JPH04160992A - Teletext receiving system for mobile body - Google Patents

Abstract

PURPOSE:To make it possible to receive teletext at a mobile body such as electric car by using a plurality of antennas constituting a diversity antenna to receive teletext by switching each antenna at an interval of at least 1sec+ or -0.5 sec. CONSTITUTION:Four antennas 30a-30d are installed on the roof of body of an electric car with their horizontal directions made different by 90 deg. from one another, and they receive radio wave coming nearly in all directions of 360 deg., and via switching section 41 in an underfloor unit 40 hanged under the floor of car body 1, booster 42, and ghost reduction tuner 43a, a previously set channel television broadcasting signal is obtained. The television broadcasting signal thus obtained is supplied to a discriminating circuit 44, and the discriminating circuit 44 discriminates a synchronous signal level contained in the broadcasting signal, controls the switching section 41 for selection of antenna line so as to be able to obtain a synchronous signal with the best level to constitute so called a diversity antenna. In this case, this discriminating circuit 44 carries out level discrimination at an interval of one second under the control of timer circuit 45.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a teletext receiving system for a mobile body suitable for application to one mounted on a mobile body such as a train.

[Summary of the invention]

The present invention provides a teletext receiving system mounted on a moving object such as a train, in which a diversity antenna is configured with a plurality of antennas for reception, and each antenna is switched at intervals of at least 1 second ± 0.5 seconds. This allows the teletext antenna to be received well using the ubiversity antenna.

[Prior Art] In recent years, a television receiver is attached to a moving body such as a train, and passengers are served by receiving images reproduced from a VTR or the like. In this case, some trains are equipped with an antenna installed on the roof of the train, which receives television broadcast signals from a transmitting station on the ground and displays the images.

[Problems to be Solved by the Invention] However, such television broadcast signals can only be received when driving in a place with relatively good radio wave conditions. In other words, in the case of a mobile vehicle traveling in an area with many buildings and other obstacles, such as in a city center, there are few places where the broadcast signal from the transmitting station can be received well without unnecessary radiation, so it is necessary to move the regular television antenna. If the device was simply attached to the body, the reception would be very poor, often resulting in images that were not suitable for practical use. For example, in the case of the train on the Yamahira Line, which runs through almost the center of Tokyo, the distance from the transmitting station is very close, and the area is in a strong electric field area where even a simple structure antenna would normally be able to receive good reception. There are so many obstacles such as this that it is nearly impossible to receive television broadcasts without ghosting using conventional technology.

In addition, radio waves for teletext broadcasting are transmitted using part of the television broadcast signal, but since this teletext signal is transmitted as digital data, ghosts are extremely difficult to generate. It was impossible to receive teletext on mobile devices.

Furthermore, if the direction of the transmitting station as seen from the mobile object is constantly changing, it is not impossible to keep the antenna pointing in the direction of the transmitting station, but it requires complex tracking equipment.
In general, reception is often done using a fixed antenna, which also causes poor reception conditions. For example, in the case of a train that runs in a loop around a transmitting station (such as the Yamahira line in Tokyo), the direction of the transmitting station as seen from the train is 360 degrees in one lap.
It was impossible to always receive good reception with a fixed antenna.

To solve this problem, when receiving television broadcasts on a mobile object such as a car, multiple antennas are installed, and reception is performed by switching to the one with the best reception among the multiple antennas. A so-called diapersity antenna is being constructed. In this case, the receiving state is determined in one field or one frame cycle of the received video signal, and the antenna is sequentially switched to an antenna with the best receiving state, thereby minimizing disturbances in the received image. According to this diversity antenna, the possibility of good reception is higher than when reception is performed using only one antenna.

However, since teletext is transmitted as digital data, if the received data is interrupted during reception of the teletext program, a reception error occurs and the teletext program cannot be decoded.

Therefore, if teletext is received using a diversity antenna, a reception error will occur each time the antenna is switched, making it impractical to receive teletext using a diversity antenna that frequently switches the receiving antenna.

An object of the present invention is to enable a mobile object such as a train to receive text broadcasting satisfactorily.

[Means for Solving the Problems] The present invention provides, for example, as shown in FIG. 1, a plurality of antennas (30a), (30b),
(30c).

(30d) and the plurality of antennas (30a), (
30b), (30c).

(30d), an antenna switching means (41) for selecting the antenna with the best reception condition; and a television broadcast reception tuner (43) for demodulating the signal from the antenna selected by the antenna switching means (41). , a teletext decoder (46) that demodulates the teletext signal from the output of the second tuner (43), and this teletext decoder (46).
) Display means (101) for displaying the output of (10
2).

(103) . . . (124) are provided, and the antenna switching means (41) switches the plurality of antennas at intervals of at least 1 second ± 0.5 seconds.

[Operation] In teletext broadcasting, one screen is transmitted in approximately 0.5 seconds using the vertical blanking period of the television broadcast signal.

Therefore, the antenna switching means should be switched for at least 1 second ±
By changing the frequency to 0.5 seconds, teletext 1
The reception antenna is less likely to switch while receiving a screen image, and teletext can be received better using the diversity antenna.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 4.

In this example, it is applied to a reception system that displays teletext on a television receiver installed on a train.
First, the overall configuration of this receiving system will be explained.

In Figures 1 and 2, (1) shows the body of the train, and the side of this body (1) has six doors (entrances and exits) on each side.
(11), (12), (13)...(16)
and (17), (1B).

(19)...(22) are provided, and television receivers (101), (102), (
103)...(124) are installed. For example, as shown in FIG. 2, television receivers (117) and (118) are attached to the upper portions of the left and right door compartments of the door (19). In this case, each television receiver (
101), (102), (103)...(
124) is a thin type using a liquid crystal panel or the like.

And, each of these television receivers (101), (
102).

(103) ... (124) displays teletext, and four antennas are used to receive this teletext (30a), (30b), (30c),
(30d) is attached around the ventilators (3) and (4) on the roof (2) of the vehicle body (1).

In this case, each antenna (30a), (30
b), (30c).

As shown in FIG.
1).

(32) and a reflector (33) arranged at a predetermined interval.
coaxial cable (35) via matching transformer)
(see Fig. 3), and this coaxial cable (35) is connected to a switch (41) in an underfloor unit (40), which will be described later. The lengths of the two conductor rods (31) and (32) are selected according to the frequency of the receiving channel, and the reflector (33) is made by combining these two conductor rods (31) and (32). It is longer than its length.

And four antennas (30a), (30b)
, (30c).

The antennas (30d) are installed at different angles by 90° in the horizontal direction, the antennas (30a) and (30b) are installed in front and behind the ventilator (3) (in a direction parallel to the rail), and the antennas (30c) , (30d) are attached to the left and right sides (direction perpendicular to the rail) of the ventilator (4) next to the ventilator (3).

Here, to explain in detail the installation of the antenna to the ventilator, there are multiple ventilators (3), (4), (5)... attached to the roof (2) of this vehicle body (1). , this ventilator (3), (4), (
5)... are so-called push-in ventilators that function as ventilation devices that push outside air into the interior of the car during driving, and each ventilator (3), (4)
, (5)... are the four corner legs (3aC (4a),
(5a)... is fixed to the rooftop (2) with bolts (23). In this case, each ventilator (3), (
4), (5)... are installed insulated from the vehicle body (1).

Then, the two antennas (30a) and (30b) are attached using the bolts (23) fixing the legs (3a) at the four corners of the ventilator (3). In addition, the four corner legs of the ventilator (4) next to the ventilator (3) (
Attach the two antennas (30c) and (30d) using the bolts (23) that fix 4a).

This antenna (30c) and (3
0d) to the ventilator (4) is shown in an enlarged view.A U-shaped cover (24) is attached around the ventilator (4) with a hole (23). In this case, the cover (24) should not block the ventilation portion (4b) of the ventilator (4). Antenna (30c) and (30d) are placed on the top of this cover (24).
) is fixed at one end of the connecting member (34), and a reflector (33
) at the other end, and conductor rods (31) and (3
2) Fix. Here, two conductor rods (31) and (3
2) is fixed to the connecting member (34) with a predetermined gap provided. Further, the connecting member (34) is made of an insulating material. In addition, in this example, the conductor rods (31), (32) and the reflector (33) are made of angle material with an L-shaped cross section,
This allows for easy installation.

Here, the distance H in the height direction between the upper end of each ventilator and the lower end of the reflector (33) is at least 15 mm, and the horizontal width between each ventilator and the reflector (33) is at least 15 mm. 2On++n, and a reflector (3
3) Height B shall be 70 mm or more. In this case, the larger the height 81 width with respect to the ventilator and the height B of the reflector (33) itself, the better the characteristics of the antenna.
In reality, the size of equipment that can be mounted on the rooftop (2) is determined by standards such as vehicle limits, so it is not possible to install a very large antenna, and it is limited to the above value or a value slightly larger than this value. .

In this way, four antennas (30a), (30
b).

By installing (30c) and (30d), the respective antennas (30a), (30b), (
30c) and (30d) are conductor rods (31).

(32) receives only the radio waves in the direction in which it is installed, and the radio waves directed toward the conductor rods (31) and (32) from the opposite side (ventilator side) are blocked by the reflector (33), and the reflected radio waves cause stationary It is possible to suppress the generation of waves. Therefore,
4 antennas (30a) with different installation positions by 90 degrees
, (30b), (30c), and (30d), it is possible to receive radio waves coming from all directions of almost 360°.

Then, four antennas (30a
), (30b), (30c), '(30d
) is connected by a coaxial cable (35) to a switch (41) in an underfloor unit (40) suspended under the floor of the vehicle body (1). This underfloor unit (40) houses the equipment for receiving teletext broadcasting, and the switch (4) selects the received signal supplied from one of the antennas under the control of a discrimination circuit (44), which will be described later. output. The received signal output from this switch (41) is then transferred to a booster (42).
The ghost reduction tuner (43) receives the television broadcast signal of a preset predetermined channel through the ghost reduction tuner (43). In this case, the ghost reduction tuner (43) performs ghost reduction of the received broadcast signal using the GCR signal etc. inserted during the vertical retrace period, and together with the tuning section and the intermediate frequency amplification/demodulation section, the ghost reduction tuner (43) performs ghost reduction of the received broadcast signal. Equipped with a removal filter, a GCR signal extraction circuit, a comparison circuit, a control circuit, etc., it compares the GCR signal distorted due to diffused reflection of radio waves with a reference signal and suppresses the reflected wave signal. .

In this example, the television broadcast signal of a predetermined channel obtained by the ghost reduction tuner (43) is supplied to the discrimination circuit (44).
), the level of the synchronization signal included in the television broadcast signal received by the switch (41) is determined, and the antenna line selected by the switch (41) is set to the one that provides the best level of synchronization signal, thereby creating a so-called diversity antenna. Configure. In this case, a timer circuit (45) is connected to this discrimination circuit (44), and the above-mentioned level discrimination is performed every second under the control of the timer circuit (45). That is,
The timer circuit (45) supplies a judgment control signal to the discrimination circuit (44) every time the time equivalent to one second is counted, and the discrimination circuit (44) performs level discrimination every time this judgment control signal is supplied. That's what I do. Therefore, the switch (4
The switching of antenna lines in 1) is performed at intervals of one pole even when the radio wave condition is the worst, and when the reception condition of any of the switched antennas is good, the level judgment is performed every second. A synchronization signal above a certain level is detected and 1
Receive signals from the same antenna for more than two seconds.

Then, the television broadcast signal obtained by the ghost reduction tuner (43) is supplied to a teletext decoder (46), and the teletext decoder (46) produces two characters multiplexed in the vertical blanking period of the broadcast signal. etc. to obtain teletext signals. In this case, when a plurality of teletext programs are being transmitted using the television broadcast signal of one channel, and data for at least one screen of a preset teletext program is obtained, the teletext decoder (46) This data is stored in the connected memory (47). That is, the teletext decoder (46) determines whether each received teletext screen is complete.
When it is determined that data for even one complete screen has been obtained using this circuit, if this data is a needed teletext program, it is stored in the memory (47).

In this case, the transmission of data for one screen of a teletext program is as follows:
This is usually done for about 0.5 seconds to 1 second. Therefore, when good reception continues for at least 0.5 seconds to 1 second, one screen worth of teletext data can be received, and when the good reception continues, multiple screens (i.e. one You can receive all pages of teletext programs or multiple teletext programs).

Then, the data of the predetermined teletext program stored in the memory (47) in this way is sent to the teletext decoder (46).
The characters represented by the data are read out sequentially.

A video signal for displaying a figure or the like as an image is output from the underfloor unit (40) via a coaxial cable. In this case, the output video signal is a baseband video signal (ie, a video signal that is not RF modulated).

Further, in this example, a power supply circuit (48) is provided in the underfloor unit (40), and a DC low voltage power is outputted from this power supply circuit (48).

A coaxial cable for outputting a video signal from this underfloor unit (40) is connected to a three-way divider (61) attached to the vehicle body (1) to supply an output video signal. In addition, the power output from the power supply circuit (48) is also connected to the three-way divider (
61). This 3-part divider (61) has a built-in amplifier, and is designed to amplify the supplied base) Z-nd video signal by 3 times and then distribute it into 3 parts. By doing so, the gain of the input video signal and the gain of the distributed output video signal become equal. In this case, amplification is performed using the power output from the power supply circuit (48).

Then, the 1st. 2nd゜3rd
Of the distributed outputs, the first distributed output is sent to the first two-way divider (7
1), the second distributed output is supplied to the connection terminal (62) provided on the connection surface on the first end (one end) side of the vehicle body (1), and the third distributed output is supplied to the vehicle body (1). is supplied to a connection terminal (63) provided on the connection surface on the second end (other end) side. In addition, the power supplied to the three-way divider (61) is also supplied to the first
2 distributors (71).

This first two-way divider (71) has a built-in amplifier and is designed to amplify the supplied baseband' video signal twice and then divide it into two parts. With this configuration, the gain of the input video signal and the gain of the distributed output video signal are equal, similar to the above-described three-way divider (61).

In this case, amplification is performed using power supplied from the power supply circuit (48) via the three-way divider (61).

Then, the first distribution output distributed by the first two-way divider (71) is supplied to the second two-way divider (72) connected to the rear stage, and the second distribution output is supplied to the second two-way divider (72) connected to the rear stage. It is supplied to the thirteenth two-way distributor (83). In this case, the 3-distributor (61)
The power supplied from the side is divided into two distributors (second and thirteenth) (
72) and (83).

This second two-way divider (72) is connected to the first two-way divider (71).
), the supplied baseband video signal is amplified twice and then distributed into two, and the first distribution output is sent to the television receiver (1) installed in the car.
01), and the second distribution output is supplied to a third two-way divider (73) connected to the subsequent stage.

Hereinafter, a two-way divider (73) connected to the subsequent stage in the same manner,
(74), (75)...(82), after doubling the supplied baseband video signal, it is divided into two, and the first distribution output is sent to the corresponding one installed in the car. Television receiver (103), (104),
(105) ... (111), and the second distribution output is connected to the two-way divider (74), (75),
(76)...supply to (82). However, the second distribution output of the twelfth two-way divider (82) connected last is supplied to the television receiver (112).

In this case as well, the power supplied from the preceding two-way divider is supplied to the television receiver connected from each two-way divider and the second-stage two-way divider.

Furthermore, the first distribution output of the thirteenth two-way divider (83) connected to the second distribution output side of the first two-way divider (71) is connected to a television receiver (113) installed in the vehicle. The second distributed output is supplied to the fourteenth two-way divider (84) connected to the subsequent stage.

Hereinafter, a two-way divider (85) connected to the subsequent stage in the same manner,
(86), (87)...(93), after doubling the supplied baseband video signal, it is divided into two, and the first distribution output is sent to the corresponding one installed in the car. Television receiver (114), (115),
(116) ... (123), and the second distribution output is connected to the subsequent stage of the two-way divider (86), (87
), (88)...(93). However, the second distribution output of the 23rd two-way divider (93) connected last is supplied to the television receiver (124).

In this case as well, the power supplied from the preceding two-way divider is supplied to the television receiver connected from each two-way divider and the second-stage two-way divider.

In addition, the connection terminals (62) and (63) provided on the connection surface
) is connected to the video signal input terminal of the connected vehicle (not shown) when other vehicles not equipped with a tuner etc. are connected in front and behind. This makes it possible to supply video signals. In this case, the power required by the video distributors and television receivers of the front and rear vehicles is supplied from power supply circuits within each vehicle.

Next, the television receiver (
101), (102), (103)...(
124) to display teletext images will be described.

First, a teletext program is received and the necessary teletext program data is stored in the memory (47) connected to the teletext decoder (46). In this case, if the reception condition of the television broadcast signal is good, the storage work in the memory (47) will be completed in a short time, but in reality, the service is performed while the vehicle (1) is running. Therefore, when the reception condition becomes good and the teletext decoder (46) obtains at least one screen worth of data of the teletext program required, the obtained screen data is is stored in the memory (47), and the previously stored data of the same hege is updated with the newly received data.

In this case, the direction of the transmitting station as seen from the vehicle (1) changes as it travels, but the four antennas (30a), (30b), (30c), (
A diversity antenna is configured to determine which of the antennas (30d) can provide good reception, and each of the antennas (30a).

(30b), (30c), and (30d) are sequentially connected to the tuner (43) side by a switch (41), and the receiving state at the ghost reduction tuner (43) is sequentially judged by a judgment circuit (44). , connect to the antenna that provides the best broadcast signal.

In this case, under the control of the timer circuit (45), the judgment circuit (44) judges the receiving state every second, and the receiving antenna is switched at least every second. There is a high possibility that data for at least one screen of a teletext program will be obtained while receiving a signal from In other words, if the receiving antenna switches while receiving data for one screen, the teletext decoder (46) will temporarily interrupt the received data at the time of this switching, and will not be able to complete one complete screen. The data for one screen will not be sent, and a reception error will occur. Normally, data for one screen is sent every 0.5 seconds to 1 second, and in this example, it is sent at least every 1 second. Since the receiving antenna is switched, there is a high possibility that at least one screen worth of data of a teletext program can be obtained while receiving a signal from one antenna, and at least one screen worth of characters is stored in the memory (47). Broadcast data can be stored and teletext data can be updated sequentially.

In addition, it is only when the reception condition is very good that the teletext decoder (46) can obtain the screen of the teletext program required by the teletext decoder (46). This is when the vehicle is stopped at a station, etc. That is, for example, in the case of a train that runs in the city center and stops at various stations, it will stop at a station for about 10 seconds to 1 minute every 2 to 3 minutes, and it is possible to receive more than one screen of teletext programs during this stop. There is a high possibility that teletext can be received relatively frequently.

When the teletext data can be loaded into the memory (47) connected to the teletext decoder (46) in this way, the data of the teletext program to be displayed at predetermined intervals is read out and the video signal for displaying the teletext is read out. create and
This video signal is sent to each distributor (61).

(71) to (93) to the television receiver (10).
1) to (124), and the teletext program is displayed on television receivers (101) to (124) installed in the vehicle. In this case, for example, a plurality of types of teletext are displayed sequentially in cycles of several minutes to several tens of minutes.

In the above-mentioned embodiment, the receiving antenna is switched at an interval of at least 1 second, but if the receiving antenna is switched at an interval of at least 1 second ± 0.5 seconds, the above-mentioned embodiment Almost the same effect can be obtained. In this case, shorten the minimum switching time (then it will take less time to search for an antenna that can receive good reception, but a reception error may occur where the antenna switches while receiving one screen of teletext data). more likely to.

Conversely, the longer the minimum switching time is, the less likely a reception error will occur where the antenna switches while receiving one screen of teletext data. It takes time. Therefore,
The minimum interval for switching the receiving antenna is 1 second ± 0.5
It is best to keep it in seconds.

Further, in the above embodiment, only the teletext receiving equipment was installed, but a video reproducing device such as a VTR may be provided to display the replayed video alternately with the teletext program.

Also, there are four receiving antennas (30a).

Although the diversity antenna is configured with (30b), (30c), and (30d), the diversity antenna may be configured with more antennas.

Furthermore, in the above-mentioned embodiment, the receiving system was installed in a train, but the present invention can also be applied to other moving objects (cars, ships, etc.).

Furthermore, it goes without saying that the present invention is not limited to the above-mentioned embodiments, and can take various other configurations.

[Effects of the Invention] According to the present invention, the receiving antenna is less likely to switch while receiving one screen of teletext broadcasting, the occurrence of reception errors is reduced, and the reception of teletext broadcasting is improved using the diversity antenna. This makes it possible to receive teletext broadcasts satisfactorily on a mobile object using an antenna device with a relatively simple configuration.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing one embodiment of the present invention, Fig. 2 is a partially cutaway perspective view showing how the system of one embodiment is installed on a vehicle body, and Fig. 3 shows the main parts of one embodiment. FIG. 4 is a side view showing essential parts of one embodiment. (1) is the vehicle body, (3), (4) ... (8) is the henchilator, (30a). (30b), (30c), (30d) are antennas, (40) are underfloor units, (41) are switching devices, (4
3) is a ghost reduction tuner, (46) is a teletext decoder, (47) is a memory, (48) is a power supply circuit, (61) is a three-way divider, and (62). (63) are connection terminals, (71), (72)...(
93) is a two-way divider, (101), (102)...
- (124) is a television receiver.

Claims (1)

[Scope of Claims] A plurality of antennas mounted on a moving object, an antenna switching means for selecting an antenna with the best reception condition among the plurality of antennas, and a signal from the antenna selected by the antenna switching means. a television broadcast reception tuner for demodulating a teletext signal, a teletext decoder for demodulating a teletext signal from the output of the tuner, and a display means for displaying the output of the teletext decoder; A teletext receiving system for a mobile object, in which antenna switching is performed at intervals of at least 1 second ± 0.5 seconds.