JPS6352713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A conventional direction finder subjects a received radio wave to amplitude modulation with a constant low frequency signal to observe the direction of arrival of the radio wave. However, when the frequency of the received wave exceeds the VHF band, by using phase or frequency modulation, it is possible to prevent a decrease in accuracy due to noise and improve stability. The present invention further improves the accuracy and stabilizes operation of such a direction finder by further eliminating the influence of noise.

FIG. 1 is a block diagram of an embodiment of the present invention, in which the outputs of frame antennas 1 and 2 arranged orthogonally to each other are applied to balanced modulators 3 and 4, and the outputs S of a rectangular wave signal generator 5, The output of the balanced modulator and the output of the omnidirectional vertical antenna 6 are combined by a combining circuit 7. This combined output is amplified by a high frequency amplifier 8, an intermediate frequency amplifier 9, etc., and is applied to a frequency discriminator 11 via an amplitude limiter 10. The outputs S and C of the signal generator 5 are, for example, 133Hz rectangular waves having a phase difference of 90 degrees as shown in FIG. Switch control signals such as b, c, d and A, B, . are obtained.

FIG. 3 is a plan view of the frame-shaped antennas 1 and 2. If radio waves arrive from the direction of arrow p, each antenna generates an output proportional to the lengths o _q and o _r , respectively. Since this output is modulated by the signals S and C in the balanced modulators 3 and 4, as shown in FIG.
Signals as shown by Ms and Mc are obtained. That is, the amplitudes of the signals Ms and Mc are proportional to the above o _q and o _r , and the polarity of the high frequency component is reversed depending on the sign of the signals S and C, as shown by the solid line and dotted line. Further, the vertical antenna 6 sends out a signal L having a phase difference of 90 degrees from the frame antennas 1 and 2, but this is directly added to the synthesis circuit 7 without phase shifting. Therefore, this signal L has a phase difference of 90 degrees with respect to both the solid line part and the dotted line part of the signals Ms and Mc, as shown by the broken line part in FIG. Combine Mc and L and send out a signal like H. In other words, with respect to the high frequency component of the signal L, the solid line portion of the signals Ms and Mc has a 90 degree lead phase, and the dotted line portion has a 90 degree lag phase, then the part where the signals Ms and Mc both have a lead phase In this case, the phase of the signal H advances by a large width and becomes a phase, and the phase of the signal H becomes a phase that lags by a wide range. Also the signal
In a portion where one of Ms and Mc is in a leading phase and the other is in a lagging phase, the signal H has an appropriate leading or lagging phase than the signal L depending on the magnitude of the signals Ms and Mc. Moreover, such phase fluctuations occur only at the rising and falling points of the rectangular low-frequency signals S and C, and the frequency of the high-frequency signal substantially decreases in the process of leading phase and increases in the process of lagging phase. . For this reason, as shown in FIG.
When the output of F is added to the frequency discriminator 11, it becomes F
The detection output signal shown in is obtained.

As shown in Figure 1, switch circuits 13, 14, 1
5, 16 to the storage circuits 17, 1.
In addition to 8, 19, 20, switch circuits 21,
The outputs of each memory circuit are added to an adder circuit 25 via 22, 23, and 24. Switch circuit 13-1
6 is applied and closed for a short time only when the signals a, b, c, and d are applied, so that the memory circuit 1
7, the pulse Fa in the signal F is sampled and its amplitude w is stored as shown by Ma in FIG. amplitude x,
y, z are stored as Mb, Mc, Md. Further, since the switch circuits 21 to 24 are closed by the signals A, B, and the outputs Ma, Mb, Mc, and Md of the memory circuits 17 to 20 are sent to the adder circuit 25, the outputs Ma, Mb, Mc, and Md are one quarter of the signals S and C. Two addresses are sequentially added every cycle and the sum is sent out. That is, during the period when the switch circuits 21 and 22 are closed, the outputs w and x of the memory circuits 17 and 18 are output to the adder circuit 25.
, the sum is sent out, and then 22 and 2
3 is closed, the outputs x and y of the memory circuits 18 and 19 are added to the adder circuit 25, and the sum thereof is sent out. Through this operation, the adder circuit 25 sends out a staircase wave signal as shown by G in FIG.
Therefore, as shown in FIG. 1, the signal G is converted into a rectangular wave S,
When the fundamental wave component such as C is added to the filter 26 for extracting it, a sinusoidal waveform output as shown by K in FIG. 2 is obtained. This signal K is applied to the phase detector 27 together with the reference phase signal obtained from the signal converter 12 to detect the phase φ.
The arrival azimuth θ of the radio waves as shown by the arrow p in the figure is displayed. That is, by the above azimuth angle θ, the second
The amplitudes of the balanced modulation signals Ms and Mc in the figure are determined, and the amplitudes w, x, y, and z of each pulse in the figure F are determined by these amplitudes. The staircase wave G has its amplitude w, x, y, z a quarter of that of the rectangular modulated waves S, C.
It is obtained by adding each cycle. Therefore, when the fundamental wave component K included in the staircase wave G is extracted, its phase angle φ corresponds to the arrival azimuth q of the radio wave.

As explained in the embodiments above, the direction finder of the present invention uses rectangular wave low-frequency modulation signals S and C, and uses the signals S and C to balance-modulate the frame-shaped antenna output. By directly combining the outputs of the signals to form a phase modulated wave corresponding to the arrival direction of the radio waves, the frequency modulation components are concentrated in the rising and falling portions of the signals S and C. A pulse signal F is obtained by frequency discrimination of this signal, and by sequentially adding the amplitude of each pulse every quarter period of the signals S and C, a staircase wave corresponding to the phase modulated wave is formed, and its basic The direction of arrival of radio waves can be determined by detecting the phase of the wave components. In other words, since the azimuth information is concentrated only on the rising and falling parts of the rectangular wave and only the information in these parts is sampled, it is possible to prevent a decrease in accuracy due to the effects of various noise components included in the flat part of the rectangular wave. Precise measurements can be made. Moreover, the amplitudes of the pulses are added two times every quarter cycle to form a staircase wave, and the fundamental wave is extracted to detect the phase, so a sufficiently large output can be obtained and high sensitivity can be obtained. Operates stably. Furthermore, even if the radio waves contain audio or other signals, the difference between the frequency modulation components in the rising and falling parts of the signals S and C and the frequency modulation components in the adjacent parts can be obtained and the above-mentioned processing can be performed. Therefore, errors caused by the audio signal and the like can be easily prevented.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of an embodiment of the present invention, and Figure 2 is a diagram of the first embodiment.
FIG. 3 is a plan view of a part of FIG. 1. In the figure, 1 and 2 are frame antennas, 3 and 4 are balanced modulators, 5 is a signal generator, 6 is a vertical antenna, 7 is a combining circuit, 8 is a high frequency amplifier, 9 is an intermediate frequency amplifier, and 10 is an amplitude limiter, 11 is a frequency discriminator, 12 is a signal converter, 1
3, 14, 15, 16 are switch circuits, 17, 1
8, 19, 20 are memory circuits, 21, 22, 23,
24 is a switch circuit, 25 is an adder circuit, 26 is a filter, 27 is a phase detector, and 28 is a display.

Claims (1)

[Claims] 1. A device that balance-modulates the outputs of a pair of antennas whose directivities are orthogonal to each other with two rectangular waves having a phase difference of 90 degrees and synthesizes them into an omnidirectional antenna output; a device that amplifies the output and performs frequency discrimination; a device that samples the output of the frequency discrimination device at each rise and fall point in the two rectangular waves and stores the sampled values; and each of the storage devices mentioned above. A device for sequentially adding two outputs of the rectangular wave every quarter period of the rectangular wave to form one staircase wave and obtaining a fundamental sine wave component included in the staircase wave, and a phase of the fundamental sine wave component. What is claimed is: 1. A direction finder comprising: a device that detects and displays the direction of arrival of radio waves;