JP2509964Y2 - Car TV Diversity-Receiver - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a vehicle-mounted receiving device, and more specifically, it is equipped with a plurality of antennas and a receiving circuit, has a small distortion contained in a signal, and has an S / N ratio. The present invention relates to a signal-switching type diversity receiver that selects a signal from the better receiving circuit and outputs it to the output.

[Prior Art] When receiving a radio wave in a moving vehicle, stable reception may not be possible depending on the conditions of the incoming radio wave, such as when there is an obstacle in the arrival direction of the radio wave or when interference due to a reflected wave exists.

Therefore, conventionally, a vehicle-mounted receiver is equipped with a diversity receiving device in which a plurality of antennas having different directivities are arranged at appropriate positions of the vehicle, and the antenna with the best reception condition is switched and selected for reception. To be done.

[Problems to be Solved by the Invention] In the above-described vehicle-mounted AV system having the diversity reception function, the television receiver is designed so that the antennas can be switched during the vertical blanking period to ensure stable reception even while the vehicle is running. However, for example, when the vehicle is moving in a valley of a building and the reception conditions become the worst, the antennas frequently switch, so the noise generated at the time of switching causes the image to be disturbed, and a buzzing noise occurs at each switching of antennas. Occurs, and the quality of the audio signal is also deteriorated, which is a practical problem.

By the way, when the video monitor device is installed toward the vehicle driver, there are devices that are considered not to display an image on the monitor while the vehicle is traveling, as a principle of safe driving. When receiving television, only the audio signal is received.

However, the video signal circuit is operating when receiving the television audio signal, and the buzz sound generated at the time of switching the antenna sneaks into the audio signal circuit, which causes a problem that a high-quality audio signal cannot be received.

The present invention has been made in view of the above circumstances, and has
It is an object of the present invention to provide a vehicle-mounted diversity receiver capable of receiving a high-quality reception of a television audio signal as an output audio signal of an FM receiver in an in-vehicle AV system including a receiver.

[Means for Solving the Problems] In order to achieve the above object, in a diversity receiver of a vehicle-mounted television according to the present invention, a television receiving circuit for receiving a television broadcast, an audio signal of the television broadcast, and an FM broadcast radio wave are provided. The first FM receiving circuit that can receive both, the second FM receiving circuit that receives radio waves in the FM broadcast band, and the television receiving circuit and the first FM receiving circuit set to the same receiving frequency and receive And a television audio diversity circuit that compares the outputs of the receiving circuits and switches and selects one of the receiving circuits.
And an FM diversity circuit that sets the first and second FM reception circuits to the same reception frequency, performs reception, compares the outputs of the reception circuits, and switches and selects one of the reception circuit outputs. .

[Operation] The television receiving circuit and the first and second FM receiving circuits each include an intermediate frequency amplifying circuit, take out a part of the signal from these intermediate frequency amplifying circuits, and suppress distortion and noise components contained in the signal. A residual difference signal is generated.

When receiving the audio signal of the TV, the difference signal is output from the TV audio receiving circuit and the first FM receiving circuit capable of receiving the TV audio, and the levels of the difference signal are compared in the TV audio diversity circuit. . From the comparison result, the demodulated output is obtained after the television audio diversity circuit switches and selects the one of the television receiving circuit and the first FM receiving circuit that has the less distortion and noise components contained in the signal.

Therefore, while the vehicle is running, the receiving circuit output on the side with the better antenna input condition is selected from the two television audio receiving circuits. Further, when receiving the FM radio wave, similarly, the output of the receiving circuit of the first and second FM receiving circuits on the side with favorable antenna input conditions is switched and selected by the FM diversity circuit.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an in-vehicle AV system composed of two receiving systems of a TV and an FM. It should be noted that this block diagram shows only the configuration of each circuit that functions while the vehicle is traveling, and the circuit portion that functions when the vehicle is stopped is omitted.

In the figure, reference numeral 10 denotes a television receiving antenna, which represents a state in which a single antenna is selected and fixed by a diversity function for antenna switching (not shown) while the vehicle is traveling. 12 is a TV tuner for selecting the received wave, 5
It outputs 8.75MHz video carrier and 54.25MHz audio carrier signal. 13 is a video intermediate frequency amplifier circuit, which has the above 58.7
Amplifies a 5M Hz signal. Reference numeral 14 is a video amplifier circuit, the output of which is supplied to the monitor device and displays the image received by the monitor, but does not function while the vehicle is running.

Next, 15 is the audio carrier input signal of 54.25 MHz above 10.
It is a frequency converter that beats down to 7M Hz. 16 is a circuit that amplifies the intermediate frequency signal of 10.7 MHz,
The amplified and band-limited signal is output to the output terminal 16b, and the difference signal to be input to the television audio diversity circuit 17 of the next stage is output to the terminal 16a. This difference signal uses a part of the S-meter output voltage having a good selectivity characteristic. When the voltage taken out from the S-meter circuit passes through the filter, distortion and noise components contained in the signal are suppressed. Only the main component is detected and output to the output terminal 16a.

The television audio diversity circuit 17 is a signal switcher for comparing the qualities of the two systems of intermediate frequency signals and selectively switching and outputting one of the signals of good quality. This diversity circuit 17 compares terminals 17a and 17b to which signals of two systems of a TV audio intermediate frequency signal and an FM intermediate frequency signal are input with the difference signal levels of the above two systems to be input to difference signal input terminals 17d and 17e. A comparator, a changeover switch for selecting one of the intermediate frequency signals according to the comparison result, and an output terminal 17c for sending the selected signal to the demodulator 18 at the next stage.

Next, the receiver of the present invention comprises first and second FM receiver circuits, of which the first receiver circuit has an RF section whose reception frequency band is extended to the VHF band so that a television audio signal can be received. Have In the figure, 20 and 21 are receiving antennas and 22
Are tuner circuits, and 23 and 24 are intermediate frequency amplifier circuits. In the tuner 22, 22a is a first receiving circuit, and the FM frequency band and the television frequency band are within the receivable range. Also, the FM tuner 22b is a normal FM that covers the FM band.
It has the same standard as the radio.

23 is an output terminal for amplifying the intermediate frequency signal of the first receiving circuit
A band-limited signal is output to 23b and a difference signal is output to output terminal 23a. This difference signal is generated by a circuit that outputs a residual main component in which the distortion and noise components contained in the signal are suppressed in the same manner as the television audio intermediate frequency amplifier circuit 16. 24 is a circuit having almost the same specifications as the above-mentioned intermediate frequency signal amplifier circuit 23, and is provided with a terminal 24b for outputting the intermediate frequency signal of the second FM receiving circuit and a difference signal output terminal 24a.

Reference numeral 25 is an FM demodulator by selectively switching one of the signals output from the first and second receiving circuits.
It is an FM diversity circuit to send to 26. This circuit 25
The configuration of is substantially the same as that of the TV audio diversity 17, and the signal input terminals 25a and 25b and the difference signal input terminals 25d and 25
e, and an output terminal 25c.

Next, the operation of the circuit shown in FIG. 1 will be described. The operating conditions of this circuit are that TV and FM are not received at the same time. When receiving TV sound, the TV receiving circuit and the first FM receiving circuit are in operation,
It is set to receive the same reception channel. Also,
When receiving FM, the first and second FM receiving circuits are set to the same reception frequency.

First, when receiving television sound, an intermediate frequency signal obtained from the signal received by the antenna 10 is input to one input terminal 17a of the television audio diversity circuit 17, and the antenna 20 is received at the other input terminal 17b. The intermediate frequency signal obtained from the obtained signal is input. At the same time, the residual difference signals in which distortion and noise components are suppressed are respectively supplied from the intermediate frequency signals of the two systems to the input terminals 17d and 17e of the diversity circuit 17, and the difference signal levels of the two systems are compared by the comparator. It

As a reason for suppressing the distortion and noise components from the intermediate frequency signal and generating the difference signal, the distortion and noise components included in the received signal increase or decrease mainly depending on the multipath of the antenna input signal and the electric field strength. Therefore, the quality of the radio wave input to the antenna can be roughly determined from these two parameters.

If the distortion and noise components contained in one of the receiving circuit signals out of the signals output from the two intermediate frequency amplifiers 16 and 23 are larger than the other, the difference signal level obtained is small, so The switch is switched to the side with the higher difference signal level. That is, two antennas 1
The television audio diversity circuit 17 selects the intermediate frequency signal output from the receiving circuit on the side where the radio waves input to 0 and 20 are better, and the demodulator 18 demodulates the intermediate frequency signal to obtain an audio signal.

As a result, the television audio signal is received by the two receiving circuits and the signal of one receiving circuit having a good receiving condition is selected while the vehicle is running in which the antenna input condition is apt to change, but the video signal circuit does not operate. Since it is in the state, a high-quality audio signal can be reproduced without the buzz sound being mixed into the audio signal circuit.

Similarly, in the case of FM reception, two intermediate frequency signals obtained from the first and second FM receiving circuits are input to the FM diversity circuit 25, and from the comparison result of the difference signals obtained from these intermediate frequency signals, The FM diversity circuit 25 selects the receiving circuit output on the side where the distortion and noise components contained in the frequency signal are small. Therefore, FM broadcasting can always be received in the best condition. Then, some noise is generated in the two diversity circuits 17 and 25 at the time of signal switching, and these noises can be suppressed by the noise canceller circuits provided in the demodulators 18 and 26.

Note that, in addition to the antenna 10, a plurality of antennas are connected to the television tuner 12, and while the vehicle is stopped, the antenna can be switched to the antenna with the best reception state at the time of diversity switching (not shown), as in the conventional example.

[Advantages of the Invention] As described above, according to the diversity receiver of the vehicle-mounted television according to the present invention, the television receiving circuit, the first FM receiving circuit capable of receiving both the television and the FM, and the second
FM receiver circuit, TV audio diversity circuit, FM
Since the diversity circuit is provided, when receiving TV sound while traveling in an area where the conditions of the radio waves input to the antenna are constantly changing, the TV receiving circuit and the first FM
Of the two receiving circuits of the receiving circuit, the signal of one receiving circuit having a good antenna input condition is switched and selected by the television audio diversity circuit, and a high-quality television audio signal can always be received. Further, since the video signal circuit while the vehicle is traveling is placed in the non-operating state, there is no inconvenience that the buzz sound of the video circuit is mixed into the audio signal circuit.

Further, when receiving an FM broadcast, the FM diversity circuit similarly switches and selects the FM receiving circuit signal on the side with favorable antenna input conditions from the two systems of FM receiving circuits.

[Brief description of drawings]

FIG. 1 is a block diagram showing a diversity receiver of a vehicle-mounted television according to the present invention. 10,20,21 ……… Reception antenna, 12 ……… TV tuner, 16 ……… Audio intermediate frequency amplification circuit, 17 ………… TV audio diversity circuit, 22 ……… FM tuner, 23,24
……… FM intermediate frequency amplifier circuit, 25 ……… FM diversity circuit.

Claims (1)

(57) [Scope of utility model registration request] 1. A television receiving circuit for receiving television broadcasting,
A first FM receiving circuit capable of receiving both the audio signal of the TV broadcast and the FM broadcast radio wave, and a second FM receiving circuit for receiving the radio wave of the FM broadcast band
Of the above-mentioned FM receiving circuit and the above-mentioned television receiving circuit and the first FM receiving circuit are set to the same receiving frequency to perform reception, and the outputs of the receiving circuits are compared, and either one of the receiving circuits is switched and selected. A circuit, and the first and second
An in-vehicle television, comprising: an FM diversity circuit that sets the FM reception circuit to the same reception frequency, performs reception, compares the outputs of the reception circuits, and switches and selects one of the reception circuits. Diversity receiver.