JP2001091646A - Doppler radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To favorably maintain and improve velocity calculation accuracy even when a pulse width of a transmission wave is shortened. SOLUTION: In a prior system (a), a velocity calculation result from a reception signal is outputted as it is, but in this Doppler radar device (b) and (c), velocity calculations from the reception signal are closely performed and an averaged result of this is used as a Doppler velocity calculation result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a Doppler radar device that contributes to weather disaster prevention.

[0002]

2. Description of the Related Art As is well known, a Doppler radar device which contributes to weather disaster prevention such as down-burst / micro-burst detection at an airport and cell tracking in lightning prediction generally has a spatial length of 250 to 1000 in a distance direction.
m. The pulse width of the transmission wave is shorter than the required resolution due to the restriction on the average transmission power. Therefore, signal processing is performed at intervals longer than the space length of the transmission wave.

[0003] However, a received signal obtained from a transmission wave having a short pulse width has a low S / N ratio, so that the speed calculation accuracy is deteriorated. However, no effective means for solving this problem has been conventionally obtained.

[0004]

As described above, in the conventional Doppler radar apparatus, especially in the case of weather, the pulse width of the transmitted wave may be shortened due to the restriction of the average transmission power. And the S / N ratio becomes low,
There was a problem that the speed calculation accuracy deteriorated.

It is an object of the present invention to provide a Doppler radar apparatus which solves the above-mentioned problem and which can maintain and improve the speed calculation accuracy satisfactorily even if the pulse width of a transmission wave is shortened.

[0006]

In order to achieve the above object, a Doppler radar device according to the present invention transmits a transmission wave having a pulse width shorter than a required spatial resolution, and transmits a transmission wave having a pulse width shorter than the required spatial resolution. The Doppler velocity is calculated at a density higher than the required spatial resolution, and the average of the velocity is obtained by a range method.

Specifically, a transmitting means for transmitting a transmission wave having a pulse width shorter than a required spatial resolution to a space, and a receiving means for receiving a reflected wave of the transmission wave transmitted to the space by the transmitting means. For the output of the receiving means, a range corresponding to the pulse width of the transmission wave as a speed calculation unit,
A signal processing device for averaging the speed calculation results for the required spatial resolution.

That is, according to the above configuration, even if the calculation result in the speed calculation unit varies, uniform data can be obtained by the averaging process, thereby improving the accuracy of the Doppler speed calculation result. It becomes possible.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a configuration of a Doppler radar apparatus according to the present invention, in which an intermediate frequency signal having a frequency fi generated by a COHO oscillator 11 and a local oscillation signal having a frequency fLo generated by a local oscillator 12 are mixed. 13 to generate a transmission signal having a frequency f0.
Sent to The transmission signal input to the transmitter 14 is power-amplified by a power amplifier 141, and then sent to a klystron or magnetron modulator 142.
It is pulsed based on the repetitive transmission pulse from the high voltage modulation circuit 143. The transmission pulse signal generated by the transmitter 13 in this way is supplied to the antenna device 16 via the circulator 15 and sent out to space.

The transmission wave of the frequency f0 transmitted from the antenna device 16 returns upon hitting a target (raindrops or the like), but is accompanied by the Doppler frequency fd due to the movement of the target.

The received signal (frequency fr = f0 + fd) received by the antenna device 16 is amplified by the high-frequency amplifier 17 via the circulator 15, mixed with the local oscillation signal by the mixer 18, and converted into an intermediate frequency (frequency). fi +
fd), after being amplified by the intermediate frequency amplifier 19, mixed by the mixers 20 and 21 with the intermediate frequency signals (fi) having a phase difference of 90 ° with each other by the phase detector 22 to perform quadrature detection. The signal is sent to the signal processing device 23.
The signal processing device 25 generates a video signal from the quadrature detection signal during reception, obtains a Doppler speed, and performs a rainfall conversion process.

The processing contents of the signal processing device 23 which characterizes the present invention in the above configuration will be described.

As described above, a received signal obtained from a transmission wave having a short pulse width has a problem that the S / N ratio is low and the Doppler velocity calculation accuracy is poor. However, a shorter pulse width translates into a shorter space length, which can be an advantage by improving the processing scheme. Focusing on this point, the present invention is characterized in that the data is not thinned out, the Doppler velocity is calculated in units of the space length of the pulse width, and the accuracy is improved by averaging the Doppler velocity.

FIG. 2 is a processing block diagram of the present invention and a conventional Doppler velocity calculation method. In FIG. 2, the case of (a) without range averaging is a conventional calculation method, and the methods of (b) and (c) for performing range averaging are the present invention.

In the conventional method, the speed calculation result from the received signal is output as it is. However, in the present invention, the speed calculation from the received signal is performed densely, and the averaged result is used as the Doppler speed calculation result.

A specific description will be given with reference to FIG.

FIG. 3 shows an example of a comparison between the conventional system and the system of the present invention with respect to the Doppler velocity calculation unit with respect to the transmission pulse width.

FIG. 3A shows a conventional system in which a klystron type transmission tube is used. In this case, since the power efficiency is high, the transmission average power is not so limited, and the pulse width can be increased to increase the received signal strength. Therefore, the transmission pulse width is 2 μs
, The speed calculation unit is 2 μs (distance resolution 300
m) or more.

FIG. 3B shows a conventional system in which a magnetron type transmission tube is used. In this case, transmission is performed with a pulse width of 0.5 μs due to transmission power restrictions, but the speed calculation unit is 2 μs (distance resolution 300 m).
Or more, and even if data is obtained in units of 0.5 μs, the data will be thinned out.

FIG. 3C shows the method of the present invention, in which the transmission pulse width is 0.5 μs, the speed calculation unit is 0.5 μs, and as shown in FIG. Perform averaging. As a result, even if the calculation result in the speed calculation unit varies, uniform data can be obtained by the averaging process, whereby the accuracy of the Doppler speed calculation result can be improved.

FIG. 5 shows the result of calculating the Doppler velocity calculation accuracy by computer simulation under the conditions shown in FIG. In FIG. 5, the speed calculation accuracy (deviation from the true value) with respect to the average number of ranges has the following relationship. Sd (m) = Sd (1) / √m Here, Sd (m) is the speed calculation accuracy [m / s] when averaging the m range, and Sd (1) is the speed calculation accuracy [m when the range averaging is not performed. / S] and m is the average number of ranges.

The reason why the above equation is satisfied is that the probability distribution of the velocity calculated by the Doppler radar is a normal distribution centered on the true value. As described above, the Doppler speed is calculated densely in the distance direction and the range averaging is performed, thereby improving the speed calculation accuracy.

Therefore, according to the above configuration, even if the pulse width of the transmission wave is shortened, the speed calculation accuracy can be maintained and improved satisfactorily. In particular, even when a magnetron is used for the transmission tube, speed calculation accuracy equal to or higher than that of a klystron can be obtained.

[0025]

As described above, according to the present invention, it is possible to provide a Doppler radar device which can maintain and improve the speed calculation accuracy satisfactorily even if the pulse width of the transmission wave is shortened.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a Doppler radar device according to an embodiment of the present invention.

FIG. 2 is a processing block diagram showing a comparison between the present invention and a conventional Doppler velocity calculation method.

FIG. 3 is a diagram showing an example of a comparison between a conventional method and a method according to the present invention with respect to a Doppler velocity calculation unit with respect to a transmission pulse width.

FIG. 4 is a diagram showing conditions for calculating Doppler velocity calculation accuracy by computer simulation.

FIG. 5 is a view showing an example of a result of calculating Doppler velocity calculation accuracy by computer simulation under the conditions shown in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... COHO oscillator 12 ... Local oscillator 13 ... Mixer 14 ... Transmitter 141 ... Power amplifier 142 ... Modulator 143 ... High voltage modulation circuit 15 ... Circulator 16 ... Antenna device 17 ... High frequency amplifier 18 ... Mixer 19 ... Intermediate frequency amplifier 20 ... Mixer 21 ... Mixer 22 ... Phase detector 23 ... Signal processing device

Claims (2)

[Claims] 1. A transmission wave having a pulse width shorter than a required spatial resolution is transmitted, a Doppler velocity is calculated at a density higher than the required spatial resolution from a received signal of the reflected wave, and the average of the velocity is obtained by a range method. A Doppler radar device. 2. A transmitting means for transmitting a transmission wave having a pulse width shorter than a required spatial resolution to a space, a receiving means for receiving a reflected wave of the transmission wave transmitted to the space by the transmitting means, A Doppler radar device comprising: a signal processing device that averages a speed calculation result for a required spatial resolution using a range corresponding to a pulse width of the transmission wave as a speed calculation unit for an output of the means. .