JPH0449803B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION When one end of a horizontal antenna parallel to the ground is grounded and the reception output is taken out from the other end, a cardioid curve sensitivity characteristic is obtained in response to changes in the direction of incidence of radio waves. Therefore, a direction finder can be obtained using such an antenna, but the present invention uses an electronic switching circuit to obtain a waveform output corresponding to the arrival direction of the radio wave, and also to suppress the noise component when the radio wave is weak. To provide an antenna device that prevents measurement errors from increasing due to radio waves, or enables accurate azimuth measurement even when the AGC operation of a receiver is not completed due to intermittent radio waves. It is.

The present invention involves arranging a plurality of band-shaped antenna elements on a conductor plate that can be considered as a ground plane, such as the fuselage of an airplane or the roof of a car, so that their central portions are insulated from each other and intersecting each other. Both ends of each antenna element are grounded alternately with a phase difference corresponding to the above-mentioned crossing angle, and the outputs obtained from the other ends are combined, and one vertical antenna element is further provided at the crossing point to combine the outputs of this antenna element. The above-mentioned combined output is combined with an appropriate phase. Therefore, the arrival direction of the radio wave can be determined from the phase angle of the signal obtained by amplitude or phase detection of the above-mentioned combined output without requiring any mechanical movable part such as rotating the antenna.
In addition, by providing a vertical antenna element, the combined antenna output can be increased or a phase modulated output can be obtained. Therefore, errors due to noise are reduced and accurate direction measurement can be performed, and even in cases where the AGC circuit does not function sufficiently due to intermittent radio waves, direction measurement can be performed without any problem using the phase modulation output. Furthermore, since the vertical antenna element is arranged at the center of the strip antenna element, there is no fear that its directivity characteristics will be disturbed.

FIG. 1 is a longitudinal cross-sectional view of an embodiment of the present invention, and FIG. 2 is a partially cutaway plan view thereof. The conductor plate 1 is, for example, the fuselage of an airplane or the roof of an automobile. A circular hole 2 is provided in this conductor plate 1, and two band-shaped antenna elements 4 and 5 are attached to the inner surface of an insulator plate 3 which closes the hole and are perpendicular to each other. These antenna elements are formed so that their widths gradually increase at both ends, and intersect at the narrow center portions of the antenna elements so as not to touch each other. Furthermore, a shallow pail-shaped conductor plate 6 whose peripheral edge is connected to the conductor plate 1 is provided inside the circular hole 2, and a conical raised portion 7 is formed in the center of the conductor plate 6, so that this substantially grounded conductor plate 6 is provided. The distance between the conductor plate 6 and the antenna elements 4, 5 is increased according to their widths. That is, antenna elements 4 and 5 are designed to have a constant characteristic impedance regardless of their position. A housing 8 housing an electronic switching circuit, a combining circuit for each antenna output, etc. is attached to the back side of the conductor plate 6, and both ends of the band-shaped antenna elements 4, 5 are connected to this housing using coaxial cables 9, 9, . . . It is guided into the body. Furthermore, the antenna element 4,
A vertical antenna element 10 protruding to the outside of the insulator plate 3 is provided at the intersection at the center of the antenna element 5, and its base is guided into the housing 8 so as not to come into contact with the antenna element. The housing 8 is connected to a cable 11 that accommodates a switching signal to be applied to the switching circuit, a necessary power source, etc., and a coaxial cable 12 that leads a signal obtained by combining the outputs of each of the antenna elements to the main body of the direction finder. There is.

FIG. 3 is a longitudinal cross-sectional view of another embodiment of the present invention, in which the conductor plate 1 is the roof of an automobile, and a housing 13 with a top cover made of an insulator is fixed to the roof with a suction cup or a magnet 14. There is. A ground conductor plate 6, band-shaped antenna elements 4 and 5, a housing 8, etc. are provided in the housing, and a vertical antenna element 10 is made to protrude upward from the center of the housing 13.

FIG. 4 is a plan view of the antenna elements 4, 5, and 10, and a diagram showing the configurations of the electronic switching circuits 15, 16, the phase adjustment circuit 17, and the combining circuit 18 connected thereto. The output is conducted by the coaxial cable 12 to a receiver. Further, the switching circuits 15 and 16 are connected to terminals 19 and 20 by the cable 11 shown in FIG. 1 or 3.
As shown in FIGS. 5A and 5B, a rectangular switching signal with a phase difference of 90 degrees corresponding to the intersecting angle of antenna elements 4 and 5 is applied, and vertical antenna element 10
The output is connected via the changeover switch 21 to the phase adjustment circuit 17 or the communication transmitter/receiver via the cable 22. That is, when the signal A is positive, the lower end of the antenna element 4 is grounded by the resistor 23 equal to the characteristic impedance and the output is sent from the upper end, as shown in FIG. 6, and when the signal A is negative, conversely, the upper end is grounded. The output is applied to the combining circuit 18 from the lower end. Furthermore, during the period when the signal B is positive, the right end of the antenna element 5 is grounded through a resistor 24 equal to the characteristic impedance, and the output is sent out from the left end, as shown in FIG.
Conversely, during the negative period, the left end is grounded and the output is sent from the right end.

FIG. 7 shows cardioid curves R and S showing the directivity of the antenna elements 4 and 5 in the state shown in FIG.
2 shows a directivity curve of the combined output of these elements 4 and 5, that is, a cardioid curve T obtained by combining curves R and S. However, when the polarity of signal A in FIG. 5 is reversed,
The upper end of the antenna element 4 shown in the figure is grounded, and the output is sent out from the lower end. Therefore, the curve R in FIG. 7 has a shape that is upside down with respect to the origin O, and therefore the composite curve T has a shape that is rotated 90 degrees to the left. That is, periods a, b, c in Fig. 5,
At d, the combined directivity of the antenna elements 4 and 5 rotates intermittently at 90 degree intervals as shown by cardioid curves T, U, V, and W in FIG. Therefore, assuming that radio waves are incident from the direction indicated by arrow z, the combined output of the band-shaped antenna elements 4 and 5 during the above periods a, b, c, and d is respectively O.
-t, O-u, O-v, O-w. 9th
Figure C shows the combined output of elements 4 and 5 in this case.

Further, since the vertical antenna element 10 is non-directional, its output maintains a constant amplitude regardless of the incident direction and time of the radio waves, as shown in FIG. 9D. Therefore, if the switch 21 in FIG. 4 is kept in the state shown in the figure, this output is sent via the phase adjustment circuit 17 to the combining circuit 18 in addition to the combined output of the band-shaped antenna elements 4 and 5 as shown in FIG. 9C. It will be done. For this reason, the vertical antenna element 1 is controlled by the phase adjustment circuit 17.
When the phase of the output of 0 is made the same phase as the output of the strip antenna elements 4 and 5, the output of the combining circuit 18 is as shown in FIG.
become that way. This composite output is connected to the coaxial cable 12
When the signal is guided to the receiving circuit and amplitude detection is performed, Fig. 9
A low frequency signal corresponding to the link line C in the figure is obtained as shown in FIG. Therefore, by applying this signal to, for example, a narrow band filter, extracting a sine wave component having the same frequency as the rectangular wave in FIG. The direction of incidence of radio waves can be detected. In other words, in this case, since the output of the vertical antenna element 10 is combined with the outputs of the strip antenna elements 4 and 5 in the same phase, the amplitude increases as shown in FIG. The influence of high frequency noise components is removed and accurate direction detection can be performed.

In addition, the phase adjustment circuit 17 shown in FIGS. 4 and 6
When the output of the vertical antenna element 10 is phase-shifted by about 90 degrees and a phase difference of 90 degrees is given between the output of the vertical antenna element 10 and the composite output of the strip antenna elements 4 and 5, the phase of the output of the composite circuit 18 becomes as shown in FIG. It changes depending on the amplitude of the combined output of the band-shaped antenna elements 4 and 5 as shown in FIG.
Therefore, in the receiving circuit, when the output of the cable 12 is applied to an amplitude limiter to have a constant amplitude and then applied to, for example, a frequency discriminator, a pulse signal as shown in FIG. 9G can be obtained. When this signal is applied to a narrowband filter as described above to extract a sine wave component having the same frequency as the rectangular wave shown in FIG. 5, the direction of arrival of the radio wave is indicated by the phase of this signal.
That is, by providing a vertical antenna element 10 that can obtain an output with a constant amplitude regardless of the direction in which radio waves arrive, and by shifting the phase of the output and combining it with the output of the strip antenna element, a phase or frequency modulated wave is obtained. Even when the automatic gain control circuit of the amplifier does not function due to intermittent radio waves, it is possible to obtain accurate azimuth measurements.

Although the above explanation uses two band-shaped antenna elements arranged perpendicular to each other, such a device produces an octant error due to the relationship between the length of the antenna element and the wavelength of the radio wave. . However, for example, when four antenna elements are arranged at 45 degree intervals, the octant circle error disappears and becomes relatively small16
Since only the circular error remains, highly accurate azimuth measurement can be performed over a wider frequency range.

Additionally, since the antennas of communication transmitters and receivers are often tuned to the receiving frequency, if the frequency of direction-finding radio waves is the same as the frequency band used for communication, interference will cause large errors in direction-finding. . In such a case, the cable 22 shown in FIG.
By connecting the vertical antenna elements 10 to a communication transceiver and sharing the vertical antenna element 10, the above-mentioned difficulties are eliminated. Note that in such a case, the communication receiving circuit can be used as an amplifier section of the direction finder.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a partially cutaway plan view of FIG. 1, FIG. 3 is a longitudinal sectional view of another embodiment of the invention, and FIG. A diagram showing the electrical configuration of an embodiment of the present invention, FIG. 5 is a switching signal waveform diagram of the strip antenna element in FIG. 4, and FIG. 6 shows a circuit of the device in FIG. 7 is a directional characteristic curve of the strip antenna element in the state shown in FIG. 6, FIG. 8 is a directional characteristic curve in each switching state of the antenna element, and FIG. 9 is a waveform explaining the operation of the embodiment of the present invention. It is a diagram. In the figure, 1 is a conductor plate, 2 is a circular hole, and 3 is a conductor plate.
is an insulator plate, 4 and 5 are strip antenna elements, 6 is a conductor plate, 7 is a raised portion, 8 is a housing, 9 is a coaxial cable, 10 is a vertical antenna element, 11 is a cable,
12 is a coaxial cable, 15 and 16 are switching circuits, 1
7 is a phase adjustment circuit, and 18 is a synthesis circuit.

Claims (1)

[Claims] 1 A plurality of strip antenna elements are superimposed on a substantially grounded conductive plate at an appropriate distance so that their central portions are insulated and intersect with each other, and both ends of each antenna element are a plurality of electronic switching circuits that are alternately grounded at a constant period with a phase difference corresponding to the angle and transmit the received output from the other end; and a vertical antenna element disposed in the center of the strip antenna element; An antenna device for a direction finder, comprising a circuit that combines the outputs of each of the electronic switching circuits and the output of the vertical antenna element in an appropriate phase relationship.