JPH01112185A - Radar device with direction discriminating function - Google Patents

Abstract

PURPOSE:To accurately obtain direction and approach information on a target object by synthesizing a pattern in the projection quadrature of >=2 pseudo- random code signals and a reception quadrature which is switched to a high speed, and performing correlative processing and detecting a fine reflected signal from a target in the detection quadrature. CONSTITUTION:Antennas for transmission and reception positioned on diagonals are provided in pairs. A pattern for transmission has pseudo-random codes different from upper and lower (right and left) patterns. A reception pattern is discriminated by switching receiving antennas 13 and 14 by a microwave switch 19. Correlators 26-29 perform correlation with two kinds of the same codes as that of two kinds of pseudo-random codes used to modulate a sent signal, or a one-bit leading code and a one-bit leading code. In this case, if the output level of the correlator 28 rises in a period wherein the circuit 19 connects the antenna 13 to a demodulator 21, a target detection signal is outputted to the output side of a comparator 302 and the output terminal X3 of a decision device 30.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a direction identification function that detects a target by performing correlation processing on a detection signal of a reflected wave from a target using radio waves modulated with a pseudo-random code. The present invention relates to a radar device having:

[Prior art and problems to be solved by the invention]

Traditionally, as an active target detection device, target detection uses a single pseudo-random code signal to correlate the reflected signals from the target in all directions with the same transmitting and receiving antenna, and detects only when the target approaches. Radar devices are known. This is to detect when the distance to the target has become less than a predetermined value, in which case the direction of the target cannot be detected.

Signal waveforms in the signal correlation method generally used for target approach detection will be explained with reference to FIG. The continuous wave signal excited by the transmitter is phase modulated into one of two states, O and π, by a pseudorandom code symbol before being emitted from the antenna. The frequency of the signal reflected by the target changes due to the Doppler effect, but the received wave phase and amplitude are also influenced by the target distance.

This reflected signal is then received by an antenna and subjected to mixed homodyne detection with the unmodulated original signal. After passing through the receiver, the degree of correlation (phase shift by θ) between the received signal and the transmitted signal is determined, and a Doppler signal is extracted by a bandpass filter.

A conventional target detection system is shown in FIG. In the device shown in FIG.
The signal is modulated with a pseudorandom code generated from the source and then radiated to the outside via the omnidirectional transmitting/receiving antenna 1. The radio waves radiated to the outside are reflected by the target object and reach the circulator 4 via the antenna 1. The output of this circulator 4 is sent to the demodulator 3-2 to generate the radio frequency (
R, F) output is homodyne detected and the power divider 5
The output is divided into two parts. This distributed signal is the same code as the pseudo-random code generated from the pseudo-random code generator 7 in the first and second correlators 8-1 and 8-2, but with a 1-bit delay and a code that is 1-bit delayed.
Correlation is taken using a bit-advance code.

The signal from the correlator 8-1 outputs a correlated signal when the round trip distance of the radio wave to the target approaches within the propagation distance of 1 bit of the code, and the signal from the correlator 8-2 is always uncorrelated. Since these two signals are signals, the determiner 9
If the target is located within the set range and the target is reflecting radio waves, a detection signal will be output.

In this way, the conventional device can detect when the target approaches within the distance.

However, when trying to detect the approach of a target object in the air and the direction in which the target object exists using a radar device, conventional devices only detect when the target has approached within the distance, and cannot detect the direction of the target. The problem is that it is not possible.

SUMMARY OF THE INVENTION An object of the present invention is to enable a radar device to detect a target object by not only detecting that it has approached within a distance of the target, but also detecting the quadrant in which the target exists.

[Means for solving problems]

According to the present invention, two transmitting antennas and two receiving antennas are provided, and a switch is provided to generate a plurality of types of pseudo-random codes and alternately switch between the two receiving antennas. A plurality of correlators for detecting correlation with a received pseudorandom code are provided, a comparator is provided for comparing levels of correlation outputs of the plurality of correlators, and a switching unit is provided for switching the comparison output. A radar device having a direction identification function is provided.

〔Example〕

A radar device having a direction identification function as an embodiment of the present invention is shown in FIG.

FIG. 1 is constructed as follows. The antenna section includes a pair of transmitting antennas 11. ．． 12 and receiving antennas 13 and 14. The oscillation wave from the radio frequency oscillator 1-5 is
distributor] 6 to a pair of modulators 17 and 18, and the output modulated by an external input is sent to a transmitting antenna 11.
, 12.

The reception inputs from the pair of reception antennas 13 and 14 are sent together with the clock of a clock generator 20 to a microwave switching circuit 19 for switching, and the switching output is sent together with the output of a radio frequency oscillator 15 to a demodulator. The demodulated output of the demodulator 21 is sent to the power divider 2
2 and divided into 4 parts.

The oscillation output of the voltage controlled oscillator 23 is sent to first and second pseudorandom code generators 24 and 25, the first outputs are sent to the modulators 17 and 18, respectively, and the second outputs are sent to the correlator. 26 and 29, and the third outputs are sent to correlators 27 and 28, respectively. The outputs of the correlators 26-29 are sent to the determiner 30 via low-pass filters 31-34.

The determiner 30 includes two comparators 301 and 302 and two switches 303 and 304. The correlators 26 and 2
The outputs of 7 are sent to comparator 3 via filters 31 and 32, respectively.
01, are compared and output to switch 303, and the outputs of correlators 28 and 29 are sent to filters 33 and 34, respectively.
is input to the comparator 302 via the switch 3 and compared.
Output to 04. The output of the clock generator 2o is input to the first and second switches 303 and 304, and is input to the switches together with the outputs of the comparators 301 and 302, and the first switch 303 outputs The second switch 304 provides an output X 3 , X <.

In the device shown in FIG. 1, the radio frequency (RF) output from the oscillator 15 is divided into two by the distributor 16 and distributed, and then the modulator 17 generates a pseudo-random code generated by the first pseudo-random code generator 24. After being modulated, the signal is radiated upward from the transmitting antenna 11 to the outside. Also, the modulator 18
After being modulated with a pseudo-random code generated by the second pseudo-random code generator 25, the signal is radiated downward from the transmitting antenna 12 to the outside.

The radiated radio waves are reflected by the target object and received by the left receiving antenna 13 or the right receiving antenna 14, and after being alternately switched by the microwave switching circuit 19, the received radio waves are output from the oscillator 15 by the demodulator 21. The radio frequency output is used for homodyne detection and demodulation.

The homodyne-detected signal is transmitted to the power divider 22 by 4
A code delayed by the reflection time τ (see Fig. 2 (4)) from the reference pseudorandom code (the leftmost output of 24) that was distributed and used for radio frequency modulation in the correlator 26, and a code identical to the reference. Correlation is taken with the code (see FIG. 2 (2)) (second left output of 24) which is delayed by one bit.

Further, the correlator 27 takes a correlation with the 1-bit advance code (see FIG. 2 (3)) (third left output of 24).

Similarly, the correlator 28 calculates the correlation with the 1-bit delayed code generated by the pseudo-random code generator 25, and the correlator 28
One is to take the correlation with the 1-bit advance.

The outputs from the four correlators 26, 27, 28, and 29 are integrated through low-pass filters 31, 32, 33, and 34, respectively, and a determiner 30 determines the direction of the target object.

Next, the function of the correlator will be explained. For example, correlator 26
performs the multiplication of the two inputs via a balanced modulator. This 2
In terms of human power, the input from below is a pseudorandom signal, and the input from the left is a power divider output signal. The correlator output is a Doppler frequency analog signal if there is a correlation, and is a 0 signal (no signal) if there is no correlation.

Next, a method for detecting the area where a target object exists will be explained with reference to FIG.

Four antennas are installed at 90° intervals, and those located diagonally are made into pairs, and one of the two pairs is used as a transmitting antenna and the other is used as a receiving antenna. Among these, the transmission pattern is the dotted line portions 33 and 34 in FIG. 3(1), and this transmission pattern is always transmitted.

In order to distinguish whether there is a reflection for either the upper or lower pattern, the pseudorandom code is made different for the upper and lower (or left and right) patterns.

On the other hand, the reception pattern is 31 in Figure 3 (2).
, 32, and as with the transmission pattern, the receiving antennas 13 and 14 are connected to the microwave switch 19 in order to distinguish from the left or right (or upper or lower) pattern.
Identification is performed by switching.

Correlators 26, 27, 28, and 29 perform correlations with the two types of pseudorandom codes used to modulate the transmission signal, respectively, with the same code, but with a 1-bit delay and a 1-bit advance. At this time, based on the correlation signal from the correlator, the determination unit 30 performs multiplication and integral calculations on the two sets of signals to create four types of composite patterns (35, 3B, 37,
38) is obtained. For example, when a target approaches from the lower left and the round trip time of radio waves between the radar device according to the present invention and the target becomes less than 1 bit corresponding time, the radio waves emitted from the lower transmitting antenna 12 are used for modulation. Since there is a significant correlation between the pseudorandom code that was received and the code that is delayed by 1 bit from this code (generated by the pseudorandom code generator 25 and output to the correlator 28), the microwave switch circuit 19 During the period when the antenna 13 and the demodulator 21 are connected, the correlator 28
The output of is at a high level compared to the outputs of other correlators.

Therefore, during this period, a target detection signal is output from the comparator 302 in the determiner 30 and sent to the switch 304. This switch 304 synchronizes the output of the comparator 302 to the output terminal X3 or another output terminal X4 with the reception switching of the left and right reception antennas 13, 14 by a timing pulse signal generated by the clock generator 20. However, the target detection signal is switched by the microwave switch circuit 1.
Since the target detection signal appears at the output side of the comparator 302 only during the period when the signal is connected to the left receiving antenna 13, the target detection signal is output to the output terminal X3 of the determiner 30. Similarly, if the target approaches from the top left, it is X2, if it approaches from the top right, it is X, ,
A target detection signal is output from. The area where the target object exists can be confirmed.

Above and below the transmission pattern (transmission 33, 34) ((1
, ) figure〉, left and right sides of the reception pattern (31, 32) ((2
) figure) and composite patterns (35, 36, 37, 38)
(Figure (3)) was explained. It can also be transformed in three ways: up and down, left and right, and composite. For example, in the diagram (5), the upper and lower divisions are code 1 and code 2.
If the left and right divisions in figure (4) are the left antenna and the right antenna, then in the composite pattern, as shown in figure (6), X+, X2 . The outputs of x, .

〔Effect of the invention〕

According to the present invention, a pattern is synthesized between the projection quadrant of two or more pseudorandom code signals and a rapidly switched reception quadrant, and correlation processing is performed to detect a weak reflected signal of a target within the detection quadrant. Not only can you approach within the distance of an object, but you can also accurately obtain target direction information.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a radar device with a direction identification function as an embodiment of the present invention, Fig. 2 is a diagram of various modulation codes and output waveforms of a distributor in the present invention, and Fig. 3 is a target object in the present invention. Fig. 4 is a signal waveform diagram to explain the operation of target object detection using signal correlation, and Fig. 5 shows approach detection using the conventional method. FIG. 11, 12... transmitting antenna, 13, 14...
Receiving antenna, 15...R, F oscillator, 16...
・Distributor, 1.7.18...Modulator, 19...Microwave switching circuit, 20...Clock generator, 21...Demodulator, 22...Power divider, 23...・Voltage controlled oscillator, 24, 25...
- Pseudo-random code generator, 26-29...correlator, 30...determiner, 31-34...low-pass filter. (1) Transmission pattern (2) Figure 3 Figure 2

Claims (1)

[Scope of Claims] Two transmitting antennas and two receiving antennas are provided, and a switch is provided to generate a plurality of types of pseudo-random codes and alternately switch between the two receiving antennas, so that the transmitting pseudo-random code and the receiving antenna can be switched alternately. A plurality of correlators for detecting correlation with a pseudorandom code are provided, a comparator is provided for comparing levels of correlation outputs of the plurality of correlators, and a switching section is provided for switching the comparison outputs. Radar device with direction identification function.