JPS6010269B2 - direction finder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In a direction finder that uses a directional frame antenna or an adkotok antenna and an omnidirectional vertical antenna, the follower generally moves only the output of the omnidirectional antenna by one 90 degrees. In addition to the phase box, it was combined with the output of the directional antenna.

However, in such a direction finder, since the output of the phase shifter changes depending on the frequency, for example, when using a frame antenna, when the reception frequency is low, the sense determination ratio, that is, the vertical antenna output and the directional antenna output The ratio between the two images decreases by 4.0, resulting in blurred sense and decreased sensitivity. Furthermore, as the reception frequency increases, there is a drawback that the sensing becomes unclear due to an excessive sense determination ratio, and a complicated circuit is required to eliminate this drawback. Therefore, the present invention provides a direction finder which is simple in construction and free from the above-mentioned drawbacks. FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, in which a two-core cable 5 is connected to two frame-shaped antennas 1 and 2, which are arranged so that their directivities are orthogonal to each other, via transformers 3 and 4, respectively. , 6 are connected.

In addition, the neutral points of the primary windings of the transformers 3 and 4 are connected, and a line 7 having the same inductance as the frame antennas 1 and 2 is inserted in series between this connection and the ground. A cable 5 is connected between both ends of the ring via a transformer 8 having the same characteristics as the transformers 3 and 4.
, 6 are connected to the same two-core cable 9. That is, the frame-shaped antennas 1 and 2 are also used as vertical antennas for determining the sense corresponding to the height thereof, and the output impedance of this vertical antenna and the frame-shaped antenna are the same, and their outputs have the same characteristics. Transmitted on cables 5, 6 and 9. Therefore, by guiding the output of each antenna to the receiving device 10 using this cable, the relationship between the phase and amplitude of the signals can be kept constant. In the receiving device 1, the outputs of the cables 6 and 6 are connected to balanced modulators 1 and 1, respectively.
.

The modulated waves applied from the oscillator 13 to the modulators 11 and 12 are given a phase difference of 90 degrees, and the outputs of the respective modulators are combined and applied to the phase shift circuit 14. Further, the output of the cable 9 is applied to a phase shift circuit 16 via an equivalent circuit 15 having input/output characteristics equivalent to those of the balanced modulators 11 and 12. Above 2
The outputs of the two phase shift circuits 14 and 16 are combined and the amplifier 17
The output is amplified by the detector 18 and the 13 groups g
demodulates the low frequency signal. By applying this reproduced low frequency signal to the phase measuring circuit 19 together with the reference phase signal obtained from the oscillator 13 and detecting the phase, the arrival direction of the radio wave can be determined. Figures 2a and 2b are circuit examples of the phase shift circuits 14 and 16 in Figure 1, respectively, in which a capacitive reactance xc and a resistor R or an inductive reactance XI and a resistor R are connected in series to a field effect transistor FET. The connection part is set as the output terminal C, or the gate of the transistor is set as the input terminal 1.

Therefore, the amplification factor of the transistor FET is 〃, and the internal resistance is y
, and let the inputs of terminals 1 in circuits a and b be e, ev, respectively, and the outputs of terminals ○ be E, ev, then the following holds true.

Therefore, if the IJ factors Xc, XI and the resistance R are selected so that xc. ．． ．． ．． ．． ．． [3, E, X. is obtained.

In this way, the phase shift circuits 14 and 16 shown in FIG. 1 have complementarity so that their total phase shift amount is always 90 degrees regardless of the frequency. In addition, in the {3'th equation above, the output e of the frame antenna is proportional to the frequency of the received radio wave, the output ev of the vertical antenna is proportional to the square of the frequency, and the reactance x is proportional to the frequency. In the end, the ratio I of the outputs of the phase shift circuits 14 and 16
Ev/B,l takes a constant value regardless of frequency. That is, since the sense determination ratio does not change depending on the receiving frequency, by setting el and ev appropriately in advance, a clear sense determination can always be made regardless of changes in the frequency of the received radio waves. Note that FIGS. 3a and 3b show other examples of the phase shift circuits 14 and 16, and the reference numerals of each part are the same as in FIG. 2.

That is, in this circuit, the following holds true, and the above-mentioned equation '3' can be obtained from these.

Therefore, the phase shift circuit of FIG. 3 also has complementarity and can keep the sense determination ratio constant regardless of frequency. As mentioned above, the phase shifters 14 and 16 give a positive phase shift to the outputs of the frame antennas 1 and 2, and a negative phase shift to the vertical antenna, so that the sum of the phase shifts becomes the frequency. The angle is always 90 degrees regardless of the angle, and this output is combined and sent to amplifier 1.
7 and is demodulated by a detector 18.

Therefore, by detecting the phase of the demodulated wave with the phase measuring circuit 19, the arrival direction of the received radio wave can be measured. In the embodiment shown in FIG. 1, the outputs of the frame antennas 1 and 2 are balanced-modulated with low-frequency signals having a phase difference of 90 degrees.
The direction of arrival of the radio wave is measured based on the phase of the demodulated wave, but it is also possible to measure the direction by, for example, adding the outputs of the frame antennas 1 and 2 to a goniometer and driving the goniometer with a servo mechanism. It is possible. Furthermore, low frequency modulation can be added to the output of the vertical antenna, and it is of course also possible to provide an independent vertical antenna separately from the frame antenna. Furthermore, an Adcock antenna can be used as the directional antenna, but in this case, depending on the configuration of the output circuit, the sense determination ratio may be inversely proportional to the frequency. In such a case, the same effect can be obtained by using the complementary phase shift circuits a and b shown in FIGS. 2 and 3 in reverse. As explained above, the present invention performs synthesis through a pair of complementary phase shift circuits such that the total phase shift amount is always 90 degrees regardless of the frequency, and it requires a complex circuit regardless of the frequency of the received radio waves. It is possible to always make clear sense decisions without the need for such things.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of an embodiment of the present invention, Figures 2 and 3 are
This is an example of a part of the circuit shown in the figure. In the figure, 1 and 2 are frame antennas, 3, 4, and 8 are transformers, 7 is a coil, 5, 6, and 9 are cables, 1 is a receiving device, 11 and 12 are balanced modulators, and 15 is a In the equivalent circuit, 13 is a low frequency oscillator, 14 and 16 are complementary phase shift circuits, 17 is an amplifier, 18 is a detector, and 19 is a phase measurement circuit. O/
Nezujiz Yugewokame

Claims (1)

[Claims] 1. A balanced modulator that modulates one of the outputs of a directional antenna or an omnidirectional vertical antenna with a low frequency signal, and an equivalent circuit that has input/output characteristics equivalent to that of the modulator and can add the output of the other, and the above-mentioned a pair of complementary phase shift circuits to which the outputs of a directional antenna and an omnidirectional vertical antenna are added so that the total phase shift amount is always 90 degrees regardless of frequency; the balanced modulator and the complementary phase shift circuit; a circuit that synthesizes and amplifies the outputs of the directional and omnidirectional antennas that have passed through one of the circuits and the other of the equivalent circuit and the complementary phase shift circuit; and a circuit that detects the output of the amplifier circuit and demodulates the low frequency signal. A direction finder characterized by a circuit for detecting