JPH049477B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a moving target display device (hereinafter referred to as "MTI").
This invention relates to an improvement of a built-in test signal generator (hereinafter referred to as "BITE signal generator") for a radar device equipped with a BITE signal generator (hereinafter referred to as "BITE signal generator").

[Prior art]

First, a conventional built-in test (hereinafter referred to as "BITE") of this type will be explained. Figure 1 is a block diagram of a radar device equipped with MTI that has been commonly used in the past. In the figure, 1 is an antenna, 2 is a transmitter, 3 is a duplexer that switches between transmission and reception, and 4 is a BITE signal generator. 5 is a combiner for combining the received signal from the duplexer 3 and the BITE signal from the BITE signal generator 4, 6 is a receiver, 7 is an MTI signal processor, and 8 is a display.

Conventionally, in this type of MTI radar equipment,
The BITE signal from the BITE signal generator 4 must be a signal that simulates the reflected signal from a stationary target and the reflected signal from a moving target, so two or more high-frequency oscillators with fixed frequencies are used for switching. It is common to use a voltage-controlled high-frequency oscillator to vary the voltage.

However, even if a fixed-frequency high-frequency oscillator or a voltage-controlled high-frequency oscillator is used, it is impossible to keep the oscillation frequency completely constant due to aging and temperature changes. The drawback is that it is not possible to completely simulate a target or a reflected signal from a moving target with a certain Doppler frequency.

[Summary of the invention]

This invention was made to improve these conventional problems, and it is possible to detect stationary targets and stationary targets by using part of the transmitted signal from the transmitter as is or by modulating it by 0°/180°. A BITE signal generator that simulates a reflected signal from a moving target is provided.

[Embodiments of the invention]

FIG. 2 is a block diagram of a BITE signal generator showing an embodiment of the present invention, in which 9a and 9b are changeover switches, 10 is a 180° phase shifter, 11 is a pulse modulator, and 12 is a controller.

In FIG. 2, _X1 , which is a part of the transmitted signal, is switched in the changeover switch _9a by the changeover signal The signal is input to the changeover switch 9b through the controller 10, and is switched by the changeover signal _X2 from the controller 12 to become the output signal _X3 , which is then output to the pulse modulator 11 by the pulse modulation signal _X4 from the controller. It is pulse modulated and becomes the BITE signal _X5 .

FIG. 3 is a diagram explaining the time waveforms of each part in FIG. 2, where a is a transmission pre-trigger and T is a pulse repetition period. b is a switching signal _X2 from the controller 12, which is synchronized with the transmission pre-trigger and is switched to the switching signal X2 at every pulse repetition period T.
a and 9b are switched at the same time. c is the output signal _X3 of the changeover switch 9b; if it does not pass through the 180° phase shifter, the phase is 0°; if it does, the phase is 180°;
This shows that the signal is 180° modulated. d
is a pulse modulation signal from the controller 12,
In synchronization with the transmission pre-trigger, the pulse modulator 11 is turned ON for a time τ within the pulse repetition period T, and the BITE signal X ₅ shown in e is output.

Figure 4 shows the output signal _X3 of the changeover switch 9b.
2 is a diagram showing the spectrum of , where ₀ in the diagram is the frequency of the transmitted signal. As is clear from Figure 4, the frequency components of the transmitted signal _{are 0} and ₀ ±1/T, ₀ ±2/
The frequency components of T, ... are pressed, and only the frequency components of ₀ ±1/2T, ₀ ±3/2T, ₀ ±5/2T... exist. In other words, there is only a reflected signal from the moving target, especially a reflected signal from the moving target having a Doppler frequency that is half the pulse repetition frequency, and the BITE signal shown in FIG. 5 is output as the output of the pulse modulator. get.

Next, in FIG. 2, the changeover switches 9a,
When 9b is not switched, the phase of the output signal _X3 of the changeover switch 9b is always constant, so the frequency of _X5 is the same as the frequency of _X1 , which is part of the above-mentioned transmitted signal, This will simulate the reflected signal from a stationary target.

In the above explanation, a 180° phase shifter was used for 0°/180° phase modulation, but 0°/180° phase shifter was used by other means.
The same effect can be obtained by performing 180° phase modulation.

Further, in the above description, the pulse modulator is used after 0°/180° phase modulation, but the same effect can be obtained even if this order is reversed.

〔Effect of the invention〕

As explained above, this invention uses part of the transmitted signal as it is or performs 0°/180° phase modulation to detect the reflected signal from a completely stationary target and a moving target having a constant Doppler frequency. This has the effect of stably simulating reflected signals and supplying stable BITE signals for MTI radar equipment.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional radar device equipped with MTI, FIG. 2 is a block diagram of a BITE signal generator showing an embodiment of the present invention, and FIG.
A diagram explaining the waveforms of each part in the figure, Figure 4 is the same as Figure 2.
FIG. 5 is a diagram illustrating a spectrum of a 0°/180° phase modulation output, and FIG. 5 is a diagram illustrating an example of a BITE signal in the present invention. In the figure, 1 is an antenna, 2 is a transmitter, 3 is a duplexer, 4 is a BITE signal generator, 5 is a combiner, 6 is a receiver, 7 is an MTI signal processor, 8 is a display, 9a and 9b are switches switch, 10 is a 180° phase shifter, 11 is a pulse modulator, 12 is a controller, X ₁
is part of the transmission signal, X ₂ is the changeover switch control signal,
X ₃ is 0°/180° phase modulation output signal, X ₄ is pulse modulation signal, X ₅ is BITE signal generator output signal, T is pulse repetition period, τ is pulse modulation signal width, ₀ is transmission frequency be. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In the built-in test signal generator of a radar device equipped with a moving target display device, there is a changeover switch that selects whether to use a part of the transmitted signal as it is or 180° phase modulation, and the above-mentioned changeover switch is used as the transmission pre-trigger. a controller that switches in synchronization; and a pulse modulator that pulse-modulates the output of the changeover switch using a pulse modulation signal from the controller to generate a signal that stably simulates a reflected signal from a stationary target and a moving target. A built-in test signal generator characterized by comprising: