JPS6019841B2 - antenna device - Google Patents

Description

Detailed Description of the Invention The present invention relates to an antenna device that combines signals from multiple antennas and uses a phase shift circuit to change the directivity of the antenna. By using a capacitive diode, the directivity can be easily varied.

Ghosting is one of the problems that is currently attracting attention in urban areas.

This is because, as shown in Figure 1, the turtle wave emitted from the transmitting station 1 is reflected by the high-rise building 3 and the power transmission line 4 before it reaches the antenna 2, and reaches the antenna 2 later than the desired radio wave a which directly enters the antenna 2. This is a phenomenon that occurs due to the screen of a television receiver being extremely difficult to view. As a countermeasure against this ghost, there is a method of using an antenna with a large number of elements as shown in FIG. 2A and making the directivity loose as shown in FIG. ′
A method of using two or more antennas 5, 5' and combining the signals from these antennas 5, 5' with a mixer 6 to sharpen the directivity, or using two antennas 7, 7' of the same configuration as shown in Fig. 4. A method has been adopted in which the signals from the antennas 7, 7' are combined via a phase shifter 8, and the directivity is sharpened by controlling the phase shifter 8 to change the directivity.

In FIG. 2, arrow a indicates a desired wave, and arrow 6 indicates a ghost wave. 0 Among the methods described above, the most effective one is the one using the phase shifter 8 shown in FIG.

First, a conventional device using the phase shifter 8 will be explained with reference to FIG. The signal input from one antenna 7' is first passed through the VHFlow/VHFhigh filter 81 to VHFl.
The signal is separated into the ow channel signal and the VHFhi axis channel signal.

Thereafter, each signal passes through the corresponding phase shift circuits 82 and 83 and is mixed again at the VHFlow/VHFhigh filter 84. An air variable capacitor is used as a variable part in the series resonant circuit in the phase shift circuits 82 and 83, and the directivity can be changed by adjusting this air variable capacitor. The input signal is controlled by a fixed attenuator 85 to have the same amplitude as the signal output from the filter 84, and is combined with the signal from the filter 84 in a mixing circuit 86 to become the output of the phase shifter 8. , into a television receiver (not shown). However, in this case, since the direction of the ghost wave differs depending on the channel of the television signal, the phase shift circuits 82 and 83 must be adjusted each time the channel is changed, which is a practical inconvenience. The present invention eliminates the above-mentioned conventional drawbacks, and one embodiment thereof will be described below with reference to FIG. 6.

It should be noted that circuits in the figure having the same functions as those in FIG. 5 are given the same numbers and their explanations will be omitted. In the figure, reference numeral 9 denotes an electronic tuning circuit, which has a control voltage output terminal corresponding to each channel.
This control voltage output terminal is applied to the phase shift circuits 87 and 881 via the respective voltage adjustment circuits 10.

At this time, the voltage adjustment circuit 10' or VHF10w connected to the channel selection voltage output terminal corresponding to the first to third channels
The voltage adjustment circuit 10 connected to the phase shift circuit 87 and connected to the output terminals corresponding to the fourth and subsequent channels is VHFhi.
gh phase shift circuit 88, and each of the phase shift circuits 87 and 88 uses a variable capacitance diode instead of an air variable capacitor as the variable part of the resonant circuit, and the phase shift is performed by adjusting the voltage applied to the variable capacitance diode. Change the amount, that is, the directionality.

11! Shows a touch piece for channel selection.

In the above configuration, "to adjust the amount of phase shift, press the channel selection pin on the television receiver (not shown), press the touch panel 11 on the left end while watching the broadcast of the first channel, for example.
to adjust the voltage control circuit 10 for the best image quality. Perform this operation for each channel. Therefore, once the voltage adjustment circuit 10 is adjusted so that a predetermined voltage is applied to the phase shift circuits 87 and 88, after performing a channel selection operation on the television receiver, the corresponding touch piece 11 By touching , the corresponding voltage adjustment circuit 10 and phase shift circuits 87 and 88 operate, and the best image with fewer ghosts can be obtained over all channels. 0 In the above embodiment, a touch piece was used, but a general switch may be used.

As explained above, according to the present invention, by performing the channel selection operation on the television receiver and closing the corresponding switch such as a touch piece, it is possible to obtain the best image without ghosts on any channel. Obtainable.

Brief explanation of the drawings Figure 1 is a diagram for explaining ghosts, Figures 2, 3, and 4 are diagrams for explaining countermeasures against ghosts, and Figure 5 is a diagram for explaining a conventional phase shift circuit. A block diagram of the antenna device used. FIG. 6 is a block diagram of the antenna device in one embodiment of the present invention.

7,7'...Antenna, 81,84...VHFlow/VHFHigh filter evening, 85...
Fixed attenuator, 86... Mixing circuit, 87, 88...
...Phase shift circuit, 9...Tuning selection circuit, 10...Voltage adjustment circuit.

Figure 1 Figure 2 Figure 5 Figure 3 Figure 4 Figure 6

Claims (1)

[Claims] 1 a plurality of antennas; a phase shift circuit that receives a signal from at least one of the antennas;
means for combining the signal passed through the phase shift circuit with the signal from another antenna; a variable capacitance diode is inserted into the resonant section of the phase shift circuit, and a control voltage corresponding to each channel of the television receiver is provided. 1. An antenna device comprising a means for extracting the control voltage and applying the control voltage to a variable capacitance diode of the phase shift circuit to control directivity.