JP2007170846A - Radar system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radar system which can detect velocity components with high precision by gaining the number of pulse hit without impairing coverage. <P>SOLUTION: The radar system transmits a plurality of signals and receives reflected echoes in one PRI by changing the center frequency of a radar pulse. This allows a plurality of reflected echoes from the same target to be received in one PRI. For example, in PRI1 reflected echoes with center frequencies of f0, f1 are received. In PRI2 reflected echoes with center frequencies of f0, f1, and f2 are received. By separating and processing these reflected echoes by center frequency, larger numbers of reception of reflected echoes from the same target can be acquired as compared to a conventional radar system. An increase in the number of reception leads to the integral of radar pulses, thereby improving performance in detecting the target. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radar apparatus such as a weather radar.

For example, as described in Non-Patent Document 1, in a pulse radar device, it is effective to increase a transmission pulse repetition frequency (PRF) in order to detect a target velocity component with high accuracy. However, there is a close relationship between the PRF and the radar coverage, that is, if the PRF is increased, the pulse interval (PRI) is shortened, so that the coverage is desperately narrowed. If the PRF is increased to improve the speed detection performance in this way, the radar coverage becomes narrower as a price.
Takashi Yoshida “Revised Radar Technology”, IEICE (1996)

As described above, in the existing radar apparatus, there is a conflicting requirement that the coverage is narrowed if an attempt is made to improve the speed component detection performance.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a radar apparatus capable of detecting a speed component with high accuracy without impairing the coverage.

  In order to achieve the above object, according to one aspect of the present invention, a transmitter that transmits a radar pulse, a receiver that receives a pulse echo based on the radar pulse and outputs a received signal, and processes the received signal A signal processing unit that obtains target information, and the transmission unit includes a transmission frequency variable unit that varies the center frequency of the radar pulse into a plurality within an assigned frequency band for each pulse repetition period, The reception unit includes separation means for separating pulse echoes based on radar pulses having different center frequencies for each of the center frequencies, and the signal processing unit uniformly processes reception signals based on the separated pulse echoes. The radar apparatus is characterized in that the target information is obtained.

  By taking such a means, a plurality of radar pulses having different frequencies are transmitted in one PRI. As a result, the number of pulse hits can be increased more than that of the existing radar apparatus, and by integrating the received signals, it is possible to improve the processing accuracy and the speed detection function. In addition, since it is not necessary to change the PRF of the transmission signal having a certain center frequency, the area of the coverage can be maintained as it is. Accordingly, it is possible to provide a radar apparatus that can detect a velocity component with high accuracy without impairing the coverage.

  The frequency band of the transmission signal is allocated to the radar apparatus according to its use / function (allocation frequency band), and the center frequency of the transmission signal is generated to be a certain frequency in the allocation frequency band. According to the present invention, the number of hits is detected by changing the center frequency of a transmission signal to be emitted by using a plurality of frequencies within the allocated frequency band for each transmission, and the speed component detection function is improved.

  A feature of the present invention is that it has a function of changing the transmission frequency of a radar pulse radiated into space by changing the center frequency and the frequency characteristics of the bandpass filter 11 each time a radar pulse is transmitted, and A feature is that a plurality of signals having different center frequencies are simultaneously and uniformly processed.

  According to the present invention, it is possible to provide a radar apparatus that can earn a large number of pulse hits without impairing the coverage and can detect a speed component with high accuracy.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a functional block diagram showing a radar apparatus according to the present invention. In FIG. 1, a transmission seed signal generator 13 sends a transmission seed signal in accordance with the timing given from the timing controller 7. This transmission seed signal is mixed with the signal sent from the local oscillator 8 by the mixer 12 and frequency-converted, and the image frequency component signal is removed by the band-pass filter 11 to extract only the signal of the desired frequency component. . After that, it is amplified by the amplifier 10, passes through the circulator 2, and then is radiated to the space via the antenna 1. Here, the oscillation frequency of the local oscillator 8 and the pass frequency band of the bandpass filter 11 are controlled by the frequency control unit 9.

  The echo signal reflected from the target is input from the antenna 1, passes through the circulator 2, and is then amplified by the amplifier 3. Thereafter, the signal is mixed with the signal transmitted from the local oscillator 8 in the mixer 4 and frequency-converted. The image frequency component signal is removed by the band-pass filter 5, and only the signal having the desired frequency component is input to the signal processing unit 6. Processed.

  FIG. 2 is a functional block diagram showing the signal processing unit 6 of FIG. The received signal input from the bandpass filter 5 of FIG. 1 is converted into a digital signal by the A / D converter 21 and then a signal having a desired center frequency is required by the digital filter 22, the digital filter 23, and the digital filter 24. The number is separated and extracted. The separated signals (center frequencies f0, f1, and f2, respectively) are detected by the detectors 25, 26, and 27, and the obtained reception levels are sequentially stored in the memory 28 in consideration of the transmission timing. The The stored signal is used uniformly for each PRI, and the data processing unit 29 generates processing data such as amplitude data and speed data.

  FIG. 3 is a diagram illustrating an example of a processing timing chart in the radar apparatus of FIG. 1. For each PRI, transmission signals having center frequencies f0, f1, and f2 are transmitted at a certain timing, and reflection echoes are received. At a certain point on the timing chart, reflected echoes having different distances and different center frequencies are simultaneously received. This is separated for each center frequency by the signal processing unit 6, and the reception timing is calculated from the known transmission timing.

  In an existing radar apparatus, a radar pulse is transmitted only once for each PRI (for example, only a transmission signal having a center frequency f0). That is, since only one type of transmission signal is transmitted / received for each PRI, the maximum number of hits can be obtained for the PRI, and the detection performance is limited.

  In contrast, in this embodiment, by changing the center frequency of the radar pulse, a plurality of signals are transmitted and a reflected echo is received in one PRI. That is, a plurality of reflected echoes from the same target can be received in one PRI. For example, in PRI1 of FIG. 3, reflected echoes of center frequencies f0 and f1 are received, and in PRI2, reflected echoes of center frequencies f0, f1 and f2 are received. Therefore, by separating and processing these reflected echoes for each center frequency, it is possible to acquire a larger number of received reflected echoes from the same target than existing radar devices. The increase in the number of receptions leads to the integration of radar pulses, which makes it possible to improve the target detection performance.

  Furthermore, an increase in the number of receptions of reflected echoes leads to an improvement in the speed observation performance of the reflector. This will be described with reference to FIG. FIG. 4 is a diagram in which FIG. 3 is separated and arranged for each center frequency. In the existing radar apparatus, the velocity component of the target is merely calculated based on the reflected echoes received by PRI1 and PRI2, but in this embodiment, PRI1 ′ and PRI1 ″ are between PRI1 and PRI2. It can exist as if the PRF has increased. Since the speed observation performance is proportional to the PRF, according to this embodiment, the speed observation performance can be improved. Moreover, since the PRI interval is not different from that of the existing radar apparatus, the radar coverage can be kept as it is. For these reasons, it is possible to provide a radar apparatus that can detect a velocity component with high accuracy without impairing the coverage.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

The functional block diagram which shows the radar apparatus which concerns on this invention. The functional block diagram which shows the signal processing part 6 of FIG. The figure which shows an example of the timing chart of the process in the radar apparatus of FIG. The figure which separated and arranged the timing chart of FIG. 3 for every center frequency.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Aerial line, 2 ... Circulator, 3 ... Amplifier, 4 ... Mixer, 5 ... Band pass filter, 6 ... Signal processing part, 7 ... Timing control part, 8 ... Local oscillator, 9 ... Frequency control part, 10 ... Amplifier, 11 DESCRIPTION OF SYMBOLS ... Band pass filter, 12 ... Mixer, 13 ... Transmission type signal generation part, 21 ... A / D conversion part, 22 ... Digital filter, 23 ... Digital filter, 24 ... Digital filter, 25 ... Detection part, 26 ... Detection part, 27 ... detection unit, 28 ... memory, 29 ... data processing unit

Claims (2)

A transmission unit that transmits a radar pulse; a reception unit that receives a pulse echo based on the radar pulse and outputs a reception signal; and a signal processing unit that processes the reception signal to obtain target information,
The transmission unit includes a transmission frequency variable means for varying the center frequency of the radar pulse in plural within an assigned frequency band for each pulse repetition period,
The receiving unit includes separation means for separating pulse echoes based on radar pulses having different center frequencies for each center frequency,
The radar apparatus according to claim 1, wherein the signal processing unit uniformly processes a received signal based on the separated pulse echo to obtain the target information. The transmission frequency varying means is
A bandpass filter for removing unnecessary components for each radar pulse having a different center frequency;
The radar apparatus according to claim 1, further comprising: a frequency control unit that switches and controls a pass frequency band of the band filter for each transmission of the radar pulse.

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