JP2000275329A - Doppler radar apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a maximum measurable radius and to surely remove secondary echoes. SOLUTION: Local oscillation signals whose frequencies are different from each other are frequency-converted into transmission frequencies by an IF signal (4, 6), they are pulse-modulated (7), and they are power-amplified (8). One is converted into horizontally polarized waves, the other is converted into vertically polarized waves, they are changed over alternately at a transmission repetition cycle (9), and they are radiated to a space (10, 11), Respective echoes are captured, and they are divided into systems 15 to 18 used to extract the echo component of the horizontally polarized waves and systems 27 to 30 used to extract the echo component of the vertically polarized waves. A inear phase detection is executed regarding outputs of the respective systems (19 to 24, 31 to 35). A phase difference is compensated regarding linear phase detection outputs of the respective systems (25, 26, 36, 37). Therefore, a maximum observation radius RMAX is set at RMAX=c/fr [where fr represents a transmission repetition frequency and (c) represents the velocity of light].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in, for example, a weather radar for three-dimensionally grasping wind speed, rainfall, snowfall, and weather conditions, and in particular, observes a long distance while securing a maximum detection speed. Doppler radar device for a vehicle.

[0002]

2. Description of the Related Art A conventional weather radar uses a single transmission frequency, single polarization type Doppler radar device which does not control the phase of a transmission wave, and has a maximum detection speed VMAX and a maximum measurable radius RMAX. Is determined from the following equations (1) and (2).

VMAX = λ · fr / 4 (1) RMAX = c / (2 · fr) (2) where λ: transmission wavelength fr: transmission repetition frequency c: light speed Usually, rainfall or the like to be observed The transmission repetition frequency is set to about 1 kHz in order to target the meteorological particles. Therefore, the maximum measurable radius is about 150 km.

[0004] Here, when weather particles exist beyond the maximum measurable radius, a phenomenon occurs in which a signal is received as if it were an echo from a target within the maximum measurable radius (secondary echo). . This situation is shown in FIGS.

FIG. 4 shows a case where there is no echo beyond the maximum observation radius, and FIG. 5 shows a case where there is an echo beyond the maximum observation radius. That is, as shown in FIG. 4A, when the true echo has no echo beyond the maximum observation radius determined by the transmission repetition frequency, as shown in FIG. 4B, only the true echo component is included in the received signal. Appears. However, FIG.
As shown in FIG. 5, when a true echo has an echo farther than the maximum observation radius, as shown in FIG. 5B, the received signal mixes the echo as a secondary echo into an echo component within the maximum observation radius. Would.

Conventionally, therefore, a method has been used in which a radio wave is transmitted while the transmission repetition frequency is switched for each certain range, and the difference in the position where an echo appears when a signal is received is removed.

[0007]

However, if the method of switching the transmission repetition frequency is used as described above, the transmission repetition frequency is preferentially selected when observing the velocity component of the target weather particle. As a result, there is a disadvantage that the maximum measurable radius is suppressed to about 150 km. Further, when echoes are continuous in the radar beam direction, there is a disadvantage that it is impossible to remove the secondary echo mixed in the primary echo.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a Doppler radar device which solves the above-mentioned drawbacks and can surely remove a secondary echo while dramatically increasing the maximum measurable radius.

[0009]

In order to achieve the above object, a Doppler radar device according to the present invention is configured as follows.

(1) First and second frequencies different from each other
First and second local oscillators for generating a frequency signal of
A third local oscillator for generating an intermediate frequency signal for converting the first and second frequency signals to a transmission frequency;
The first and second frequency signals output from the first and second local oscillators are frequency-converted into transmission frequencies with intermediate frequency signals output from the third local oscillator, and pulse modulation is performed. After amplification, one is converted to horizontal polarization and the other is converted to vertical polarization, and transmission means for outputting alternately at a transmission repetition cycle, and horizontally and vertically polarized waves output from this means are radiated into space. An antenna device that captures each echo, and a system that captures the echo captured by the antenna device and extracts the horizontal-polarized echo component and a system that extracts the vertical-polarized echo component. Receiving means for performing linear phase detection on the output, and a phase difference compensation means for compensating the phase difference for the two systems of linear phase detection outputs obtained by the receiving means,
It is characterized in that the maximum observation radius RMAX is RMAX = c / fr, where fr: transmission repetition frequency c: light speed.

(2) In the configuration of (1), the transmission means includes a signal selection means for alternately selecting and outputting the first and second frequency signals in a transmission repetition cycle, and a frequency output from the switching circuit. Frequency conversion means for mixing the signal with an intermediate frequency signal output from the third local oscillator and converting the signal into a transmission frequency; pulse modulation means for performing pulse modulation on the frequency signal obtained by this means; Power amplifying means for power amplifying the output to generate a transmission pulse,
Among the transmission pulses output from this means, the transmission pulse based on the first frequency signal is converted into a horizontal polarization, and the transmission pulse based on the second frequency signal is converted into a vertical polarization, and the horizontal polarization and the vertical polarization are converted. And a polarization switching means for alternately outputting the same in a transmission repetition cycle.

(3) In the configuration of (2), the reception device mixes the horizontally and vertically polarized echo components captured by the antenna device with the output of the third oscillator, respectively, and And a phase detector for linearly phase-detecting the echo components of the horizontally polarized wave and the vertically polarized wave frequency-converted by the means, respectively, by the output of the third local oscillator. I do.

(4) In the configuration of (2) or (3), further, a clock generation means for mixing the outputs of the first and second local oscillators and extracting a low-frequency component thereof to generate a clock signal. And a control means for determining a transmission repetition cycle based on the clock signal generated by this means and controlling the signal selection means, the pulse modulation means, and the polarization switching means.

(5) In the configuration of (4), the control means further generates a sampling clock having a frequency which is an integral multiple of the transmission repetition period, and the phase difference compensating means is obtained by the receiving means. Each of the two phase detection outputs is converted into a digital signal based on a sampling clock generated by the control means.

[0015]

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

FIG. 1 shows the configuration of an embodiment of the Doppler radar apparatus according to the present invention, wherein 1 is a frequency (f1 -f).
IF), a first high-stable local oscillator for generating a first local oscillation signal having a frequency (f2 -fIF), and a second high-stable local oscillator for generating a second local oscillation signal having a frequency (f2-fIF). The first and second local oscillation signals generated by these local oscillators 1 and 2 are mixed by a mixer 12 and then mixed with a low-pass filter 1.
3 is supplied. This low-pass filter 13 is a mixer 1
The low frequency component fCLK (= | f1 -f2 |) is extracted from the output of the control circuit 2 and the output is supplied to the control circuit 14 and used as a timing signal.

Here, fCL is calculated from the signals of the local oscillators 1 and 2.
The purpose of generating K is to compensate for a phase difference generated in a round trip in a radio wave propagation path due to a difference in transmission frequency described later.

On the other hand, the first and second local oscillation signals output from the local oscillators 1 and 2 are supplied to a switching circuit 3. The switching circuit 3 switches and outputs the first and second local oscillation signals every pulse hit by a trigger signal from the control circuit 14, and the output is generated by the IF local oscillator 5 by the mixer 4. After being mixed with the IF signal, it is supplied to the high-pass filter 6. The high-pass filter 6 extracts a high-frequency component (f1 or f2) from the output of the mixer 4, and the output is supplied to a pin modulator 7.

The pin modulator 7 performs pulse modulation on the output signal of the high-pass filter 6 based on a trigger signal from the control circuit 14. The output of the pin modulator 7 is power-amplified by the transmission tube 8, and then the polarization switching circuit 9 Supplied to The polarization switching circuit 9 alternately outputs H (horizontal) polarization and V (vertical) polarization every pulse hit according to a trigger signal from the control circuit 14, and outputs an H polarization output (f1), V polarization output (f
2) is radiated as a transmission repetition pulse through the circulators 10 and 11 to a predetermined coverage area by a not-shown two-frequency shared antenna device.

The signal received by the antenna device is transmitted via the circulators 10 and 11 to the TR limiter 1.
5, 27. These TR limiters 15, 2
Numeral 7 limits large power input due to unnecessary radio waves. The respective outputs are amplified by high frequency amplifiers 16 and 28, respectively, and output to mixers 17 and 29 at the next stage.

The mixer 17 mixes a signal generated by the first local oscillator 1 and having a frequency of f 1 -f IF with a signal received from the high-frequency amplifier 16, and outputs an output of the filter 1.
8 is supplied. The filter 18 extracts the H polarization component from the input signal.
Are mixed with the fIF generated by the fIF oscillator 5 and the fIF whose phase is shifted by 90 degrees by the 90-degree shifter 19, whereby the quadrature detection signals IH and QH in the complex form are mixed.
Get. The output of each of the mixers 20, 21 is a filter 23, 2
After unnecessary components are removed in step 4, the signals are converted into digital signals by A / D (analog / digital) converters 25 and 26 and output to a signal processing circuit (not shown).

On the other hand, the mixer 29 includes the second local oscillator 2
Is mixed with the signal received from the high-frequency amplifier 28 at a frequency of f2 -fIF, and its output is supplied to a filter 30. The filter 30 extracts a V-polarized component from an input signal, and its output is
FIF generated by the fIF oscillator 5 and f-phase shifted by 90 degrees by the 90-degree shifter 19, respectively.
IF, thereby producing a complex form of quadrature detection signal I
V and QV are obtained. After the unnecessary components are removed from the outputs of the mixers 32 and 33 by the filters 34 and 35, they are converted into digital signals by A / D converters 36 and 37 and output to a signal processing circuit (not shown).

The A / D converters 25, 26, 36,
The conversion process at 37 is performed based on the sample clock n / fCLK generated by the control circuit 14.

The operation of the above configuration will be described below with reference to FIGS.

FIG. 2 shows transmission timings of H-polarized light and V-polarized light in the transmission system. In the control circuit 14, a clock fCLK (= | f1 -f) generated from the first and second local oscillation signals generated by the first and second local oscillators 1 and 2 is used.
2 |), a trigger signal is generated at the timing shown in FIG. This trigger signal is supplied to the switching circuit 3, the pin modulator 7, and the polarization switching circuit 9.

On the other hand, the first and second local oscillation signals generated by the first and second local oscillators 1 and 2 are selectively derived at the timing of the trigger signal by the switching circuit 3, respectively, and After being mixed with the IF signal generated by the oscillator 5, the signal is input to the high-pass filter 6, where the signal of the transmission frequency f1 or f2 is obtained.

This signal is supplied to the control circuit 14 by the pin modulator 7.
After being pulse-modulated based on the trigger signal from the transmitter, the power is amplified by the transmission tube 8, and the frequency f1 is
When the frequency is f 2, the light is transmitted to the space via the circulator 10 and an antenna device (not shown). Sent to FIG. 2B shows the transmission timing of the H polarization, and FIG. 2C shows the transmission timing of the V polarization.

The radio wave radiated from the antenna device reaches the meteorological particles, becomes an echo and is again captured by the antenna device.
It is input to circulators 10 and 11. Here, FIG.
As shown in (5), the V polarization is transmitted in the middle of the transmission timing of the H polarization and the H polarization is transmitted in the middle of the transmission timing of the V polarization. Therefore, the echo of the H-polarized transmission radio wave is input to the circulator 11, and the echo of the V-polarized transmission radio wave is input to the circulator 10. However, H polarization and V
Since the polarization planes are orthogonal to each other, the signals having different polarization planes are input after being attenuated by the degree of separation IH-V.

Thus, the input received signal is
TR limiter 1 for controlling large power input due to noise, etc.
After passing through 5 and 27, they are amplified by high frequency amplifiers 16 and 28, respectively, and output to mixers 17 and 29 at the next stage.

In the mixer 17 of the H polarization system, the frequency is f
It is mixed with the signal of 1-fIF. The components from the V polarization are also attenuated by the degree of separation IH-V and input to the mixer 17, so that the components are similarly mixed. However, since the frequency of the V-polarized input signal is f2, the output of the mixer 17 is distributed at a frequency different from the H-polarized component by fCLK.
Therefore, if the H polarization is extracted by the filter 18 at the subsequent stage using this, the degree of separation IH can be further increased.

Similarly, in the mixer 29 of the V polarization system, the signal is mixed with a signal having a frequency of f2-fIF. The component from the H polarization is also attenuated by the degree of separation IV-H to the mixer 29 and is similarly mixed. However, since the frequency of the H polarization input signal is f1, the output of the mixer 29 is
The V polarization component is distributed at a frequency different from fCLK. Therefore, if the V-polarized wave is extracted by the filter 30 at the subsequent stage, the degree of separation IV can be further increased.

The received signals obtained by the filters 18 and 30 are subjected to quadrature detection by mixers 20, 21, 32 and 33, respectively, and become complex signals.
After unnecessary waves are removed at 35, the A / D converters 25, 2
6, 36, and 37, and are converted into digital signals.

FIG. 3 shows a manner in which a signal farther than the maximum observation radius determined by the transmission repetition frequency is extracted by the above-described procedure. That is, the true echo is shown in FIG.
As shown in (a), the signal is received even if it is longer than the maximum observation radius determined by the transmission repetition frequency. Here, the transmission trigger timing has a period T (= 1/1, as shown in FIG. 3B).
(Transmission repetition frequency)). In contrast,
The received signal of the H-polarized wave receiving system is as shown in FIG. 3C, and the received signal of the V-polarized wave receiving system is as shown in FIG. 3D. Therefore, the echo observation start position is shown in Fig. 3.
3C, 3D (in FIG. 3C, 3T,
At the time of 5T,..., 2T, 4T, 6T,.
), It is possible to receive an echo within a radius approximately twice as large.

However, since the frequency of the transmitted transmission signal is different between the H-polarized wave and the V-polarized wave, the phase delay generated during the round trip on the radio wave propagation path is different. This is a serious problem for Doppler radar devices that attempt to observe Doppler frequency from received signals. Therefore, fCLK obtained by mixing the outputs of the first and second local oscillators 1 and 2 is frequency-divided by n in the control circuit 14, and the A / D converters 25 and 2 are used as sampling clocks.
6, 36, and 37 to sample the received signal.
Thus, a received signal can be captured at a position where the phase difference is an integral multiple of 2π, that is, at a position where the phase difference is 0. As a result, it is possible to compensate for the phase difference between the H-polarized signal and the V-polarized signal.

Therefore, in the Doppler radar device having the above-described configuration, the total degree of separation between the two receiving systems depends on the difference between the H and V polarizations switched at each pulse hit and the transmission frequency also switched at each pulse hit. Multiplied by the degree of separation. In particular, in an application for observing meteorological particles, the two receiving systems operate in a manner similar to that of effectively operating at the transmission repetition frequency fr / 2. Therefore, the maximum measurable radius is twice as large as the above-mentioned equation (2). In addition, since the two receiving systems operate in the same manner as operating at the transmission repetition frequency fr / 2 effectively,
The secondary echo can be almost completely removed.

In the circuit of FIG. 1, the case where the phase detection circuits 19 to 26 and 31 to 37 are constituted by analog circuits has been described.
Similar processing can be realized by using a digital IQ detection circuit that performs D conversion.

[0037]

As described above, according to the present invention, it is possible to provide a Doppler radar apparatus capable of reliably removing a secondary echo while dramatically increasing the maximum measurable radius.

[Brief description of the drawings]

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

FIG. 2 shows an H-polarized wave (f1) and a V-polarized wave (f2) of the embodiment.
FIG. 4 is a timing chart showing transmission timings of FIG.

FIG. 3 is a conceptual diagram showing a state in which a signal that is longer than a maximum observation radius is extracted in the embodiment.

FIG. 4 is a conceptual diagram showing a state of a received signal with respect to a true echo when there is no echo beyond a maximum observation radius in a conventional Doppler radar device.

FIG. 5 is a conceptual diagram showing a state of a received signal with respect to a true echo in a case where an echo is present beyond a maximum observation radius in a conventional Doppler radar apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st highly stable local oscillator 2 ... 2nd highly stable local oscillator 3 ... Switching circuit 4 ... Mixer 5 ... IF local oscillator 6 ... High-pass filter 7 ... Pin modulator 8 ... Transmission tube 9 ... Polarization switching circuit 10, 11: circulator 12: mixer 13: low-pass filter 14: control circuit 15, 27: TR limiter 16, 28: high-frequency amplifier 17, 29: mixer 18, 30 ... polarization component extraction filter 19, 31: 90 degrees Shifters 20, 21, 32, 33 ... Mixers 23, 24, 34, 35 ... Filters 25, 26, 36, 37 ... A / D converters

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J070 AB06 AC06 AD05 AD15 AD17 AE12 AE13 AH34 AH39 AH50 AJ04 AJ10 AK01 AK04 AK10 BA01

Claims (5)

[Claims] A first and a second local oscillator for generating first and second frequency signals having different frequencies from each other; and an intermediate frequency signal for converting the first and second frequency signals into a transmission frequency. And a third local oscillator for generating the first and second local oscillators, and transmitting an intermediate frequency signal output from the third local oscillator to the first and second frequency signals output from the first and second local oscillators, respectively. A transmission means for converting the frequency into a frequency, applying pulse modulation and amplifying the power, converting one into horizontal polarization and the other into vertical polarization, and outputting the same alternately at a transmission repetition cycle, and a horizontal polarization output from this means. An antenna device that radiates waves and vertically polarized waves into space and captures respective echoes; a system that captures echoes captured by the antenna device and extracts echo components of the horizontal polarization; A receiving unit for distributing to a system for extracting a co component and performing linear phase detection on an output of each system, and a phase difference compensating unit for compensating a phase difference for the two systems of linear phase detection outputs obtained by the receiving unit. A Doppler radar apparatus characterized in that the maximum observation radius RMAX is RMAX = c / fr, where fr: transmission repetition frequency c: light speed. 2. The signal processing apparatus according to claim 1, wherein said transmitting means includes a signal selecting means for alternately selecting and outputting said first and second frequency signals at a transmission repetition cycle; Frequency conversion means for mixing the intermediate frequency signal output from the device and converting it to a transmission frequency; pulse modulation means for performing pulse modulation on the frequency signal obtained by this means; And a power amplifying means for generating, from among the transmission pulses output from this means, a transmission pulse based on the first frequency signal is converted into a horizontally polarized wave, and a transmission pulse based on the second frequency signal is converted into a vertically polarized wave; 2. The Doppler radar device according to claim 1, further comprising: a polarization switching unit that alternately outputs the horizontal polarization and the vertical polarization at a transmission repetition cycle. 3. The frequency conversion means for mixing the horizontally and vertically polarized echo components captured by the antenna device with the output of the third oscillator to convert the echo components into an intermediate frequency. 3. The Doppler radar according to claim 2, further comprising: phase detection means for linearly detecting the echo components of the horizontally polarized wave and the vertically polarized wave frequency-converted by the means, respectively, based on the output of the third local oscillator. apparatus. 4. A clock generating means for mixing the outputs of the first and second local oscillators and extracting a low-frequency component thereof to generate a clock signal, based on the clock signal generated by the means. 4. The Doppler radar device according to claim 2, further comprising a control unit that determines a transmission repetition period and controls the signal selection unit, the pulse modulation unit, and the polarization switching unit. 5. The control unit further generates a sampling clock having a frequency that is an integral multiple of the transmission repetition period, and the phase difference compensating unit calculates two phase detection outputs obtained by the receiving unit. 5. The Doppler radar device according to claim 4, wherein said digital signal is converted into a digital signal based on a sampling clock generated by said control means.