JPS5926909B2 - Interference wave direction separation device for direction finder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The directivity of the antenna can be determined by mechanically rotating the directional antenna itself or a goniometer to which its output is applied, or by purely electrical methods such as balanced modulation of the antenna's output with a low frequency signal. The direction of arrival of radio waves can be determined by substantially rotating the .

In such a direction finder, if there was interference waves, conventionally the direction corresponding to the combined output was indicated, which could lead to large erroneous observations.

Therefore, in the present invention, when two interference waves are received, the direction of arrival of each radio wave can be separated and measured separately.

FIG. 1 shows an embodiment of the present invention in which two directional loop antennas 1 and 2 are arranged so that their directivities are orthogonal to each other, and their outputs are applied to balanced modulators 3 and 4.

In addition, from the low frequency oscillator 5, two waves having a phase difference of 90 degrees are generated.
The antenna output is balanced modulated by taking two outputs and applying each of them to the modulators 3 and 4 above, and adding them to the combiner 6.

To this combiner 6 is further added via a switch 7 an output obtained by shifting the output of the omnidirectional antenna 8 by 90 degrees from a phase shifter 9.

The output of the synthesizer 6 is applied to a receiving section 10 for amplification, frequency conversion, etc., and the output is applied to a detector 11.

Further, the output of the wave detector 11 is applied to a band-removed wave detector 12 to remove the low frequency components contained therein, and the output is applied to a wave detector 14 via a tuned amplifier 13.

The changeover switch 15 applies the output of the detector 11 or 14 to the cathode ray tube drive circuit 16 together with the low frequency signal of the reference phase obtained from the oscillator 5, and the output of the circuit is applied to the deflection plate of the cathode ray tube 17 and the electron flow control grid. It is.

In the above-mentioned apparatus, when there is no interference wave, the output of the detector 11 is applied to the drive circuit 16 as shown in the figure, and the switch 7 is first opened for observation.

That is, the outputs of the antennas 1 and 2 are balanced modulated with low frequency signals having a phase difference of 90 degrees, and the modulated outputs are combined, so that the same effect as when the antennas are directly rotated can be obtained.

Therefore, when this output is amplified, detected, and applied to the horizontal and vertical deflection plates of the cathode ray tube 17 through the drive circuit 16 together with the low frequency signal of the reference phase, a propeller-shaped figure is drawn as is well known.

Next, the switch 7 is closed, and the signal obtained by shifting the output of the omnidirectional antenna by 90 degrees is further synthesized, and the 1 drive circuit 1
At step 6, when the low frequency signal is applied to the electron beam control grid of the cathode ray tube 17, a bart-shaped figure appears eccentrically and a sense instruction is given.

Therefore, as is well known, the direction of arrival of radio waves can be determined by the propeller-shaped figure and this sense.

However, in such a conventional device, when there is interference between two radio waves, only one direction is measured, which is obtained by combining the arrival directions of each radio wave according to the radio wave intensity ratio.

Therefore, in such a case, the switch 15 is switched to apply the output of the detector 14 to the drive circuit 16, and the switch 7 is first opened for observation.

That is, if the signals sent out from the combiner 6 are a and b in FIG. 2 when each of the two interference waves is received individually, the combiner sends the combined signal to the receiver 10.
Add to.

Since the band-removing P-wave device 12 removes the low frequency component contained in the output of the detector 11, only the signal of the beat frequency component is applied to the tuned amplifier 13.

Therefore, if the tuning frequency of the amplifier 13 is adjusted appropriately, 2
A signal as shown in FIG. 2C having a frequency equal to the difference between the two interference waves is amplified, detected by the wave detector 14, and applied to the cathode ray tube drive circuit 16.

For this reason, two propeller-shaped figures p and q are drawn on the cathode ray tube 17 in FIG. is instructed.

Therefore, when switch 7 is then closed, FIG. 2a.

The signal b changes like d and e, and the signal C changes like f.

Since this signal f is detected and applied to the drive circuit 16, when the potential of the electron beam control grid of the cathode ray tube is controlled by the reference low frequency signal obtained from the oscillator 5 by the seven drive circuits, the solid line in FIG. The bart-shaped figures x and y shown in are eccentrically drawn to form the propeller-shaped figure p,
A sense instruction for q is given.

That is, with this sense instruction, in the case of FIG. 3a, the arrival directions of the two interference waves are respectively arrows S and t, and
Also, in the case of b, it can be known that they are S and U.

As described above, the device of the present invention detects the arrival direction of radio waves by selecting and amplifying the signal of the beat frequency when there are a plurality of interference waves.

In other words, the amplitude of the beat frequency signal becomes zero at the point in time when the amplitude of either one of the received wave signals a and b becomes zero, as shown in FIG. 2C.

Therefore, by detecting the phase at which the output of the detected beat frequency signal becomes zero, the direction of arrival of each radio wave can be detected separately.

Therefore, according to the present invention, large erroneous observations due to interference can be prevented, and the arrival directions of two radio waves can be observed simultaneously.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a waveform diagram explaining the operation of the device in FIG. 1, and FIG. 3 is a diagram showing figures displayed by the device in FIG. 1. This is a diagram. In the figure, 1 and 2 are directional antennas, 3 and 4 are balanced modulators, 5 is a low frequency oscillator, 6 is a combiner, 7 is a switch, 8 is an omnidirectional antenna, 9 is a 90 degree phase shifter, 10 is a receiving section, 11 is a wave detector, 12 is a band-removed wave detector, 13 is a tuning amplifier, 14 is a wave detector, 15 is a changeover switch, 16 is a cathode ray tube 1 drive circuit, and 17 is a cathode ray tube.

Claims (1)

[Claims] 1. When multiple interference waves are received in a direction finder that determines the arrival direction of radio waves by detecting the phase with respect to the rotation period of the balanced modulated output of an antenna whose directivity is mechanically or electrically rotated, An interference wave direction separation device comprising means for amplifying and detecting these beat frequency signals, and means for detecting a phase at which the amplitude of the detected output becomes zero.