JPS58777A - Direction finding device - Google Patents

Abstract

PURPOSE:To read an arrival bearing of a radio wave in a short time, by signal-processing a receiving signal so that a pattern indicating a radio wave arrival direction can be drawn on a cathode ray tube immediately, in a state that an antenna is rotating. CONSTITUTION:A switching signal generated by a switching signal generator 6 is applied to a switch 7, switches an output of an antenna 1 between 0 deg.C-360 deg.C, and is supplied to a receiver 2. Subsequently, in a time division output F, the maximum value Vm of a detecting output V is detected, by which a threshold level Vs is calculated. Subsequently, when this detecting output V erases a receiving output within an angle range exceeding a value of said threshold level Vs, a discrete receiving output H is obtained. When an output between 90 deg.C-270 deg.C of this discrete receiving output H is erased as a gate a unilateral direction indicating pattern can be drawn on a cathode ray tube, and an arrival bearing of radio waves can be grasped in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a direction finding device using a small antenna.

Conventionally, this type of device uses an antenna that can obtain a 80' symmetrical cartzoid pattern (pattern 1 = stnT), and measures direction by finding the direction in which the received levels of both patterns are equal. There was something.

FIG. 1 shows both patterns of the above-mentioned antenna, and the direction of the straight line connecting the equal reception level points P, , P2 is the same as the direction of the arriving radio wave.

FIG. 2 shows an example of an antenna configuration that provides a 1800 symmetrical pattern. In the figure, (1) is an antenna element, a decoy is a ground plate, 03 is a changeover switch, and αω is a terminal resistor. One side of the antenna element (1) is terminated by a changeover switch αJ, and a signal is taken from the other side. By changing the terminal to be taken out, the cardioid pattern is reversed by 180 degrees.

With such a conventional method, there are two methods for detecting the equal reception level points Pi and P2 of the two patterns shown in Fig. Utilizing the fact that the envelope signal phase of the AM wave generated from the received level difference is reversed by 180 degrees with respect to the axis of symmetry when the pattern is switched at a constant cycle, the Louvomotor is rotated by the AM wave envelope detection signal, and the antenna is There is a method in which the servo motor is rotated to point in the direction in which the radio waves arrive (when the direction in which the radio waves arrive coincides with the equal level direction of both patterns, a non-modulated state occurs and the servo motor stops).

However, in this conventional method, since the direction is measured by rotating the antenna, a certain amount of time is required, and short signals are difficult to measure.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and in order to make it possible to measure even short signals in the direction finding device using the antenna as described above, the received signal is processed. The object of the present invention is to provide a direction finding device that displays the results on a cathode ray tube and reads the direction from the display pattern in a short time.

An embodiment of the present invention will be described below with reference to the drawings.

(3) FIG. 3 shows a direction finding device according to an embodiment of the present invention, in which (1) is a small antenna that can obtain a 180° symmetrical cardioid pattern, and (7) is the small antenna (1). A selector switch that switches between both patterns, (6)
is a switching signal generator (2) which applies a switching signal to the switching switch (7) to switch between both patterns at a constant cycle;
is a receiver, (8) is a video signal processor that processes the video received by the receiver (2) using a switching signal from the switching signal generator (6), and (3) is a video signal processor that amplifies the output thereof. The video amplifier (4) is a cathode ray tube for displaying its output as an image, and (5) is a motor for rotationally driving the small antenna (1).

FIG. 4 shows the reception output of the antenna (1), where A is the output when the switch (7) in FIG. 3 is on the terminal 2 side, and B is the output when it is on the terminal 1 side.

Figure 5 shows the directivity of the antenna when the switch (7) in Figure 3 is switched, C is the directivity when the switch (7) is set to the terminal 2 side, and D is the directivity when the switch (7) is set to the terminal 2 side. .

Fig. 6 1(b) shows the switch (7) in Fig. 3 from θ to 360°.
The signals are switched at intervals as shown in the pulse signal E in FIG. 6(a), and the shaded area is the output level. In the figure (bl), F is a time-division output that shows the directional output C shown in Fig. j85 when the switching signal E is logic "O", and the directional output shown in Fig. 5 when the switching signal E is logic "1".

Fig. 7 (bl indicates the output during signal processing of the output F of Fig. 6 (bl) by the video signal processor (8); The output in the angle range exceeding the threshold value v1 is deleted.

FIG. 8 shows an image of the output H of FIG. 7 fbl displayed on a cathode ray tube.

FIG. 9 shows an image in which one of the images in FIG. 8 has been deleted.

■ in Figure 10 fa+ is the 6th time-divided by the switch (7).
Figure (shows the output obtained by synchronously detecting the reception output F of bl with a switching signal.J shows the other reception output that has been canceled by synchronous detection.K is the signal obtained by waveform shaping the above ■), and L shows a waveform obtained by phase-shifting the above K by 906.

Next, the operation will be explained. The switching signal generator in Figure 3 (
The switching signal generated in step 6) is given to a switch (7), which switches the output of the antenna (1) between 00 and 360 degrees and supplies it to the receiver (2). The detection output of the receiver (2) is the 6th
The angles at which the switched outputs have the same value are 0° and 180°.

FIG. 6 (The maximum @Vm of the detection output V is detected in the time-division output F of bl, and the threshold value Vs is calculated from this.

This threshold value Vm is a value determined by the directivity characteristics of the antenna used, and in the case of a cardioid s-shaped pattern, Vi = 0.7. By erasing the received output in the angle range exceeding the value Vs, the seventh
The discrete reception output H of (bl) is obtained.

This output H has a maximum value of 06 or 180°.

On the other hand, the output obtained by synchronously detecting the time-division output F of the 6th ward system using the switching signal is shown in Figure 10 fa+! Then, waveform-shape this ■ to create a signal with a K waveform, and phase shift K by 90° to create a signal with an L waveform.

By the L signal in Figure 10! 90° to 270° of the discrete reception output H of Fig. 187 fbl (this range is based on the incoming radio waves, and a unidirectional direction indicating pattern is drawn on the cathode ray tube as shown in Fig. 9. Once the image is obtained, the direction θ of the incoming radio wave can be determined from this image.

As described above, according to the present invention, by signal processing the received signal, the received signal can immediately draw a pattern indicating the direction of arrival of the radio wave on the cathode ray tube while the antenna is rotated. The arrival direction of radio waves can be read in a short time, and the 180° ambiguity in the reading direction is eliminated.Furthermore, the display pattern is sharper, so
This also has the effect of reducing errors in reading direction.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a cardioid pattern with 1800° symmetry, FIG. 2 is a block diagram of an antenna that can obtain a cardioid pattern with 180° symmetry, and FIG. 3 is a block diagram of a direction finding device according to an embodiment of the present invention. , Figure 6 is a diagram showing the time-divided output of A and B in Figure 4, Figure 7 is a diagram showing the images drawn in ,
This figure shows the detection ratio of FIG. 6, and FIG. 9 is a diagram showing the detection ratio of FIG. 8 when the other one is removed. (1)...Antenna, (7)...Switcher, (6)...
...Switching signal generator, (8)...Video signal processor,
(4)... Braun tube, F... Time-divided received signal, H... Discrete received signal. Agent Makoto Kuzuno - Figure 3 Figure 4 Figure 6 Figure 7 Figure 10

Claims (1)

[Claims] (An antenna that can obtain a cardioid pattern with 11180° symmetry, a switch for switching between the two patterns of the antenna, and a switching signal generator that applies a switching signal to the switch for switching between the two patterns at a constant cycle; Among the time-divided received signals by the switch, the signal in the section above the level where the received signals of both patterns are at the same level is deleted to create a discrete received signal, and the time-divided received signal is further transferred to the above. A video signal processor that gates the discrete received signal with a signal obtained by 90° summation of signals synchronously detected by the switching signal, and a cathode ray tube that displays the output of the video signal processor, the display of the cathode ray tube. A direction finding device characterized by determining the direction of arrival of radio waves from the direction of the maximum level of Rin.