JP3500580B2 - Radar equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device capable of observing with high range resolution.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional radar device.
"Introduction to Radar Syste" by Merrill I. Skolnik
ms ”2d ed., McGraw-Hill Book Co., New York, 19
FIG. 80 is a configuration diagram of a radar device based on the contents described in 80.

In FIG. 3, 1 is a trigger signal generator for generating a trigger signal according to a predetermined pulse repetition frequency, 3 is a coherent oscillator for outputting a continuous wave of an intermediate frequency, 4 is a mixer (A) for frequency conversion, 5 Is an amplifier (A) that amplifies a signal in the intermediate frequency band, 6 is a stabilized local oscillator that outputs a continuous wave of a radio frequency, 7 is a mixer (B) that performs frequency conversion, and 8 is a signal that amplifies the radio frequency band High output amplifier, 9 is a duplexer, 10 is an antenna, 1
1 is a mixer (C) for frequency conversion, 12 is an amplifier (B) for amplifying an intermediate frequency band signal, 13 is a mixer (D) for frequency conversion, and 14 is a range compression for pulse-compressing a received signal in the range direction. Reference numeral 15 is a display for displaying a reception signal pulse-compressed in the range direction as the antenna rotates, and reference numeral 17 is a chirp signal generator for generating a chirp signal.

Next, the operation will be described. The trigger signal generator 1 generates a trigger signal as shown in FIG. 4 based on the pulse repetition frequency fPRF. The chirp signal generator 17 generates a chirp signal (also referred to as a linear FM signal) shown in Expression 1 when k is a constant according to the trigger signal of the trigger signal generator 1. FIG. 5 shows the chirp signal waveform.

[0005]

[Equation 1]

However, in the equation 1, the first term on the right side is the equation 2
Τ is the pulse width of the chirp signal.

[0007]

[Equation 2]

In the coherent oscillator 3, the intermediate frequency is fI
If F, then the continuous signal s2 (t) shown in Equation 3 is generated.

[0009]

[Equation 3]

In the mixer (A) 4, the coherent oscillator 3
And the output of the chirp signal generator 17 are mixed,
The signal s3 (t) shown in Expression 4 is output and amplified by the amplifier (A) 5.

[0011]

[Equation 4]

In the stabilized local oscillator 6, the radio frequency is changed to fRF.
Then, the continuous signal s4 (t) shown in Formula 5 is generated.

[0013]

[Equation 5]

In the mixer (B) 7, after the output of the stabilized local oscillator 6 and the output of the amplifier (A) 5 are mixed, the signal is amplified by the high output amplifier 8 and the signal s5 (t) shown in Formula 6 is output. It However, in Expression 6, A0 represents the amplitude of the signal s5 (t) after being amplified by the amplifier (A) 5 and the high-power amplifier 8.

[0015]

[Equation 6]

The output s5 (t) of the high power amplifier 8 is radiated toward the target from the antenna 10 via the transmission / reception switch 9. The reflected wave reflected by the target passes through the antenna 10 and the duplexer 9 again, and then is mixed with the output s4 (t) of the stabilized local oscillator 6 and the mixer (C) 11 to obtain the signal s6 (t) shown in Formula 7. Become.
However, in the right-hand side of Equation 7, τD is the delay time based on the distance from the antenna 10 to the target, and A1 is the amplitude.

[0017]

[Equation 7]

The signal s6 (t) is amplified by the amplifier (B) 12, and then is mixed in the mixer (D) 13 by the coherent oscillator 3
Is mixed with the output s2 (t) to obtain the signal s7 (t) shown in Expression 8.
However, in Expression 8, A2 on the right side represents the amplitude of the signal s7 (t).

[0019]

[Equation 8]

In the range compressor 14, the mixer (D)
13 output s7 (t) and chirp signal generator 17 output s1 (t)
The correlation with and is calculated according to Equation 9, and s8 (t) is output. However, in Equation 9, * represents a complex conjugate and η is s1
It represents the time difference between the time waveform of (t) and the time waveform of s7 (t).
As shown in FIG. 6, s8 (t) has a waveform in which the pulse width is compressed to 1 / (kτ).

[0021]

[Equation 9]

An angle signal associated with the rotation of the antenna 10 is input from the antenna 10 to the display unit 15. Based on this angle signal, the output of the range compressor 14 is displayed in synchronization with the trigger signal from the trigger signal generator 1. To be done.

[0023]

Since the conventional radar device is constructed as described above, when the pulse repetition frequency becomes high, the s5 (t) radiated from the antenna 10 on the display 15 as shown in FIG. 7 is displayed. The echo due to the signal, the echo due to the s5 (t− (1 / fPRF)) signal emitted next, and the echo due to the s5 (t− (2 / fPRF)) signal emitted next are superimposed, so the range Range ambiguity occurs even when range compression is performed by the compressor 14, and the display 1
There was a problem that the image displayed in No. 5 became unclear.

The present invention has been made to solve the above problems, and an object thereof is to suppress the phenomenon of range ambiguity.

[0025]

A radar apparatus according to a first aspect of the present invention provides a trigger signal generator for outputting a trigger signal corresponding to a pulse repetition frequency, and a predetermined time width based on the output of the trigger signal generator. A random signal generator that generates a random signal and that generates a signal that is uncorrelated with the random signal generated based on the trigger signal generator at another time, and a coherent oscillator that outputs a continuous wave at an intermediate frequency. , A mixer (A) that mixes the output of the random signal generator and the output of the coherent oscillator, an amplifier (A) that amplifies the output of the mixer (A), and a stabilizer that outputs a continuous wave of a radio frequency A local oscillator, a mixer (B) for mixing the output of the stabilized local oscillator and the output of the amplifier (A), and a high amplifier for amplifying the output of the mixer (B). Force amplifier, a transmission / reception switch connected to the high-power amplifier, an antenna connected to the transmission / reception switch, a reflected wave from the target received by the antenna and passed through the transmission / reception switch, and the stabilizing local portion. A mixer (C) for mixing the output of the oscillator, an amplifier (B) for amplifying the output of the mixer (C), a mixer (D) for mixing the output of the coherent oscillator and the output of the amplifier (B), A range compressor for calculating the correlation between the output of the mixer (D) and the output of the random signal generator, and an angle signal accompanying the rotation of the antenna are input from the antenna and generated by the trigger signal generator. It is provided with a display for displaying the output of the range compressor in synchronization with the trigger signal.

The radar device according to the second aspect of the present invention generates a trigger signal generator that outputs a trigger signal corresponding to the pulse repetition frequency, and generates a random signal over a predetermined time width based on the output of the trigger signal generator. , And a random signal generator that generates a signal that is uncorrelated with the random signal generated based on the trigger signal generator at other times, a coherent oscillator that outputs a continuous wave of an intermediate frequency, and the random signal generator. A mixer (A) that mixes the output of the mixer with the output of the coherent oscillator, an amplifier (A) that amplifies the output of the mixer (A), a stabilized local oscillator that outputs a continuous wave of radio frequency, and A mixer (B) for mixing the output of the stabilized local oscillator and the output of the amplifier (A), and a high-power amplifier for amplifying the output of the mixer (B) A duplexer connected to the high-power amplifier, an antenna connected to the duplexer, a reflected wave from the target received by the antenna and passed through the duplexer, and an output of the stabilized local oscillator. A mixer (C) for mixing, an amplifier (B) for amplifying the output of the mixer (C), a mixer (D) for mixing the output of the coherent oscillator and the output of the amplifier (B), and the mixer (D). ) Output, the correlation between the phase compensator that compensates the phase change due to the temporal change of the distance from the antenna to the target, and the correlation between the output of the phase compensator and the output of the random signal generator is calculated. Range compressor, an azimuth compressor for compressing in the azimuth direction based on the output of the range compressor, and the azimuth pressure in synchronization with the trigger signal generated by the trigger signal generator. Those having a display for displaying the output of the vessel.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 is a block diagram showing a first embodiment of the present invention, in which 1 is a trigger signal generator which outputs a trigger signal corresponding to a pulse repetition frequency, and 2 is based on the output of the trigger signal generator 1. A random signal generator for generating a random signal over a predetermined time width τ, and a signal uncorrelated with the random signal generated based on the trigger signal generator 1 at another time, 3 is an intermediate frequency , A coherent oscillator that outputs a continuous wave of
Mixer (A) for mixing the output of the coherent oscillator 3 with an output of the amplifier (A) for amplifying the output of the mixer (A) 4, a stabilized local oscillator 6 for outputting a continuous wave of a radio frequency, 7 is a mixer (B) for mixing the output of the stabilized local oscillator 6 and the output of the amplifier (A) 5, 8 is a high output amplifier for amplifying the output of the mixer (B) 7, 9
Is a transmission / reception switch connected to the high output amplifier 8, 10 is an antenna connected to the transmission / reception switch 9, 11 is received by the antenna 10, and the reflected wave from the target passing through the transmission / reception switch 9 and the above A mixer (C) that mixes the outputs of the stabilized local oscillator 6, an amplifier (B) that amplifies the output of the mixer (C) 11, and a mixer 13 that amplifies the output of the mixer (C) 11.
A mixer (D) for mixing the output of the amplifier (B) 12 with an output of the amplifier (B) 12, a range compressor 14 for calculating the correlation between the output of the mixer (D) 13 and the output of the random signal generator 2,
Reference numeral 15 is a display for displaying an output of the range compressor in synchronization with a trigger signal generated by the trigger signal generator 1 from an angle signal input from the antenna 10 in accordance with the rotation of the antenna 10.

Next, the operation will be described. First, the trigger signal generator 1 generates a trigger signal at a pulse repetition frequency of fPRF as shown in FIG. In addition, as shown in FIG. 8, the random signal generator 2 is synchronized with the trigger signal.
A random signal with pulse width τ is generated. This random signal consists of uncorrelated random numbers for each τ0, such as a Gaussian random number, a uniform random number, or a value such that 1 or -1 appears at random according to τ0 that satisfies τ0 << τ . Such a random signal is generated every 1 / fPRF, but it is assumed that there is no correlation between the random signals.

FIG. 9 shows, as an example, a random signal that is zero-ordered and held in the interval of τ0 centered on the random number generated every τ0. The spectrum of this random signal in the time domain is shown in FIG.

As another example, FIG. 11 shows a random signal in which each section of τ0 is weighted around a random number generated for each τ0. If distributions such as Hanning, Hamming, and Taylor are used for this weighting, the spectrum shown in FIG. 11 is obtained, and the side lobe level of the spectrum shown in FIG. 10 is -13.2 dB.
It is possible to set A lower than that of.

Equation 10 shows a general random signal. However, if N = [τ / τ0] and N is an even number, then Equation 10
, Rand1 (n) is the value of the n-th random number among (2N + 1) random numbers, and w (t) is the waveform held in the 0th order of τ0 or the waiting waveform centered on the random number generated every τ0. . Δ (t) is the Dirac delta function.

[0032]

[Equation 10]

In the equation 10, the symbol before w (t) is an arithmetic symbol representing the convolution integral.
Is defined by

[0034]

[Equation 11]

Further, t = nτ0 (n = -N / 2, ..., -1, 0,
In the case of considering a function rand2 (n) in which the value of +1 or -1 appears randomly in (1, ..., N / 2), s9
Instead of (t), it becomes s10 (t) shown in Expression 12.

[0036]

[Equation 12]

[Mathematical formula-see original document] However, sig (t) in the equation 12 is expressed by the equation 13, and is a function in which the sine wave of the frequency fsig lasts in the interval of τ0.

[0038]

[Equation 13]

If s10 (t) is shown as an example in FIG.
It becomes 3.

The coherent oscillator 3 generates a continuous signal s2 (t) having the intermediate frequency fIF shown in Formula 3.

In the mixer (A) 4, the coherent oscillator 3
Output and the output of random signal generator 2 s9 (t) or s10
(t) is mixed and the signal s11 (t) shown in equation 14 is output,
It is amplified by the amplifier (A) 5.

[0042]

[Equation 14]

The stabilized local oscillator 6 generates a continuous signal s4 (t) of the radio frequency fRF shown in equation (5).

In the mixer (B) 7, after the output of the stabilized local oscillator 6 and the output of the amplifier (A) 5 are mixed, the signal is amplified by the high power amplifier 8 and the signal s12 (t) shown in the equation 15 is output. It However, in Expression 15, A0 represents the amplitude of the signal s12 (t) after being amplified by the amplifier (A) 5 and the high-power amplifier 8.

[0045]

[Equation 15]

The output s12 (t) of the high-power amplifier 8 is radiated from the antenna 10 toward the target through the transmission / reception switch 9. The reflected wave reflected by the target passes through the antenna 10 and the duplexer 9 again, and then is mixed with the output s4 (t) of the stabilized local oscillator 6 by the mixer (C) 11 to obtain the signal s13 (t) shown in Formula 16. Becomes However, on the right side of Equation 16, τD is the antenna 10
The delay time based on the distance from the target to the target, A1 is the amplitude.

[0047]

[Equation 16]

The signal s13 (t) is amplified by the amplifier (B) 12, and then is mixed in the mixer (D) 13 by the coherent oscillator 3
Is mixed with the output s2 (t) to obtain the signal s14 (t) shown in Expression 17. However, in Expression 17, A2 on the right side represents the amplitude of the signal s14 (t).

[0049]

[Equation 17]

In the range compressor 14, the mixer (D)
13 output s14 (t) and random signal generator 2 output s9
The correlation with (t) or s10 (t) is calculated according to Equation 18, and s15 (η) is output. However, in Equation 18,
* Represents a complex conjugate, and η is the time difference between the time waveform of s9 (t) and s14 (t), or the time waveform of s10 (t) and s14.
It represents the time lag from the time waveform of (t).

[0051]

[Equation 18]

In the display unit 15, the angle signal accompanying the rotation of the antenna 10 is input from the antenna 10, and the range compressor 14 is synchronized with the trigger signal generated by the trigger signal 1.
The output of is displayed.

Embodiment 2. 2 is a block diagram showing a second embodiment of the present invention, in which 18 is an antenna 1
A phase compensator for compensating for a phase change due to a temporal change in the distance from 0 to a target, 16 is an azimuth compressor for compressing in the azimuth direction based on the output of the range compressor,
Reference numeral 15 is a display that is displayed based on the outputs of the azimuth compressor 16 and the trigger signal generator 1, and the others are the same as in FIG.

Next, the operation will be described. From the trigger signal generator 1 and the random signal generator 2 to the mixer (D) 1
The processing up to 3 is the same as that of the first embodiment of the present invention.
The phase compensator 18 compensates the output of the mixer (D) 13 for a change in phase due to a change over time in the distance from the antenna 10 to the target. The output of the phase compensator 18 is input to the range compressor 14 to perform exactly the same operation as described in the first embodiment of the present invention. Then, as the output of the range compressor 14, s15 (t) shown in Expression 18 is input to the azimuth compressor 16 at the pulse repetition period (= 1 / fPRF). In the azimuth compressor 16, after the range curvature correction, multiple data s1 of s15 (t) in the same range bin
For 6 (t), the correlation with the azimuth reference function s17 (t) stored in the azimuth compressor 16 is calculated as shown in Expression 19, and s18 (t) is calculated. This correlation operation is the same for other range bins, and is performed over the entire required range width. However, in Expression 19, μ represents the time difference between the time waveform of s16 (t) and the time waveform of s17 (t).

[0055]

[Formula 19]

The display 15 displays the output from the azimuth compressor 16 based on the trigger signal output from the trigger signal generator 1.

[0057]

According to the first aspect of the invention, a random signal having a pulse width τ is output from the random signal generator at a pulse repetition frequency.
Since these random signals generated by fPRF are uncorrelated with each other, there is an advantage that echo superposition phenomenon, that is, range ambiguity does not occur. Also, the pulse width τ
Since τ0 is a non-correlated random number, the autocorrelation function s19 (η) of the random signal s9 (t) or s10 (t) shown in Formula 20 has a sharp peak at η = 0. This means that pulse compression, that is, range compression is possible. As an example, s19 (η) is shown in FIG. By the way, since the pulse width τ is compressed to τ0, the pulse compression rate is τ / τ0.

[0058]

[Equation 20]

Further, according to the second invention, in addition to the effect of the first invention, the range ambiguity does not occur, so that the degree of freedom in selecting the pulse repetition frequency is increased. It is possible to obtain a two-dimensional image that does not cause a certainty.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a radar device according to the present invention.

FIG. 2 is a diagram showing a second embodiment of a radar device according to the present invention.

FIG. 3 is a diagram showing a configuration of a conventional radar device.

FIG. 4 is a diagram showing a trigger signal output from a trigger signal generator in a time domain.

FIG. 5 is a diagram showing a chirp signal output from a chirp signal generator in a time domain.

FIG. 6 is a diagram showing, in the time domain, a correlation calculation result output from a range compressor when a chirp signal is used.

FIG. 7 is a diagram showing a state in which radar echoes are superimposed, which is also the same as when a chirp signal is output from a range compressor.

FIG. 8 is a diagram showing, in the time domain, a random signal output from a random signal generator in synchronization with a trigger signal.

FIG. 9 is a diagram showing an example of a waveform of a random signal generated by a random signal generator.

10 is a diagram showing a spectrum of the random signal shown in FIG.

FIG. 11 is a diagram showing another example of the waveform of the random signal generated by the random signal generator.

12 is a diagram showing a spectrum of the random signal shown in FIG.

FIG. 13 is a diagram showing still another example of the waveform of the random signal generated by the random signal generator.

FIG. 14 is a diagram showing an autocorrelation function of a random signal.

[Explanation of symbols]

1 Trigger signal generator 2 Random signal generator 3 Coherent oscillator 4 mixer (A) 5 Amplifier (A) 6 Stabilized local oscillator 7 Mixer (B) 8 High output amplifier 9 duplexer 10 antennas 11 Mixer (C) 12 Amplifier (B) 13 Mixer (D) 14 range compressor 15 Indicator 16 Azimuth compressor 17 Chirp signal generator 18 Phase compensator

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-60-262079 (JP, A) JP-A-2002-139565 (JP, A) JP-A-2001-100980 (JP, A) JP-A-3-138589 ( JP, A) JP-A 1-214788 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13/95

Claims (2)

(57) [Claims] 1. A trigger signal generator that outputs a trigger signal corresponding to a pulse repetition frequency; a random signal is generated for a predetermined time width based on the output of the trigger signal generator; A random signal generator that generates a signal that is uncorrelated with the random signal generated based on the trigger signal generator, a coherent oscillator that outputs a continuous wave of an intermediate frequency, an output of the random signal generator, and the coherent A mixer (A) that mixes the outputs of the oscillators, an amplifier (A) that amplifies the output of the mixer (A), a stabilized local oscillator that outputs a continuous wave of a radio frequency, and an output of the stabilized local oscillator. A mixer (B) that mixes the outputs of the amplifier (A), a high-power amplifier that amplifies the output of the mixer (B), and a transmitter connected to the high-power amplifier. A duplexer, an antenna connected to the duplexer, a mixer (C) that mixes the reflected wave from the target received by the antenna and passed through the duplexer with the output of the stabilized local oscillator; An amplifier (B) for amplifying the output of the mixer (C), a mixer (D) for mixing the output of the coherent oscillator and the output of the amplifier (B), an output of the mixer (D) and the random signal generation. And a range compressor that calculates a correlation with a random signal generated by the signal generator, and an angle signal that accompanies the rotation of the antenna is input from the antenna and synchronized with the trigger signal generated by the trigger signal generator. A radar device comprising: a display for displaying the output of the compressor. 2. A trigger signal generator that outputs a trigger signal corresponding to a pulse repetition frequency; a random signal is generated for a predetermined time width based on the output of the trigger signal generator; A random signal generator that generates a signal that is uncorrelated with the random signal generated based on the trigger signal generator, a coherent oscillator that outputs a continuous wave of an intermediate frequency, an output of the random signal generator, and the coherent A mixer (A) that mixes the outputs of the oscillators, an amplifier (A) that amplifies the output of the mixer (A), a stabilized local oscillator that outputs a continuous wave of a radio frequency, and an output of the stabilized local oscillator. A mixer (B) that mixes the outputs of the amplifier (A), a high-power amplifier that amplifies the output of the mixer (B), and a transmitter connected to the high-power amplifier. A duplexer, an antenna connected to the duplexer, a mixer (C) that mixes the reflected wave from the target received by the antenna and passed through the duplexer with the output of the stabilized local oscillator; An amplifier (B) that amplifies the output of the mixer (C), a mixer (D) that mixes the output of the coherent oscillator and the output of the amplifier (B), and the output of the mixer (D) from the antenna. A phase compensator for compensating for a phase change due to a temporal change in the distance to the target, and a range compressor for calculating a correlation between an output of the phase compensator and a random signal generated by the random signal generator. And the output of the azimuth compressor in synchronization with the azimuth compressor that compresses in the azimuth direction based on the output of the range compressor and the trigger signal generated by the trigger signal generator. Radar apparatus characterized by comprising a display for.