JPH02210983A - Diversity system for on-vehicle television receiver - Google Patents

Abstract

PURPOSE:To improve the VHF reception function and to cope with disturbance of a picture due to movement by providing a VHF exclusive booster circuit and a boost switching circuit controlling the booster circuit. CONSTITUTION:A level of antennas 1-4 latched by latch circuits 2a -2d is compared with a maximum value level of a maximum detection circuit 4 and the result of comparison is inputted to an antenna changeover circuit 6. Then the antenna with a maximum level for 1H is supported. The selected antenna signal passes through a filter 7a and is separated into UHF and VHF signals. The separated signal is boosted by a UHF booster 8b and a VHF booster 8a, and mixed by a filter 7b and outputted to a TV tuner 1. The booster 8a is controlled by a boost changeover circuit 9 receiving an RF AGC signal and brought into the through-state.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a diversity system for in-vehicle TV,
In particular, the present invention relates to a vehicle-mounted TV-specific diversity system suitable for VHF weak electric fields and VHF medium electric fields.

[Conventional technology]

Conventional devices are only equipped with a UHF boost circuit, and no consideration has been given to image stabilization effects in the VHF band.

Note that related devices of this type include, for example, Japanese Patent Publication No. 63-22650.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into account the reception function of weak electric fields and medium electric fields in the VHF band, and there is a problem with image stability in the VHF band.

The purpose of the present invention is to improve the VHF reception function in weak and medium electric fields by providing an additional circuit to the VHF radio wave reception circuit, and to cope with the image disturbance caused by movement, which is the original purpose of the in-vehicle TV. .

[Means to solve the problem]

The above object is achieved by adding a dedicated VHF booster circuit to the front stage of the antenna output output from the diversity system to the tuner system, and adding a boost switching circuit for controlling the booster circuit.

[Effect]

The VHF boost circuit exhibits a boost function effect in the weak and medium electric fields of VHF, and operates in the same way as a home TV in terms of stability.

As a result, the reception condition of the in-vehicle TV improves in the entire VHF range, and the reception condition can be improved even when the radio waves themselves are subject to rapid changes, which are unique to mobile devices, and UH
Since it becomes possible to respond to changes in radio wave conditions from the F band to the VHF band and from the VHF band to the UHF band, malfunctions will not occur.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

Figure 1 shows a diversity system exclusively for in-vehicle TVs, which has a built-in VHF booster circuit and VHF boost switching circuit.

1 is an in-vehicle TV tuner system that includes a diversity system, horizontal synchronization signal, and vertical synchronization signal.

This type outputs a video signal and an RF AGC signal, and inputs the maximum level antenna signal output from the diver system. 5 is a timing generation circuit that generates antenna switching timing using a horizontal synchronization signal and a vertical synchronization signal, and the timing generation signal is output to the antenna switching circuit 6.

Antennas 1 to 4 are switched at respective timings. 2
α~2d is a latch circuit that holds the signal switched by the antenna switching circuit, and 4 is the latched antenna 1
This is a maximum value detection circuit that selects the largest one among the 4 signals. The levels of antennas 1 to 4 latched by 2(L to 2d) are compared with the maximum level of antenna 4 by comparison circuits 31 to 3d, and the comparison results are input to the antenna switching circuit.

Hold the antenna at maximum level during IH.

The antenna signals selected in the above system are:

It passes through a 7α filter and is separated into UHF-VHF. The separated signal is an 8cL UHF booster 8
It is boosted by VHF booster b, mixed by filter b, and output to the tuner. However, VH
The F booster is controlled by a boost switching circuit that receives an RFAGC signal, and becomes a through state in a strong electric field.

〔Effect of the invention〕

According to the present invention, image stability can be improved in weak and medium electric fields in the VHF band.

This has the effect that a stable screen can be obtained even with severe changes in radio wave conditions, which are problems specific to in-vehicle TVs, and changes in radio wave conditions from the UHF band to the VHF band and from the VHF band to the UHF band.

[Brief explanation of the drawing]

The drawing is a block diagram of one embodiment of the present invention. 1...TV tuner. 2CL~2b...Antenna 1~Antenna 4 latch circuit. 31 to 3d...Antenna 1 to antenna 4 comparison circuits. 4... Maximum value detection circuit. 5... Timing generation circuit. 6...Antenna switching circuit. 7α, 7b...Filter 8 (L...VHF exclusive booster 8b...UHF exclusive booster 9...VHF boost switching circuit.

Claims (1)

[Claims] 1. In a car-mounted TV consisting of a display system, tuner system, and diver system,
A diversity system for in-vehicle TVs that features a VHF band booster and a boost switching circuit.