JP4017621B2 - Wireless redistribution system for terrestrial digital TV broadcasting - Google Patents

Description

  The present invention relates to a wireless redistribution system for terrestrial digital TV broadcasting.

  Japan's terrestrial digital TV broadcasting has started on December 1, 2003 in the three major metropolitan areas of Kanto, Chukyo, and Kinki. Terrestrial digital TV broadcasting uses OFDM (Orthogonal Frequency Division Multiplexing), which is resistant to multipath interference, and there is almost no multiplex image (ghost disturbance) generated in analog TV broadcasting, etc., and stable high image quality. Can receive. Terrestrial digital TV broadcasting is broadcast in the UHF band (470 to 770 MHz).

  As a form of receiving a terrestrial digital TV broadcast by a terrestrial digital TV receiver, there are generally the following forms.

(1) A terrestrial digital TV broadcast signal is received by an outdoor antenna. A terrestrial digital TV broadcast signal received by an outdoor antenna is distributed to each room by an antenna cable and guided to a TV terminal provided on the wall surface of each room. Then, the antenna terminal of the terrestrial digital TV receiver is connected to the TV terminal provided on the wall surface of each room via an antenna cable.
In such a receiving mode, it is necessary to connect the antenna terminal of the terrestrial digital TV receiver to the TV terminal provided on the wall surface by using an antenna cable, so that the beauty is impaired and the wiring is troublesome. There is. In addition, since the layout of the TV receiver is limited, there is a problem that the degree of freedom of the installation position of the TV receiver is hindered.

(2) Without installing an antenna on the rooftop (on the roof), install a UHF antenna (for example, UDMF62: made by Japan Antenna) on the eaves or veranda, and then pull the antenna cable indoors to receive digital terrestrial TV Connect directly to the antenna terminal of the machine.
Even in such a reception mode, it is necessary to draw the antenna cable into the room and connect it to the terrestrial digital TV receiver. This causes a problem in that the appearance is impaired and the wiring is troublesome. In addition, since the layout of the TV receiver is limited, there is a problem that the degree of freedom of the installation position of the TV receiver is hindered.

(3) The terrestrial digital TV broadcast signal is received by the indoor antenna connected to the terrestrial digital TV receiver.
In such a receiving mode, there is no restriction on the layout of the TV receiver due to the wiring of the antenna cable, but there is a problem that a radio wave blocking loss occurs in the room. In particular, the UHF band used for terrestrial digital TV broadcast signals has a larger attenuation loss when passing through buildings than the VHF band used for terrestrial analog TV broadcasts. There is a problem that the installation position is limited.

  Therefore, an indoor re-transmission system has been developed in which a terrestrial digital TV broadcast signal input indoors is amplified by a wireless transmitter and retransmitted wirelessly to a TV receiver (Japanese Patent Laid-Open No. 2004-128719, JP, 2004-12720, A). In this indoor retransmission system, UHF band terrestrial digital TV broadcast signals input indoors are amplified and retransmitted as they are without frequency conversion.

  In the frequency band of the UHF band, as will be described later, since the transmission output level of the wireless transmitter is limited to a very low level, there is a problem that the transmission distance is almost short distance transmission only.

  In addition, when both the direct broadcast radio wave transmitted from the broadcasting station and the retransmitted radio wave transmitted from the wireless transmitter are received and input from the indoor receiving antenna, the signal of the same frequency channel is input to the TV receiver. As a result, there is a case where interference cannot be received due to the interference of the same channel.

In order to prevent this, there is a problem that a device for preventing the deterioration of the terrestrial digital TV broadcast signal due to the interference with the same channel is separately required for the antenna and the circuit.
JP 2004-128719 A Japanese Patent Laid-Open No. 2004-12720

  Therefore, the present applicant can prevent the occurrence of interference interference on the same channel of the terrestrial digital TV broadcast signal by performing the frequency conversion on the transmitter side, and does not require the frequency conversion on the receiver side. A wireless redistribution system for TV broadcasting (not known at the time of this application) has been developed.

  Hereinafter, a wireless redistribution system for terrestrial digital TV broadcasting developed by the present applicant will be described.

  This wireless redistribution system is made using the following actual situations (1) and (2).

(1) As will be described later, in addition to the UHF band, the stationary TV receiver for terrestrial digital TV broadcasting includes a VHF_Low / High band (VHF1ch to VHF12ch), a VHF_MID band (C13ch to C22ch), and a VHF_SHB band (C23ch). ~ C63ch) are often designed to be received.

(2) Further, as described later, in the weak radio wave standard, the restriction on the electric field strength for the frequency band of 322 MHz or less and 150 GHz or more is looser than the restriction of the electric field strength for the frequency band of 322 MHz to 150 GHz.

  The wireless redistribution system for terrestrial digital TV broadcasting developed by the present applicant is capable of receiving VHF band TV broadcast signals in addition to UHF band TV broadcast signals, which are the frequency bands of terrestrial digital TV broadcast signals. A TV receiver, a redistribution transmitter, and a redistribution receiver are provided.

  The transmitter for redistribution collectively converts the frequency of the terrestrial digital TV broadcast signal input from the outdoor antenna to the frequency of the vacant channel in the VHF band of 322 MHz or less, and then amplifies and transmits the signal wirelessly. The receiver for redistribution receives and amplifies the signal transmitted from the transmitter, and then supplies it to the TV receiver. The TV receiver views a terrestrial digital TV broadcast by designating a VHF channel.

  The frequency conversion is performed by mixing all the received terrestrial digital TV broadcast signals (reception signals) and local signals from the oscillation unit that transmits at a fixed frequency by a mixer. From the mixer, an addition signal and a subtraction signal of each received signal and the local signal are output. For example, assuming that the frequency of the received signal is fa and the frequency of the local signal is fb, an addition signal having a frequency of fa + fb and a subtraction signal having a frequency of fa−fb are output from the mixer. Then, only the subtraction signal is extracted by the filter.

  By the way, depending on the region (for example, Kinki wide area, Kanto wide area, Chukyo wide area), broadcasting stations of terrestrial digital TV broadcasting are different, and reception channels (frequency) are different. Therefore, even if the local frequency fb is set so that the frequency of the subtraction signal of the mixer corresponding to all of the received terrestrial digital TV broadcast signals becomes the frequency of an empty channel in the VHF band of 322 MHz or less in a certain area. In other regions, the frequency of the subtracting signal of the mixer corresponding to the received terrestrial digital TV broadcast signal may exceed 322 MHz. In such a case, since the retransmission output is limited with reference to a TV broadcast signal whose subtracted signal frequency exceeds 322 MHz, there is a problem that the transmission distance is shortened.

  An object of the present invention is to provide a radio redistribution system for terrestrial digital TV broadcasting that can automatically adjust a local frequency so that a frequency after frequency conversion is 322 MHz or less.

  In addition, the present invention provides a radio redistribution system for terrestrial digital TV broadcasting that can notify the user when the frequency after frequency conversion exceeds 322 MHz and can change the local frequency by the user. The purpose is to provide.

  According to the first aspect of the present invention, terrestrial digital TV broadcast radio applied to a TV receiver capable of receiving a VHF band signal in addition to a UHF band signal which is a frequency band of a terrestrial digital TV broadcast signal. This is a redistribution system that receives a terrestrial digital TV broadcast signal received by an outdoor antenna, converts the frequency of the input terrestrial digital TV broadcast signal to the frequency of an empty channel in the VHF band, and then amplifies it. A transmitter for wireless transmission, and a receiver that receives and amplifies a signal transmitted from the transmitter and then supplies the signal to the TV receiver. The transmitter generates a local signal. A frequency synthesizer and a mixer that mixes the input terrestrial digital TV broadcast signal and the local signal, and the input terrestrial digital TV broadcast signal Frequency converting means for collectively converting the frequency of an empty channel in the VHF band of 22 MHz or less, signal detecting means for detecting a signal exceeding 322 MHz from the output of the frequency converting means, and a signal exceeding 322 MHz is detected by the signal detecting means If this is the case, the frequency of the local signal output from the frequency synthesizer is automatically changed, and the local frequency is automatically set to such a local frequency that no signal exceeding 322 MHz is detected by the signal detecting means. And a local frequency control means for adjusting the output to a frequency and a transmission means for amplifying and transmitting the output of the frequency conversion means when a signal exceeding 322 MHz is not detected by the signal detection means. .

  According to the second aspect of the present invention, terrestrial digital TV broadcast radio applied to a TV receiver capable of receiving a VHF band signal in addition to a UHF band signal which is a frequency band of a terrestrial digital TV broadcast signal. This is a redistribution system that receives a terrestrial digital TV broadcast signal received by an outdoor antenna, converts the frequency of the input terrestrial digital TV broadcast signal to the frequency of an empty channel in the VHF band, and then amplifies it. A transmitter for wireless transmission, and a receiver for receiving and amplifying a signal transmitted from the transmitter and supplying the TV receiver to the TV receiver. The transmitter generates a local signal. A frequency synthesizer and a mixer that mixes the input terrestrial digital TV broadcast signal and the local signal, and receives the input terrestrial digital TV broadcast signal Frequency converting means for collectively converting the frequency of an empty channel in the VHF band of 22 MHz or less, signal detecting means for detecting a signal exceeding 322 MHz from the output of the frequency converting means, and a signal exceeding 322 MHz is detected by the signal detecting means If it is, the notification means for informing the user of the fact, the input means for allowing the user to input a local signal change command, and the output from the frequency synthesizer when the local signal change command is input by the input means. Local frequency control means for changing the frequency of the local signal to be transmitted, and transmission means for amplifying and transmitting the output of the frequency conversion means when the signal detection means does not detect a signal exceeding 322 MHz. It is characterized by that.

  According to the present invention, the local frequency can be automatically adjusted so that the frequency after frequency conversion is 322 MHz or less.

  Further, according to the present invention, when the frequency after frequency conversion exceeds 322 MHz, this can be notified to the user, and the user can change the local frequency.

  Embodiments of the present invention will be described below with reference to the drawings.

[1] Description of a terrestrial digital broadcast TV receiver to which the present invention is applied

  Table 1 shows each reception channel and center frequency of terrestrial digital TV broadcasting.

  The reception channels of terrestrial digital TV broadcasting are UHF13ch to UHF62ch. The center frequency is 473 + 1/7 MHz for 13 ch, 479 + 1/7 MHz for 14 ch, and 767 + 1/7 MHz for 62 ch.

  Since the frequency band in which terrestrial digital TV broadcasting is introduced is in the range of UHF13 channel to 62 channels, it is necessary that the frequency can be received as the reception frequency range of the terrestrial digital broadcast TV receiver.

  Currently, broadcasting has started in December 2003 in three major metropolitan areas (Kanto, Chukyo, and Kinki). Tables 2, 3, and 4 show the reception channel, center frequency, and broadcasting station in the Kinki wide area and the Chukyo wide area, respectively.

  On the other hand, in the reception form of the current terrestrial analog TV broadcasting, including collective housing joint listening, joint reception accounts for almost half of all households. Most of the transmission bands in these hearing facilities are not widened to the UHF band, and UHF TV broadcasts are VHF_Low / High (VHF low / high band), VHF_MID (VHF midband) and VHF_SHB (VHF super band). In many cases, the data is down-converted to a low-frequency free channel (a channel that is not broadcast in the area) such as a high band.

  For this reason, joint reception is also assumed especially for a stationary TV receiver for terrestrial digital TV broadcasting. Therefore, the reception channel range of the receiver for terrestrial digital broadcasting is VHF_Low / High in addition to the UHF band. It is specified in the ARIB standard ARIB STD-B21 that it is desirable to support the band (VHF1ch to VHF12ch), the VHF_MID band (C13ch to C22ch) and the VHF_SHB band (C23ch to C63ch).

  Therefore, the stationary TV receiver for terrestrial digital TV broadcasting also receives the VHF_Low / High band (VHF1ch to VHF12ch), VHF_MID band (C13ch to C22ch) and VHF_SHB band (C23ch to C63ch) in addition to the UHF band. It is thought that it is often designed to be possible.

  Table 5 shows each reception channel and center frequency in the VHF_Low / High band (VHF1ch to VHF12ch).

  Table 6 shows each reception channel and center frequency of the VHF_MID band (C13ch to C22ch).

  Table 7 shows each reception channel and center frequency of the VHF__SHB band (C23ch to C63ch).

  In the present invention, VHF_Low / High band (VHF1ch to VHF12ch), VHF_MID band (C13ch to C22ch) and VHF_SHB band (C23ch to C63ch) can be received (selected) in addition to the original UHF band 13ch to 62ch (470MHz to 770MHz). The TV receiver for terrestrial digital TV broadcasting is applicable.

[2] Explanation of weak radio wave standards

  The weak radio wave standard will be described. The standard for weak radio waves is defined by the Ordinance of the Ministry of Internal Affairs and Communications as radio equipment that emits extremely weak radio waves, and is defined by the electric field strength at a point of 3 meters.

  FIG. 1 and Table 8 show the electric field strength (allowable value) for the frequency band defined by the weak radio wave standard.

  As shown in Table 8, the allowable value is limited to 500 μV / m for frequency bands of 322 MHz or less and 150 GHz or more. In addition, for the frequency band from 322 MHz to 10 GHz, the allowable value is limited to 35 μV / m in consideration of interference protection for land mobile service, UHF TV broadcasting, fixed service, and space service (earth station). For the frequency band from 10 GHz to 150 GHz, the allowable value is limited to 3.5 fμV / m (f is the used frequency band (GHz)) in consideration of the system noise temperature, the reception bandwidth, and the like.

  A wireless system based on the weak radio wave standard can be designed relatively freely, as long as the electric field strength shown in Table 8 is satisfied, since there are no restrictions on the frequency, modulation method, and communication method.

[3] Specific explanation of the subject of the present invention

  As described above, in the radio retransmission system for terrestrial digital TV broadcast signals already developed by the present applicant, frequency conversion is performed with all the received terrestrial digital TV broadcast signals (received signals) at a fixed frequency. The local signal from the oscillating unit is mixed by a mixer. From the mixer, an addition signal and a subtraction signal of each received signal and the local signal are output. For example, assuming that the frequency of the received signal is fa and the frequency of the local signal is fb, an addition signal having a frequency of fa + fb and a subtraction signal having a frequency of fa−fb are output from the mixer. Then, only the subtraction signal is extracted by the filter.

  For example, when the local frequency fb is set to 224 MHz and the subtraction signal between the received signal and the local signal is extracted by a filter, the VHF transmission channel (channel after frequency conversion), the center frequency, the broadcasting station, and the Corresponding UHF channels are as shown in Table 9.

  Table 10 shows the VHF transmission channel, center frequency, broadcast station, and corresponding UHF channel after frequency conversion in the Kanto wide area when the same local frequency fb is set to the same frequency (224 MHz).

  Therefore, in the Kanto wide area, considering the bandwidth of 5.6 MHz, VHF_SHB C39 (Nippon Television), VHF_SHB C40 (NHK education), and VHF_SHB C41 (NHK synthesis) exceed the frequency of 322 MHz. In this case, since the retransmission output is limited based on these TV broadcast signals, the transmission distance is shortened.

[4] Description of the terrestrial digital TV broadcast wireless retransmission system of the present invention

  FIG. 2 shows an outline of a wireless redistribution system for terrestrial digital TV broadcasting.

  A terrestrial digital TV broadcast signal is received by the outdoor antenna 1 provided on the rooftop. The terrestrial digital TV broadcast signal received by the outdoor antenna 1 is guided to the TV terminal 3 provided on the wall surface of the room by the antenna cable 2.

  A transmitter 4 for redistribution is connected to the TV terminal 3. The transmitter 4 transmits all terrestrial digital TV broadcast signals obtained from the TV terminal 3 to all broadcast reception channels (terrestrial digital TVs) so that the terrestrial digital TV broadcast signals are multiplexed on empty channels in the VHF band (in this example, VHF_SHB band). (Broadcast receiving channel) is collectively converted in frequency, and then retransmitted wirelessly from the transmitting antenna 45 with a weak radio wave below the permissible value (500 μV / m) of the weak radio wave standard.

  A redistribution receiver 5 is connected to a TV receiver 6 for terrestrial digital TV broadcasting. In addition to the original UHF band 13ch to 62ch (470 MHz to 770 MHz), the TV receiver 6 for terrestrial digital TV broadcasting includes a VHF_Low / High band (VHF1ch to VHF12ch), a VHF_MID band (C13ch to C22ch), and a VHF_SHB band ( (C23ch to C63ch) can also be received (selection viewing is possible).

  The receiver 5 receives the redistributed signal transmitted from the transmitter 4 by the receiving antenna 51, amplifies the received signal to a predetermined level that can be received by the TV tuner in the TV receiver 6, and then receives the TV receiver. Send to 6.

  The TV receiver 6 views a terrestrial digital TV broadcast by designating a VHF_SHB channel.

  FIG. 3 shows the configuration of the transmitter 4.

  The transmitter 4 includes a UHF receiver 41, a frequency converter 42, a changeover switch 43, a VHF transmitter 44, a transmission antenna 45, a 322 MHz super signal detector 46, and a controller 47.

  The terrestrial digital TV broadcast signal received by the outdoor antenna 1 is amplified by the UHF receiver 41 and then sent to the frequency converter 42. In the frequency conversion unit 42, all the received terrestrial digital TV broadcast signals (reception signals) and the local signals from the frequency synthesizer unit 101 are mixed by the mixer 102. The frequency fb of the local signal output from the frequency synthesizer unit 101 is controlled by the control unit 47. From the mixer 102, an addition signal and a subtraction signal of each received signal and the local signal are output. For example, assuming that the frequency of the received signal is fa and the frequency of the local signal is fb, an addition signal having a frequency of fa + fb and a subtraction signal having a frequency of fa−fb are output from the mixer 102. The output of the mixer 102 is sent to the filter 103, and only the subtraction signal is extracted. As this filter, as will be described later, when the initial set value fb1 of the local frequency fb is 212 MHz, for example, an LPF that passes only a signal of 600 MHz or less is used.

  As will be described later, the frequency fb of the local signal is such that the frequency (fa−fb) of the subtraction signal output from the mixer 46 is an empty channel in the VHF band (in this example, the VHF_SHB band) and is a weak radio wave standard. Is automatically adjusted so that the frequency becomes a frequency of 322 MHz or less.

  For example, when the frequency fb of the local signal is adjusted to 224 MHz, the VHF transmission channel, the center frequency, and the broadcast station after frequency conversion are as shown in Table 9 in the Kinki wide area.

  The terrestrial digital TV broadcast signal frequency-converted to the VHF_SHB band by the frequency conversion unit 42 is sent to the changeover switch 43. The changeover switch 43 is controlled by the control unit 47. When the transmitter 3 is powered on, the changeover switch 43 is switched to the a side. Further, the local frequency fb is controlled by the control unit 47 so as to be the initial set value fb1. When the transmitter 3 is powered on, the terrestrial digital TV broadcast signal frequency-converted to the VHF_SHB band by the frequency converter 42 is sent to the 322 MHz super signal detector 46 via the changeover switch 43.

  As shown in FIG. 4, the 322 MHz super signal detector 46 includes a 322 MHz super signal detector 201 that detects a level V2 of a signal exceeding 322 MHz of the input signal, a reference voltage generator 202 that generates a reference voltage V1, and a comparator. 203. The comparator 203 compares the voltage V2 (the level of the signal exceeding 322 MHz) output from the 322 MHz super-signal detector 201 with the reference voltage V1, and if V2> V1, the H level signal Vout is expressed as V2 ≦ V2. If V1, an L level signal Vout is output.

  The controller 47 captures the output signal of the 322 MHz super signal detector 46 from the time when a certain time has elapsed after the transmitter 3 is turned on. If the output signal Vout of the 322 MHz super signal detection unit 46 is L level, the control unit 47 switches the changeover switch to the b side.

  If the output signal Vout of the 322 MHz super signal detection unit 46 is at the H level, the control unit 47 performs adjustment processing of the local frequency fb. In the adjustment process of the local frequency fb, the local frequency fb is switched from the initial set value fb1 to fb2, fb3,... Every predetermined time so as to gradually increase. In this example, the local frequency fb is changed every 6 MHz of the TV channel.

  When the output signal Vout of the 322 MHz super signal detector 46 becomes L level, the local frequency is fixed to the local frequency at that time, and the changeover switch is switched to the b side. Thereby, the adjustment process of the local frequency fb is completed.

  For example, if the initial set value fb1 of the local frequency fb is 212 MHz, the frequency after frequency conversion for the UHF 24 channel (539 + 1/7 MHz, NHK synthesis) exceeds 322 MHz in the Kinki wide area. Therefore, the local frequency fb is changed from the initial set value fb1 to fb2 = 218 MHz. When the local frequency fb is changed to 218 MHz, the frequency after the frequency conversion for the UHF 24 channel (539 + 1/7 MHz, NHK synthesis) becomes 322 MHz or less, so the output signal Vout of the 322 MHz super-signal detection unit 46 becomes L level. . Therefore, the switch 43 is switched to the b side.

  When the switch 43 is switched to the b side, the terrestrial digital TV broadcast signal frequency-converted to the VHF_SHB band by the frequency converter 42 is sent to the VHF transmitter 44 via the switch 43. The TV broadcast signal sent to the VHF transmission unit 44 is amplified by the VHF transmission unit 44 and then wirelessly transmitted from the transmission antenna 45. The VHF transmission unit 44 performs AGC so that the signal level transmitted wirelessly does not exceed the allowable value according to the weak radio wave standard.

  FIG. 5 shows the configuration of the receiver 5.

  The receiver 5 includes a receiving antenna 51 and a VHF receiving unit 52.

  The terrestrial digital TV broadcast signal after frequency conversion wirelessly transmitted from the transmitter 4 is received by the receiving antenna 51. The frequency-converted terrestrial digital TV broadcast signal received by the receiving antenna 51 is amplified by the VHF receiver 52, and then the VHF reception-compatible terrestrial digital broadcast TV in the TV receiver 6 for terrestrial digital TV broadcast. Sent to the tuner.

  The user can view the digital terrestrial broadcast by designating the VHF_SHB channel on the TV receiver 6. In the example shown in Table 9, by specifying the channel “C27”, the TV receiver 6 performs a channel selection operation for selecting the channel “C27”, and the terrestrial digital TV broadcast of the UHF 13 channel is broadcast. Will be.

  In the above embodiment, the frequency conversion unit 42 converts the frequency of the terrestrial digital TV broadcast signal into the frequency of the empty channel in the VHF_SHB band. However, the frequency of the terrestrial digital TV broadcast signal is converted to VHF_Low / High. The frequency may be converted to a frequency of an empty channel in the band or the VHF_MID band.

  In the above embodiment, since the frequency conversion is performed by the transmitter 4, it is possible to prevent the occurrence of the same channel interference of the terrestrial digital TV broadcast signal. Further, since the transmitter 4 converts the frequency of the terrestrial digital TV broadcast signal into the frequency of the VHF band that allows the TV receiver 6 to perform channel selection operation, the receiver 5 changes the frequency of the received signal to the original frequency. Since there is no need to return, there is an advantage that the circuit configuration of the receiver is simple and inexpensive. Furthermore, since the local frequency can be automatically adjusted so that the frequency after frequency conversion is 322 MHz or less, which is loosely limited by the weak radio wave standard, the signal level output from the VHF transmitter 44 is set to a high level. Can do.

  FIG. 6 shows a modification of the transmitter 4.

  In FIG. 6, the same components as those in FIG.

  In this transmitter 4A, the output signal Vout of the 322 MHz super signal detector 46 is input to the controller 47A and also to the 322 MHz super signal notifier 48. The controller 47A controls the changeover switch 43 based on the output signal Vout of the 322 MHz super signal detector 46 as in the first embodiment, but does not automatically change the local frequency fb. That is, when the output signal Vout of the 322 MHz super signal detector 46 is at the H level, the control unit 47A maintains the changeover switch 43 on the a side, and the output signal Vout of the 322 MHz super signal detector 46 is at the L level. If there is, the selector switch 43 is switched to the b side.

  When the output signal Vout of the 322 MHz super signal detector 46 is at the H level, the super 322 MHz super signal notifier 48 informs the user that the transmission channel should be switched by light emitting diode display, buzzer, or the like.

  When the user is notified that the transmission channel should be switched by the 322 MHz super signal notification unit 48, the transmission channel switching instruction unit 49 inputs a transmission channel switching instruction to the control unit 47A. When the transmission channel switching instruction is input from the transmission channel switching instruction unit 49, the control unit 47A changes the local frequency. That is, the local frequency is changed to a frequency 6 MHz higher than the current local frequency.

It is a graph which shows the electric field strength (allowable value) with respect to the frequency band defined by the weak radio wave standard. It is a schematic diagram which shows the outline | summary of the radio | wireless redistribution system of terrestrial digital TV broadcasting. It is a block diagram which shows the structure of a transmitter. It is a block diagram which shows the structure of the 322 MHz super signal detection part 46 of FIG. It is a block diagram which shows the structure of a receiver. It is a block diagram which shows the other example of a transmitter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outdoor antenna 4, 4A Transmitter 5 Receiver 6 TV receiver 41 UHF receiving part 42 Frequency conversion part 43 Changeover switch 44 VHF transmission part 45 Transmission antenna 46 322MHz super signal detection part 47, 47A Control part 48 322MHz super signal alerting part 49 Transmission channel switching instruction section 51 Receiving antenna 52 VHF receiving section

Claims (2)

A terrestrial digital TV broadcast wireless redistribution system applied to a TV receiver capable of receiving a VHF band signal in addition to a UHF band signal which is a frequency band of a terrestrial digital TV broadcast signal,
A transmitter that receives a terrestrial digital TV broadcast signal received by an outdoor antenna, converts the input terrestrial digital TV broadcast signal to a frequency of a vacant channel in the VHF band, and then amplifies and wirelessly transmits the signal. And a receiver for receiving and amplifying a signal transmitted from the transmitter and supplying the signal to the TV receiver,
The transmitter is
A frequency synthesizer for generating a local signal, and a mixer that mixes the input terrestrial digital TV broadcast signal and the local signal, and the input terrestrial digital TV broadcast signal has a VHF band of 322 MHz or less. Frequency conversion means that converts the frequency to the frequency of the empty channel at once,
Signal detection means for detecting a signal exceeding 322 MHz from the output of the frequency conversion means;
When a signal exceeding 322 MHz is detected by the signal detection means, the frequency of the local signal output from the frequency synthesizer is automatically changed, and a signal exceeding 322 MHz is not detected by the signal detection means. Local frequency control means for automatically adjusting the local frequency to such a local frequency, and when the signal detection means does not detect a signal exceeding 322 MHz, the output of the frequency conversion means is amplified and transmitted. Transmission means,
A terrestrial digital TV broadcast wireless redistribution system comprising: A terrestrial digital TV broadcast wireless redistribution system applied to a TV receiver capable of receiving a VHF band signal in addition to a UHF band signal which is a frequency band of a terrestrial digital TV broadcast signal,
A transmitter that receives a terrestrial digital TV broadcast signal received by an outdoor antenna, converts the input terrestrial digital TV broadcast signal to a frequency of a vacant channel in the VHF band, and then amplifies and wirelessly transmits the signal. And a receiver for receiving and amplifying a signal transmitted from the transmitter and supplying the signal to the TV receiver,
The transmitter is
A frequency synthesizer for generating a local signal, and a mixer that mixes the input terrestrial digital TV broadcast signal and the local signal, and the input terrestrial digital TV broadcast signal has a VHF band of 322 MHz or less. Frequency conversion means that converts the frequency to the frequency of the empty channel at once,
Signal detection means for detecting a signal exceeding 322 MHz from the output of the frequency conversion means;
In the case where a signal exceeding 322 MHz is detected by the signal detection means, notification means for informing the user to that effect,
Input means for allowing the user to input a local signal change command;
If a signal exceeding 322 MHz is not detected by the local frequency control means for changing the frequency of the local signal output from the frequency synthesizer and the signal detection means when a local signal change command is input by the input means Transmitting means for amplifying and transmitting the output of the frequency converting means;
A terrestrial digital TV broadcast wireless redistribution system comprising:

Images