna unit 101 and a signal processing unit 102.

  In FIG. 6, the radar controller 1 of the signal processing unit 102 gives the antenna control data to the antenna controller 2 of the antenna unit 101. In response to this, the antenna controller 2 gives the scanning controller 30 the transmission beam directing direction, and gives the transmitter 4 transmission timing.

  The scanning controller 30 transmits the element phase shift data to the common transmitting / receiving antennas # 1 to #N. The transmitter 4 supplies the transmission chirp signal to the transmission / reception shared antenna 14 via the horizontal distribution / combination circuit 15. The transmission / reception shared antenna 14 includes a plurality of antenna elements 51, a plurality of transmission units 54 for controlling the gain and phase of a transmission wave, and a vertical distribution / combination circuit 55. Then, the transmission / reception shared antenna 14 radiates a chirp signal in the designated direction.

  The received signal is captured by the transmission / reception shared antennas # 1 to #N, and is input to the receiver 70 via the vertical distribution / combination circuit 55 and the horizontal distribution / combination circuit 15. The receiver 70 performs frequency conversion and digital conversion of the received signal. The converted received digital signal is input to the signal processor 19 of the signal processing unit 102 via the signal transmission interface 9. The signal processor 19 sends target detection data to the tracking controller 11. The tracking controller 11 calculates target position data, outputs the target position data to the display unit 12, and displays the target symbol on the display unit 12.

  The receiver 70 has a configuration similar to that of the receiver 8 shown in FIG. 3 and outputs a reception digital signal of a sum signal (Σ) and a difference signal (ΔAZ, ΔEL) related to a normal target and a transponder.

  FIG. 7 is a functional block diagram showing an example of the signal processor 19 shown in FIG. The signal processor 19 includes a normal target and a processing system for only the transponders 1 to M in accordance with the received data system which is the output of the receiver 70 that has been separated. As in the first embodiment, separate signal detection processing is performed for each of the normal target system and the transponder system.

  The normal target system detects a normal target via the pulse compression processing unit 402, the MTI processing unit 403, the CFAR processing unit 404, the detection processing unit 405, and the angle measurement processing unit 406. On the other hand, in the transponder system, the transponders 1 to M are detected via the pulse compression processing unit 402, the transponder detection processing unit 405, and the angle measurement processing unit 406.

The features of the radar device according to the second embodiment will be described below.
[8] The radar antenna 100 of the radar device is a phased array antenna having a common transmitting / receiving aperture.
[9] The transmission wave from the phased array antenna is defined as a pencil beam.
[10] In the reception phase of the radar device, a pencil beam is formed by analog synthesis.
[11] The reception band of the receiver of the radar device is set to several times to several tens times the transmission band according to the target number of flight.
[12] The transponder gives the received signal a frequency shift corresponding to the identification frequency for each flying target and a delay for avoiding transmission blind, and transmits the radar transmission wave after frequency-shifting and returning it. Specifically, a digital RF memory and an NCO are used.
[13] The radar device receives a return signal from the transponder and performs a digital operation circuit for performing a frequency shift by a digital I / Q circuit after A / D conversion according to the number of normal targets and flying targets. Implement as many as you want.
[14] In the signal processing in the radar device, the transponder tracking and the skin track tracking are simultaneously performed by identifying the signal shifted in frequency for each target.

  According to the above configuration, the number of transmission waves from the radar device may be only one, and it is possible to distinguish between a normal target and a flying target by performing frequency identification while simultaneously receiving a plurality of reception frequencies. Will be possible. In other words, the search and tracking of the normal target and the tracking of the flying target by the transponder can both be achieved by the common transmission frequency. Therefore, according to the second embodiment as well, it is possible to provide a radar apparatus capable of preventing an increase in apparatus scale regardless of the number of targets to be followed.

  In the embodiments, the term “processor” used in connection with a computer is, for example, a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a GPU (Graphics Processing Unit), or an ASIC (Application Specific Integrated Circuit). ), A simple programmable logic device (SPLD), a complex programmable logic device (CPLD), or a field programmable gate array (FPGA).

  The processor realizes a specific function based on the program by reading and executing the program stored in the memory. Instead of the memory, it is also possible to configure so that the program is directly incorporated in the circuit of the processor. In this case, the processor realizes its function by reading and executing a program incorporated in the circuit.

  While some embodiments have been described, these embodiments are presented by way of example only, and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.

  DESCRIPTION OF SYMBOLS 1 ... Radar controller, 2 ... Antenna controller, 3 ... Transmission scanning controller, 4 ... Transmitter, 5 ... Transmission antenna, 6 ... Subarray, 7 ... Reception scanning controller, 8 ... Receiver, 9 ... Signal transmission interface Reference numeral 10: signal processor, 11: tracking controller, 12: display unit, 14: transmission / reception shared antenna, 15: horizontal distribution / synthesis circuit, 19: signal processor, 30: scanning controller, 51: antenna element, 52 ... Transmission unit, 53 ... Transmission distribution circuit, 54 ... Transmission unit, 55 ... Vertical distribution / combination circuit, 61 ... Antenna element, 62 ... Reception unit, 63 ... Reception combination circuit, 70 ... Receiver, 80 ... First image Suppression filter, 81: first mixer, 82: second image suppression filter, 83: second mixer, 84: anti-alias filter, 85: first local oscillator, 86: second local oscillator, 87: A / D conversion Unit 88 digital multiplier 89 digital filter 91 digital operation circuit 100 radar antenna 101 antenna unit 102 signal processing unit 301 analog down converter 302 digital down converter 401 DBF Forming processing unit, 402: pulse compression processing unit, 403: MTI processing unit, 404: CFAR processing unit, 405: detection processing unit, 406: angle measurement processing unit, 501: image suppression filter, 502: mixer, 503: local oscillator , 504: bandpass filter, 505: high-speed A / D converter, 506: memory, 507: clock generation / control circuit, 509: digital I / Q filter, 510: multiplier, 511: digital adder, 512: high-speed D / A converter, 513 ... Image suppression filter, 514 ... Mixer, 515 ... Band filter Data.

Claims (5)

An antenna unit that captures a radio band signal in which an echo signal from a normal target and a response signal from a transponder are mixed,
A signal processing unit that processes a received signal based on the wireless band signal in a digital domain,
The antenna unit is
A local oscillator for generating a local frequency;
A converter for frequency-converting the radio band signal at the local frequency;
Digital conversion of the output of the converter, comprising a plurality of digital arithmetic circuits that respectively output digital data based on the frequency shift shown in the echo signal and the response signal,
The signal processing unit,
Based on the digital data, a beam forming processing unit that forms a reception beam corresponding to the normal target and the transponder,
A radar apparatus comprising: a detection processing unit that detects the normal target and the transponder from the formed reception beam.   2. The radar device according to claim 1, wherein the antenna unit includes a transmitting antenna that transmits a radar wave, and a receiving antenna that is formed in an opening different from the transmitting antenna and captures the radio band signal.   The radar device according to claim 2, wherein the transmitting antenna transmits the radar wave using a fan beam.   2. The radar device according to claim 1, wherein the antenna unit includes a transmitting antenna that transmits a radar wave, and a receiving antenna that is formed in a common opening with the transmitting antenna and captures the radio band signal. 3.   The radar device according to claim 4, wherein the transmitting antenna transmits the radar wave using a pencil beam.