JPH10197621A - Radar and signal receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar, e.g. a pulse radar, in which noise can be removed at the front end, i.e., the part of radar head. SOLUTION: The radar comprises means 10 for transmitting a transmission signal to the outside of the radar, means 25 for dividing an incident signal transmitted from the transmitting means 10 and reflected on an object into two, first and second receiving means 21a, 22a, 23a; 21b, 22b, 23b for receiving the divided incident signal respectively and outputting first and second receiving signals mixed with noise, and a multiplying means 26 for generating a receiving signal from which noise is removed by multiplying the first and second receiving signals mixed with noise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a radar device such as a laser radar device used as a berthing speed meter,
The present invention relates to a signal receiving device for configuring such a radar device and the like, and particularly to a radar device having improved performance by reducing noise and a signal receiving circuit.

[0002]

2. Description of the Related Art A sampling type berthing speed meter using a pulse laser radar is disclosed in Japanese Patent Publication No. 7-69423, Japanese Patent Publication No. 7-69427, and Japanese Patent Publication No. And so on. This sampling type berthing speedometer transmits a pulsed laser beam repeatedly at a fixed transmission cycle and accumulates the reflected pulses from the berthing ship, which is a reflector, by a smaller amount than the above transmission cycle. It is configured to receive the reflected pulse while extending the time axis by receiving a large number of times in the reception period that is gradually increased. This sampling type laser radar is capable of high-precision measurement by using a sharp laser pulse with a half-value width of several nanoseconds, but requires thousands of laser pulse transmission / reception for one point measurement. There is a problem that it takes time.

In order to construct a conventional pulse laser radar that does not depend on the sampling method in order to shorten the measurement time, how to reduce noise in securing the maximum measurable distance becomes a problem. Generally, in the field of signal processing, a method is known in which a logical product of signals appearing a plurality of times is taken to eliminate noise contained in these signals. That is, by creating a logical product of an apparent signal composed of a signal component and a noise component, only a noise component which is different from the signal component and has no regularity at the present time is removed.

[0004]

There are various problems that need to be solved when the above-described removal of noise components by creating a logical product is applied to a pulse laser radar.
First, since the time from transmitting the pulse signal to receiving the reflected pulse changes according to the position of the reflector,
The problem is how to store the reflected pulses received several times in the past.

[0005] The reflected pulse received a plurality of times is
If a configuration in which the data is converted into a digital signal or a frequency spectrum and stored in a memory can be adopted each time, there is no problem in the above-described data storage method. However, berthing speedometers and the like require the transmission and reception of sharp pulses with a half-value width of several nsec (frequency band: several tens of MHz) in order to achieve high detection accuracy of about several tens of centimeters. There are circumstances. Such a sharp pulse is directly transmitted to A / A without extending the time axis by the sampling method.
Conversion into a digital signal by D conversion or conversion into a frequency spectrum by fast Fourier transform or the like is difficult to realize in terms of processing speed.

For this reason, it is necessary to store past received signals using some delay circuit instead of a memory. When such a delay circuit is used, the pulse to be delayed is a sharp pulse having a half-value width of several nanoseconds, but the delay time becomes extremely long. That is, in a normal signal processing circuit, as the speed increases, the delay time is reduced to match this speed, but in a typical berthing speedometer,
If the maximum measurable distance is 200 meters, the round trip propagation distance to the reflector is 400 meters, twice this maximum distance, and the required delay time is 1.33 μs.

If a high-speed and large-delay circuit as described above is to be realized by a conventional delay circuit using lumped constants of LCs, as many as 1000 stages of cascade connection are required.
There is a problem that it is large and expensive. When a delay circuit having a distributed constant such as a coaxial cable is used, there is a problem that a length of about 160 meters is required even if the wavelength shortening effect of the relative dielectric constant is taken into consideration. If an ultrasonic delay line can be used, it is small and inexpensive, but it is difficult to realize high-frequency characteristics of about several tens of MHz with this ultrasonic delay line.

Under the circumstances described above, conventionally, in a radar device such as a berthing speedometer that transmits and receives a sharp pulse having a half-value width of several nanoseconds, a noise component is removed by creating a logical product at a front end stage. The method of doing
It has not been adopted to the inventor's knowledge. Instead of performing the noise removal processing at the front end, the distance varied by the noise is measured many times, and the statistical results are applied to these measurement results to indirectly reduce the noise generated at the front end. Back-end processing of removal has been employed.

However, the conventional noise removal by the statistical processing in the back-end requires a large amount of data to be processed, so that there is a problem that the processing is time-consuming. Accordingly, it is an object of the present invention to provide a radar device such as a laser radar device capable of removing noise in a portion of a radar head which is a front end.

[0010]

According to the present invention, there is provided a radar apparatus for transmitting a transmission signal to the outside of the apparatus, and an object among transmission signals transmitted from the transmission means. Signal dividing means for dividing the reflected incident signal into two, and first and second means for receiving each of the divided two incident signals and outputting first and second reception signals mixed with noise And multiplying means for generating and outputting a noise-removed reception signal by multiplying the first and second reception signals mixed with noise output from the first and second reception means. Have.

[0011]

According to a preferred embodiment of the present invention, the multiplying means binarizes the first and second received signals mixed with noise. And an AND circuit for creating a logical product of the binarized received signal. According to a radar apparatus according to another preferred embodiment of the present invention, the incident signal is a pulsed laser beam, the signal splitting means is a half mirror, and the receiving means is an avalanche photo.
It is composed of diodes.

[0012]

FIG. 1 is a block diagram showing the configuration of a laser radar head which is a front end portion of a berthing speedometer according to one embodiment of the present invention. This laser radar head includes a light transmitting unit 10, a light receiving unit 20, and a counter 30.

The light transmitting unit 10 includes a laser diode (LD)
11, laser diode drive circuit 12, light transmission lens 13
And a transmission synchronization signal generation circuit 14. Light receiving unit 2
0 denotes photoelectric conversion circuits 21a and 21b mainly composed of an avalanche photodiode (APD) and an amplification circuit 22.
a, 22b, voltage comparison circuits 23a, 23b, a light receiving lens 24, a half mirror 25, and an AND gate 26. As described above, the front-end portion of the light receiving unit 21 including the photoelectric conversion circuit, the amplification circuit, and the voltage comparison circuit has
The system is installed.

The transmission synchronizing signal generating circuit 13 has a frequency of 1 KH
Generates and outputs a square wave of z as a transmission synchronization signal. This transmission synchronization signal is supplied to the laser diode drive circuit 12. The laser diode drive circuit 12 generates a transmission trigger signal synchronized with the rising edge of the transmission synchronization signal, and drives the laser diode 11. The driven laser diode generates a sharp laser pulse having a half width of several nanoseconds. The laser pulse is transmitted to the ship in berthing operation while being focused by the light transmitting lens 14.

The laser pulse radiated from the light transmitting unit 10 and reflected by the ship in the berthing operation and propagated in the direction opposite to the outward path is incident on the light receiving unit and is almost equally divided by the half mirror. The light enters a first photoelectric conversion circuit 21a mainly composed of a photodiode, and the other enters a second photoelectric conversion circuit mainly composed of an avalanche photodiode. The laser pulses incident on the first and second photoelectric conversion circuits are converted into reception signals composed of sharp electric pulses having a half-value width of several nsec. These received signals are amplified by high-frequency and low-noise first and second amplifier circuits 22a and 22b, respectively, and supplied to one input terminal of the first and second voltage comparison circuits 23a and 23b.

First and second voltage comparing circuits 23a and 23b
A reference voltage generating circuit (not shown)
Supplies a constant reference voltage Vref. First
The second voltage comparison circuits 23a and 23b compare the outputs of the first and second amplification circuits 22a and 22b supplied to one input terminal with the reference voltage Vref supplied to the other input terminal, If the former is larger than the latter, the output rises to high, and if the former is less than the latter, the output falls to low, thereby receiving the analog output from each of the first and second amplifier circuits 22a and 22b. The signal is binarized.
The binary reception signal output from each of the first and second voltage comparison circuits 23a and 23b is a two-input AND gate 2
6 is supplied to each input terminal.

The waveform (A) in the waveform diagram of FIG. 2 is the output of the first voltage comparison circuit 23a. This output randomly changes between an on state and an off state based on a binarized reception signal component indicated by an upward arrow and shot noise generated inside the photoelectric conversion circuit 21a and the amplification circuit 22a in the preceding stage. And a transitional binarized noise component. Similarly, as shown in the waveform (B), the output of the second voltage comparison circuit 23b also includes a binarized reception signal component indicated by an upward arrow,
It consists of a binarized noise component that transitions between an on state and an off state irregularly based on shot noise generated inside the photoelectric conversion circuit 21a and the amplification circuit 22b in the preceding stage.

When the AND of the binarized reception signals shown in the waveforms (A) and (B) is calculated by the AND gate 26, the output signal has no regularity as shown in the waveform (C). The noises cancel each other out and disappear, and a waveform is obtained in which only the binarized received signal having the regularity at the time of origination remains. This is because two different photoelectric conversion circuits 21
The noise such as shot noise that occurs simultaneously inside each of the a and 21b includes one photoelectric conversion circuit 21a.
This is because there is no correlation as well as noise occurring at different points in (or 21b).

Referring again to FIG. 1, the counter 30 comprises:
Upon receiving a transmission trigger signal output from the laser diode drive circuit 12 at the start terminal, the counting operation is started,
When receiving the binarized reception signal after noise removal shown in the waveform (C) output from the AND gate 26 at the stop terminal, the counting operation is stopped.

The counting operation of the counter 30 is continued for a propagation time required for the laser pulse to reciprocate with the ship in berthing operation. That is, the counter 30 measures the required reciprocating propagation time τ of the laser pulse, and notifies this to a data processor (not shown). This data processor calculates the one-way propagation time τ / 2 by dividing the required round-trip propagation time τ of the laser pulse into two equal parts, and further divides this τ / 2 by the speed of light to obtain the berth. Detect the distance to the operating vessel. Further, the data processor detects the berthing speed of the berthing ship from the change speed of the distance to the berthing ship.

Although the present invention has been described above with reference to the case where the present invention is applied to a berthing speed meter, the present invention can be applied to a laser radar for a vehicle for collision prevention and the like.

Although the present invention has been described by taking the case of a laser radar for transmitting a laser pulse as an example, the present invention can be applied to a radar for transmitting a pulse of an electromagnetic wave.
When an electromagnetic wave is used, the received signal received by the antenna may be divided into two equal parts by a power divider and distributed to the receiver.

Further, the case of a radar apparatus for transmitting a laser beam or an electromagnetic wave beam and receiving a reflected wave has been exemplified. However, the present invention is applied to a receiving device that only receives an incident signal of a laser beam or an electromagnetic wave beam without transmitting a laser beam or an electromagnetic wave beam, a receiving unit of a wireless communication device, a GPS receiver, and the like. You can also.

[0024]

As described above in detail, the radar apparatus according to the present invention receives the incident signal reflected by the object and returned by dividing the incident signal substantially equally, thereby obtaining the first and second noise-containing signals. Since the received signal is generated and the received signal from which noise is removed is generated by multiplying the received signal, an ultra-high-speed D / A conversion circuit or a delay circuit with a large delay amount is used. Instead, noise can be removed at the front end stage in the radar head. As a result, compared with the conventional indirect denoising by statistical processing in the back end, a large number of target data is not required, and the processing time is greatly reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a laser radar head which is a front end portion of a berthing speedometer according to an embodiment of the present invention.

FIG. 2 is a waveform diagram illustrating the operation of the laser radar head of FIG.

[Explanation of symbols]

 10 Light transmission unit 11 Laser diode 12 Laser diode drive circuit 20 Light receiving unit 21a, 21b Photoelectric conversion circuit mainly composed of APD 22a, 22b Width circuit 23a, 23b Voltage comparison circuit 26 AND gate 30 Counter

Claims (6)

[Claims] A transmitting means for transmitting a transmission signal to the outside of the apparatus; and a signal dividing means for dividing an incident signal, which is reflected by an object, returns and enters, out of the transmission signal transmitted from the transmitting means. First and second receiving means for receiving each of the two divided incident signals and outputting first and second received signals mixed with noise; and output from the first and second receiving means. And a multiplication means for generating and outputting a reception signal from which noise has been removed by multiplying the first and second reception signals mixed with noise. 2. The multiplication unit according to claim 1, wherein the multiplication unit binarizes the first and second received signals mixed with the noise.
A laser device comprising: a value conversion circuit; and an AND circuit for forming a logical product of the binarized reception signal. 3. The method according to claim 1, wherein the incident signal is a pulsed laser beam, the signal dividing unit is a half mirror, and the receiving unit is an avalanche photodiode. Laser device. 4. A signal dividing means for dividing an incident signal into two, and first and second receiving means for receiving each of the divided incident signals and outputting first and second reception signals mixed with noise. Means, and a multiplication means for generating and outputting a reception signal from which noise has been removed by multiplying the first and second reception signals mixed with noise outputted from the first and second reception means. A signal receiving device characterized by the above-mentioned. 5. The multiplication unit according to claim 4, wherein the multiplication unit binarizes the first and second received signals mixed with the noise.
A signal receiving device comprising: a value conversion circuit; and an AND circuit that generates a logical product of the binarized reception signal. 6. The method according to claim 4, wherein the incident signal is a pulsed laser beam, the signal dividing unit is a half mirror, and the receiving unit is an avalanche photodiode. Signal receiving device.