JP3254925B2 - In-vehicle TV diversity device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-vehicle TV for automatically switching a plurality of diversity antennas mounted on a vehicle in accordance with a received electric field to receive TV broadcast waves.
The present invention relates to a diversity device.

[0002]

2. Description of the Related Art In recent years, small and light-weight, high-performance TV receivers have been developed and used in vehicles. A TV receiver mounted on a vehicle causes severe image disturbance due to fading. In order to reduce image disturbance due to such fading, a diversity system using a spatial uncorrelation between a plurality of antennas and a difference in directivity has been adopted.

[0003] A conventional on-board TV diversity apparatus will be described below. FIG. 15 shows the configuration of a conventional in-vehicle TV diversity apparatus. In FIG. 15, 1
01 to 104 are antennas, 105 is antennas 101 to 1
04, an antenna switching circuit for selectively connecting to the TV receiver 106; 107, a level detection comparison circuit for detecting the level of the video signal 109; 108, a timing control circuit;
Reference numeral 10 denotes a synchronization signal.

[0004] The operation of the in-vehicle diversity apparatus configured as described above will be described below. First, the high-frequency signals received by the antennas 101 to 104 are selectively connected to the TV receiver 106 by the antenna switching circuit 105. The TV receiver 106 performs channel selection tuning of the high frequency signal of the connected antenna, inputs the detected and amplified video signal 109 to the level detection comparison circuit 107, and inputs the synchronization signal 110 separated from the video signal 109 to the timing control circuit 108. I do. Antenna switching circuit 1
In step 05, the antennas 101 to 104 are sequentially switched during the vertical flyback period, for example, every horizontal scanning period, according to the control signal of the timing control circuit 108. The level comparison and detection circuit 107 detects and compares the level of the video signal received by each antenna at this time, and selects the antenna that has obtained the maximum reception level. The timing control circuit 108 switches to the antenna of the maximum level based on the comparison result of the level comparison detection circuit 107. And until the next vertical retrace period,
Hold that state. Thus, the vertical synchronization period (= 1)
/ 60 seconds), the antenna can be switched to the antenna that receives the maximum level.

[0005]

However, in the above-mentioned conventional in-vehicle TV diversity apparatus, when the moving speed of the vehicle is high, or when receiving a UHF band broadcast station, fading with a high receiving electric field is performed. However, there is a problem that a stable reception situation cannot be obtained when receiving the information. Further, the received electric field may include ghost-containing video or pulse noise due to multipath.
The conventional in-vehicle diversity apparatus selects an antenna only based on the electric field level, and has a problem that an antenna including a lot of ghosts or an antenna including a lot of pulse noise is selected.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. In-vehicle TVs capable of receiving a UHF signal, providing a stable reception state even when traveling at high speed, and selecting an antenna with little ghost and pulse noise. It is an object of the present invention to provide a diversity device.

[0007]

In order to achieve the above object, an in-vehicle TV diversity apparatus according to the present invention comprises a plurality of antennas mounted on a vehicle for receiving TV broadcast waves, a TV receiver, and an antenna. One according to an antenna switching control signal, an antenna switching circuit connected to an antenna input end of a TV receiver, a level detection circuit detecting and holding a peak value level of a horizontal synchronization signal of a video signal in the TV receiver,
A level comparison circuit for comparing the level held by the level detection circuit in accordance with a level comparison control signal ;
On the basis of the sync signal in the receiver, at the beginning horizontal synchronizing retrace period, the antenna connected to the TV receiver is switched to one of the antennas, at the end a horizontal synchronizing retrace period, again before switching antennas Output an antenna switching control signal to connect, sequentially to all the antennas,
After the switching, the level comparison circuit outputs a comparison control signal to compare the levels obtained by the respective antennas, and based on the comparison result of the level comparison circuit, the antenna switching control to switch to the highest level antenna. Output a signal and said antenna is selected
Control circuit for maintaining the state of the vehicle for a predetermined number of horizontal scans, and vehicle speed detection for detecting the traveling speed of the vehicle
Means and a vehicle detected by the vehicle speed detecting means
Depending on the speed, the antenna in the timing control circuit
Antenna holding horizontal scanning to control the number of horizontal scanning to hold
It is provided with means for determining the number of times .

[0008]

According to the present invention, with the above configuration, antenna selection can be performed a plurality of times during the vertical synchronization signal period with little effect of an image due to antenna switching, and the received electric field is subject to high-speed fading. In this case, a stable reception state can be obtained.

[0009]

【Example】

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to FIG. Here, an embodiment in which four antennas are switched as a plurality of antennas will be described.

In FIG. 1, reference numerals 1 to 4 are TV antennas provided on a vehicle. Reference numeral 5 denotes a diversity circuit, which includes an antenna switching circuit 6, a level comparison circuit 7, a level detection circuit 8, and a timing control circuit 8. The antenna switching circuit 6 switches the antennas 1 to 4 according to the antenna switching control signal 18, and the high frequency signal 11 of the switched antenna is connected to the antenna input terminal of the TV receiver 10. In accordance with the level comparison control signal 16, the level comparison circuit 7 compares the input level values of the respective antennas within the horizontal scanning period following the horizontal synchronization retrace period in which the level detection of all the antennas has been completed. The antenna is detected, and the detection result is output to the timing control circuit 9 . The level detection circuit 8 detects the peak value level of the horizontal synchronization signal 14 of the video signal 12 of each antenna switched within the horizontal synchronization retrace period, holds the level, and compares the held value with the level comparison circuit. 7 is output. Taimin
The control circuit 9 controls the timing of each of the antenna switching circuit 6, the level comparing circuit 7, and the level detecting circuit 8.

FIG. 2 shows a specific configuration of the TV receiver 10. In FIG. 2, 19 is a channel selection tuning circuit, 20 is a video signal receiving circuit, 21 is a sync separation circuit,
22, an intermediate frequency signal; and 23, a local oscillator signal.

The operation of the in-vehicle TV diversity apparatus configured as described above will be described below.

First, the high-frequency signal 11 received by the antennas 1 to 4 is input to the antenna switching circuit 6. The antenna switching circuit 6 switches the antenna according to the antenna switching control signal 18, and the high frequency signal 11 of the switched antenna is connected to the antenna input terminal of the TV receiver 10. The high-frequency signal 11 is selected by the channel selection tuning circuit 19 of the TV receiver 10, converted into an intermediate frequency, and becomes an intermediate frequency signal 22. The intermediate frequency signal 22 is detected and amplified by the video signal receiving circuit 20 to become the video signal 12. A vertical synchronizing signal 13 and a horizontal synchronizing signal 14 are separated from the video signal 12 by a sync separation circuit 21. The level detection circuit 8 detects and holds the peak value level of the horizontal synchronization signal 14 of the video signal 12.

FIG. 3 is a signal waveform diagram for explaining the operation of the timing control circuit 9. Timing control circuit 9
Switches the connected antenna to one of a plurality of antennas at the start of the horizontal synchronization retrace period based on the synchronization signals 13 and 14, and reconnects to the antenna before switching at the end of the horizontal retrace period. A switching control signal 19 is transmitted. This antenna switching operation is sequentially performed for all the antennas 1 to 4 using a plurality of continuous horizontal retrace periods. FIG. 3 shows the above-described antenna switching operation timing in a state where the antenna 2 is connected, as one embodiment.

The level detection circuit 8 detects a peak value level of the horizontal synchronizing signal 14 of the video signal 12 of each antenna switched within the horizontal synchronizing retrace period, holds the level, and stores the held value. Output to the level comparison circuit 7. According to the level comparison control signal 16, the level comparison circuit 7
In the horizontal scanning period following the horizontal synchronization retrace period in which the level detection of all the antennas has been completed, the input level values of the antennas are compared, the antenna of the maximum level is detected, and the detection result is transmitted to the timing control circuit 9. Output to The timing control circuit 9 sets the maximum level in the antenna switching circuit 6 by the antenna switching control signal 18 in the horizontal retrace period following the horizontal scanning period in which the level comparison operation is completed based on the comparison result by the level comparison circuit 7. Switch the connection to the output antenna.

In FIG. 3, it is assumed that the antenna 4 outputs the maximum level. After the level detection comparison, the switched antenna keeps its state for the next N horizontal scanning times. After the lapse of N horizontal scanning periods,
The operation of the level comparison / detection described above is repeated. Note that the number of horizontal scans held is the number of times that antenna level detection and comparison can be performed a plurality of times between vertical synchronization signals. 262.5 horizontal scanning lines are included in the vertical synchronization signal period, and the number of level detection / comparisons Nf in the vertical synchronization signal period is
Nf = 262.5 / (N + the number of antennas).
Therefore, when the number of antennas is four, if the number of held horizontal scans N is 127 or less, the number of level detection / comparisons Nf within the vertical synchronization signal period is two or more.

As described above, according to the present embodiment, the antenna switching is performed during the horizontal retrace period, so that the switching has almost no effect on the image, and the number of holding horizontal scans is appropriately set according to the number of antennas. By doing
The optimum antenna can be selected a plurality of times between the vertical synchronization signals, and a stable reception state with less image disturbance can be achieved even at the time of high-speed running, even when receiving a TV broadcast wave that is undergoing fading with a large fluctuation pitch. Can be secured. This is because UHF has a higher frequency band than VHF broadcasting.
This is particularly effective when receiving a broadcast.

In this embodiment, the level detection and comparison of the video signal 12 of the video signal receiving circuit 20 in the TV receiver 10 are performed. Similar effects can be obtained by comparison.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 4, 1 to 4 are antennas, 5 is a diversity circuit, 6 is an antenna switching circuit, 7 is a level comparison circuit, 8 is a level detection circuit, 9 is a timing control circuit, and 10 is a TV receiver. Are the same as those in FIG. 4 is different from the configuration of FIG. 1 in that a vehicle speed detecting means 201 for detecting the speed of a vehicle is newly provided, and an antenna holding horizontal scanning number determining means 202 for variably controlling the number of antenna switching based on a vehicle speed signal 203 is provided. This is a new point.

The in-vehicle TV diversity apparatus configured as described above is the same as that of the first embodiment shown in FIG. 1 except that the antenna holding horizontal scanning frequency determining means 202 is added. The operation will be mainly described.

First, the vehicle speed detecting means 201 detects the moving speed of the vehicle on which the TV receiver 10 is mounted, and outputs a vehicle speed signal 2
03 is output to the antenna holding horizontal scanning frequency determination means 202. The antenna holding horizontal scanning frequency determination means 202 determines the number of holding horizontal scanning frequency N based on the vehicle speed signal, and inputs the determination result to the timing control circuit 9. As the vehicle moves at a higher speed, the fluctuating cycle of the fading received by the TV broadcast wave becomes faster. Therefore, in order to stably receive a TV broadcast wave that has undergone such fading, it is necessary to reduce the number of horizontal scans held by the antenna. The antenna holding horizontal scanning frequency determining means 202 decreases the number of antenna holding scanning operations in accordance with the increase in the vehicle speed. FIG. 5 shows the antenna holding horizontal scanning frequency determining means 2.
2 shows the relationship between the vehicle speed and the number N of held horizontal scanning lines at 02.
The same effect can be obtained by either the method of changing the number of horizontal scanning lines to be held stepwise with respect to the vehicle speed as shown in FIG. 5A or the method of continuously changing the number of horizontal scanning lines as shown in FIG. 5B. The timing control circuit 9 holds the state of the selected antenna over the number of horizontal holding times according to the output of the antenna holding horizontal scanning number determining means 202.

As described above, according to the present embodiment, when the vehicle is stopped or running at a low speed, the received wave undergoes gradual fading, so that antenna switching is performed once every several fields. However, a sufficiently stable reception state can be obtained. Conversely, during high-speed running, a stable reception state cannot be obtained unless antenna switching is performed a plurality of times within the vertical synchronization signal period. Therefore, according to the present embodiment, by variably controlling the number of times of antenna switching in response to a change in the fading situation due to the vehicle speed,
By eliminating unnecessary antenna switching operations that do not contribute to the improvement of reception conditions at low speeds, it is possible to prevent voice degradation due to switching noise generated at the time of antenna switching, and obtain stable reception conditions even at high speeds. be able to.

The same effect can be obtained by the antenna holding horizontal scanning frequency determining means 202 for controlling the number of horizontal scanning operations in accordance with the oscillation frequency of the local oscillator of the channel selection tuning circuit 19 in the TV receiver. The fading situation also changes depending on the frequency of the broadcast wave, and the fluctuation period of the fading becomes shorter as the broadcast station frequency becomes higher. Therefore, as the oscillation frequency of the local oscillator of the channel selection tuning circuit 19 increases, control is performed so as to reduce the number of horizontal scans held by the antenna continuously or stepwise.

Also, since the fading frequency is proportional to the vehicle speed and the broadcasting station frequency, the number of held horizontal scans is set to be inversely proportional to the product of the vehicle speed signal 203 and the frequency of the local oscillator of the channel selection tuning circuit 19 in the TV receiver 10. , The time interval for selecting the optimum antenna can be variably controlled according to the fading situation, and the reception state can be further stabilized.

(Embodiment 3) Next, a third embodiment of the present invention will be described with reference to FIG. 6 is different from the configuration of FIG. 1 in that an electric field intensity detecting unit 301 for detecting an input electric field intensity of an antenna connected to the TV receiver 10 and an antenna holding horizontal scanning number determining unit for variably controlling the number of times of antenna switching. 303 is newly added, and the operation thereof will be described below focusing on the differences.

The input electric field strength of the antenna connected to the TV set 10 is detected by the electric field strength detection means 301. In this case, the AGC voltage of the AGC circuit in the TV receiver 10 may be used. The antenna holding horizontal scanning number determination unit 303 determines the number of holding horizontal scans in accordance with the detected electric field strength, and outputs the determination result to the timing control circuit 9. The timing control circuit 9 holds the state of the selected antenna over the number of holding horizontal scans according to the output of the antenna holding horizontal scan number determining means.

Next, a method of controlling the number of holding horizontal scans by an input electric field will be described. In the case of a weak electric field, even if the number of holding horizontal scans is reduced and the number of times to select the optimum antenna is increased, sufficient electric field strength cannot be obtained, so there is almost no improvement in image quality. Deterioration becomes noticeable. Therefore, as shown in FIG. 7, the number of holding horizontal scans is increased by the antenna holding horizontal scanning
Control is performed to prevent sound quality degradation due to switching noise due to antenna switching. In FIG. 7, the number of held horizontal scans is continuously changed. However, the same effect can be obtained by changing the number of times in a stepwise manner.

As described above, according to this embodiment, as the electric field strength of the connected antenna becomes weaker, the antenna holding horizontal scanning number determining means 303 increases the number of antenna holding horizontal scans, thereby improving image quality. Eliminates the antenna switching operation, which does not contribute to
Sound quality deterioration due to switching noise due to antenna switching can be prevented.

(Embodiment 4) Next, a fourth embodiment of the present invention will be described with reference to FIG. 8, reference numeral 401 denotes a vehicle speed detecting means, and 402 denotes a vehicle speed signal.

The in-vehicle TV diversity apparatus configured as described above is obtained by adding vehicle speed detecting means 401 for detecting the speed of the vehicle to the configuration of the first embodiment shown in FIG. The operation will be described focusing on the part.

The vehicle speed detecting means 401 is provided for the TV receiver 1
0 is detected, and a vehicle speed signal 402 is detected.
Is output to the timing control circuit 9. When the vehicle speed signal 402 falls below a predetermined speed, the timing control circuit 9 outputs each control signal at a timing as shown in FIG. 9 to select an optimal antenna.

The operation of FIG. 9 will be described below. FIG. 9 (a)
Is the (k + 1) th antenna level detection comparison timing when the vehicle speed falls below a predetermined speed before the kth antenna level comparison. Here, as an example, it is assumed that the antenna 4 is at the minimum level at the time of the (k-1) -th comparison result. Therefore, in the k-th detection comparison, the antenna is not switched to the antenna 4 during the horizontal synchronization retrace period, and is excluded from the detection comparison. In FIG. 9A,
Switching from antenna 2 to antenna 3 according to the detection comparison result. By the following k + 1th antenna level detection comparison,
If the vehicle speed exceeds a predetermined level, antenna level detection is performed at the timing described with reference to FIG. 3 of the first embodiment.

On the other hand, if not exceeded, level detection comparison is performed at the timing shown in FIG. Here, it is assumed that the antenna 2 takes the minimum level in the k-th comparison result. In the (k + 1) th antenna level detection comparison, the antenna 2 having the minimum level in the kth comparison is excluded from the level detection comparison, and the antenna 4 excluded in the kth comparison is added instead. As described above, while the vehicle speed is low, level detection and comparison are performed with three antennas, the antenna having the minimum level is excluded during the subsequent level detection comparison, and the excluded antenna is added to the detection comparison.

When the received electric field strength changes slowly while the vehicle is stopped or running at a low speed, it is very unlikely that the antenna having the minimum level will have the maximum level in the next antenna level detection comparison based on the antenna level detection comparison result. it is conceivable that.

Therefore, even if the antenna level detection comparison is performed excluding the antenna having the minimum reception level among a plurality of antennas as in the present embodiment, the reception status hardly changes and the number of times of antenna switching is reduced. Therefore, the influence of antenna switching on video and audio can be reduced.

(Embodiment 5) Next, a fifth embodiment of the present invention will be described with reference to FIG. In FIG. 10, reference numeral 501 denotes a reception signal supplied via the antennas 1 to 4 in addition to the antenna switching circuit 6,
02 is also a distributor that also supplies. The sub-antenna switching circuit 502 does not need to switch the antennas 1 to 4 by the antenna switching circuit 6 together with the sub-channel selection tuning circuit 503, the sub-video signal receiving circuit 504, and the selected channel detecting means 505.

The vehicle-mounted TV diversity apparatus configured as described above, that is, a sub-antenna switching circuit 502, a sub-channel selection tuning circuit 503, and a sub-video signal receiving circuit 504 are added to the configuration of the first embodiment shown in FIG. The operation will be described below focusing on the differences.

The received electric fields from the plurality of antennas 1 to 4 are respectively distributed by the distributor 501, and one is supplied to the antenna switching circuit 6 and the other is supplied to the sub-antenna switching circuit 502. One of the antennas input to the sub antenna switching circuit 502 is selectively connected to the sub channel selection tuning circuit 503 according to the sub antenna switching control signal 506. The selected channel detecting means 505 is the TV receiver 10,
Detect the selected channel.

On the other hand, the sub-channel selecting / tuning circuit 503 selects the same channel selected by the TV receiver 10 according to the detection result of the selected channel detecting means 505. The sub video signal receiving circuit 504 detects and amplifies the output of the sub channel selection tuning circuit 503. The level detection circuit 8 detects the peak value level of the horizontal synchronization signal output from the sub video signal reception circuit 504.

FIG. 11 is a waveform chart for explaining the antenna level detection comparison timing. The operation timing will be described below.

The timing control circuit 9 outputs the synchronization signals 13, 1
4, the antenna connected to the sub-channel selection tuning circuit 503 is switched to one of the antennas 1 to 4 at the start of the horizontal synchronization retrace period, and at the end of the horizontal retrace period,
The sub-antenna switching control signal 506 is sent to the sub-antenna switching circuit 502 so as to connect to the antenna before switching again.
Is sent. This antenna switching operation is sequentially performed for all antennas using a plurality of continuous horizontal retrace periods. The level detection circuit 8 detects the peak level of the horizontal synchronization signal output from the sub-picture signal reception circuit output of each antenna switched within the horizontal synchronization retrace period, holds the level, and converts the held value to the level. Output to the comparison circuit 7. According to the level comparison control signal 17, the level comparison circuit 7
In the horizontal scanning period following the horizontal synchronization retrace period in which the level detection of all the antennas has been completed, the input level values of the antennas are compared, the antenna of the maximum level is detected, and the detection result is transmitted to the timing control circuit 9. Output to The timing control circuit 9 sets the maximum level in the antenna switching circuit 6 by the antenna switching control signal 18 in the horizontal retrace period following the horizontal scanning period in which the level comparison operation is completed based on the comparison result by the level comparison circuit 7. Switch the connection to the output antenna.

As described above, as in the present embodiment, the antenna switching for level detection comparison is performed by distributing the antenna input and adding the sub-channel selection tuning circuit 503 and the sub-video signal receiving circuit 504 in the diversity circuit. By using the sub-antenna switching circuit 502, there is no need to switch the antenna switching circuit 6 connected to the TV receiver 10, and it is possible to reduce the influence of antenna switching on image quality and sound quality. In this case, it is not necessary to switch the sub-antenna switching circuit 502 at high speed within the horizontal synchronization return line.

In this embodiment, the selected channel detecting means 505 is provided in order to detect the channel selected by the TV receiver 10. However, the local channel in the channel selection tuning circuit 19 in the TV receiver is provided. The same effect can be obtained by sharing the oscillator in the sub-channel selection tuning circuit 503.

In this embodiment, the output of the sub-picture signal circuit is used for level detection in the level detection circuit 8, but the same effect can be obtained by using the output of the sub-channel selection tuning circuit for level detection.

(Embodiment 6) Next, a sixth embodiment of the present invention will be described with reference to FIG. 12 differs from the configuration of the fifth embodiment shown in FIG. 10 in that a level difference detection circuit 601 for detecting a difference between the level detection results of the currently selected antenna and the other antennas is newly provided. . Hereinafter, the operation will be described focusing on the difference.

The level difference detection circuit 601 detects a difference between the level detection value of the currently selected antenna and the level detection results of other antennas from the level comparison result of the level comparison circuit 7. Only when the level detection value by the selected antenna is smaller than the predetermined level from the level detection results of the other antennas,
The timing control circuit 9 controls the sub-antenna switching control signal 50 to switch the antenna to the one having the maximum level.
6 is output to the sub-antenna switching circuit 502.

As described above, according to the present embodiment, it is possible to prevent frequent switching of antennas as a result of antenna level detection and comparison due to minute electric field level fluctuation, and to reduce the influence on image quality and sound quality due to frequent antenna switching. Can be. Further, as shown in FIG. 12, when the antenna switching for detecting the antenna level has almost no effect on the image quality and sound quality of the TV receiver, the number of held horizontal scans is fixed at about several lines, so that the reception electric field can be increased. Therefore, a stable reception situation can be obtained even when the frequency greatly varies.

This embodiment is different from the first embodiment shown in FIG.
Similarly, in such a case, it is possible to prevent frequent antenna switching due to minute fluctuations in the electric field.

(Embodiment 7) Next, a seventh embodiment of the present invention will be described with reference to FIG. 13 differs from the configuration of the fifth embodiment shown in FIG. 10 in that an S / N detection circuit 701 for detecting the S / N of a video signal and an S / N comparison circuit 702 for comparing the S / N are newly provided. The operation will be described below focusing on the differences.

The S / N detection circuit 701 detects and holds the S / N of the video signal from the constant amplitude signal included in the vertical retrace period of the video signal detected and amplified by the sub-video signal receiving circuit 504. The S / N comparison circuit 702 compares the S / N value held by the S / N detection circuit 701 according to the S / N comparison control signal 703. The timing control circuit 9
A sub-antenna switching control signal 506 is output so as to sequentially switch the antenna selected by the sub-antenna switching circuit 502 during the vertical retrace period, and S
S / N comparison control signal 7 so as to compare the / N detection result.
03 is output, and when the level detection comparison result is within a predetermined level, an antenna switching control signal 18 is generated so as to select the antenna with the better S / N comparison result.

FIG. 14 shows a specific circuit configuration of the S / N detection circuit 701. In FIG.
Is a high-pass filter, 705 is an absolute value circuit, and 706 is a low-pass filter. Hereinafter, the operation will be described.

The high-pass filter 704 cuts the DC component of the constant amplitude signal of the video signal from the sub-video signal receiving circuit 504 during the vertical blanking period, and extracts an amplitude fluctuation component. The absolute value circuit 705 takes the absolute value of the output of the high-pass filter and converts the positive / negative fluctuation component into a positive value. The low-pass filter 706 outputs an amount proportional to the sum of the fluctuation components converted to a positive value.

As described above, according to the present embodiment, when the antenna level is within the predetermined level, the antenna is selected based on the S / N detection result, so that the pulse noise is reduced and the ghost is reduced and the image quality is improved. Can be selected. In this embodiment, the S / N
Since the antenna switching by detection can be performed by the sub-antenna switching circuit 502, there is almost no influence on the image quality and sound quality.

[0054]

As described above, according to the present invention, it is possible to select the antenna for outputting the maximum level a plurality of times during the vertical synchronizing signal period, and to stably receive the signal even when the received electric field is subject to high-speed fading. Can be obtained. Also, vehicle speed,
The antenna selection cycle can be controlled by the reception frequency and the electric field strength information, and the antenna selection operation according to the reception electric field can be performed. In addition, by providing a sub-antenna switching circuit and a sub-channel selection tuning circuit in the diversity circuit, switching noise due to antenna switching at the time of antenna level detection can hardly affect the sound quality of the TV receiver. Further, in the above configuration, by providing an S / N detection / comparison circuit, it is possible to select an antenna having not only an electric field level but also a small amount of ghost and pulse noise.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a configuration of a TV receiver as a main part in the first embodiment.

FIG. 3 is a waveform chart showing a timing relationship of a control signal which is a main part in the first embodiment.

FIG. 4 is a block connection diagram showing a configuration of a vehicle-mounted TV diversity device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the number of horizontal scans held by the antenna and the vehicle speed in the second embodiment.

FIG. 6 is a block diagram showing a configuration of an in-vehicle TV diversity device according to a third embodiment of the present invention.

FIG. 7 is a diagram showing the relationship between the number of horizontal scans held by the antenna and the input electric field strength in the third embodiment.

FIG. 8 is a block diagram showing a configuration of an in-vehicle TV diversity apparatus according to a fourth embodiment of the present invention.

FIG. 9 is a waveform chart showing a timing relationship of a control signal in the fourth embodiment.

FIG. 10 is a block diagram showing a configuration of a vehicle-mounted TV diversity apparatus according to a fifth embodiment of the present invention.

FIG. 11 is a waveform chart showing timing relationships of control signals in the fifth embodiment.

FIG. 12 is a block diagram showing a configuration of an in-vehicle TV diversity apparatus according to a sixth embodiment of the present invention.

FIG. 13 is a block diagram showing a configuration of an in-vehicle TV diversity apparatus according to a seventh embodiment of the present invention.

FIG. 14 is a block diagram showing a configuration of an S / N detection circuit as a main part in the seventh embodiment;

FIG. 15 is a block diagram showing a configuration of a conventional vehicle-mounted TV diversity device.

[Explanation of symbols]

 1-4 antenna 5 diversity circuit 6 antenna switching circuit 7 level comparison circuit 8 level detection circuit 9 timing control circuit 10 TV receiver 19 channel selection tuning circuit 20 video signal receiving circuit 21 synchronization separation circuit 101-104 antenna 105 antenna switching circuit 106 TV receiver 107 Level detection comparison circuit 108 Timing control circuit 201 Vehicle speed detection means 202 Antenna holding horizontal scanning frequency determination means 301 Electric field strength detection means 303 Antenna holding horizontal scanning frequency determination means 401 Vehicle speed detection means 501 Divider 502 Secondary antenna switching Circuit 503 Sub-channel selection tuning circuit 504 Sub-video signal reception circuit 505 Selected channel detection means 601 Level difference detection circuit 701 S / N detection circuit 702 S / N comparison circuit 704 High-pass filter 70 5 Absolute value circuit 706 Low pass filter

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tadaaki Ushiyama 4-3-1 Tsunashima, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture Inside Matsushita Communication Industrial Co., Ltd. (56) References JP-A-5-48505 (JP, A) Kaihei 2-143855 (JP, U) Special table Hei 5-505501 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B ⁷ /02-7/12 H04L 1/02- 1/06 H04N 3/38-5/46

Claims (11)

(57) [Claims] 1. A plurality of antennas mounted on a vehicle for receiving a TV broadcast wave, a TV receiver mounted on the vehicle,
An antenna switching circuit for connecting one of the antennas to an antenna input terminal of the TV receiver according to an antenna switching control signal; and a level for detecting and holding a peak value level of a horizontal synchronization signal of a video signal in the TV receiver. A detection circuit, a level comparison circuit that compares the level held by the level detection circuit according to a level comparison control signal,
At the start of a horizontal sync retrace period, the antenna connected to the TV receiver is switched to one of the antennas based on the synchronization signal in the TV receiver, and is switched again at the end of the horizontal sync retrace period. The antenna switching control signal is output so as to connect to the previous antenna, and after sequentially switching to all the antennas, the level comparison circuit outputs the comparison control signal so as to compare the levels obtained by the respective antennas. The antenna switching control signal is output so as to switch and select the antenna having the highest level based on the comparison result of the level comparison circuit, and the state in which the antenna is selected is set to a predetermined horizontal level.
Timing control circuit for holding the number of scans and vehicle
Vehicle speed detecting means for detecting the traveling speed of the vehicle,
Depending on the vehicle speed detected by the speed detection means.
Horizontal scanning circuit holding antenna in the imaging control circuit
An in-vehicle TV diversity device comprising an antenna holding horizontal scanning frequency determining means for controlling the number . 2. A multi-purpose television broadcasting wave receiving apparatus mounted on a vehicle.
A number of antennas, a TV receiver mounted on the vehicle,
One of the antennas is moved forward according to an antenna switching control signal.
Switching the antenna connected to the antenna input terminal of the TV receiver
Circuit and a horizontal synchronization signal of a video signal in the TV receiver
Level detection circuit that detects and holds the peak value level of the signal
And the level held by the level detection circuit.
A level comparison circuit for comparing according to a bell comparison control signal;
Based on the synchronization signal in the TV receiver, a horizontal synchronization
At the beginning of the line period, the antenna connected to the TV
Switch the antenna to one of the antennas and
At the end of the retrace period, connect to the antenna before switching again
Output the antenna switching control signal so that
After sequentially switching to the antenna, the level comparison
The circuit provides the level obtained by each antenna.
Output the comparison control signal so as to compare
Based on the comparison result of the
The antenna switching control signal so as to select switching to the antenna.
Is output, and the state in which the antenna is selected is
A timing control circuit that holds the number of scans,
Local oscillator for channel selection tuning circuit in TV receiver
In the timing control circuit according to the oscillation frequency of the
Antenna holding that controls the number of horizontal scans that hold the antenna
An in- vehicle TV diversity device comprising a horizontal scanning frequency determining means . 3. A multi-purpose television broadcast wave receiving apparatus mounted on a vehicle.
A number of antennas, a TV receiver mounted on the vehicle,
One of the antennas is moved forward according to an antenna switching control signal.
Switching the antenna connected to the antenna input terminal of the TV receiver
Circuit and a horizontal synchronization signal of a video signal in the TV receiver
Level detection circuit that detects and holds the peak value level of the signal
And the level held by the level detection circuit.
A level comparison circuit for comparing according to a bell comparison control signal;
Based on the synchronization signal in the TV receiver, a horizontal synchronization
At the beginning of the line period, the antenna connected to the TV
Switch the antenna to one of the antennas and
At the end of the retrace period, connect to the antenna before switching again
Output the antenna switching control signal so that
After sequentially switching to the antenna, the level comparison
The circuit provides the level obtained by each antenna.
Output the comparison control signal so as to compare
Based on the comparison result of the
The antenna switching control signal so as to select switching to the antenna.
Is output, and the state in which the antenna is selected is
A timing control circuit that holds the number of scans,
Detects the input electric field strength of the antenna connected to the TV receiver
Electric field intensity detecting means, and the electric field intensity detecting means
The timing control circuit according to the electric field strength detected by
Control the number of horizontal scans that hold the antenna on the road
Characterized by having means for determining the number of horizontal scans held by the antenna
In-vehicle TV diversity apparatus according to. 4. A TV receiver, comprising: a channel selection tuning circuit for selecting a high-frequency signal input to an antenna input terminal;
A video signal receiving circuit that detects and amplifies the selected intermediate frequency signal by the channel selection tuning circuit; and a synchronization separating circuit that separates a synchronizing signal from the video signal detected and amplified by the video signal receiving circuit; vehicle TV diversity apparatus according to claim 1, 2 or 3, wherein further comprising a picture tube that reflects the image from the video signal and the synchronizing signal. 5. The level detecting circuit according to claim 1, wherein the level detecting circuit detects and holds a peak value level of a horizontal synchronizing signal of the intermediate frequency signal selected by the channel selecting and tuning circuit in the TV receiver . 4. The in-vehicle TV diversity device according to 2 or 3 . 6. A timing control circuit for detecting a vehicle speed.
When the vehicle speed detected by the step is lower than a predetermined speed, the antenna switching control signal and the level comparison control signal are used to perform the level detection comparison by excluding the antenna having the minimum level in the previous level detection comparison. If the vehicle speed is still lower than the predetermined speed in the subsequent level detection comparison, instead of the antenna excluded in the previous level detection comparison, the antenna having the minimum level is excluded. 2. The in-vehicle TV diversity device according to claim 1, wherein the antenna switching control signal and the level comparison control signal are output so as to perform level detection comparison. 7. A vehicle speed detection for detecting a running speed of a vehicle.
Means, wherein the timing control circuit detects the vehicle speed.
Vehicle speed detected by the means falls below a predetermined speed
The minimum level in the previous level detection comparison.
To exclude level antennas and perform level detection comparison.
Outputs the tenor switching control signal and the level comparison control signal, and thereafter
The vehicle speed still exceeds the predetermined speed in the level detection comparison of
If it is below, exclude it during the previous level detection comparison
The antenna that was at the minimum level instead of the antenna that was
The antenna is turned off so that level detection
Outputting a switching control signal and the level comparison control signal.
The TV diver for in-vehicle use according to claim 2 or 3, wherein
Shichi equipment. 8. A selection channel detecting means for detecting a broadcasting station channel selected by a TV receiver, and selecting and tuning a channel selected by the TV receiver based on a detection result by the selection channel detecting means. Sub-channel selection and tuning circuit, a sub-video signal receiving circuit for detecting and amplifying the output of the sub-channel selection and tuning circuit, and dividing each of the plurality of antennas into two.
A distributor for connecting the distributed output of the sub-antenna to the sub-antenna switching circuit;
A sub-antenna switching circuit for connecting one of the plurality of antennas to the sub-channel selection tuning circuit in accordance with a sub-antenna switching control signal; and level detection for performing level detection on an output signal of the sub-video signal receiving circuit. and the circuit, rather than the antenna switching during the level detected by the antenna switching circuit, according to claim 1, characterized in that the addition timing control circuit for outputting the auxiliary antenna switching control signal so as to perform in the sub-antenna switching circuit Or the in-vehicle TV diversity device according to 3. 9. A sub-channel selection tuning circuit for selecting and tuning a channel selected by the TV receiver by sharing a local oscillator of a channel selection tuning circuit in the TV receiver, and the sub-channel selection tuning circuit A sub-video signal receiving circuit for detecting and amplifying the output, and each of the plurality of antennas are divided into two, and the first divided output is sent to an antenna switching circuit.
A distributor for connecting a second distribution output to a sub-antenna switching circuit; and a sub-antenna switching circuit for connecting one of the plurality of antennas to the sub-channel selection tuning circuit according to a sub-antenna switching control signal; A level detection circuit that performs level detection on the output signal of the sub-video signal receiving circuit, and outputs the sub-antenna switching control signal so that the antenna switching at the time of level detection is performed by the sub-antenna switching circuit instead of the antenna switching circuit. claim, characterized in that the addition of a timing control circuit for 1, 2 or
3-vehicle TV diversity apparatus according. 10. The level of the currently selected antenna from the result of the level comparison in the level comparing circuit,
A level difference detection circuit that detects a difference between the level detection results of the other antennas, and the level of the other antenna is higher than that of the selected antenna, and the output of the level difference detection circuit is higher than a predetermined range. 4. The in-vehicle TV diversity device according to claim 1, further comprising a timing control circuit for outputting an antenna switching control signal for switching an antenna only when the distance becomes large. 11. The in-vehicle TV diversity apparatus according to claim 8, further comprising a level detection circuit for detecting a level of an output of the sub-channel selection tuning circuit.