JPH0731234B2 - Mutual Impedance Interference Canceller for Sideband Antenna for Doppler VOR - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to a Doppler VOR (Doppler VHF Omnidirectional Rad).
High frequency (hereinafter RF
That is, it relates to a mutual impedance interference elimination device for a sideband antenna for Doppler VOR using an Alford antenna equipped with a switch circuit.

[Prior Art] Generally, a Doppler VOR device is used for giving direction information from a reference point magnetic north to an aircraft.

The antenna of this Doppler VOR device is composed of 50 sideband antennas and one carrier antenna.

The carrier antenna radiates a signal having a constant phase irrespective of the azimuth, and the sideband antenna radiates a signal whose phase changes depending on the azimuth. These two signals are received at the aircraft receiver. By comparing the two phases, the aircraft receiver can know the azimuth from the reference point, that is, the Doppler VOR local station, at the receiving point.

In the Doppler VOR device, the RF signal from the sideband transmitter 1 is supplied to the antenna switching device 2 as shown in FIG. 5, and the switching of the antenna switching device 2 causes the corresponding feeding cables 401, 402, 403. The sideband antennas 301, 302, 303 ... Are sequentially switched and fed.

Each of the side band antennas 301, 302, 303, etc. is composed of an Alford antenna installed on the circumference of a diameter of 5.1λ (frequency 108 to 118 MHz) such as a diameter of 13.3 m (frequency 115 MHz) as shown in FIG. . 5 is a carrier antenna.

[Problems to be Solved by the Invention] These sideband Alford antennas have a positional relationship that is extremely close (0.32λ) to the adjacent antenna in the arrangement, and therefore, 50 sideband Alford antennas are used. Cause mutual interference of impedance.

Mutual interference of antenna impedances adversely affects VOR course information. Therefore, when installing the sideband antenna, 50 power supply cables 401, 402, 403 from the antenna switching device 2 to the sideband antennas 301, 302, 303 are installed.
By adjusting the length of ..., the mutual impedance interference between adjacent antennas is reduced and the influence on the VOR course is eliminated. That is, the generation of parasitic current to the adjacent antenna is reduced, and re-radiation from the adjacent antenna is prevented.

The length of the conventional sideband power supply cables 401, 402, 403 is
Since the physical lengths between the sideband antennas 301, 302, 303 ... And the antenna switching device 2 are different depending on each facility, adjustment is possible only with the antennas 301, 302, 303.

For this reason, it takes a lot of complicated measurement and much time to determine the length of the power supply cables 401, 402, 403 ....

The present invention has been made in view of the above circumstances.
A mutual impedance interference elimination device for the Doppler VOR sideband antenna that reduces impedance mutual interference between adjacent sideband antennas and obtains good course information for the aircraft without complicated adjustment of the R sideband power supply cable length. The purpose is to provide.

[Means and Actions for Solving the Problems] In order to achieve the above object, the present invention provides an electronic antenna switching device for switching and feeding a high frequency signal from a sideband transmitter of a Doppler VOR to a sideband antenna, The electronic antenna switching device is provided with a side band antenna composed of an Alford antenna having a high-frequency switching circuit connected via a power supply cable, and the high-frequency switching circuit is switched corresponding to the electronic antenna switching device. The high-frequency switch circuit provided in the sideband antenna is switched in correspondence with the electronic antenna switching device to eliminate the interference of the mutual impedance of the sideband antenna.

[Embodiment] In this embodiment, as shown in FIG. 1, an antenna switching device 8 for switching and feeding an RF signal from the sideband transmitter 6 to each sideband antenna for Doppler VOR and an RF switch circuit are provided. It is composed of sideband antennas 901, 902, 903, ... 950, which are Ford antennas.

The RF signal from the sideband transmitter 6 is fed to the input terminal 7 of the antenna switching device 8, and the feeding cables 1101, 1102, 1103 ... 1150 corresponding to the switching of the antenna switching device 8 respectively.
, 950, and 950 are sequentially switched and fed to the sideband antennas 901, 902, 903 ... 950.

Embodiments of the present invention will be described in detail below with reference to FIGS.

As shown in FIG. 2, each output terminal 101 of the antenna switching device 8,
102, 103 ... (100 + n) are connected to the RF switch circuit 121 of the side band antenna 901 ... The switching circuit of the antenna switching device 8 and the RF switching circuit 121 of the sideband antenna are composed of an electronic switching circuit using the RF switching diode D.

RF switching diode D of this electronic switch circuit
By applying a forward bias voltage to the antenna switching signals S1, S2, S3 ... Sn, the antenna switching device 8 and the RF switch circuit 121 can be brought into conduction. Also, this RF
Antenna switching signals S1, S2, S3 are applied to the switching diode D.
By applying a reverse bias voltage of Sn, the antenna switching device 8 and the RF switch circuit 121 can be cut off. That is, by sequentially switching the electronic switch circuits of the antenna switching device 8 and the sideband antennas 901 ..., the 50 power supply cables 1101 ... Are brought into a conductive state at a high frequency and the RF signals from the sideband transmitters 6 are transmitted. Sideband antenna 901 consisting of Alford antenna…
The RF signal can be emitted sequentially. FIG. 3 shows the timing of antenna switching by the antenna switching signals S1, S2, S3 ... Sn.

At this time, as shown in FIGS. 4 (a) and 4 (c), the side band antenna composed of the Alford antenna in which the RF signal is not radiated is connected to the RF switching diode D from the antenna switching device 8 to the feeding cable 1101 ... A reverse bias voltage is applied from the switching signals S1 ... That are supplied through the RF switch circuit 121 provided in the balun circuit 13 of the antenna to be in the cutoff state. As a result, the balun circuit 13 of this antenna becomes non-conductive in terms of high frequency in the parts A and B, and the two elements of the antenna are separated, resulting in a high impedance. Therefore, this antenna is less likely to be affected by the radiation antenna, and re-radiation from the adjacent antenna can be suppressed without adjusting the length of the feeding cables 1101 ... FIG. 4 (b) shows a sideband antenna composed of an Alford antenna in which the RF signal is radiated, and the RF switch circuit 121 provided in the balun circuit 13 of the antenna becomes conductive.

As described above, by providing the RF switch circuit in the sideband antenna made of Alford antenna,
The feeding cable to the antenna can be unadjusted. It is also possible to improve the performance by inserting an RF switching diode into another antenna element and dividing the element.

[Advantages of the Invention] As described above, according to the present invention, impedance mutual interference between adjacent sideband antennas is reduced without complicated adjustment of the Doppler VOR sideband feeding cable length, which is favorable for aircraft. A mutual impedance interference canceller for a sideband antenna for Doppler VOR capable of giving course information can be provided.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention, FIG. 2 is a structural explanatory view showing a concrete example of the present invention, and FIG. 3 is a waveform diagram showing an example of an antenna switching signal according to the present invention. FIG. 4 is an explanatory diagram showing an example of the operation of the sideband antenna according to the present invention, FIG. 5 is a configuration explanatory diagram for explaining a conventional sideband antenna mutual impedance interference removing device for Doppler VOR, and FIG. FIG. 3 is a configuration explanatory view showing the sideband antenna of FIG. 6 ... Sideband transmitter, 8 ... Antenna switch, 90
1,902,903 …… 950 …… Sideband antenna, 121 …… R
F switch circuit, D ... RF switch diode.

Claims (1)

[Claims] 1. A plurality of power supply cables in which a high-frequency signal from a sideband transmitter of a Doppler VOR is distributed via each of a plurality of electronic switches forming an antenna switching device, and the ends of the plurality of power supply cables are connected to each other. Each sideband antenna connected via a high-frequency switch, one electronic switch of the antenna switching device and a high-frequency switch connected to the end of the power supply cable connected to the electronic switch are turned on or off at the same time. And a means for applying an antenna switching signal to each electronic switch and high-frequency switch, a mutual impedance interference canceling device for a sideband antenna for a Doppler VOR.