JP2002232333A - Diversity reception circuit in mobile communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diversity reception circuit by which an image does not flicker by noise generation while searching for the antenna of excellent sensitivity. SOLUTION: This diversity reception circuit for comparing the output signals of a plurality of the antennas 6a-6d having respective boosters 5a-5d and selecting and using the antenna of the excellent sensitivity is provided with booster power supply current abnormality detection means 2a-2d and 3a-3d, for detecting the abnormality of power supply currents supplied to the respective boosters 5a-5d. For the antennas 6a-6d of the boosters 5a-5d supplied with the power supply current from booster power sources 1a-1d for which the abnormality is detected by the booster power supply current abnormality detection means, the output signals are not compared and use is inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity receiving circuit in mobile communication, and more particularly to a vehicle-mounted TV.
The present invention relates to a diversity receiving circuit suitable for a receiver.

[0002]

2. Description of the Related Art In a receiver mounted on a moving body such as an in-vehicle TV receiver, a reception state of an antenna changes during traveling, and a reception failure may occur. Therefore, a diversity reception scheme that selects and uses a good reception state from a plurality of antennas has been widely used. Such an in-car TV
The basic configuration of the diversity receiving circuit of the receiver will be described with reference to FIG.

In FIG. 6, four antennas 6a to 6d having different directivities and the like are fixed to a vehicle. The TV diver IC 22 outputs an antenna switching signal to the RF switch 9 as described later, and the RF switch 9 selects an output signal of one of the antennas 6a to 6d based on the antenna switching signal, and
Output to 0.

The front end 20 receives the output signal of the antenna and a channel selection signal from a microcomputer, and outputs an intermediate frequency signal (I / F) of the selected channel signal to an I / F amplifier circuit 21. The I / F amplifier circuit 21 amplifies the input signal and separates the signal into a video signal and an audio signal. The audio signal drives a speaker 23, and the video signal causes a display device 24 to display an image.

[0005] The video signal (video signal) is also input to the TV diver IC 22 to monitor the level of the video signal. FIG. 8 shows a waveform diagram of the video signal. The time t on the horizontal axis in FIG. 8 shows the vertical blanking period and a part of the period of the video signal before and after the vertical blanking period, and the level on the vertical axis is the voltage level of the video signal. Become.

[0006] The pedestal level, which is the lowest potential during the vertical blanking period, is set to 75% of the maximum level, and no bright line appears at this level. The horizontal synchronization pulse and the vertical synchronization pulse are higher than the pedestal level, and the video level during the horizontal scanning period is lower than the pedestal level.

The TV diver IC 22 constantly detects the pedestal level during the vertical blanking period. If the pedestal level becomes lower than a predetermined value, the TV diver IC 22 sequentially switches to an antenna other than the antenna currently in use to change the antenna having the highest pedestal level. After that, the antenna is selected and used thereafter.

In the conventional diversity receiving circuit shown in FIG. 7, antennas 6a to 6d are used in order to maintain good receiving sensitivity.
Are amplified by the respective boosters 5a to 5d and input to the RF changeover switch 9. RF switch 9
FIG. 6 shows that the signal selected in the step is input to the front end and the RF switch 9 is controlled by the diver IC.
As described above.

Power is supplied to the boosters 5a to 5d from booster power supplies 1a to 1d. When it is physically impossible to use another line as the power supply line, as shown in FIG. 7, the DC cables are connected to the RF cables 4a to 4d.
The power supply voltage is superimposed and applied. That is, an RF signal and a booster current flow through the RF cables 4a to 4d.

FIG. 9 is a block diagram showing a configuration in which overcurrent detection circuits 25a to 25d for detecting overcurrent of a power supply when a DC power supply voltage is superimposed on RF cables 4a to 4d. Booster power supply 1a housed in main body 26
The electric current supplied to the boosters 5a to 5d from the RF cables 4a to 4d is supplied to the RF cables 4a to 4d when the cables bite into a metal part of the vehicle or when the boosters 5a to 5d fail for some reason and become short-circuited. The current flows and overcurrent is detected by the overcurrent detection circuits 25a to 25d.
When the overcurrent detection circuits 25a to 25d detect the overcurrent,
By turning off the booster power supplies 1a to 1d, it is possible to prevent smoke and ignition.

[0011]

When the antenna switching operation is performed when there is an antenna whose power supply of the booster is turned off due to some trouble as described above, for example, in FIG. 9, the RF cable 4d of the antenna 6d is connected When the vehicle bites into the vehicle and the power of the booster 5d is turned off, the broadcast radio wave is received by the antenna 6a. When the reception environment changes and the reception sensitivity is reduced to start the antenna switching operation, the antenna 6b and the antenna 6c, antenna 6
Since the switching is performed in the order of d and the antenna 6a, a large noise is generated in the failed antenna 6d and the screen flickers.

Further, as shown in FIG.
The same problem as described above occurs when d is pulled out of the main body 26 and is in an open state.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a diversity receiving circuit which does not generate noise while searching for an antenna having good sensitivity and does not flicker. To provide.

[0014]

SUMMARY OF THE INVENTION A diversity receiving circuit in mobile communication according to the present invention compares output signals of a plurality of antennas provided with respective boosters and selects and uses an antenna having a good reception condition. In the city receiving circuit, a booster power supply current abnormality detecting means for detecting an abnormality in the power supply current supplied to each of the boosters is provided, and a power supply current is supplied from the booster power supply in which the abnormality is detected by the booster power supply current abnormality detecting means. The use of the booster antenna is prohibited without comparing the output signals.

Further, in the diversity receiving circuit for mobile communication, the booster power supply current abnormality detecting means is an overcurrent detection circuit for detecting an overcurrent of the booster power supply.

Further, in the diversity receiving circuit in the mobile communication, the booster power supply current abnormality detecting means is a no-current detection circuit for detecting a no-current of the booster power supply.

In the diversity receiving circuit in the mobile communication, the booster power supply current abnormality detecting means includes an overcurrent detection circuit for detecting an overcurrent of the booster power supply, and a no-current detection circuit for detecting a no-current of the booster power supply. It was done.

Further, in the diversity receiving circuit in each mobile communication, the DC power of the booster is applied to an RF cable for transmitting the RF signal from the booster so as to be superimposed on the RF signal.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A diversity receiving circuit in mobile communication according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a vehicle-mounted T according to a first embodiment of the present invention.
It is a block diagram which shows the diversity receiving circuit of a V receiver.

In FIG. 1, four antennas 6a to 6d having different directivities and the like are fixed to a vehicle. The antennas 6a to 6d are provided with boosters 5a to 5d, respectively, and the signals received by the antennas 6a to 6d are amplified by the boosters 5a to 5d.

The boosters 5a to 5d housed in the main body 13
The booster power supplies 1a to 1d for supplying power to the microcomputer 7 are turned on by the power ON signal of the microcomputer 7, and the output current thereof passes through the overcurrent detection circuits 2a to 2d and the no-current detection circuits 3a to 3d and to the RF cables 4a to 4d. RF
The signal is superimposed on the signal and supplied to boosters 5a to 5d.

The TV diver IC 8 outputs an antenna switching signal to the RF switch 9 and the RF switch 9
Selects one of the signals from the boosters 5a to 5d according to the antenna switching signal and outputs it to the front end (F / E).

A video signal is input to the TV diver IC 8 as described in the conventional example, and an antenna switching signal is output to the RF switch 9 by monitoring the level of the video signal.

The overcurrent detection circuits 2a to 2d are
When overcurrents due to short circuits a to 5d and the RF cables 4a to 4d are detected, signals indicating the respective overcurrents are output to the microcomputer 7. In addition, the non-current detection circuit 3a
-3d is for failure of booster 5a-5d or RF cable 4
When detecting no current due to disconnection of a to 4d or disconnection of the connector, a signal indicating no current is output to the microcomputer 7.

The microcomputer 7 outputs to the TV diver IC 8 a control signal for permitting use of the antennas 6a to 6d for which no overcurrent or no current is detected, and the use of the TV diver IC 8 is permitted by the control signal. Output the selection signal only to the antenna,
No switching signal is output to antennas whose use is not permitted.

FIG. 2 shows the details of the overcurrent detection circuit 2a. Note that the current detection circuits 2b to 2d are
Is the same as The + power supply terminal of the booster power supply 1a is connected to the input terminal of the no-current detection circuit via the switch SWA and the resistor RA. In addition, booster power supply 1
The negative terminal of a is connected to the ground, and is connected to the ground of the booster via the ground wire of the RF cable.

The voltage at the point A on the input side of the switch SWA is divided by the resistors R1 and R2 and applied to the inverting input terminal of the operational amplifier 10. The voltage at the point B on the output side of the resistor RA is divided by the resistors R3 and R4 and applied to the non-inverting input terminal of the operational amplifier 10.

Normally, the voltage of the non-inverting input terminal of the operational amplifier 10 is higher than the voltage of the inverting input terminal, and the output of the operational amplifier 10 is high. The H output is input to the microcomputer 7 as an overcurrent detection signal. SWB is kept on. The operational amplifier 10 outputs H regardless of the input signal during a predetermined period when the power is turned on.

When a large current flows through the resistor RA due to a short circuit in the RF cables 4a to 4d, the voltage at the non-inverting input terminal of the operational amplifier 10 becomes lower than the voltage at the inverting input terminal due to the voltage drop of the resistor RA. The output of the amplifier 10 becomes L, and the microcomputer 7 outputs an antenna control signal for inhibiting selection of the corresponding antenna.

The output L signal of the operational amplifier 10 turns off the switch SWB and turns off the switch SWA from the microcomputer 7 to turn off the switch SWB.
WA is turned off, and the current of the corresponding booster power supply is turned off.

FIG. 3 shows the details of the non-current detection circuit 3a. Note that the current detection circuits 3b to 3d are
Is the same as The output terminal of the overcurrent detection circuit 2a is connected to the booster 5a via a resistor RB and an RF cable.

The voltage at point a on the input side of the resistor RB is equal to the resistor R5
And the voltage is divided by R6 and applied to the non-inverting input terminal of the operational amplifier 11. The voltage at point b on the output side of the resistor RB is divided by the resistors R7 and R8 and applied to the inverting input terminal of the operational amplifier 11.

Normally, the voltage at the non-inverting input terminal of the operational amplifier 11 is higher than the voltage at the inverting input terminal and the output of the operational amplifier 11 is high, and the H output is input to the microcomputer 7 as a no-current detection signal.

When current does not flow through the resistor RB due to disconnection of the RF cables 4a to 4d or the like, the voltage drop of the resistor RB stops, and the voltage of the inverting input terminal of the operational amplifier 11 becomes higher than the voltage of the non-inverting input terminal. The output of the amplifier 11 becomes L, and the microcomputer 7 outputs a signal for inhibiting the selection of the corresponding antenna.

By appropriately setting the values of the resistors R1 to R8, it is possible to set an appropriate threshold value of the booster power supply current at which overcurrent or non-charge is detected. FIG. 4 shows the relationship between the current level of the booster power supply and the overcurrent and non-charge detection levels.

With the above configuration, the antenna in which the booster power is turned off or the RF cable is disconnected is not switched and used, so that the screen does not flicker due to noise during the antenna search.

FIG. 5 is a block diagram showing a diversity receiving circuit of a vehicle-mounted TV receiver according to a second embodiment of the present invention. In this example, the boosters 5a to 5d are turned on by an ON signal from a controller that controls the diversity receiving circuit.

The output signals of the overcurrent detection circuits 2a to 2d and the output signals of the no-current detection circuits 3a to 3d are input to AND circuits 12a to 12d.
The 2d output signal is input to the TV diver IC 8 to control the selection of the antenna. Elements having the same functions as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

Also in the second embodiment, since the booster power supply is turned off or the antenna from which the RF cable is disconnected is not switched and used, the screen does not flicker due to noise during the antenna search.

Although the embodiment is configured as described above, the invention is not limited to this. For example, the effect of the invention can be obtained even if the selection of the antenna is controlled only by the overcurrent detection circuit of the booster power supply. Further, the effect of the present invention can be obtained even if the selection of the antenna is controlled only by the no-current detection circuit of the booster power supply.

[0041]

According to the diversity receiving circuit of the present invention, since a failed antenna is not searched, it is possible to prevent the screen from flickering due to noise.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a diversity receiving circuit of an in-vehicle TV receiver according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing an overcurrent detection circuit used in the diversity receiving circuit.

FIG. 3 is a circuit diagram showing a non-current detection circuit used in the diversity receiving circuit.

FIG. 4 is a diagram showing booster current levels for explaining the operation of the diversity receiving circuit.

FIG. 5 is a block diagram showing a diversity receiving circuit of a vehicle-mounted TV receiver according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing an example of a diversity receiving circuit of a conventional in-vehicle TV receiver.

FIG. 7 is a block diagram showing another example of the diversity receiving circuit of the conventional in-vehicle TV receiver.

FIG. 8 is a waveform diagram showing a TV video signal.

FIG. 9 is a block diagram showing still another example of the diversity receiving circuit of the conventional in-vehicle TV receiver.

FIG. 10 is a plan view showing a part of the diversity receiving circuit.

[Explanation of symbols]

1a, 1b, 1c, 1d Booster power supply 2a, 2b, 2c, 2d Overcurrent detection circuit 3a, 3b, 3c, 3d No current detection circuit 4a, 4b, 4c, 4d RF cable 5a, 5b, 5c, 5d Booster 6a, 6b, 6c, 6d Antenna 7 Microcomputer 8 TV Diver IC 9 RF Changeover Switch 10, 11 Operational Amplifier 12a, 12b, 12c, 12d And Circuit 13 Body 20 Front End 21 I / F Amplifier Circuit 22 TV Diver IC 23 Speaker 24 Display Device 25a to 25d Overcurrent detection circuit 26 Main body R1, R2, R3, R4, R5, R6, R7, R8, R
A, RB resistance SWA, SWB switch

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C025 AA22 BA26 5K059 CC03 DD12 DD27 EE01 5K061 AA04 BB07 CC03 CC05 CC46 EE15 HH04 JJ06 5K062 AA06 AB19 AD03 AF01 BA01 BD01 BE03

Claims (5)

[Claims] 1. A diversity receiving circuit for comparing output signals of a plurality of antennas provided with respective boosters and selecting and using an antenna having a good reception state, wherein a power supply current supplied to the respective boosters is abnormal. The booster power supply current abnormality detecting means for detecting the abnormality is provided, and the booster antenna to which the power supply current is supplied from the booster power supply in which the abnormality is detected by the booster power supply current abnormality detecting means is used without comparing the output signal without using the output signal. A diversity receiving circuit in mobile communication, wherein the diversity receiving circuit is configured to be prohibited. 2. The diversity receiving circuit according to claim 1, wherein said booster power supply current abnormality detecting means is an overcurrent detecting circuit for detecting an overcurrent of the booster power supply. 3. The diversity receiving circuit in mobile communication according to claim 1, wherein said booster power supply current abnormality detecting means is a no-current detection circuit for detecting a no-current of the booster power supply. 4. The diversity in mobile communication according to claim 1, wherein said booster power supply current abnormality detecting means is an overcurrent detection circuit for detecting an overcurrent of the booster power supply and a no-current detection circuit for detecting a no current of the booster power supply. Receiver circuit. 5. The diversity receiving circuit in mobile communication according to claim 1, wherein the DC power of the booster is applied to an RF cable for transmitting the RF signal from the booster while being superimposed on the RF signal. .