JP3353349B2 - Television receiver audio FM transmitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved FM transmitter for a television receiver, and more particularly to an improved FM transmitter mounted on a mobile body and used in combination with a diversity antenna controller.

[0002]

2. Description of the Related Art As an example of a conventional method of transmitting an audio FM transmitter of a television receiver, a vehicle-mounted liquid crystal television will be described.

[0003] A general design method of a currently mounted on-board liquid crystal television is a television transmitter comprising an FM signal generation stage for generating a composite FM signal from an audio signal and an RF modulation stage for converting into an FM wave. Equipped inside the body, F
A method of transmitting an M-wave output by a strip line antenna or an antenna made of metal parts is employed.

[0004]

The problem with the conventional method of transmitting an audio FM transmitter of a television receiver is that the FM transmitter is regulated to less than 54 dBμV / m by the 3 m method according to the Radio Law. Depending on the installation location and the position of the antenna of the FM receiver of the vehicle, the reception state is deteriorated.

[0005] This tendency becomes remarkable at the time of stereo transmission in which the receiving sensitivity of the FM receiver is substantially reduced, and the practical range is 2 m to 3 m, and the guaranteed value is 1.5 m.

The following three points can be considered as causes of such a problem.

[0007] 1) The antenna positions of the FM receiver of the vehicle include a rod antenna of a front pillar, a motor drive rod antenna of a rear fender, a printed antenna on the rear glass, and a trunk lid antenna, which are installed near the passenger seat. The distance from the television main unit is long, and the gain of the antenna alone is low, so that the reception state particularly deteriorates in the print antenna and the trunk lid antenna.

[0008] 2) It is difficult to make the directivity of the FM wave transmitted from the television main body circular, that is, to make it uniform in all directions.

There is a difference of 10 dB to 15 dB between the peak and the bottom of the directivity even if the design is devised, and the Radio Law is applied to the peak.

[0010] Therefore, if the antenna position of the FM receiver is in the bottom direction of the directivity, the reception sensitivity is deteriorated, and the reception state changes only by adjusting the direction of the television main body.

3) The antenna of the FM receiver of the vehicle is basically designed so that good sensitivity can be obtained not to the FM wave from the inside of the vehicle but to the FM wave from outside the vehicle. Conditions are bad for FM transmitters that do this.

Particularly, the heat insulating glass used in recent luxury cars greatly attenuates the FM wave, so that this tendency is enhanced.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems of the prior art, and an object of the present invention is to provide a television receiver with a high practicality after clearing the Radio Law. To provide an FM transmitter to the market.

[0014]

SUMMARY OF THE INVENTION In order to solve the above problems, a television receiver audio FM transmitter according to the present invention selects one input from a plurality of antenna inputs and supplies the selected input to a television receiver. And a television receiver, and a detector configured to detect an unselected antenna input that is not selected from an antenna selection signal of the diversity antenna controller in an apparatus including an FM transmitter that transmits an audio signal as an FM wave. A supply unit for selectively supplying an FM wave output of the FM transmitter device to each antenna input, and a control unit for controlling which antenna input the FM wave output is supplied to by the supply unit. By means of at least one of said non-selected antenna inputs To the antenna input, and supplying an FM wave output. In addition, in a device configured by a diversity antenna control device that selects one input from a plurality of antenna inputs and supplies the input to a television receiving device, a television receiving device, and an FM transmitter device that transmits an audio signal as an FM wave, Utilizing an antenna selection signal of the diversity antenna control device, a detecting means for detecting an unselected antenna input not selected for the television receiver, and controlling which antenna input the FM wave output is supplied to Control means for supplying FM waves to all of the non-selected antenna inputs.

[0015]

FIG. 1 is a block diagram of an antenna input circuit according to an embodiment of a transmission method of a television receiver audio FM transmitter according to the present invention.

This embodiment is constructed in consideration of the purpose of facilitating the explanation of the operation and the cost condition when actually applied to a product.

[0017]

A diversity antenna is composed of two antennas, each composed of two elements whose directivity is substantially orthogonal to each other, from 1.5 m to 1.5 m.
This is a four-input system that is installed at a distance of 2.0 m and combines the effects of space diversity and directivity diversity. It is the most common type that is attached to the top of the rear glass and used.

The antenna inputs (11a) to (11a) shown in FIG.
The output of the diversity antenna is connected to d).

Each antenna input is unified via DC blocking capacitors (12a) to (12d) and antenna selection switching elements (13a) to (13d), and further via a DC blocking capacitor (12e). To the tuner input (14).

On the other hand, to the input side of the antenna selection switching element, antenna selection signals (15a) to (15d) are connected via bias resistors (16a) to (16d).
A single output side has a bias resistor (16
e) is connected.

The antenna selection signal is active high, and one of the four signals is controlled to be high (5 V) and the other three to low (0 V) in both the holding period and the comparison period of the antenna input. The antenna selection switching element corresponding to the high antenna selection signal is turned on, the antenna input is electrically connected to the tuner input, and the other antenna selection switching elements are reverse-biased by the bias resistor (16e) and cut off. Then, the antenna input is electrically disconnected from the tuner input.

The above is the description of the diversity antenna input stage control.

The FM wave output (17) in FIG. 1 is an RF modulation output of the FM transmitter, and is an output in which output level management for clearing radio regulations and impedance management for achieving impedance matching with a diversity antenna are performed. It is in the form.

The output of the FM wave is a DC blocking capacitor (12
f), and is divided into four by the FM wave supply switching elements (18a) to (18d) and the DC blocking capacitor (12).
g) to (12j) are connected to the input side of the antenna selection switching element.

On the other hand, a 3V power supply (19) is connected to the input side of the FM wave supply switching element via a bias resistor (16f), and a corresponding antenna selection signal is supplied to the output side of the FM wave supply switching element by a bias resistance. (16g)
To (16j).

According to this configuration, the FM wave supply switching element corresponding to the high antenna selection signal is cut off by the reverse bias to supply the FM wave to the antenna input electrically connected to the tuner input. Instead, the FM wave supply switching element corresponding to the low antenna selection signal is turned on to supply the FM wave from the tuner input to the electrically disconnected antenna input.

As a result, it is possible to always transmit FM waves from three of the four diversity antennas without affecting the reception sensitivity of the television receiver.
The following effects are provided for the items described in the problem to be solved by the invention.

1) Since the distance between the FM wave transmitting unit and the receiving unit is 1/3 to 1/10 as compared with the print antenna and the trunk lid antenna in which the conditions of the distance and the antenna gain are strict, the receiving state is improved.

2) The diversity antenna 3
Since the element is used, the directivity is greatly improved, and since the transmitting unit is fixed, the receiving state does not change depending on the use conditions.

3) Since the FM wave transmitting section is outside the vehicle, F
The problem does not occur even in a vehicle that employs heat insulating glass that greatly attenuates M waves.

[0032]

As described above, according to the television receiver audio FM transmitter of the present invention, the practical reach of the audio FM transmitter device mounted on the in-vehicle television receiver is regulated by the Radio Law. Is significantly improved within the condition of clearing

[Brief description of the drawings]

FIG. 1 is an antenna input circuit configuration diagram of an embodiment of a transmission method of a television receiver audio FM transmitter according to the present invention.

[Explanation of symbols]

(11a) to (11d): Antenna input (12a) to (12j): DC blocking capacitor (13a) to (13d): Antenna selection switching element (14): Tuner input (15a) to (15d): Antenna selection signal (16a) to (16j): Bias resistance (17): FM wave output (18a) to (18d): FM wave supply switching element (19): 3V power supply

Claims (2)

(57) [Claims] 1. A diversity antenna control device for selecting one input from a plurality of antenna inputs and supplying the selected input to a television receiving device, a television receiving device, and an FM transmitter device for transmitting an audio signal as an FM wave. B) detecting means for detecting an unselected non-selected antenna input from the antenna selection signal of the diversity antenna control device; c) selectively supplying the FM wave output of the FM transmitter device to each antenna input. D) a control means for controlling which antenna input the FM wave output is supplied to by the supply means; and e) at least one of the non-selected antenna inputs by the control means. Television reception characterized by supplying an FM wave output to an antenna input of the television receiver Audio FM transmitter. 2. A diversity antenna control device for selecting one input from a plurality of antenna inputs and supplying the selected input to a television receiving device, a television receiving device, and an FM transmitter device for transmitting an audio signal as an FM wave. B) detecting means for detecting an unselected antenna input that is not selected for the television receiver by using an antenna selection signal of the diversity antenna control device; c) determining the FM wave output And d) supplying FM waves to all the antenna inputs of the non-selected antenna inputs. D) A television receiver audio FM transmitter comprising: ◆