JPS5829474B2 - radar couch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in radar equipment, and aims to provide a radar equipment that is less susceptible to interference.

FIG. 1 is a system diagram showing a radar device using a conventional amplification transmitter.

In this figure, 1 is a reference oscillator, which is an oscillator in an intermediate frequency band.

2 is a local oscillator, which is a radio frequency band oscillator whose frequency can be changed.

The outputs of the reference oscillator 1 and the local oscillator 2 are mixed in a mixer 3, and the sum frequency component is extracted and sent to an amplifying transmitter 4.

The transmission trigger from the trigger generator 5 passes through the transmission pulser 6 to drive the amplification transmitter 4, which divides the carrier wave signal from the mixer 3 into strips to generate transmission signals.

The transmitted signal passes through the transmitter/receiver switch 7 and is radiated from the antenna 8 as a transmitted radio wave 9, and the reflected signal 11 from the target object 10 is received by the antenna 8 again.

This received radio wave passes through the transmission/reception switch 7, is added to the mixer 13, and is mixed with the local oscillation signal from the local oscillator 2.
The difference frequency, that is, the IF of the oscillation frequency of the reference oscillator 1
The resulting signal is amplified and detected by the amplification detector 14, becomes a video signal, and is displayed on the indicator 15.

The above is operation in a normal environment, but air defense surveillance radars and the like may be intentionally interfered with.

When the intentional jamming wave 12 has a frequency approximately equal to the transmission frequency, it is displayed on the indicator 15 along the same route as the reflected signal 11.

A method for preventing such jamming waves 12 is to change the oscillation frequency of the local oscillator 2 so that the transmission frequency and the frequency of the jamming waves 120 do not match, but usually the side that emits the jamming waves 12 Then, the radar's transmission frequency will be monitored and followed, so it will be interfered with again after a while.

As described above, the conventional method has the drawback that even if the transmitting frequency is changed to avoid the jamming radio waves 12, the jamming waves 12 will be tracked after a while, and sufficient countermeasures for preventing jamming cannot be taken.

Furthermore, as a method of preventing jamming radio waves 12, a method can be considered in which a plurality of transmitting/receiving devices are provided to emit different transmitting frequencies at the same time, and the receiving side receives and processes only a specific receiving frequency, but in this case, the transmitting device The disadvantage is that more than one is required.

This invention eliminates interference by time-divisionally inserting and transmitting a local oscillation frequency and a variable frequency of another variable oscillator that is different from this local oscillation frequency within a pulse modulation period, and receiving and processing these reflected waves. This provides a means for making it difficult for the radio wave emitting side to detect the transmission frequency and for controlling it, thereby effectively preventing jamming radio waves.

This invention will be explained below.

FIG. 2 is a system diagram showing an embodiment of the present invention.

In this figure, parts common to those in FIG. 1 are given common numbers.

The difference from the conventional example shown in FIG. 1 is that the radio frequency band variable oscillator 21. Gate circuit 22, gate signal generator 23
This is the addition of .

FIG. 3 is an explanatory diagram of the operation corresponding to FIG. 2.

Next, the operation of the embodiment shown in FIG. 2 will be explained with reference to FIG.

The transmission trigger Vt of the trigger generator 5 is as shown in FIG. 3a, which generates the gate signal Vg.

Output of local oscillator 2 (frequency fl) and variable oscillator 2
1 (frequency fr) is applied to the gate circuit 22 and switched by the aforementioned gate signal Vg, as shown in FIG.
The output shown in is sent to the mixer 3.

The output (frequency fC) of the reference oscillator 1 is also applied to the mixer 3, and the sum of the two frequency components is extracted.

On the other hand, the transmission trigger Vt from the trigger generator 5 drives the amplification transmitter 4 via the transmission pulser 6, and outputs the output from the mixer 3 by dividing it into transmission pulses.

As a result, the transmission signal Vtx is 2 as shown in FIG. 3d.
The signal becomes a so-called composite transmission signal having two transmission frequencies fc +fr and fc +fl, passes through the transmission/reception switch 7, and is radiated into space from the antenna 8 as a transmission radio wave 9.

The reflected signal 11 from the target object 10 is received by the antenna 8 and guided to the mixer 13 through the transmitter/receiver switch I again.

A local oscillation signal having a frequency fl from the local oscillator 2 is applied to the mixer 13 to generate a difference IF frequency.

This IF signal Vi is illustrated as shown in FIG. 3e.

The amplified detector 14 is equipped with a filter that passes only the vicinity of the center frequency fc, and
By intentionally shifting r, the fc+fr-fl component of the IF signal Vi is removed, and the output video Vv becomes only that corresponding to the <fc acid component, as shown in FIG. 3f.

The output of the amplified detector 14 is displayed on an indicator 15.

On the other hand, from the perspective of preventing interference, since the transmitted radio waves are so-called composite radio waves with two frequencies, as mentioned above,
On the side that intentionally emits jamming radio waves (not shown), it becomes difficult to detect the frequency of the transmitted radio waves, or even if two transmitted frequencies can be detected, the frequency actually used by the radar side may be difficult to detect. Since they cannot be identified, it is not possible to determine which of the two frequencies the interfering radio wave frequency should follow, and the interfering function is greatly limited.

Of course, even if the radar side follows a frequency that is not being processed for reception, the radar side will not experience any interference.

If the radar side is tracked by the frequency of the reception processing side, it is sufficient to take measures such as changing the frequency of one or both of the local oscillator 2 and the variable oscillator 210 to escape.

By emitting two transmission radio waves and receiving only one of them, the interference function can be paralyzed and interference radio waves can be effectively prevented.

As explained above, the present invention provides a variable oscillator having a frequency different from that of a local oscillator, and a gate circuit that can switch the output signal of this variable oscillator and the output signal of the local oscillator in a pulse modulation period, and pulse modulation. Since the two signals are transmitted at different times within the period, it is possible to make it difficult to identify the frequency and give a confusing effect to the interference source side, and it is possible to paralyze the interference function by adding a simple device. It has the effect of being able to.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a conventional radar device, FIG. 2 is a system diagram showing an embodiment of the present invention, and FIG. 3 is an operation explanatory diagram corresponding to FIG. 2. In the figure, 1 is a reference oscillator, 2 is a local oscillator, 3 is a mixer,
4 is an amplification transmitter, 5 is a trigger generator, 6 is a transmission pulser,
7 is a transmitting/receiving switch, 8 is an antenna, 9 is a transmitted radio wave, 10 is a target object, 11 is a reflected signal, 12 is an interfering radio wave, 13 is a mixer, 14 is an amplification detector, 15 is an indicator, 21 is a variable oscillator , 22 is a gate circuit, and 23 is a gate signal generator. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a radar device configured to pulse-modulate a transmission frequency that is a mixture of the outputs of a local oscillator and a reference oscillator, and to transmit and receive this pulse-modulated wave by a single transmitting and receiving antenna, oscillating a frequency different from that of the local oscillator. and a gate circuit for selectively switching the output of the variable oscillator and the output of the local oscillator, and the gate circuit is configured to switch between the local oscillation frequency and the variable oscillation frequency within a pulse modulation period. A radar device featuring: