JPH08307140A - Diversity antenna system - Google Patents

Abstract

PURPOSE: To form dipole antennas whose number is equal to the number of frequency selection impedance elements while keeping the operation of each whip antenna by selecting the number of elements of whip antenna elements to be equal to the number of antenna switching circuits. CONSTITUTION: The system is provided with plural antenna elements 12a, 12b used for a whip antenna and a dipole antenna and an element selection means selecting any of the antenna elements 12a, 12b in response to a reception state signal obtained from a television receiver 2 and providing an output of a signal received by the antenna elements 12a, 12b to the television receiver 2, and frequency selection circuits 21, 22 whose impedance is zero at a set reception frequency band are connected between any of the antenna elements 12a, 12b and ground.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity antenna device installed in, for example, an automobile to receive TV radio waves.

[0002]

2. Description of the Related Art Generally, when receiving a television signal from a television receiver mounted on an automobile, a radio wave path to an antenna element is not always constant and a normal reception sensitivity cannot be obtained. There is provided a diversity antenna apparatus in which an antenna element as a path is prepared and one of the elements is selectively switched and used to obtain a good reception state.

FIG. 5 shows such a diversity antenna device 1.
3 shows the connection status of the TV receiver 2 of FIG. That is,
This diversity antenna device 1 receives a reception state signal from a television receiver 2 via a video input line 3, selects any one of the antenna elements 4 that provides optimum sensitivity according to the reception state, and selects this antenna element. The signal received at 4 can be supplied to the television receiver 2 through the antenna output line 7.

A power supply section 6 is connected to each of the diversity antenna device 1 and the television receiver 2 through a power cable 5 for supplying power for operating these circuits.

Further, such diversity antenna device 1
In the above, each one antenna element 4 can be used as a whip antenna, while two antenna elements 4 can be used to configure a dipole antenna.

[0006]

However, in such a conventional diversity antenna device, when each antenna element is used as a whip antenna, the grounding circuit E of the diversity antenna device has the above-mentioned power supply unit 6 and power supply unit as shown in FIG. Since it is formed through the cable 5, the screen of the specific channel is crushed, the color image becomes a black-and-white image, or noise is mixed in the sound.

This phenomenon is caused by the power supply section 6, the power supply cable 5, the video input line 3 and the antenna output line 7.
The circuit of the diversity antenna device is grounded through
The power supply section 6 and the power supply cable 5 operate as a part of the antenna, and the signal from the whip antenna and the signals picked up on the video input line 3 and the antenna output line 7 cancel each other at a specific frequency. ,
This is due to the occurrence of a signal dip (attenuation point) in that frequency range.

That is, due to insufficient grounding of the circuit of the diversity antenna device, the above-described screen crushing and black and white image formation occur.

On the other hand, in the form of use as a dipole antenna, since one of the pair of antenna elements is grounded in the diversity antenna device, there is no need to select this antenna element by switch switching, and the antenna switching circuit is correspondingly provided. decrease. That is, there is an inconvenience that the range of frequency selection cannot be expanded.

Further, if the number of antenna switching circuits is increased, it is necessary to increase the number of antenna elements, which causes a problem of cost increase.

The present invention has been made to solve the above problems, and the number of antenna elements of the whip antenna is the same as the number of antenna switching circuits, and the frequency selection circuit is maintained while the operation of each whip antenna is maintained. It is an object of the present invention to obtain a diversity antenna device capable of forming as many dipole antennas as the above.

[0012]

A diversity antenna device according to the present invention includes a plurality of antenna elements used as a whip antenna and a dipole antenna, and the antenna element of the antenna element according to a reception state signal obtained from a television receiver. An element selecting means for selecting one and outputting a signal received by the antenna element to the television receiver, and between one of the two antenna elements constituting the dipole antenna and the ground, The frequency selection circuit is such that the impedance becomes zero in the set reception frequency band.

[0013]

In the diversity antenna device according to the present invention, the frequency selecting means is connected to the frequency selecting means with zero impedance in a predetermined frequency range, for example, in the frequency range of 1 to 3 channels or 4 to 12 channels of television channels. Ground the antenna element well,
A dipole antenna is configured together with another antenna element corresponding to this antenna element to improve the sensitivity and to solve the problem of the conventional screen being blackened and crushed.

On the other hand, in a region other than the above frequency range, other transmission radio waves of a predetermined frequency can be used as a whip antenna together with the impedance of the frequency selecting means, so that the number of antenna switching circuits can be increased as compared with the conventional one.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an internal circuit showing a diversity antenna device of the present invention. In FIG. 1, 11 is a diversity antenna device, and 12a and 12b are a pair of a whip antenna and a dipole antenna provided in the diversity antenna device 11. It is an antenna element.

Each of these two antenna elements 1
2a and 12b are such that the upper two opposite ones are 70 cm for receiving television channels 1 to 3 and the lower two opposite ones are 35 cm, for example. It is movably supported.

Reference numeral 14 is each of the above antenna elements 1.
Fixed contacts of switches provided corresponding to 2a and 12b are electrically connected to each corresponding one of the pivotally supporting portions 13 via a print pattern or a lead wire. Reference numeral 15 denotes a movable contact piece which is selectively switched and connected to each of these fixed contacts 14.

Further, 16 is connected to the movable contact piece 15, amplifies the received signal received by each antenna element 12a, 12b, and supplies it to the television receiver 2 as an antenna output through the feeder 17 for high frequency. It is an amplifier.

On the other hand, 18 is an amplifier which receives and amplifies a signal according to the reception state output from the television receiver 2.
Reference numeral 19 is a sync separation circuit for separating a sync signal from the signal from the amplifier 18.

Reference numeral 20 is a microprocessor for outputting an antenna element selection signal corresponding to the signal according to the reception state in accordance with the timing of the synchronization signal separated by the synchronization. The microprocessor 20 is provided with the antenna element selection signal. According to the above, the movable contact piece 15 functions to switch and control one of the fixed contacts.

Further, reference numerals 21 and 22 denote frequency selection circuits respectively connected between one of the antenna elements 12a and 12b facing each other on the upper side and the ground, which are an inductance 21a and a capacitor 21b. It is composed of an inductance 22a and a capacitor 22b.

Of these, the frequency selection circuit 21
The size of each of the inductance 21a and the capacitor 21b is selected so that the impedance becomes zero when the television channel receives a radio signal having a frequency of 1 to 3 channels. For example, the inductance 21
a is 47 nH and the capacitor 21b is 39 pF.
On the other hand, the frequency selection circuit 22 has four TV channels.
Each impedance 22 is adjusted so that the impedance becomes zero when receiving the radio signal of the ~ 12 channel frequency.
The sizes of a and the capacitor 22b are selected. For example, the inductance 22a is 17 nH and the capacitor 22b is 22 pF.

In the diversity antenna device having such a configuration, the four antenna elements 12 whose directions are different depending on the control output of the microprocessor 20 based on the signal output from the television receiver 2 according to the reception state.
The movable contact piece 15 is switch-connected to either of the fixed contacts 14 so as to select either a or 12b.

By such switching connection, each one of the antenna elements 12a and 12b is used as a whip antenna, and it is possible to receive a transmission radio wave within a predetermined frequency range although the sensitivity is not sufficient. Then, the received signal is supplied to the television receiver 2 as an antenna output via the high frequency amplifier 16, and a desired image can be obtained on the screen.

On the other hand, when the television receiving sensitivity is sufficient, two antenna elements 12a and 12 are provided.
Each of b is used as a dipole antenna. This dipole antenna has two antenna elements 1 each.
Formed by 2a, 12a and 12b, 12b,
One of the antenna elements 12a and one of the antenna elements 12b must be completely grounded.

For this reason, for example, the frequency selection circuit 21 of the LC series resonance circuit configuration connected to the antenna element 12a is designed so that the impedance becomes zero in the frequency range of 1 to 3 television channels and 4 to 1
The constants of the circuit elements such as the above-described inductances are determined as described above so that the impedance becomes zero in the frequency region of two channels.

Therefore, when the television receiver 2 receives 1 to 3 channels, one of the antenna elements 12a is grounded because the impedance becomes zero, and the other antenna element as a dipole antenna is in this frequency region. The television reception signals of the first to third channels are input from the antenna element 12a with high sensitivity, and the television reception signals are transmitted via the fixed contact 14 and the movable contact piece 15 to the television receiver 2.
Is input to

On the other hand, when the television receiver 2 receives channels 4 to 12, the impedance of the frequency selection circuit 22 of the LC series resonance circuit configuration becomes zero, so that one antenna element 12b is grounded. 4-1 from the other antenna element 12b in this frequency range
A 2-channel television reception signal is input with high sensitivity, and this is input to the television receiver 2.

Therefore, all the above antenna elements 1
2a and 12b can function as a whip antenna and a dipole antenna, and the conventional inconvenience that only two antenna elements can be switched when used as a whip antenna even though there are four antenna elements 12a and 12b. It can be avoided.

When used as a dipole antenna, one of the antenna elements 12a and 12b is completely grounded, so that the signal received by the antenna element is canceled by the signal picked up by the input / output cable or the like. It is possible to prevent the occurrence of dips in the received signal in the specific frequency range, and it is possible to improve the difference in antenna sensitivity from the whip antenna gain.

In the above embodiment, the frequency selection circuit 2
Although 1 and 22 are made to resonate in series in channels 1 to 12 which are VHF frequency regions, it is optional to make them resonate in series in frequency regions other than this.
The antenna elements 12a and 12b can also be configured to be able to receive signals in the UHF frequency region.

FIG. 2 shows a sensitivity characteristic test system for a diversity antenna apparatus according to the present invention, in which each antenna element 12a is at an angle of 45 degrees with respect to a horizontal plane.
Further, each antenna element 12b is horizontally extended straight and is mounted on the measurement plate 31.

Further, a horn antenna 32 is disposed so as to face the diversity antenna device, and a tracking generator 33 can emit a signal radio wave in a television frequency range of 50 to 800 MHz. Further, a spectrum analyzer 34 is connected to the feeder 17 of the diversity antenna device.

In this sensitivity characteristic test system, the tracking generator 33 supplies signals in the VHF and UHF frequency regions to the horn antenna 32. As a result, the horn antenna 32 emits radio waves in the frequency range to the surroundings.

Therefore, the diversity antenna device receives the radio wave, selects it as described above, and inputs it to the spectrum analyzer 34 through the feeder 17, where the level of the received signal is measured.

The data thus measured are as shown in FIGS. 3 and 4. That is, FIG.
In the improved device A according to the embodiment of the present invention, the steep dip generated at 100 to 102 MHz in the conventional device B is completely removed.

Also, looking at the sensitivity characteristics of VHF and UHF over the entire frequency range, it was found that the improved device A was significantly improved as compared with the devices C and D of other companies, and particularly in the low range of VHF. A sensitivity improvement of 20 dB or more was observed from the high frequency region to the high frequency region.

[0038]

As described above, according to the present invention, a plurality of antenna elements used as a whip antenna and a dipole antenna, and one of the above-mentioned antenna elements depending on a reception state signal obtained from a television receiver. And an element selecting means for outputting the signal received by the antenna element to the television receiver, and setting reception between any one of the two antenna elements constituting the dipole antenna and the ground. Since it is configured to connect the frequency selection circuit that impedance becomes zero in the frequency band, the number of the antenna elements of the whip antenna is the same as the number of antenna switching circuits, and the number of frequency selection circuits is maintained while maintaining the operation of each whip antenna. The effect that only the dipole antenna can be formed is obtained. .

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a diversity antenna device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a sensitivity characteristic test system of the diversity antenna device of the present invention.

FIG. 3 is a sensitivity characteristic diagram showing sensitivity characteristics of the present invention and the conventional diversity antenna device measured by the sensitivity characteristic test system of FIG.

FIG. 4 is a sensitivity characteristic diagram showing sensitivity characteristics of the present invention and the conventional diversity antenna device measured by the sensitivity characteristic test system of FIG.

FIG. 5 is a configuration diagram showing a connection state of a diversity antenna device of the related art and the present invention to a television receiver.

[Explanation of symbols]

 2 TV receiver 11 Diversity antenna device 12a, 12b Antenna element 21, 22 Frequency selection circuit

Claims (1)

[Claims] 1. A plurality of antenna elements used as a whip antenna and a dipole antenna,
A diversity antenna apparatus comprising: an element selecting means for selecting one of the antenna elements and outputting a signal received by the antenna element to the television receiver according to a reception state signal obtained from the television receiver. A diversity antenna device, wherein a frequency selection circuit having an impedance of zero in a set reception frequency band is connected between any one of the two antenna elements constituting the dipole antenna and the ground.