JPH0534442A - Pulse compression radar device - Google Patents

Abstract

(57) [Abstract] [Purpose] In a pulse compression radar, the amplitude of the pilot pulse signal input to the receiving system is made completely flat, and the gain control of the receiving system is performed with high accuracy. A switch 16 is provided between the mixer 15 and the pulse compression filter 17, and is controlled by using a gate signal G _P output from the timing generation circuit 5,
The received signal from the target object is input to the pulse compression filter 17 as it is, and the pilot pulse signal bypasses the pulse compression filter 17 and is input to the addition circuit 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse compression radar, and more particularly to a gain control device therefor.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a pulse compression radar device having a conventional gain control device disclosed in, for example, Japanese Patent Application Laid-Open No. 2-10907, in which reference numeral 1 is an intermediate frequency band reference oscillator. Reference numeral 2 is a first frequency modulation circuit (transmission signal generation circuit) for generating a transmission expanded pulse signal in the intermediate frequency band, and 3 is a pilot pulse in the intermediate frequency band having an intra-pulse modulation characteristic that is almost opposite to that of the expanded pulse signal. A second frequency modulation circuit (pilot signal generation circuit) for generating a signal, 4 is an adder circuit for adding the output signals A and B of both frequency modulation circuits 2 and 3 and 5 is a circuit of both frequency modulation circuits 2 and 3 A timing generation circuit for generating a timing signal for controlling the frequency modulation operation, 6 creates a sum signal of the output frequency of the adder circuit 4 and the output frequency of the local oscillator 7 in the high frequency band. Engager, 8 and 12 gate circuits, the power amplifier 9, the 10 duplexer, 11 is aerial.

Further, 13 is a directional coupler as an input end of a pilot signal receiving system, 14 is a high frequency amplifier, and 15 is a mixer for producing a difference signal between the output frequency of the high frequency amplifier 14 and the output frequency of the local oscillator 7. , 17 is a pulse compression filter, 19 is a gain controllable intermediate frequency amplifier, 20
Is a detector and 21 is an automatic gain control circuit.

Next, the operation will be described with reference to the waveform diagrams of FIGS. 3 and 4. The sine wave signal in the intermediate frequency band of the frequency f ₀ oscillated from the reference oscillator 1 is divided into two and added to the first frequency modulation circuit 2 and the second frequency modulation circuit 3, respectively. A pulse signal P _T (see FIG. 3 (c)) from the timing generation circuit 5 is added to the frequency modulation circuit 2, and the input sine wave signal is frequency-modulated by Δ around the frequency f _0. (See Fig. 4 (a) and (b)),
It is divided into pulses and output as a transmission stretched pulse signal A in the intermediate frequency band. This output time relationship is as shown in FIG.

Similarly, a pulse signal P _P from the timing generation circuit 5 is also applied to the frequency modulation circuit 3 (see FIG. 3 (d)).
And the input sine wave signal has a characteristic substantially opposite to that of the transmission stretched pulse signal A and Δ ′ about the frequency f _0.
After being frequency-modulated only (see (d) and (e) in Fig. 4), the pilot pulse signal B in the intermediate frequency band is divided into pulses.
Is output as. This output time relationship is as shown in FIG. 3 (b).

The outputs A and B of both frequency modulation circuits 2 and 3 are added by an adder circuit 4 and sent to a mixer 6, where they are mixed with the output of a local oscillator 7 in the high frequency band to obtain a sum frequency. High-frequency pulse signal, gate circuit 8
Sent to. The transmission gate signal G _T (see FIG. 3 (e)) from the timing generation circuit 5 is applied to the gate circuit 8, and only the high frequency transmission pulse signal is extracted from the high frequency pulse signal. Then, the high frequency transmission pulse signal is power-amplified by the power amplifier 9 and radiated as a transmission signal from the antenna 11 to the air via the duplexer 10.

The transmission signal radiated in the air as described above reaches a target object (not shown) and is reflected. The reflected signal (received signal) from the target object is received by the antenna 11, then passes through the duplexer 10 again, and the directional coupler 1
After passing through 3, the signal is high-frequency amplified by the high-frequency amplifier 14 in the subsequent stage and input to the mixer 15. A high frequency band local oscillation signal from the local oscillator 7 is applied to the mixer 15, and an intermediate frequency reception signal which is a difference frequency is obtained at the output thereof. After this, this intermediate frequency reception signal is input to the pulse compression filter 17, where the reception signal undergoes pulse compression processing, and as shown in FIG. 4 (c), the reception compressed pulse signal having a pulse width of approximately 1 / Δ. Will be output. After this, the received compressed pulse signal is transmitted to the intermediate frequency amplifier 19
After being amplified by, the signal is detected by the wave detector 20 and becomes a video reception signal D (see FIG. 3 (g)) and is sent to a signal processing device (not shown) in the subsequent stage.

The high frequency pulse signal output from the mixer 6 is also sent to the gate circuit 12, where it is gated by the gate signal G _P from the timing generation circuit 5 (see FIG. 3 (f)), Only the high frequency pilot pulse signal is taken out. This high frequency pilot pulse signal is injected at a predetermined level from the directional coupler 13 during the radar down time T ₁ , is then high frequency amplified by the high frequency amplifier 14, and is input to the mixer 15 at the subsequent stage. Then, as in the case of the received signal, the output of the mixer 15 becomes an intermediate frequency pilot pulse signal. Then, this intermediate frequency pilot pulse signal is input to the pulse compression filter 17. Here, since the pilot pulse signal is subjected to frequency modulation having a characteristic almost opposite to that of the transmission stretched pulse A as shown in FIGS. 4 (d) and 4 (e), after passing through the pulse compression filter 17, As shown in FIG. 4 (f), the output pulse waveform has a pulse width almost equal to that of the input and the amplitude thereof is substantially flat. Then, the pilot pulse signal having a flat amplitude is detected by the detector 20 to obtain the video signal E (see FIG. 3).
(See (g)) and output.

The video signal E is also applied to the automatic gain control circuit 21 in the subsequent stage. The automatic gain control circuit 21 verifies the level of the video signal E by the pilot pulse signal, creates a gain control signal V _E proportional to the difference between it and the reference value V _R (see FIG. 4 (g)), and outputs the gain control signal V _E. Amplifier 1
I am returning to 9. As a result, the gain is automatically adjusted so that the level of the video signal E by the pilot pulse signal is always constant. That is, the gain of the intermediate amplifier 19 is kept constant against changes in transmission characteristics such as changes in gain of the high frequency amplifier 14 and the mixer 15 due to changes in transmission frequency and changes in temperature. And such a function is indispensable in a radar system having a signal processing device (not shown) for automatically detecting a target in the latter stage.

[0010]

Since the conventional pulse compression radar apparatus is constructed as described above, the pilot pulse signal is affected by the characteristics of the pulse compression filter,
There is a problem that the amplitude cannot be perfectly flat and the gain control of the receiving system cannot be performed with high accuracy.

The present invention has been made to solve the above problems, and is a pulse compression radar provided with a gain control device for completely flattening the amplitude of a pilot pulse signal for gain control. The purpose is to obtain the device.

[0012]

A compression radar device according to the present invention is provided with a changeover switch which operates in response to a timing signal for extracting a pilot pulse signal in the preceding stage of the pulse compression filter, and a pilot pulse signal for a receiving system is provided with a pulse compression filter The output is output to the subsequent stage without passing through, and an adder is provided so as to be added to the received signal that has passed through the pulse compression filter.

[0013]

According to the present invention, the receiving system is provided with the changeover switch and operated by using the timing signal for extracting the pilot pulse signal, and the pilot pulse signal of the receiving system bypasses the pulse compression filter and is output to the subsequent stage,
Since the adder adds the received signal that has passed through the pulse compression filter, the pilot pulse is not affected by the pulse compression filter.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A gain control device for a pulse compression radar according to an embodiment of the present invention will be described below with reference to the drawings. 1, the same reference numerals as those in FIG. 2 denote the same or corresponding parts, and
6 is a changeover switch for changing the pilot pulse signal injected into the receiving system so as not to pass through the pulse compression filter 17 during the radar idle period, and 18 is the changeover switch 1
Pilot pulse signal from 6 and pulse compression filter 1
An adder circuit for adding the received signal from 7 and a pulse modulator circuit 23.

Next, the operation will be described. Reference oscillator 1
The intermediate frequency band sine wave signal of frequency f ₀ oscillated from
And one of them is added to the frequency modulation circuit 2, and the pulse signal P from the timing generation circuit 5 is supplied in the same manner as in the conventional case.
After being frequency-modulated by Δ by _T around frequency f ₀ by _T (see FIGS. 4 (a) and 4 (b)), it is divided into pulses and output to the adder circuit 4 as a transmission expansion pulse signal A in the intermediate frequency band. To be done. The sine wave signal of the other intermediate frequency band divided into two is applied to the pulse modulation circuit 23, where it is divided into pulses and output to the addition circuit 4 as an unmodulated pilot pulse signal B '.

Then, the transmission expansion pulse signal A and the unmodulated pilot pulse signal B'are added together in the adding circuit 4 and sent to the mixer 6 in the subsequent stage. Since the operations from the mixer 6 to the mixer 15 are the same as those shown in FIG. 2, the description thereof will be omitted and the signal processing after the mixer 15 will be described. The output of the mixer 15 is input to the changeover switch 16. The changeover switch 16 is the timing generation circuit 5
A gate signal G _P (see FIG. 3 (f)) is added to the pulse compression filter 17 from the target object at the timing of the gate signal G _P , while the pilot pulse signal is pulsed. It is switched so as to bypass the compression filter 17 and be input to the addition circuit 18. And in the pulse compression filter 17,
Pulse compression processing similar to that in the case of FIG. 2 is performed, and the received signal becomes a received compressed pulse signal and is output to the addition circuit 18. Then, the pilot pulse signal and the received compressed pulse signal are added by the adder circuit 18, and this is output to the intermediate frequency amplifier 19. Since the subsequent operation is the same as the conventional one, its description is omitted here.

As described above, according to this embodiment, the mixer 15
Switch 1 between the pulse compression filter 17 and the
6 is provided and is controlled by using the gate signal G _P output from the timing generation circuit 5, the received signal from the target object is directly input to the pulse compression filter 17, and the pilot pulse signal is input to the pulse compression filter 17. Since the bypass pulse is input to the adder circuit 18, the pilot pulse signal is not affected by the pulse compression filter 17 and is input to the intermediate amplifier 19 as a signal having a completely flat amplitude. When the control accuracy in 21 is improved and the influence of the pulse compression filter 17 on the change of the transmission frequency and the temperature change is small, the gain control of the receiving system can be performed accurately. Further, since the pilot pulse signal is not processed by the pulse compression filter 17, it can be used without being modulated.

Although the pilot pulse signal is used without being modulated in the above embodiment, the pilot pulse signal may be modulated as shown in FIG. That is, in FIG.
The modulation circuit 22 receives the pulse signal P _P from the timing generation circuit 5 (see FIG. 3 (d)), modulates the sine wave from the reference oscillator 1 such as frequency modulation that does not affect amplitude characteristics, and Alternatively, the pilot pulse signal of the intermediate frequency band may be output to the adder circuit 4, and the same effect as that of the above-described embodiment can be obtained.

[0019]

As described above, according to the pulse compression radar device of the present invention, the receiving system is provided with the changeover switch, and the pilot pulse signal of the receiving system is operated by using the timing signal for extracting the pilot pulse signal. By bypassing the pulse compression filter and outputting it to the subsequent stage, and adding it with the received signal that has passed through the pulse compression filter by the adder, the pilot pulse signal is not affected by the pulse compression circuit and its amplitude is completely Gain control of the reception system can be performed with a flat pilot pulse signal, and particularly when the influence of the pulse compression filter on changes in the transmission frequency and temperature changes is small, the gain control of the reception system can be performed with extremely high accuracy. There is an effect that it can be done.

[Brief description of drawings]

FIG. 1 is a block diagram of a pulse compression radar device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional pulse compression radar device.

FIG. 3 is an operation waveform diagram of the present invention and the conventional compression radar device.

FIG. 4 is an operation explanatory view of the compression radar device of the present invention and the conventional compression radar device.

FIG. 5 is a block diagram of a compression radar device according to another embodiment of the present invention.

[Explanation of symbols]

1 Reference oscillator 2 Frequency modulation circuit 4 adder circuit 5 Timing generation circuit 13 Directional coupler 16 Changeover switch 17 Pulse compression filter 18 Adder circuit 19 Intermediate frequency amplifier 20 detector 21 Automatic gain control circuit 23 Pulse modulation circuit

Claims (2)

[Claims] 1. A reception system having a pulse compression circuit, wherein a pilot pulse signal generated in a transmission system is input to the reception system,
In a pulse compression radar device equipped with a gain control circuit for comparing and expanding this with a reference level to control the gain of an amplifier in a receiving system, a reference oscillator for generating a reference pulse signal and a transmission pulse for receiving the output of the reference oscillator. A first frequency modulation circuit for outputting a signal, a second frequency modulation circuit for receiving the output of the reference oscillator and outputting a pilot pulse signal, and a combination of the outputs of the first and second frequency modulation circuits 1 adder, a transmission system including a timing signal generating circuit that generates a timing signal for extracting the transmission pulse signal and the pilot pulse signal from the signals added by the first adder, and the transmission pulse signal Of the reflected signal and the pilot pulse signal, and transmits them to the pulse compression filter in the subsequent stage, and the directional coupler. A selector switch which is inserted between the encoder and the pulse compression filter and which receives the timing signal for extracting the pilot pulse signal of the timing generator and outputs the pilot pulse signal to the subsequent stage without passing through the pulse compression filter. A second adder for adding the reflected signal processed by the pulse compression filter and the pilot pulse signal output to the subsequent stage without passing through the pulse compression filter, and amplifying the output of the second adder A pulse compression radar device, comprising: an amplifier for controlling the gain of the amplifier, and a gain control circuit for controlling the gain of the amplifier by comparing and expanding a pilot pulse signal of the amplifier output with a reference level. 2. The second frequency modulation circuit outputs a non-modulated pilot pulse signal or a pilot pulse signal which is modulated with no change in amplitude. Pulse compression radar device.