JPH1048329A - Radar transmitter/receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obviate the mutual correlation and prevent the mutual interference by providing one of the same chirp signal generating signal generating outputs to set the transmitting frequency LO to the lower side frequency for the transmitting signal of up-chirp and the other to set the LO to the upper side frequency of down-chirp for the transmitting signal. SOLUTION: The transmitting frequency LO of a local oscillator 9' is lowered such that a first radar transmitter/receiver can detect the frequency component within a region higher than the oscillation frequency of a local oscillator and a second radar transmitter/receiver can detect the frequency component within the lower region. Within a range in which the frequency is adjusted after the common local oscillator is produced, the first and second radar transmitter/ receiver uses common parts. A common pulse modulator 1 is used such that with respect to a first TRX, the station transmitted signal frequency in the lower side of the transmitting signal is used for the station transmitted signal and with respect to a second TRX, the station transmitted signal frequency in the lower side of the transmitting signal to equivalently set the first TRX to up-chirp and the second TRP to down-chirp so that the mutual interference is prevented by obviating the mutual correlation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a radar transmitting / receiving apparatus, and more particularly to a radar transmitting / receiving apparatus using a synthetic aperture antenna.

[0002]

2. Description of the Related Art Synthetic aperture radars are used as remote sensing means for acquiring various high-resolution microwave images of the earth's surface because they are not affected by weather day or night.

[0003] In a radar transmitting / receiving apparatus (synthetic aperture radar) using such a synthetic aperture antenna, high resolution can be obtained, so that the distribution of vegetation on the ground, the degree of deforestation, the degree of desertification, the soil moisture, the snow It provides important reference data for understanding the degree of marine oil pollution, degree of marine destruction, degree of sea ice distribution, and glacier fate. Furthermore, not only can we quickly grasp the current status of natural disasters such as earthquakes, volcanic eruptions, and floods,
It is also used for monitoring and countermeasures.

FIG. 2 shows a configuration diagram of an example of such a synthetic aperture radar. The radar transmitting / receiving apparatus shown in FIG. 2 has a so-called chirp modulation (Chirp Modulatio) in which the frequency changes linearly in order to apply linear frequency modulation.
n) An up-converter 2 which receives the oscillation frequency of the local oscillator 9 and the output of the chirp modulator 1 as inputs and increases the frequency, a band-pass filter 3 for band-limiting the output, and a micro-frequency converter having an increased frequency. An amplifier 4 for amplifying a wave and sending the amplified wave to an antenna 11;
An amplifier 5 for amplifying a microwave which is a received wave by
The output of the amplifier 5 and the output of the local oscillator 9 are input, a down converter 6 for lowering the frequency and facilitating the handling, a band pass filter 7 for limiting the output band, and an AGC (Automatic Gain Control) function And an amplifier 8 for keeping the output level constant, and a signal processing unit 10 for processing various signals.

The signal processing section 10 performs synchronous detection of the received input wave, lowers the frequency, and processes the signal.
At this time, a plurality of the same devices (in particular, a satellite or an airborne synthetic aperture radar transmitting / receiving device using a chirp signal) use a plurality of the same devices (here, the same configuration is indicated by a dash and shown below). There are many cases.

Here, since the spectrum of the transmission frequency is distributed to some extent above and below the local oscillators 9 and 9 ', the problem of mutual interference 12 exists in principle. In order to solve this problem, the above-mentioned first synthetic aperture radar transmission / reception apparatus and the second synthetic aperture radar transmission / reception apparatus having the same configuration and indicated by a dash are modulated and synchronized with each other. In addition, the bandpass filters 7, 7 'may be used, and further, the first synthetic aperture radar transmitting / receiving apparatus may be up-chirped, that is, the frequency may be increased with time, while the second synthetic aperture radar transmitting apparatus may be down-converted. A configuration in which distribution is performed during chirp, that is, during frequency down with the passage of time, is adopted to prevent mutual interference to some extent.

[0007]

However, in such a configuration, there is a fatal defect that it is necessary to synchronize modulation between the two synthetic aperture radar transmitting / receiving apparatuses.
For this reason, not only may the overall system configuration be complicated, but there is also a concern about an increase in weight and an increase in size.

[0008] Here, chirp modulation (Chirp Modulatio)
n) is a type of FM-CW radar, which is used to obtain an image signal by measuring the frequency proportional to the distance of the target object by linearly increasing and decreasing the frequency with time. You.

The radar apparatus disclosed in JP-A-2-129580 and JP-A-2-22586 has a plurality of pulsed radar antennas that use two kinds of synthesized signals whose frequencies are offset as transmission signals. Then, even if there is one type of frequency of the local oscillator, by changing the pulse compression modulation for the output signal of the transmission signal generator of the same frequency and passing the reception signal through a pulse compression filter corresponding to each frequency modulation expansion pulse, This pulse compression filter suppresses mixing of received signals between the antennas. In addition, the number of transmission signal generators and pulse modulation generators corresponding to each pulse is not used, and the combination can be suppressed by changing the combination. Performance can be maintained.

However, in such a configuration, it is indispensable to pass through a pulse compression filter, and linear frequency modulation, that is, chirp modulation (Chirp modulation) is required.
There is no mention of M).

The radar apparatus disclosed in Japanese Utility Model Laid-Open Publication No. Hei 5-6658 makes the difference between the transmission frequencies of the respective channels equal to an integral multiple of the transmission repetition frequency. Are combined to suppress each other's interference waves, but there is no mention of linear frequency modulation.

An object of the present invention is not only to prevent mutual interference, but also to eliminate the need for synchronizing modulation with each other, simplifying the overall configuration, and avoiding an increase in weight or an increase in radar transmission / reception. It is to provide a device.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a radar transmitting / receiving apparatus according to the present invention comprises: a radar transmitting / receiving apparatus having a local oscillator for both the other apparatus; The up-chirp signal set to the lower frequency with respect to the transmission signal frequency as the oscillation frequency of the transmission signal, and the other device sets the down-chirp set to the upper frequency with respect to the transmission signal frequency as the oscillation frequency of the local oscillator. A chirp signal is used.

Here, the one and the other devices have a common microwave circuit configuration. A radar transmitting / receiving apparatus according to another aspect of the present invention includes the one and the other apparatus, wherein the chirp modulator linearly modulates the frequency, the local oscillator, the modulation output of the chirp modulator, and the oscillation of the local oscillator. An up-converter to which an output is input, a first band-pass filter, a first amplifier for amplifying a transmission signal after passing through the first band-pass filter, and a transmission signal amplified by the first amplifier An antenna for transmitting to the air or underwater, a second amplifier for amplifying a received signal,
A down-converter to which a received signal amplified by the second amplifier and an oscillation output of the local oscillator are input; a second band-pass filter to which an output of the down-converter is input; A signal processing unit that obtains an image signal from a received signal that has passed through the filter. The frequency of the local oscillator is adjusted so that the oscillation frequency of the local oscillator is different from that of the other device.

[0015]

FIG. 1 is a block diagram showing the configuration of an embodiment of a radar transmitting / receiving apparatus according to the present invention. FIG.
In the embodiment, the radar transmitting / receiving apparatus of the present embodiment includes a first radar transmitting / receiving apparatus and a second radar transmitting / receiving apparatus.

As shown in the upper part of FIG. 1, the first radar transmitting / receiving apparatus includes a signal processing unit 10 for obtaining image data from an obtained received signal, and a so-called chirp modulation (linearly modulating frequency). Chirp Modulation) A chirp modulator 1 for obtaining an output, and an up converter 2 for increasing the frequency from the output of the modulator 1 and the output of the local oscillator 9
And a band-pass filter (BPF) 3 and an amplifier 4 for band-limiting and amplifying the output, an amplifier 5 for amplifying a signal received by the synthetic aperture antenna 11, and a frequency based on the output of the amplifier 5 and the output of the local oscillator 9. A down-converter 6 to be lowered and restored, a band-pass filter (BPF) 7,
And an amplifier 8 with AGC.

The second radar transmitting / receiving device (lower side) is indicated by common reference numerals since it is common to the above-mentioned first radar transmitting / receiving device. However, the local oscillator 9 'is slightly different from the local oscillator 9 of the first radar transmitting / receiving apparatus only in the oscillation frequency (LO), as shown in the lower part of FIG.

In FIG. 1, the first radar transmission / reception apparatus can detect a frequency component higher than the oscillation frequency of the local oscillator 9, but the second radar transmission / reception apparatus can detect a low frequency component. , The oscillation frequency (LO) of the local oscillator 9 'is lowered. Adjustment of the frequency is within the scope of making after making a common local oscillator. That is, there is an advantage that the first and second radar transmitting and receiving apparatuses can use common components.

The up-converter 2 has an oscillation frequency (L) of a local oscillator 9 of a lower side band.
O), and the amplifier converter 2 ′ is an upconverter using the oscillation frequency (LO) of the local oscillator 9 ′ of the upper side band. Note that the amplifier 8 has a function of making the output level of the received signal constant.

With such a configuration, the chirped pulse modulator and the like are shared, and the local oscillation signal of the LO is adjusted to be above or below the transmission signal, so that equivalently up-chirp, A synthetic aperture radar transmitting / receiving device (T) that can generate a down-chirp signal, eliminate signal correlation between devices, has a simple system configuration, and reduces weight.
RX).

Using a shared pulse modulator, a first TRX
, The local oscillation signal is transmitted to the lower side of the transmission signal, the second TRX
The first TRX is equivalently up-chirp and the second TRX is down-chirp by using the local signal frequency above the transmission signal to prevent mutual interference by eliminating the mutual correlation. doing.

[0022]

As described above, according to the radar transmitting / receiving apparatus of the present invention, the same chirp signal generation output is used to avoid mutual interference between the radar transmitting / receiving apparatuses (TRX).
One is up-chirp for the transmission signal with LO as the lower frequency, and the other is for the transmission signal with LO as the upper frequency and down-chirp, thereby eliminating mutual correlation, The above-mentioned problem is solved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a radar transmitting / receiving apparatus according to the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional radar transmitting / receiving apparatus.

[Explanation of symbols]

 1,1 'chirp modulator 2,2' upconverter 3,3 ', 7,7' bandpass filter 4,4 ', 5,5', 8,8 'amplifier 6,6' downconverter 10,10 ' Signal processing unit 11, 11 'Antenna 12 Mutual interference

Claims (4)

[Claims] 1. A radar transmitting / receiving apparatus comprising a local oscillator and a local oscillator, wherein said one apparatus includes an up-chirp set as an oscillation frequency of said local oscillator at a frequency lower than a transmission signal frequency. A radar transmission / reception apparatus, wherein the other apparatus uses a down-chirp signal set to an upper frequency with respect to the transmission signal frequency as an oscillation frequency of the local oscillator. 2. The radar transmitting / receiving apparatus according to claim 1, wherein said one and said other apparatuses have a common microwave circuit configuration. 3. An up-converter to which a chirp modulator for linearly modulating a frequency, a local oscillator, a modulation output of the chirp modulator, and an oscillation output of the local oscillator are input. A first band-pass filter, a first amplifier for amplifying the transmission signal after passing through the first band-pass filter, and a transmission signal amplified by the first amplifier for transmission into the air or water. An antenna, a second amplifier for amplifying a received signal, a downconverter to which a received signal amplified by the second amplifier and an oscillation output of the local oscillator are inputted, and an output of the downconverter to be inputted. A second bandpass filter,
The radar transmitting / receiving apparatus according to claim 1, further comprising: a signal processing unit that obtains an image signal from a reception signal that has passed through the second bandpass filter. 4. The oscillating frequency of the local oscillator is one of
4. The radar transmitting / receiving apparatus according to claim 3, wherein the other apparatus performs frequency adjustment differently.