JP2553711B2 - Radar equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar apparatus in which a phased array antenna for transmission and a digital beamforming antenna capable of forming a multi-beam for reception are combined, and in particular, transmission pulse repetition. The present invention relates to a radar device capable of observing targets existing in a plurality of different directions within a cycle.

[Prior Art] FIG. 4 shows a conventional radar apparatus of this kind disclosed in
FIG. 1 is a block diagram showing a radar device disclosed in Japanese Patent Application Laid-Open No. 63-167287 and Japanese Patent Application Laid-Open No. 63-167288. In the figure, 101
Divides a transmission pulse, which is modulated and transmitted from an oscillating circuit (not shown), into an arbitrary number of sub-pulses, and each of the phase shifters of first to n-th receiving modules 201 to 20n described later.
This is a transmission pulse division / distribution circuit that distributes and outputs each to 2011, and the division into sub-pulses is performed based on target number information transmitted from a reception beam processing device (not shown) of the radar device. Reference numeral 102 denotes a transmission beam control circuit for separately setting and controlling the phase shift amount of each of the phase shifters 2011 of the first to n-th transmission / reception modules 201 to 20n described below for each of the divided sub-pulses. The setting of the phase amount is performed based on the target azimuth / distance information transmitted from the reception beam processing device (not shown).

The first to n-th transmission / reception modules 201 to 20n are disposed corresponding to the respective element antennas 301 to 30n of the array antenna 300, and transmit a transmission beam to a target (not shown) through each corresponding element antenna. It is a module that performs the radiation and the reception of reflected waves from targets in the radiation beam. These modules are, for example, in the case of the first transmission / reception module 201, the transmission beam control circuit corresponding to each subpulse of the subpulse train F ₁ added from the transmission pulse division / distribution circuit 101.
A phase shifter 2011 for performing phase processing in an amount corresponding to the command C ₁ applied from 102, a transmitting amplifier 2012 for amplifying the phase shift processing each sub-pulse was circulator (duplexer)
In 2013 etc., each amplified sub-pulse is supplied to the corresponding element antenna 301 and radiated to the target, and the reflected signal from the target received by the same element antenna 301 is reflected by its own module. Circulator 2013 taken in 201, receiver 2014 for phase-detecting the reflected signal (high-frequency signal) taken in and separating it into element I and element Q containing amplitude information and phase information, and this phase-detected received signal And an A / D converter 2015 that quantizes each of the elements I and Q and converts them into a digital signal. Digital signals (DI, DQ) converted in this way
It is sent to each distribution circuit 400 as the received data R ₁ to R _n of respective modules 201 to 20n.

The distribution circuit 400 is a circuit for distributing the reception data R _{1 to} R _n of each of the modules 201 to 20 _n into one set and distributing the set to an arbitrary number (m in this example).
R ₁ to R _n are respectively transmitted to the first to m beam forming circuit 501～50M.

These beam forming circuits 501 to 50m receive the received data R ₁
By controlling the amplitude and phase content to the desired each with to R _n, a circuit formed on each different receive beams, respectively the desired direction.

FIG. 5 shows another conventional example of this type of radar apparatus.
FIG. 1 is a block diagram showing a holographic radar disclosed in Japanese Patent Application Laid-Open No. 63-187180. While the conventional example shown in FIG. 4 uses an array antenna for both transmission and reception, this conventional example does not FIG. 1A shows a transmitting system, and FIG. 1B shows a receiving system. Referring to FIG.
Reference numeral 5 denotes a transmitter, 5 denotes a transmitter, 6 denotes a beam steering computer, 7 denotes a transmission antenna, and in correspondence with FIG.
The transmitter 5 corresponds to an oscillation circuit or the like and a transmission pulse division / distribution circuit 101, the beam steering calculator 6 corresponds to the transmission beam control circuit 102, and the transmission antenna 7 corresponds to the array antenna 300. I do. 4B, which shows a receiving system, 1 is a receiving antenna, 2 is a local oscillation distribution circuit, and 3 is a beam forming circuit. In correspondence with FIG. 4, the receiving antenna 1 is an array antenna 30.
At 0, the local distribution circuit 2 includes the first to nth transmission / reception modules 201.
~ 20n each receiver 2014, each A / D converter 2015 and distribution circuit 400
The beam forming circuit 3 includes a first to mth beam forming circuit 501.
Equivalent to ~ 50m.

As shown in FIG. 6 and FIG. 7, the radar device combining the phased array antenna for transmission and the digital beam forming antenna capable of forming multiple beams for reception as shown in FIG. 4 and FIG. , One transmit pulse equal to the number of receive beamforming subpulses
Divided into A, B, C, D, E and each target direction θ _A , θ _B , θ _C , θ _D , θ _E
To the non-transmission period T _F within the pulse repetition period.
By receiving the reflected wave from the target, it is possible to observe the target existing in a plurality of different directions within the pulse repetition period.

[Problems to be Solved by the Invention] The conventional radar apparatus of this type is configured as described above. However, in such a configuration, the target number that can be dealt with is limited to the number of reception beams. Even if the number of sub-pulses can be increased, the transmission pulse width becomes longer due to the increase in the number of sub-pulses, and during transmission, reception becomes impossible due to the effect of the output energy.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a radar device that can observe many targets without increasing the number of subpulses and can easily cope with short-range targets. And

[Means for Solving the Problem] A radar device according to the present invention is based on the Doppler frequency of each target obtained by processing each received beam output by a frequency analysis means, and the decimation number of the transmission pulse for each target. While obtaining the required number of pulses, thinning control means for adjusting the target direction for each pulse, and transmission timing control means for controlling the transmission timing of pulses corresponding to the required number of pulses from this thinning control means, The transmission beam control means for controlling the transmission beam in each target direction based on this timing and the target direction from the thinning control means is provided, and the center frequency is set based on the Doppler frequency for each target, and each reception beam output is set. Is provided with pre-processing means for limiting the signal bandwidth of the above and making the number of processed signal points uniform.

[Operation] In the present invention, the observation of the low speed target does not have to be performed every time, focusing on the point that the sub-pulses can be thinned according to the target speed, and based on the thinning number obtained from the Doppler frequency of each target by the thinning control means. After obtaining the required number of pulses after thinning and the target direction of the number of pulses adjusted accordingly, the transmission timing control means and the transmission beam control means control the transmission timing and the transmission direction of each pulse based on these. Therefore, many targets can be observed without increasing the number of subpulses. Further, by inputting each received beam output to the frequency analysis means through the preprocessing means for limiting the signal bandwidth based on the target Doppler frequency, the number of processed signals of the high speed target in the frequency analysis means is equal to that of the low speed target. The calculation load can be made uniform.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to the apparatus shown in FIG. 5, wherein 1 is a receiving antenna, 2 is a local oscillator, 3 is a beam forming circuit, and 4 is a mobile station. Phaser group, 5 is a transmitter, 6 is a beam steering computer,
Reference numeral 7 is a transmitting antenna, and 8 is provided for each output of each reception beam formed by the beam forming circuit 3. The output is subjected to frequency analysis by Fast Fourier Transform to obtain a target Doppler frequency (speed information). The fast Fourier transformer (FFT) 9 for detecting the number of transmission pulses is thinned out for each target (beam) using the calculation formula described later based on the Doppler frequency detected by each FFT8. Target for each pulse (beam) accordingly
A thinning-out number calculating circuit for adjusting the direction, a required pulse number calculating circuit 10 for calculating a required pulse number based on the thinning-out number for each target from the thinning-out number calculating circuit 9, and 11 corresponds to a transmission timing control means of the present application. The transmission timing generation circuit generates a transmission timing signal for controlling the transmission timing of the pulse corresponding to the required pulse number sent from the required pulse number calculation circuit 10. This timing signal is supplied to the transmitter 5. To control the timing of each pulse applied from the transmitter 5 to the phase shifter group 4,
It is also supplied to the beam steering computer 6 corresponding to the beam control means of the present application to control the timing of setting the phase shift amount of the phase shifter group 4 based on the target (beam) direction information from the thinning-out number calculation circuit 9. Further, 12 is a bandpass filter (BPF) whose center frequency is set according to the target Doppler frequency detected by each FFT 8, 13 is a resampling circuit for resampling the output of each BPF 12, 14 is beam forming It is a changeover switch that first inputs the output of each reception beam from the circuit 3 directly to the corresponding FFT 8 and then inputs it via the corresponding BPF 12 and resampling circuit 13 after the elapse of a time set by a timer or the like. The thinning-out number calculating circuit 9 and the required pulse number calculating circuit 10 constitute thinning-out control means 15 of the present application, and the BPF 12 and the resampling circuit 13 constitute pre-processing means 16.

In the radar device configured as described above, each changeover switch 14 is connected to the contact 14a side at the time of starting the observation, and the output of each reception beam formed by the beam forming circuit 3 is frequency-adjusted by the FFT 8. analysis to each beam target Doppler frequency (velocity information, i.e., the Doppler frequency f _d, the radial velocity v, when the transmission wavelength is lambda, a relationship of f _d = 2v / λ) that exists in the direction of the measurement Then, the center frequency of each BPF 12 is set based on the result. Further, the thinning-out number calculating circuit 9 calculates the thinning-out number for each target (beam) according to the measured Doppler frequency, and adjusts the target (beam) direction for each pulse after thinning. The required pulse number calculation circuit 10 calculates the required number of pulses from the thinning number for each beam obtained as described above, and sends the obtained required pulse number information to the transmission timing generation circuit 11. Based on this, the transmission timing generation circuit 11 generates a transmission timing signal as shown in FIG. The timing signal controls the transmitter 5 and also controls the beam steering computer 6 to which the target (beam) direction information adjusted as described above is given, and transfers the signal to the beam steering computer 6 for setting the transmission direction of each sub-pulse. The data transfer timing with the phaser group 4 is simultaneously controlled. That is, as shown in FIGS. 3 (a) to 3 (f), the high-speed targets A and C perform observation each time a pulse is transmitted, but the low-speed targets B, D, E and F A plurality of targets are observed with one sub-pulse by thinning out sub-pulses within a range that does not generate the ambiguity of the Doppler frequency according to the radial velocity. For example, subpulse numbers # 2 and #
4 is used to observe targets B and D when transmitting odd-numbered pulses, and targets E and F when transmitting even-numbered pulses.

As described above, by using the sub-pulse in a plurality of targets in a time-sharing manner according to the target radial speed, many targets can be observed without increasing the number of sub-pulses, and observation of a short-distance target becomes easy. For example, in the conventional example, the seventh
As shown in the figure, only 5 targets could be observed with 5 sub-pulses, but in the present embodiment, as shown in FIGS. You will observe the goal.

Where the target Doppler frequency in each beam is fd _i
Then, the sampling interval Δt required to prevent ambiguity is determined by the sampling theorem. Given in. Therefore, assuming that the pulse repetition period is T ₀ as shown in FIG. 2, this Doppler frequency fd _i
The decimation numbers n _i allowed for However, [] represents a Gauss symbol and represents the maximum integer that does not exceed the value in [].

Given in. The thinning-out number n _i indicates that the pulse is transmitted once per n _i times of transmission to the target.
From the decimation number n _i for each target direction, the target (beam) direction given to the beam steering computer 6 to share the pulse between the targets to be decimated is adjusted,
The required pulse number M given to the transmission timing generation circuit 11 is determined in the required pulse number calculation circuit 10 by the following equation.

However, {} represents the minimum value of the integers exceeding the value in {}.

By the way, when the thinning control as described above is performed, the observation time for each target is constant, but the sampling interval and the number of pulse hits change according to the Doppler frequency of the target, so that each received beam output depends on the target radial velocity. The FFT score of changes and the calculation load becomes unbalanced. This means that it is not possible to determine in advance which is high speed or low speed, and therefore it is necessary to provide an expensive FFT or other frequency analysis means capable of performing high speed processing for all received beam outputs. Therefore, in this embodiment, the BPF 12, the resampling circuit 13, and the changeover switch 14 are provided in front of each FFT 8. That is, in the second and subsequent observations, each changeover switch 14 is connected to the contact 14b side and the BPF 12 and the resampling circuit 13 are used to limit the signal bandwidth of the high-speed target, and then resampling is performed. Convert to a sampling rate equivalent to the slow target. As a result, the FFT score can be kept constant regardless of the target radial speed, and the calculation load can be made uniform. That is, the frequency analysis means such as FFT may be provided with similar performance which is not so high speed. As described above, reducing the sampling rate by the BPF and the resampling circuit is a well-known technique as signal preprocessing.

Although the FFT is used as the frequency analysis means for detecting the Doppler frequency from the output of each reception beam in the above embodiment, it may be based on MEM (Maximum Entropy Method). Further, in the above-described embodiment, the FFT is provided only for the thinning control, but the FFT may be inserted in the output of each reception beam to be used for the reception beam processing in the subsequent stage. Further, when a frequency analysis means such as an FFT is already used in the reception beam processing device, it can be used without newly providing it.

Further, although the thinning-out number calculating circuit 9 and the required pulse number calculating circuit 10 which constitute the thinning-out control means 12 can be realized by a combinational circuit of various arithmetic units for executing the above-mentioned arithmetic expressions, they must be executed by a program using a microprocessor. Is also possible. Further, the transmission timing generation circuit 11 and the beam steering computer 6 can be realized by a configuration similar to the conventional one except that the inputs are different.

Further, in the above embodiment, an example in which the present invention is applied to the one shown in FIG. 5 is shown, but the present invention can be similarly applied to the one shown in FIG. 4 in which an array antenna is used for both transmission and reception.

[Effects of the Invention] As described above, according to the present invention, the transmission pulse is thinned according to the Doppler frequency obtained by processing each reception beam output by the frequency analysis means, so that the number of sub-pulses is increased. Many targets can be observed without doing so, and it becomes easy to deal with short-range targets. Further, since each received beam output is configured to be input to the frequency analysis means via the preprocessing means for limiting the signal bandwidth based on the target Doppler frequency, the high speed target processed signal points in the frequency analysis means are set to low speed. It is possible to make it equal to the target, and there is an effect that the calculation load can be made uniform.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main structure of an embodiment of the present invention, FIGS. 2 and 3 are timing charts for explaining an operation of the embodiment, and FIG. 4 is a block showing a structure of a conventional example. FIGS. 5 (a) and 5 (b) are block diagrams showing the configurations of the transmission system and the reception system of another conventional example, and FIGS. 6 and 7 are timing charts for explaining the operation of the conventional example. is there. 1 is a receiving antenna, 2 is a local distribution circuit, 3 is a beam forming circuit, 4 is a phase shifter group, 5 is a transmitter, 6 is a beam steering computer (transmission beam control means), 7 is a transmitting antenna, and 8 is an FFT. (Frequency analysis means), 9 is a thinning-out number calculation circuit, 10 is a required pulse number calculation circuit, 11 is a transmission timing generation circuit (transmission timing control means), 12 is BPF, 13 is a resampling circuit, 14 is a changeover switch, 15 Is thinning control means, and 16 is preprocessing means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomomasa Kondo 5-1-1, Ofuna, Kamakura City, Kanagawa Sanryo Electric Co., Ltd. Information Electronics Laboratory (56) Reference JP-A-63-65391 (JP, A) JP-A-63-65390 (JP, A) JP-A-57-108780 (JP, A) JP-A-64-79683 (JP, A)

Claims (1)

(57) [Claims] 1. A phased array antenna is used for transmission, and a digital beam forming antenna capable of forming multi-beams is used for reception, and each of the transmission beams is generated by generating a pulse corresponding to a target number within a transmission pulse repetition period. Doppler frequency of each target obtained by processing each received beam output by frequency analysis means in a radar device that transmits in the target direction and receives reflected waves from the target when not transmitting within the pulse repetition period Based on the above, the thinning-out number of the transmission pulse is calculated for each target to obtain the required number of pulses, and the thinning-out control means for adjusting the target direction for each pulse and the pulse corresponding to the required number of pulses from the thinning-out control means Timing control means for controlling the transmission timing of, and this timing and the thinning control means And the transmission beam control means for controlling the transmission beam in each target direction based on the target direction from, and the center frequency is set based on the Doppler frequency for each target to limit the signal bandwidth of each reception beam output. A radar device comprising a pre-processing unit for equalizing the number of processed signals.