JPH0627229A - Radar eqipment - Google Patents

Abstract

PURPOSE:To obtain a radar equipment for searching a target through spread spectrum method in which conversion rate of an A/D converter and operating load of a search signal processor are prevented from increasing when a target existing in a blind range is detected. CONSTITUTION:A modulator 6 receives a COHO(COHerent Oscillator) signal from a coherent oscillator 3 and spread codes from an I channel spread code generator 4 and a Q channel spread code generator 5 generating Q channel component shifting at a timing different from that of the I channel component and produces a transmission signal. An A/D converter 8 quantizes received signals detected through a phase detector 7. An I channel demodulator 9 and a Q channel demodulator 10 perform product sum operation on the received signals and spread codes thus carrying out demodulation processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device that spreads a spectrum when searching for the purpose of improving confidentiality and removing an interfering wave.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a conventional radar device. In the figure, 1 is an antenna for both transmission and reception, 2 is a transmission / reception switch for switching transmission / reception of the antenna 1, and 3 is COH.
A coherent oscillator that generates an O (COHerrent Oscillator) signal, 7 a phase detector that phase-detects the received signal, 8 an A / D converter that quantizes the phase-detected received signal, and 9 represents a quantized received signal. An I channel demodulator 10 that multiplies an I channel (Inphase CHANNEL) component by a spreading code is a Q channel (Quadratune CHAN) of a quantized received signal.
A N-channel (NEL) component by a spreading code, a Q-channel demodulator,
Reference numeral 11 is a search signal processor that detects a target from the received signal, 12 is a display that displays the search signal processing result, 13 is a modulator that generates a transmission signal from the COHO signal and the spread code, and 14 is a spread code. Is a spread code generator.

The operation of the conventional radar device will be described with reference to FIG. The spreading code output from the spreading code generator 14 takes a value of +1 to -1 when the transmission / reception switch 2 is in the transmitting state, and takes a value of 0 when the transmitting / receiving switch 2 is in the receiving state. In FIG. 5, assuming that the code unit time of the spread code is τ, the transmission time of the duplexer 2 is 7τ, the reception time of the duplexer 2 is 12τ, and the I channel and the Q channel have the same code array. The time chart of is shown. The transmission signal is the modulator 13
It is generated by multiplying the COHO signal by the spread code in the antenna and is radiated from the antenna 1 to the free space.

Here, FIG. 6 shows a spectrum of a transmission signal by the spread code of FIG. When the peak power of the transmission spectrum during non-modulation is 0 dB, the peak power of the transmission spectrum modulated by the spread code is suppressed by 7.4 dB. In the radar device, suppressing the peak power of the transmission spectrum during searching means reducing the risk of detection of the transmission signal, that is, improving the confidentiality. Further, by spreading the frequency component of the transmission signal over a wide band, when an interfering wave is received, the interfering wave component can be separated and removed on the frequency axis.

Next, the demodulation process will be described. 0.5
A transmission signal reflected by a target existing at a distance of rcτ [where c is the speed of light and r is an arbitrary real number] is received again from the antenna 1 after a delay of rτ. The received signal separated into the I channel component and the Q channel component by the phase detector 7 is A
It is quantized by the / D converter 8. The quantized received signal is an I channel demodulator 9 and a Q channel demodulator 1
In 0, the product sum operation is performed with the spread code delayed by kτ [where k is an integer obtained by rounding off the decimal point of r]. In addition, in FIG. 5, the envelopes of the signals received by being reflected by the target A existing at the distance of 4.5 cτ and the target B existing at the distance of 4,25 cτ, and the received signals after phase detection of the respective envelopes are shown.

Assuming that the sampling period of the A / D converter 8 is equal to the code unit time of the spread code, the detected received signal of the target A has peaks of +1 to -1 in both the I channel and the Q channel. In contrast to the sampling at the position, the received signal after detection of the target B has an instantaneous value of 0.
It is sampled at the position. In this case, it can be seen that the target A received signal is demodulated as desired, but the target B received signal is not demodulated. On the other hand, when sampling is performed twice per code unit time, the reception signal of the target B is also demodulated as desired, but the transfer rate of the data input to the search signal processor 11 is doubled, and the calculation load is also doubled. Increase. Generally, in the search radar device, there is a demand to reduce the calculation load of the signal processor as much as possible, and therefore, the detection of a target existing in a distance that cannot be demodulated [hereinafter referred to as a blind range] is sacrificed.

[0007]

In the radar apparatus as described above, the conversion speed of the A / D converter and the calculation load of the search signal processor increase in order to detect the target existing in the blind range. There was a point.

The present invention has been made to solve such a problem, and detects a target existing in the blind range without increasing the conversion speed of the A / D converter and the calculation load of the search signal processor. The purpose is to do.

[0009]

A radar device according to the present invention has a function of generating a spread code in which an I channel component and a Q channel component are displaced at different timings to modulate a transmission signal and demodulate a reception signal. It is a thing.

[0010]

By intentionally shifting the timing at which the I channel component and the Q channel component of the spread code are displaced, the blind range of the blind range can be increased without increasing the conversion speed of the A / D converter and the calculation load of the search signal processor. The target can be detected.

[0011]

【Example】

Example 1. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 to 3 and 7 to 12 are exactly the same as the above-mentioned conventional device. Reference numeral 4 is an I channel spreading code for generating an I channel component of the spreading code, 5 is a Q channel spreading code generator for generating a Q channel component of the spreading code, and 6 is a modulator for generating a transmission signal from the COHO signal and the spreading code. is there.

The operation of the radar device according to the present invention will be described with reference to FIG. The spreading codes output from the I-channel spreading code generator 4 and the Q-channel spreading code generator 5 are +1 to -1 when the transmission / reception switch 2 is in the transmitting state.
, Takes a value of 0 in the receiving state. Further, it is characterized in that the timings at which the I channel component and the Q channel component of the spread code are displaced are intentionally shifted.
In FIG. 2, the spread code unit time is τ, the transmission / reception switch 2 has a transmission time of 7τ, and the transmission / reception switch 2 has a reception time of 12.
A time chart is shown on the assumption that τ and the Q channel component of the spread code are displaced by 0.5τ after the I channel component. The transmission signal is generated by multiplying the COHO signal and the spread code in the modulator 6, and is radiated from the antenna 1 to the free space.

Here, FIG. 3 shows the spectrum of the transmission signal by the spreading code of FIG. When the peak power of the transmission spectrum during non-modulation is 0 dB, the peak power of the transmission spectrum modulated by the spread code is suppressed by 7.4 dB. Since the peak power of the transmission spectrum is suppressed to the same level as conventional radar equipment,
It can be seen that the features of improved confidentiality and separation of interfering waves are maintained in the radar device according to the present invention.

Next, the demodulation process will be described. 0.5
A transmission signal reflected by a target existing at a distance of rcτ [where c is the speed of light and r is an arbitrary real number] is received again from the antenna 1 after a delay of rτ. The received signal separated into the I channel component and the Q channel component by the phase detector 7 is A
It is quantized by the / D converter 8. The quantized received signal is an I channel demodulator 9 and a Q channel demodulator 1
0 and (k−0.5) τ [where k
Is an integer obtained by rounding off the part after r to the decimal point] and the product-sum operation is performed with the spreading code delayed. In addition, in FIG. 2, the distance is 4.5c.
The envelopes of the signals received by reflecting on the target A existing at τ and the target B existing at 4.25cτ and the received signals after phase detection of each are shown.

Assuming that the sampling period of the A / D converter 8 is equal to the code unit time of the spread code, the received signal after detection of the target A is sampled at the peak positions of +1 to -1 in the I channel. On the other hand, the Q channel is sampled at a position where the instantaneous value is zero. Goal B
The received signal after detection is sampled at a position where the instantaneous value is 0 on the I channel, while the + signal on the Q channel is +
Sampled at peak positions of 1 to -1. In this case, it can be seen that either the I channel or the Q channel is demodulated as desired, and there is no blind range as in the conventional radar device. That is, A
The target existing in the blind range can be detected without increasing the conversion speed of the / D converter 8 and the calculation load of the search signal processor 11.

[0016]

Since the present invention is constructed as described above, it has the following effects.

The target existing in the blind range can be detected without increasing the conversion speed of the A / D converter and the calculation load of the search signal processor.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a time chart of the radar device according to the present invention.

FIG. 3 is a diagram showing a spectrum of a transmission signal in the radar device of the present invention.

FIG. 4 is a block diagram showing a conventional radar device.

FIG. 5 is a time chart of a conventional radar device.

FIG. 6 is a diagram showing a spectrum of a transmission signal in a conventional radar device.

[Explanation of symbols]

 1 Antenna 2 Transmission / Reception Switcher 3 Coherent Oscillator 4 I Channel Spreading Code Generator 5 Q Channel Spreading Code Generator 6 Modulator 7 Phase Detector 8 A / D Converter 9 I Channel Demodulator 10 Q Channel Demodulator 11 Search Signal Processing Display 12 Display

Claims (1)

[Claims] 1. A transmission / reception common antenna, a transmission / reception switch for switching transmission / reception of this antenna, and COHO (COHer).
and a coherent oscillator for generating an ent Oscillator signal and an I channel (Inpha) of a spread code.
se CHANNEL) component and a spread channel Q channel (Quadr) that displaces at a different timing from the I channel component.
attune channel), a Q channel spreading code generator, a modulator that generates a transmission signal from the COHO signal and the spreading code, a phase detector that phase-detects the reception signal received by the antenna, and the phase detection A / D (Analog) that quantizes the received signal detected by the detector
g to Digital) converter, an I channel demodulator that multiplies the received signal quantized by this A / D converter by the I channel component and the Q channel component of the spread code, the Q channel demodulator, and the I channel demodulator described above. Device and a search signal processor for detecting a target from a received signal demodulated by a Q-channel demodulator.