JPH042912B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention irradiates radio waves to a target such as an aircraft, a flying object, or a vehicle, and uses the reflected waves reflected from the target as a medium to generate radio waves relative to the target. This article relates to the improvement of a pulse modulation tracking radar that tracks distance and relative speed by receiving reflected waves from the target using a narrowband receiver and automatically tracking the relative distance and speed to the target. be.

[Conventional technology]

A conventional example of a tracking radar will be explained using the conventional example shown in FIG. 4 and the time chart shown in FIG. Fourth
In the figure, a transmission source output 4 produced by a transmission source 3 is pulse-modulated by a pulse modulator 5 using a reference pulse 2, which is the output of a reference pulse generator 1, and is then pulse-modulated by a pulse modulator output 6 to a power amplifier. 7 to become a power amplifier output 8 which is transmitted via a circulator 9 by an antenna 10 as a transmission power 11 towards a target 12 .

The reflected wave 13 from the target 12 is T (seconds) from the transmission.
is delayed, and the transmission signal frequency is shifted by the relative speed between the target 12 and the tracking radar, and is received by the antenna 10, resulting in an antenna sum output of 14. intermediate frequency converted signal 42 produced by transmission source 3;
is controlled by the circulator 9 by the fourth mixer 50.
is mixed with the antenna sum output 14 supplied via the antenna sum output 51 to become the fourth mixer output 51, which is amplified by the third intermediate frequency amplifier 52 to become the third intermediate frequency amplifier output 53, and then to the amplitude detector. 54
The amplitude is detected by , resulting in an amplitude detector output 55 as shown in FIG. Amplitude detector output 55
is synchronized in the pulse comparator 56 using a bipolar pulse 37 as shown in FIG. 3, resulting in a pulse comparator output 31 as shown in FIG. This results in a low-pass filter output 33 proportional to the difference τ between the center of the amplitude detector output 55 and the center of the bipolar pulse 37, which is input to the delay oscillator 34. This delay oscillator 34 creates a delay oscillator output 35 that generates a pulse delayed by a time corresponding to the delay time from transmission to reception, and the delay oscillator output 35 is input to a bipolar pulse generator 36. A negative feedback loop is constructed so that the pulse becomes a bipolar pulse 37 as shown in FIG. 3, and the low-pass filter output 33 becomes zero.

Further, the third intermediate frequency amplifier output 53 is mixed with the Doppler shift frequency signal 41 created by the speed signal generator 40 by the fifth mixer 57 to become the fifth mixer output 58, and the frequency discriminator A loop is configured to output a relative speed signal 39 that controls the Doppler shift frequency signal 41 that is the output of the speed signal oscillator 40 so that the frequency of the fifth mixer output 58 that is the input signal of the speed signal oscillator 38 is always constant.

In the tracking radar with such a configuration, the fourth mixer output 51 obtained by irradiating radio waves toward the target 12 and converting the frequency of the reflected wave 13 reflected from the target 12 is a broadband intermediate frequency signal. The signal-to-noise ratio is not very good. Furthermore, it is susceptible to radio wave interference and has poor sensitivity, making it difficult to track the target 12 over long distances.

[Problem that the invention seeks to solve]

By the way, conventional tracking radar can be roughly divided into:
There are pulse modulation methods and continuous wave methods, but with the continuous wave method, it is difficult to make the receiver highly sensitive because the radio waves that the tracking radar itself irradiates on the target always leak into the receiver inside the tracking radar itself. It was cool. For this reason, the pulse modulation method is relatively often used in tracking radars. Pulse modulation type tracking radar requires a wide receiver bandwidth due to the pulse modulation format used, so the receiver noise increases and the sensitivity is not very good. Furthermore, because the receiver bandwidth is wide, it is vulnerable to radio wave jamming by the target side, which is a serious drawback. Therefore, by narrowing the frequency variable range of the intermediate frequency signal so that the receiver bandwidth can be made as narrow as possible at the front stage of the receiver,
There is a strong demand for higher sensitivity and improved anti-jamming capabilities.

[Means for solving problems]

In view of the above points, the present invention corrects the output of the intermediate frequency converter by the shift in the Doppler frequency caused by the relative speed of the target and the tracking radar, and at the same time,
By converting the frequency of the target reflected wave using a switching signal for mixing that is two-phase modulated with 0 phase and π phase, the detection of the distance error signal is performed by a synchronous wave device, and the intermediate frequency amplifier is also The objective is to narrow the frequency bandwidth and provide a highly sensitive tracking radar that is less susceptible to noise.

The present invention transmits a pulse-modulated transmission signal as a radio wave, and the reflected wave from the target of the transmitted radio wave is delayed by a certain time due to propagation, and the Doppler frequency is shifted by the relative speed of the target and the tracking radar. The received signal obtained by receiving the signal is branched, the non-phase modulated signal is used as a switching signal in a mixer, the signal reduced to an intermediate frequency is used as a reference signal for a synchronous detector, and the other branched signal is used as a switching signal. The received signal is converted into an intermediate frequency using a switching signal for two-phase modulated mixing of 0 and π radians in another mixer, and the signal is synchronously detected by the reference signal and output from the synchronous detector. using this synchronous detector output and a signal synchronized with the transmission signal, controlling the two-phase modulated switching signal so that the phase thereof is switched by π radians at approximately the center position of the reception signal, The above problem is solved by making it possible to detect the position of the received signal and configuring a negative feedback loop for synchronizing the received signal.

[Effect]

Before explaining the embodiment of FIG. 1 in detail, the principle of the present invention will be explained using the time chart of FIG. 2.

In Figure 1, monopulse antenna sum output 14
is the second mixer 16 along with the two-phase modulator output 20.
is mixed at the second mixer output 22,
If the center angular frequency of the second mixer output 22 is ωi, a pair of Sinωit-Sinωit is output to the second mixer output 22, which is synchronously detected by the synchronous detector 24 and becomes the distance error signal 31. . As shown in Figure 2,
If at that time there is a difference of τ between the center of the signal of the monopulse sum output 14 and the phase switching position of the two-phase modulator output 20, the bipolar pulse 37 of the distance error signal 31 becomes asymmetric, and the low-pass filter 32 results in a low-pass filter output 33 which is a DC signal proportional to τ. Using this low-pass filter output 33, the phase switching position of the two-phase modulator output 20 is made to coincide with the center of the signal of the monopulse antenna sum output 14 that was received immediately before.

Also, a frequency discriminator 38, a speed signal oscillator 4
0, the first mixer 15 and the second mixer 1 by the frequency conversion control loop of the Doppler shift correction mixer 17
In order to output the Doppler shift frequency signal 41 which is the output of the speed signal generator 40 and the relative speed signal 39 to be controlled, the band of the intermediate frequency amplifier is made narrow so that the frequency of each output of 6 is always constant. However, the signal is transmitted without any problem.

〔Example〕

Embodiments of the tracking radar according to the present invention will be described below with reference to the drawings.

In FIG. 1, first, a distance signal detection method will be described.

Reference pulse 2 which is the output of reference pulse generator 1
The transmission source output 4, which is the output of the transmission source 3, is passed through the pulse modulator 5 to become the pulse modulator output 6, which is amplified by the power amplifier 7 and becomes the power amplifier output 8.
The transmission output 11 is irradiated toward the target 12 by the monopulse antenna 10 via the circulator 9.

The reflected wave 13 from the target 12 is received by the monopulse antenna 10, and part of it becomes the monopulse antenna sum output 14, which is branched to each of the first mixer 15 and the second mixer 16, and then sent to the Doppler shift correction mixer. Using the Doppler shift corrected intermediate frequency conversion signal 18 obtained from 17 and the two-phase modulator output 20 obtained from two-phase modulator 19, the frequency is converted to the output of the first mixer 15 and the second mixer output 21, respectively. be done.

The output of the first mixer 15 is amplified by the first intermediate frequency amplifier 22 and becomes the first intermediate frequency amplifier output 23, which becomes a reference signal for the synchronous detector 24.

The second mixer output 21 is output from the switch signal generator 2
5 is amplified in a second intermediate frequency amplifier 28 through a first switch 27 operated by a switch signal generator output 26, which is the output of the switch signal generator 26, and becomes a second intermediate frequency amplifier output 29, which is amplified in a synchronous detector 24. Synchronous detection is performed.

Then, a distance error signal is obtained as an output of the synchronization detector 24 via a second switch 30 which is switched in synchronization with the first switch 27 by the switch signal generator output 26.

The distance error signal 31 is input to a low pass filter 32, becomes a low pass filter output 33, and is input to a delay oscillator 34. The delay oscillator 34 outputs a delayed pulse 35 with a delay amount proportional to the low-pass filter output 33, and this delayed pulse 35 is input to a bipolar pulse generator 36 and becomes a bipolar pulse 37. This bipolar pulse 37 modulates the phase of the Doppler shift-corrected intermediate frequency conversion signal 18 in a two-phase modulator 19, resulting in 0 phase and π phase.
A two-phase modulated two-phase modulator output 20 is created. That is, the components from the distance error signal 31 to the generation of the two-phase modulator output 20 form a negative feedback loop to control the two-phase modulator output 20 so that the distance error signal 31 becomes zero. In other words, the monopulse sum output 14 just received
The phase switching position of the phase modulator output 20 is controlled to match the center of the signal.

Next, a method for detecting speed signals will be described. The monopulse antenna sum output 14 is output from the first mixer 1
5, the frequency is converted into a first intermediate frequency output 23 by a first intermediate frequency amplifier 22, and the frequency is discriminated by a frequency discriminator 38 to obtain a relative velocity error signal 39 between the target 12 and the tracking radar.
Output. The relative velocity error signal 39 is input to a velocity signal generator 40 to generate a Doppler frequency signal 41.
Output to. The Doppler shift corrected mixer 17 creates a Doppler shift corrected intermediate frequency converted signal 18 from the Doppler shifted frequency signal 41 and the intermediate frequency converted signal 42 which is the output of the transmission source 3. That is, the components from the relative velocity error signal 39 to the generation of the Doppler shift correction intermediate frequency conversion signal 18 constitute a return loop to convert the Doppler shift correction intermediate frequency so that the relative velocity error signal 39 becomes zero. Controls the conversion signal 18. In other words, the frequency of the first mixer output 22 is controlled to be always constant.

Next, a method for detecting angle signals will be described. The azimuth angle difference output 43 of the monopulse antenna 10 is
The third mixer 44 converts the frequency, and the first switch 27 uses the switch signal generator output 26 which is the output of the switch signal generator 25
The mixer output 45 and the second mixer output 22 are alternately switched to become the first switch output 46, which is amplified by the second intermediate frequency amplifier 28 and becomes the second intermediate frequency amplifier output 29, which is output by the synchronous detector 24. The signal is synchronously detected and becomes a synchronous detector output 47, which is input to the second switch 30, and is switched in synchronization with the first switch 27 by the switch signal generator output 26, thereby generating an azimuth error signal 48 and a distance error signal. Get 31.

With the above embodiment, it can be explained that it is possible to realize a tracking radar that can obtain the distance error signal 31, the relative velocity error signal 39, and the azimuth error signal 48 by a simple method using a common narrow band intermediate frequency amplifier. Ta.

Note that by performing the same processing as the azimuth angle difference output 43 for the elevation angle difference output 49 of the monopulse antenna 10, an elevation angle error signal can be obtained.

〔Effect of the invention〕

Since the frequency bandwidth of the intermediate frequency amplifier can be significantly narrowed, it is possible to realize a tracking radar with extremely high sensitivity and high anti-jamming ability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the tracking radar according to the present invention, FIG. 2 is a time chart for explaining the embodiment of the present invention shown in FIG.
FIG. 4 is a time chart for explaining the conventional example, and FIG. 4 is a block diagram showing an embodiment of the conventional tracking radar. In the figure, 1 is a reference pulse generator, 2 is a reference pulse, 3 is a transmission source, 4 is a transmission source output, 5 is a pulse modulator, 6 is a pulse modulator output, 7 is a power amplifier, 8 is a power amplifier output, 9 is a circulator,
10 is a monopulse antenna, 11 is a transmission output, 1
2 is a target, 13 is a reflected wave, 14 is a monopulse antenna sum output, 15 is a first mixer, 16 is a second mixer, 17 is a Doppler shift correction mixer, 18 is a Doppler shift correction intermediate frequency conversion signal, and 19 is a 2-phase modulator, 20 is the 2-phase modulator output, 21 is the second mixer output, 22 is the first intermediate frequency amplifier,
23 is the output of the first intermediate frequency amplifier, 24 is the synchronous detector, 25 is the switch signal generator, 26 is the output of the switch signal generator, 27 is the first switch, 28 is the second intermediate frequency amplifier, and 29 is the second intermediate frequency amplifier. Frequency amplifier output, 30 is a second switch, 31 is a distance error signal, 32 is a low pass filter, 33 is a low pass filter, 34 is a delay oscillator, 35 is a delay pulse, 36
37 is a bipolar pulse generator, 37 is a bipolar pulse, 38 is a frequency discriminator, 39 is a relative velocity error signal, 40 is a speed signal generator, 41 is a Doppler frequency signal, 42... is an intermediate frequency conversion signal, 43 is an azimuth angle difference output , 44 is the third mixer, 45 is the third mixer output, 46 is the first switch output, 47 is the synchronous detector output, 48 is the azimuth error signal, 49 is the height angle difference output, and 50 is the fourth mixer. 51 is the fourth mixer output, 52 is the third intermediate frequency amplifier, 53 is the third intermediate frequency amplifier output, 54 is the amplitude detector, 55 is the amplitude detector output, 56 is the pulse comparator, 57 is the fifth Mixer, 58 is the fifth mixer output. In addition,
The same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a tracking radar that transmits a transmission output to a target, receives a reflected wave from the target, and extracts a relative velocity error signal and a distance error signal, the transmission output frequency is mixed with the received signal. a Doppler shift correction mixer that generates a Doppler shift correction intermediate frequency signal for outputting a signal lower by a predetermined frequency by a Doppler frequency signal output from a speed signal oscillator and an intermediate frequency conversion signal output from a transmission source; A two-phase modulator that modulates the Doppler shift correction intermediate frequency signal generated from the Doppler shift correction mixer by O and π for each pulse and outputs it, and the received signal and the Doppler shift correction intermediate frequency signal generate a predetermined frequency from the transmission output frequency. A first mixer that outputs a low signal, and a Doppler shift-corrected intermediate frequency signal that is two-phase modulated with the received signal and the two-phase modulator, generates a two-phase modulated signal that is lower than the transmission output frequency by a predetermined frequency. a second mixer for outputting, a first intermediate frequency amplifier for amplifying and outputting the output signal of the first mixer, and a second intermediate frequency amplifier for amplifying and outputting the output signal of the second mixer.
A tracking radar comprising: an intermediate frequency amplifier; and a synchronous detector that synchronously detects the output signal of the first intermediate frequency amplifier with the output signal of the second intermediate frequency amplifier and outputs a distance error signal. 2 A monopulse antenna that receives the reflected wave from the target and outputs a sum signal and a difference signal, and a difference signal received by the monopulse antenna and a Doppler shift correction intermediate frequency signal output from the Doppler shift correction mixer, adjust the transmission output frequency. A third mixer outputs a signal lower by a predetermined frequency, and the output of the second mixer and the output of the third mixer are switched to either one by the output of the switch signal generator and sent to the second intermediate frequency amplifier. a first switching device that outputs;
A patent characterized in that it is equipped with a second switching device that switches the output of the synchronous detector in synchronization with the first switching device using the output of the switch signal generator to output a distance error signal and an azimuth error signal. A tracking radar according to claim 1.