Frequency conversion transmission system

Abstract

To inexpensively provide a frequency conversion transmission system capable of transmitting broadcast channels of BS / CS left-handed circular IF signals even when an existing transmittable frequency band is within 2150 MHz or 2602 MHz.SOLUTION: A frequency converter 10 performs down-conversion of a frequency band for UHF terrestrial digital broadcasting signals to a lower frequency band, performs down-conversion of a frequency band for BS left-handed or CS left-handed circular IF reception signals to a vacant frequency band caused by the down-conversion of the frequency band for UHF terrestrial digital broadcasting signals, and then, performs transmission. A terminal 22 inputs BS left-handed or CS left-handed circular IF reception signals obtained by returning transmitted IF reception signals to the original frequency band and UHF terrestrial digital broadcasting signals obtained by frequency conversion, to a TV 23. The TV 23 is made to be capable of receiving the UHF terrestrial digital broadcasting signals obtained by the frequency conversion using a pass-through function.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a frequency conversion transmission system that enables advanced wideband satellite digital broadcasting to be transmitted using existing receiving facilities. [Background technology]

[0002] The history of satellite broadcasting in Japan began with the start of BS analog broadcasting, followed by BS digital broadcasting and 110°CS broadcasting. The frequency bands transmitting the corresponding BS·CS intermediate frequency signals (BS·CS-IF signals) were also successively updated, with the maximum transmission frequency expanded from 1335MHz to 1550MHz to 2150MHz to 2602MHz. Furthermore, regular broadcasting of advanced wideband digital satellite broadcasting (ISDB-S3, 4K8K broadcasting, BS / CS left-hand circular polarization broadcasting) began on December 1, 2018. Advanced wideband digital satellite broadcasting further adds BS / CS left-hand circular polarization IF signals in the frequency band of 2224MHz to 3224MHz. For this reason, in order to transmit BS / CS left-hand circular polarization IF signals of advanced wideband digital satellite broadcasting in in-building TV signal receiving equipment such as shared receiving equipment, all receiving equipment such as coaxial cables, amplifiers, splitters / distributors, receiver terminals, and serial units must be modified to equipment capable of transmitting the frequency band from 2224MHz to 3224MHz.

[0003] However, the maximum transmission frequencies of existing receiving equipment differ depending on when it was constructed, and upgrading all of the receiving equipment to equipment with a maximum transmission frequency of 3,224 MHz in order to receive advanced wideband satellite digital broadcasting would require significant renovation costs, and depending on the equipment, the change may be impossible or difficult. Therefore, a frequency conversion transmission system has been proposed that can transmit broadcast channels (frequency bands) in BS / CS left-hand circular polarization IF signals, even if the existing frequency bands that can be transmitted are up to 2150 MHz or 2602 MHz (see Patent Document 1).

[0004] FIG. 11 is a functional block diagram showing the configuration of a frequency conversion transmission system 100 capable of transmitting broadcast channels of BS / CS left-hand circular polarization IF signals that have been proposed in the past, and FIGS. 12(a), 12(b), and 12(c) show the transmission frequency arrangement for the frequency conversion transmission system 100 shown in FIG. 11. As shown in these figures, the frequency conversion transmission system 100 includes a BS / CS antenna 111 and a UHF antenna 112. The received signals output from the BS / CS antenna 111 are a BS right-handed IF signal and a 110° CS right-handed IF signal, and a BS left-handed IF signal and a 110° CS left-handed IF signal, and their frequency bands are shown in Fig. 12(a). The received signals output from the UHF antenna 112 are UHF terrestrial digital signals, and their frequency bands are shown in Fig. 12(a). The received signals output from the BS / CS antenna 111 and the UHF antenna 112 are input to an input terminal (IN) a of a frequency conversion device 110. In the frequency conversion device 110, the received signal from the BS / CS antenna 111 is input to a splitter (DIM) a, and split into a BS right-handed IF signal and a 110° CS right-handed IF signal, and a BS left-handed IF signal and a 110° CS left-handed IF signal. The split BS right-handed IF signal and 110° CS right-handed IF signal are adjusted to a predetermined level by an amplifier (AMP) a and an attenuator (ATT) a. The split BS left-handed IF signal and 110° CS left-handed IF signal are amplified to a predetermined level by an AMP b and distributed by a distributor (DIV) a.

[0005] The BS left-handed IF signal and the 110° CS left-handed IF signal distributed by the distributor (DIV) a are input to band pass filters (BPF) a1 to BPFm1, respectively, and the frequency band of the specified BS left-handed channel or CS left-handed channel is extracted for each channel. The extracted reception signal of the specified BS channel or CS channel is frequency converted by converters (CONV) a1 to CONVm1, respectively. CONVa1 to CONVm1 down-convert the frequency band of the BS left-handed channel or CS left-handed channel to the CATV band, which is a frequency band that can be transmitted by the shared receiving equipment line. For example, as shown in Figure 12 (a) and (b), three BS left-handed channels and five CS left-handed channels in the frequency band of 2224.41 MHz to 3223.25 MHz are down-converted to the CATV band for each channel. In this case, since the frequency band of 470 MHz to 770 MHz in the CATV band is used for transmitting UHF terrestrial digital signals, the frequency band that can be used for down-conversion is set to the frequency band of 90 MHz to 470 MHz.

[0006] The received signals of each of the BS left-handed channel and CS left-handed channel, which have been down-converted by CONVa1 to CONVm1, have unnecessary wave components removed by BPFa2 to BPFm2, and the frequency band for each channel is extracted.The levels are then adjusted to predetermined levels by ATTa1 to ATTm1, and the received signals of all channels are mixed in mixer (MIX) a. Also, the UHF terrestrial digital signal output from the UHF antenna 112 is input to INb of the frequency converter 110 and adjusted to a predetermined level by AMPc and ATTb. The down-converted BS left-handed channel and CS left-handed channel received signals and the UHF terrestrial digital signal from ATTb are mixed in MIXc, and the received signal mixed in MIXc and the BS right-handed IF signal and 110° CS right-handed IF signal from ATTa are mixed in MIXb and output from the frequency converter 110 via the output terminal OUTa. The transmission frequency arrangement of the received signal output from the output terminal OUTa is as shown in Figure 12 (b). This received signal is transmitted to the shared receiving equipment line, amplified by booster (AMP) d, and then distributed to multiple signals by DIVb, and one distributed received signal is distributed in sequence by DIVa1 and DIVb1 connected in cascade, and one of the distributed outputs of DIVb1 is pulled into the house of the apartment house 120.

[0007] A DIVc1 is provided in each house of the apartment building 120, and a signal distributed by the DIVc1 can be supplied to each room. A wall terminal Ta, a terminal device 122, and a television (TV) 123 are provided in each room, and a received signal brought into the house is distributed by the DIVc1, and one of the distributed signals is supplied to the wall terminal Ta. The wall terminal Ta and INc of the terminal device 122 are connected by a cable, and a received signal having the transmission frequency arrangement shown in Fig. 12(b) is input to INc. In the terminal 122, the received signal having the transmission frequency arrangement shown in Fig. 12(b) input from INc is input to DIMb and demultiplexed into a BS right-handed IF signal and a 110° CS right-handed IF signal, a BS left-handed IF signal and a 110° CS left-handed IF signal, and a UHF digital terrestrial signal. The demultiplexed BS right-handed IF signal and 110° CS right-handed IF signal are amplified to a predetermined level by AMPf. The demultiplexed BS left-handed IF signal and 110° CS left-handed IF signal, and a UHF digital terrestrial signal are input to DIMc and demultiplexed into a BS left-handed IF signal and a 110° CS left-handed IF signal, and a UHF digital terrestrial signal. The demultiplexed BS left-handed IF signal and 110° CS left-handed IF signal are amplified to a predetermined level by AMPg, and are distributed by DIVc.

[0008] The BS left-handed IF signal and the 110° CS left-handed IF signal distributed by DIVc are input to BPFa3 to BPFm3, respectively, and the down-converted frequency bands of the left-handed and CS left-handed channels are extracted for each channel. The extracted BS and CS channel reception signals are frequency-converted for each channel by CONVa2 to CONVm2, respectively. CONVa2 to CONVm2 up-convert the BS left-handed and CS left-handed channels to return to their original frequency bands for each channel. For example, as shown in Figures 12(b) and 12(c), the frequency bands of each of the three BS left-handed channels and five CS left-handed channels transmitted in the CATV band up to 470 MHz are up-converted to return to the original frequency bands of 2224.41 MHz to 3223.25 MHz.

[0009] The reception signals of the BS left-handed circular polarization channel and the CS left-handed circular polarization channel up-converted by CONVa2 to CONVm2 are subjected to removal of unnecessary wave components by BPFa4 to BPFm4 to extract the frequency band for each channel, and the reception signals of all channels are mixed by MIXd. The reception signals of the BS left-handed circular polarization channel and the CS left-handed circular polarization channel up-converted and mixed by MIXd, and the BS right-handed IF signal and the 110° CS right-handed IF signal from AMPf are mixed by MIXe and output from OUTb of the terminal device 122. The UHF terrestrial digital signal split by DIMc is amplified to a predetermined level by AMPh and output from OUTc of the terminal device 122. By connecting the OUTb and OUTc of the terminal device 122 to the input terminal of the TV 123 with a cable, the TV 123 can receive the UHF terrestrial digital signal, the BS right-handed IF signal and the 110° CS right-handed IF signal, the BS left-handed IF signal and the 110° CS left-handed IF signal. In other words, TV123 allows you to watch terrestrial digital broadcasting channels, BS right-hand and BS left-hand BS broadcasting channels, and CS right-hand and 110°CS left-hand CS broadcasting channels. In this way, the frequency conversion transmission system 100 is capable of transmitting broadcast channels (frequency bands) in BS / CS left-handed circular polarization IF signals, even if the existing transmittable frequency band is up to 2150 MHz or 2602 MHz. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent Publication No. 2021-40291 Summary of the Invention [Problem to be solved by the invention]

[0011] In the conventional frequency conversion transmission system, even if the existing frequency band that can be transmitted is up to 2150MHz or 2602MHz, it is possible to transmit the broadcast channel (frequency band) of the BS / CS left-handed IF signal, but the terminal installed in front of the TV upconverts each channel, so the configuration of the upconverting converter becomes complicated. Usually, the BPF extracts the frequency band for each channel, so BPFs with steep cutoff characteristics, such as SAW (Surface Acoustic Wave) filters, are required for the number of channels to be upconverted, which causes the terminal to become expensive. As another method, the input signal may be converted into a digital signal collectively, and then upconverted using an LSI (Large Scale Integration) that performs digital processing such as frequency conversion for each channel. However, the LSI must be equipped with not only the frequency conversion function but also functions such as steep digital filters and AD / DA converters, which makes it an expensive component, and therefore the price of the terminal is also high. Furthermore, in the previously proposed frequency conversion transmission systems, only one frequency conversion device is required per apartment building, so the cost per household is not that high. However, a terminal unit is required for each household that wants to watch BS / CS left-hand rotation IF signal broadcast channels, which creates the problem of a large cost burden.

[0012] Therefore, an object of the present invention is to provide an inexpensive frequency conversion transmission system that can transmit broadcast channels in BS / CS left-hand circular polarization IF signals, even if the existing transmittable frequency bands are up to 2150 MHz or 2602 MHz. [Means for solving the problem]

[0013] The frequency conversion transmission system of the present invention is a frequency conversion transmission system in which a transmitter and a receiver are connected by a transmission line, and the transmitter includes a first downconverter that downconverts a first frequency band of a UHF digital terrestrial signal of digital terrestrial broadcasting broadcasted in the UHF band to a second frequency band that can be transmitted by the transmission line and is available lower than the frequency band of the UHF digital terrestrial signal, a second downconverter that downconverts a third frequency band of a first IF received signal, which is a BS left-hand circular polarization or CS left-hand circular polarization intermediate frequency signal, to a fourth frequency band including the first frequency band that has been downconverted by the first downconverter and made available, and a third frequency band that includes the first frequency band that has been downconverted by the first downconverter to a fourth frequency band including the first frequency band that has been downconverted by the first downconverter to a fourth frequency band. The antenna includes a mixing means for transmitting a mixed reception signal obtained by mixing a UHF terrestrial digital signal, a first IF reception signal of the fourth frequency band downconverted by the second downconverter, and a second IF reception signal which is an intermediate frequency signal of BS right-hand rotation and CS right-hand rotation, to the transmission path, and the receiving unit includes an upconverter for converting the first IF reception signal of the fourth frequency band transmitted through the transmission path back to the original first IF reception signal of the third frequency band, and the most important feature of the antenna is that the UHF terrestrial digital signal of the second frequency band transmitted through the transmission path, the first IF reception signal of the third frequency band upconverted by the upconverter, and the second IF reception signal transmitted through the transmission path are output from the receiving unit.

[0014] In the frequency conversion transmission system of the present invention, one transmitting unit is installed in an apartment building, and the mixed receiving signal transmitted from the transmitting unit to the transmission path is drawn into each home in the apartment building, and a terminal device serving as the receiving unit installed in each home receives the mixed receiving signal. Furthermore, in the frequency conversion transmission system of the present invention, the second downconverter has a first local oscillator and a second local oscillator which have different local oscillation frequencies, and by switching to the first local oscillator, the third frequency band of BS left-hand circular polarization is selected and downconverted to the fourth frequency band, and by switching to the second local oscillator, the third frequency band of CS left-hand circular polarization is selected and downconverted to the fourth frequency band. Furthermore, in the frequency conversion transmission system of the present invention, the first downconverter has a plurality of first frequency conversion blocks, the first frequency band of the UHF terrestrial digital signal is divided into a plurality of frequency bands, and the second frequency band is divided into a plurality of frequency bands, and each divided frequency band of the first frequency band is downconverted to each divided frequency band of the second frequency band by the plurality of first frequency conversion blocks, and a guard band is provided between each divided frequency band of the second frequency band. Furthermore, in the frequency conversion transmission system of the present invention, the booster provided in the transmission line has amplification means for amplifying a plurality of split reception signals obtained by splitting the mixed reception signal into signals in different frequency bands. Furthermore, in the frequency conversion transmission system of the present invention, the output from the receiving unit is received by a digital broadcast receiving device, and the digital broadcast receiving device is capable of receiving UHF terrestrial digital signals in the second frequency band due to a pass-through function. Effect of the Invention

[0015] In the frequency conversion transmission system of the present invention, the transmission section down-converts the frequency band of the UHF terrestrial digital signal of terrestrial digital broadcasting broadcast in the UHF band to an available frequency band that can be transmitted on the transmission line, down-converts the frequency band of the BS left-hand rotation or CS left-hand rotation IF reception signal to a frequency band including the available UHF band, and transmits it together with the down-converted UHF terrestrial digital signal. In the reception section, the down-converted IF reception signal is up-converted back to the frequency band of the IF reception signal in the original frequency band, and output together with the transmitted UHF terrestrial digital signal. In this case, the UHF terrestrial digital signal is down-converted and transmitted, but the digital broadcast receiving device that receives the output of the reception section is capable of receiving the down-converted UHF terrestrial digital signal by the pass-through function. As a result, in the frequency conversion transmission system of the present invention, since the frequency band of the UHF terrestrial digital signal and the frequency band of the IF reception signal of BS left-hand circular polarization or CS left-hand circular polarization are down-converted, it is possible to down-convert multiple channels in the frequency band at once. Also, since the frequency band of the IF reception signal of BS left-hand circular polarization or CS left-hand circular polarization is up-converted, it is possible to up-convert multiple channels in the frequency band at once. As a result, the configuration of the frequency conversion transmission system of the present invention is simplified and can be provided at low cost. Note that, in the frequency conversion transmission system of the present invention, even if the frequency band that can be transmitted by the existing transmission line is up to 2150 MHz or 2602 MHz, it is possible to transmit BS left-hand circular polarization or CS left-hand circular polarization broadcasting channels. [Brief description of the drawings]

[0016] [Figure 1] 1 is a functional block diagram showing a configuration of a frequency conversion transmission system according to an embodiment of the present invention; [Diagram 2] 13 is a diagram showing a configuration of a modified example of a U / V conversion unit in the frequency conversion transmission system according to an embodiment of the present invention. [Diagram 3] 11A and 11B are diagrams showing configurations of a modified example of CONV1 (CONV3) and another modified example in the frequency conversion transmission system according to the embodiment of the present invention. [Figure 4] FIG. 13 is a diagram showing a configuration of a modified example of BPF1 in the frequency conversion transmission system according to the embodiment of the present invention. [Diagram 5] FIG. 2 is a diagram showing a transmission frequency arrangement in a frequency conversion transmission system according to an embodiment of the present invention. [Figure 6] FIG. 11 is a diagram showing another transmission frequency arrangement in the frequency conversion transmission system according to the embodiment of the present invention. [Figure 7] FIG. 11 is a diagram showing a configuration of a modified example of AMP4 (AMP5) in the frequency conversion transmission system according to the embodiment of the present invention. [Figure 8] FIG. 11 is a diagram showing the configuration of another modified example of AMP4 (AMP5) in the frequency conversion transmission system according to the embodiment of the present invention. [Figure 9] 2 is a diagram showing a transmission frequency arrangement in the UHF band in a frequency conversion transmission system according to an embodiment of the present invention. FIG. [Figure 10] 1A and 1B are functional block diagrams showing the configuration of a frequency conversion transmission system according to an application example of the present invention, and diagrams showing an outline of a frequency arrangement. [Figure 11] FIG. 1 is a functional block diagram showing a configuration of a conventional frequency conversion transmission system. [Figure 12] FIG. 1 is a diagram showing a transmission frequency arrangement of a conventional frequency conversion transmission system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] In the frequency conversion transmission system of the present invention, the transmitting section down-converts the frequency band of the UHF terrestrial digital signal of terrestrial digital broadcasting broadcasted in the UHF band to an available frequency band that can be transmitted on the transmission line, and transmits the down-converted signal. The upper limit frequency of the frequency band that can be transmitted on the transmission line is set to 2150 MHz or 2602 MHz. Then, the frequency band of the BS left-hand circular polarization or CS left-hand circular polarization IF reception signal is down-converted to the frequency band including the down-converted and available UHF band, and transmitted. The receiving section up-converts the frequency band of the IF reception signal transmitted on the transmission line to return it to the original frequency band. The returned IF reception signal and the transmitted UHF terrestrial digital signal are input to a digital broadcast receiving device. Although the UHF terrestrial digital signal has been down-converted, the pass-through (registered trademark) function of the digital broadcast receiving device makes it possible to receive the down-converted UHF terrestrial digital signal. As a result, the frequency conversion transmission system of the present invention can transmit BS left-handed or CS left-handed broadcasting channels even if the existing frequency band that can be transmitted is up to 2150 MHz or 2602 MHz. Furthermore, since multiple channels in a frequency band can be down-converted (up-converted) collectively, the configuration of the frequency conversion transmission system of the present invention is simplified, and the object of the present invention is achieved, which is to provide the frequency conversion transmission system of the present invention at low cost. Pass-through (registered trademark) is a method of transmitting terrestrial digital broadcasting or satellite broadcasting without changing the modulation method, and includes a same-frequency pass-through method that transmits broadcasting in the same frequency band when transmitting, and a frequency conversion pass-through method that changes the frequency band when transmitting. Naturally, digital broadcasting receivers can receive broadcasting transmitted in the same frequency band, but many digital broadcasting receivers support the frequency conversion pass-through method and can receive broadcasting that has been changed to a specified frequency band and transmitted. The present invention is premised on the fact that the digital broadcasting receiver supports the frequency conversion pass-through method. EXAMPLES

[0018] The frequency conversion transmission system 1 of the embodiment of the present invention can transmit broadcast channels in BS / CS left-hand circular polarization IF signals even if the upper limit frequency of the frequency band that can be transmitted on the transmission path is up to 2150 MHz or 2602 MHz. Figure 1 shows a functional block diagram showing the configuration of the frequency conversion transmission system 1 of the embodiment of the present invention, and Figures 5(a)(b)(c) show the transmission frequency arrangement for the frequency conversion transmission system 1 shown in Figure 1. As shown in these figures, the frequency conversion transmission system 1 of the embodiment of the present invention is composed of a BS / CS antenna 11 and a UHF antenna 12, a frequency conversion device 10 as a transmitter, a common receiving facility line 30 as a transmission path, and a terminal device 22 as a receiver. The upper limit of the frequency band that can be transmitted in the common receiving facility line 30 is 2150 MHz or 2602 MHz, and the terminal device 22 is installed in each house of the apartment building 20. The received signals output from the BS / CS antenna 11 are a BS right-handed IF signal and a 110° CS right-handed IF signal, and a BS left-handed IF signal and a 110° CS left-handed IF signal, and the frequency bands are shown in Figure 5(a) as BS right-handed, 110° CS right-handed, BS left-handed, and 110° CS left-handed. Figure 5(a) shows the frequency arrangement of the received signals input to the frequency conversion device 10. In the frequency arrangement shown in FIG. 5(a), the frequency band of 90MHz to 108MHz is specified as the VHF-Lo band, the frequency band of 108MHz to 170MHz is specified as the MID band, the frequency band of 170MHz to 222MHz is specified as the VHF-Hi band, and the frequency band of 222MHz to 470MHz is specified as the super high band, all of which are frequency bands that can be transmitted through the common receiving equipment line 30. The received signal output from the UHF antenna 12 is a UHF terrestrial digital signal, and its frequency band is shown as UHF terrestrial digital in FIG. 5(a). The frequency band (UHF band) of the UHF terrestrial digital signal is a frequency band of 470MHz to 770MHz, which is a frequency band that can be transmitted through the common receiving equipment line 30. The received signal output from the BS / CS antenna 11 is input to the input terminal (IN) 1 of the frequency conversion device 10, and the received signal output from the UHF antenna 12 is input to the input terminal (IN) 2 of the frequency conversion device 10.

[0019] In the frequency converter 10, a signal received by a BS / CS antenna 11 input to IN1 is input to a splitter (DIM) 1 and split into a BS right-handed IF signal and a 110° CS right-handed IF signal, and a BS left-handed IF signal and a 110° CS left-handed IF signal. The split BS right-handed IF signal and the 110° CS right-handed IF signal are level-adjusted to a predetermined level by an amplifier (AMP) 1 and an attenuator (ATT) 1, and input to a mixer (MIX) 1. The demultiplexed BS left-handed IF signal in the frequency band of 2224.1 MHz to 2680.87 MHz and 110° CS left-handed IF signal in the frequency band of 2708.75 MHz to 3223.25 MHz are amplified to a predetermined level by AMP2, and unnecessary wave components are removed by band pass filter (BPF) 1. In this case, the pass band of BPF1 is selected to be either the frequency band of 2224.1 MHz to 2680.87 MHz or the frequency band of 2708.75 MHz to 3223.25 MHz. In other words, the selected BS left-handed IF signal or 110° CS left-handed IF signal passes through BPF1.

[0020] The frequency band of the BS left-handed IF signal or the 110° CS left-handed IF signal selected by BPF1 is down-converted by converter (CONV) 1. In this case, the local oscillator (Lo) in CONV1 is set to a local oscillation frequency (Lo frequency) corresponding to the frequency band of the BS left-handed IF signal or the 110° CS left-handed IF signal selected by BPF1, and the Lo frequency is set to 1911 MHz when the BS left-handed IF signal is selected, and the Lo frequency is set to 2454 MHz when the 110° CS left-handed IF signal is selected. As a result, when the BS left-handed IF signal is selected, the frequency band of the BS left-handed IF signal is down-converted to a frequency band of 313.41 MHz to 769.87 MHz, and when the 110° CS left-handed IF signal is selected, the frequency band of the 110° CS left-handed IF signal is down-converted to a frequency band of 254.75 MHz to 769.25 MHz. In this way, CONV1 down-converts multiple channels in the frequency band of the selected IF signal all at once. Also, CONV1 down-converts the BS left-handed IF signal or the 110° CS left-handed IF signal in a frequency band that exceeds the frequency band that can be transmitted by the selected common receiving equipment line 30 to a wideband frequency band of the super high band and UHF band, which are vacant frequency bands that can be transmitted by the common receiving equipment line 30. Figure 5(b) shows the case where a 110° CS left-handed IF signal is selected.

[0021] The BS left-handed IF signal or the 110° CS left-handed IF signal down-converted by CONV1 is level-adjusted by ATT2 to a predetermined level and input to mixer (MIX)2. Also, the UHF terrestrial digital signal output from the UHF antenna 12 input to IN2 is level-adjusted by AMP3 to a predetermined level and input to the U / V conversion unit 13. In the U / V conversion unit 13, the UHF terrestrial digital signal has unnecessary wave components removed by BPF2, which has a passband of 470MHz to 770MHz, and is input to CONV2. In CONV2, the frequency band of the UHF terrestrial digital signal is down-converted to the VHF band of VHF-Lo band or VHF-Hi band. Currently, VHF broadcasting is not being performed, so the VHF band is vacant. In CONV2, multiple channels in the frequency band of the UHF terrestrial digital signal are down-converted collectively. The UHF terrestrial digital signal down-converted to the VHF band by CONV2 is level-adjusted by ATT3 to a predetermined level and input to MIX2. In MIX2, the down-converted BS left-handed IF signal or 110° CS left-handed IF signal is mixed with the down-converted UHF digital terrestrial signal and input to MIX 1. In MIX1, the BS right-handed IF signal and 110° CS right-handed IF signal from ATT1 are mixed with the mixed received signal from MIX2 and output from output terminal (OUT) 1.

[0022] The frequency arrangement of the received signal output from OUT1 of the frequency conversion device 10, which is the transmitting section, is as shown in Fig. 5(b). This received signal is transmitted through the common receiving equipment line 30. In this case, the frequency band of the BS left-handed IF signal or the 110° CS left-handed IF signal is considered to be a wide band, but since it can be down-converted using a frequency band including the UHF band, it becomes possible to transmit the BS left-handed IF signal or the 110° CS left-handed IF signal. The received signal transmitted through the common receiving equipment line 30 is amplified by a booster (AMP) 4 and then distributed into multiple signals by a distributor (DIV) 2, and one of the distributed received signals is amplified by a booster (AMP) 5 and then distributed in sequence by the cascaded DIV3 and DIV4, and one of the distributed outputs of DIV4 is led into the apartment building 20. DIV5 is provided in each house of the apartment building 20, and signals distributed by DIV5 can be supplied to each room. A wall terminal 21, a terminal device 22, and a television (TV) 23 are provided in each room, and a received signal brought into the house is further distributed by DIV5, and one of the distributed signals is supplied to the wall terminal 21. The wall terminal 21 and IN3 of the terminal device 22 are then connected by a cable, and a received signal with the transmission frequency arrangement shown in Fig. 5(b) is input to IN3.

[0023] In the terminal 22, the received signal having the transmission frequency arrangement shown in Fig. 5(b) input from IN3 is input to DIM6 and demultiplexed into a BS right-handed IF signal and a 110° CS right-handed IF signal, a BS left-handed IF signal or a 110° CS left-handed IF signal, and a UHF digital terrestrial signal. The demultiplexed BS right-handed IF signal and 110° CS right-handed IF signal are amplified to a predetermined level by AMP6 and input to MIX3. The demultiplexed BS left-handed IF signal or 110° CS left-handed IF signal, and a UHF digital terrestrial signal are amplified to a predetermined level by AMP7 and input to DIM7. In DIM7, the signal is demultiplexed into a BS left-handed IF signal or a 110° CS left-handed IF signal, and a UHF digital terrestrial signal. The demultiplexed BS left-handed IF signal or 110° CS left-handed IF signal is input to CONV3 and up-converted collectively so that the frequency band of the BS left-handed IF signal or 110° CS left-handed IF signal is the original frequency band. In this case, when the 110° CS left-handed IF signal is selected and down-converted to the frequency band of 254.75 MHz to 769.25 MHz and transmitted as shown in FIG. 5(b), the frequency band of the 110° CS left-handed IF signal is up-converted to the frequency band of 2708.75 MHz to 3223.25 MHz. In CONV3, a plurality of channels in the frequency band of the BS left-handed IF signal or the 110° CS left-handed IF signal are up-converted collectively. The Lo frequency in CONV3 is set to 2454 MHz because it is the same frequency as the Lo frequency in CONV1 of the frequency conversion device 10.

[0024] The BS left-handed IF signal or 110° CS left-handed IF signal upconverted by CONV3 is input to MIX3 and mixed with the BS right-handed IF signal and 110° CS right-handed IF signal. The BS right-handed IF signal and 110° CS right-handed IF signal, as well as the BS left-handed IF signal or 110° CS left-handed IF signal mixed by MIX3 are output from OUT2 of the terminal device 22. The UHF terrestrial digital signal split by DIM7 is output from OUT3 of the terminal device 22. By connecting OUT2 and OUT3 of the terminal device 22, which is a receiving unit, to an input terminal of a television (TV) 23 with a cable, the TV 23 can receive the BS right-handed IF signal and 110° CS right-handed IF signal, the BS left-handed IF signal, or the 110° CS left-handed IF signal. The transmitted UHF terrestrial digital signal is downconverted to a frequency band lower than the original frequency band, but can be received by the pass-through (registered trademark) function of the TV 23. In other words, on TV23, you can watch terrestrial digital broadcasting channels, BS right-hand and BS left-hand BS broadcasting channels, and CS right-hand and 110° CS left-hand CS broadcasting channels.

[0025] <Components> FIG. 2 shows a functional block diagram illustrating a configuration of a modified example of the U / V conversion unit 13 in the frequency conversion device 10. The U / V conversion unit 13' of the modified example shown in Fig. 2 divides the frequency band of the UHF terrestrial digital signal into multiple blocks and down-converts each block to a different frequency band. The down-conversion frequency arrangement is shown in Fig. 9(a) and (b), and an image of the frequency conversion of the down-conversion by the U / V conversion unit 13 and the U / V conversion unit 13' will be described with reference to Fig. 9(a) and (b). Fig. 9(a) shows an image of frequency conversion in the U / V conversion unit 13 shown in Fig. 1, and since the U / V conversion unit 13 performs frequency conversion using one local oscillator (Lo), it can be described as a 1Lo method. In the 1Lo method, as shown in Fig. 9(a), the frequency band of channels (ch) 16ch to 27ch of the UHF terrestrial digital signal is frequency converted by a Lo of 398MHz and down-converted to a frequency band of 90MHz to 162MHz. The down-converted frequency band is a frequency band consisting of the VHF-Lo band and the MID band. In the U / V conversion unit 13' of the modified example, the UHF terrestrial digital signal is divided by the DIV 13a, but the number of divisions is the same as the number of blocks into which the UHF terrestrial digital signal is divided. Each of the division signals divided by the DIV 13a is input to the BPF 2a to BPF 2n. Each of the BPF 2a to BPF 2n has a passband for the frequency band of each divided block, and the UHF terrestrial digital signal of the frequency band of each block is output from each of the BPF 2a to BPF 2n. The UHF terrestrial digital signal of the frequency band of each block is input to the CONV 2a to CONV 2n and frequency-converted. The CONV 2a to CONV 2n down-convert the frequency band of each block to a prescribed frequency band of the VHF band, which is different from each other. The UHF terrestrial digital signal of each block down-converted by the CONV 2a to CONV 2n is input to the BPF 3a to BPF 3n, and unnecessary wave components are removed. The outputs from the BPFs 3a to 3n are level-adjusted by the ATTs 3a to 3n so that the UHF terrestrial digital signals for each block are at a predetermined level, and are then input to the MIX 13b, where the UHF terrestrial digital signals for each of the multiple blocks are mixed.

[0026] Fig. 9(b) shows an image of frequency conversion in the U / V conversion unit 13' of the modified example shown in Fig. 2, and since the U / V conversion unit 13' converts frequencies using multiple local oscillators (Lo), it can be described as a multiple Lo method. In the case shown in Fig. 9(a), the number of blocks is 3 (=n), the first block is made up of a frequency band including UHF channels 16ch to 18ch, the second block is made up of a frequency band including UHF channels 21ch to 24ch, and the third block is made up of a frequency band including UHF channels 23ch to 27ch, and the frequency band of the UHF terrestrial digital signal is divided into three. The UHF terrestrial digital signal of each block is input to CONV2a, CONV2b, and CONV2c, respectively, and frequency converted. The Lo of CONV2a is set to 398MHz, and the frequency band of UHF channels 16ch to 18ch is down-converted to the frequency band of VHF-Lo band (VHF channels 1ch to 3ch) of 90MHz to 108MHz. The Lo of CONV2b (not shown) is set to 348MHz, and the frequency band of UHF channels 21ch to 24ch is down-converted to the frequency band of VHF channels 4ch to 7ch in the VHF-Hi band. Furthermore, the Lo of CONV2c (not shown) is set to 338MHz, and the frequency band of UHF channels 23ch to 27ch is down-converted to the frequency band of VHF channels 8ch to 12ch in the VHF-Hi band of 170MHz to 222MHz. In this case, each block performs frequency conversion by providing a guard band for each frequency arrangement. In addition, since the frequency allocation of VHF channels 7ch and 8ch overlap by 2MHz, 7ch and 8ch are used as guard bands. In this way, by providing a guard band, a BPF with a steep cutoff characteristic is not required, and the frequency arrangement can be realized with inexpensive filter configurations of BPF2a to BPF2n and BPF3a to BPF3n. Note that UHF channels 24 and 23, which are down-converted to VHF channels 7 and 8, overlap by 2 MHz, so are shown as 24' and 23', and although some of the channels overlap, they cannot be received because the amplitude is cut by BPF3a to BPF3n, resulting in a large deviation and poor C / N ratio. As described above, in the case of a multiple Lo system in which the U / V conversion unit 13 is the modified U / V conversion unit 13' shown in Figure 2, the transmission frequency arrangement of the UHF terrestrial digital signal transmitted over the shared receiving equipment line 30 will be as shown in Figure 6(b).

[0027] Next, FIG. 3(a) shows a functional block diagram illustrating a modified example of CONV1 (CONV3) in frequency conversion device 10, and FIG. 3(b) shows a functional block diagram illustrating another modified example. The modified CONV1' shown in FIG. 3(a) has two local oscillators Lo1 and Lo2, and the local oscillation frequency (Lo frequency) from Lo1 and Lo2 is switched by a switch (SW) 1 and supplied to the mixer. When the BS left-handed IF signal is selected, SW1 is switched to the Lo1 side, and the Lo frequency of Lo1, 1911 MHz, is supplied to the mixer, and the frequency band of the BS left-handed IF signal is down-converted to a frequency band of 313.41 MHz to 769.87 MHz. When the 110° CS left-handed IF signal is selected, SW1 is switched to the Lo2 side, and the Lo frequency of Lo2, 2454 MHz, is supplied to the mixer, and the frequency band of the 110° CS left-handed IF signal is down-converted to a frequency band of 254.75 MHz to 769.25 MHz. The frequency conversion image of the modified CONV1' in this case is as shown in FIG. 5(a)(b). In addition, the modified CONV3' has the same circuit configuration as the modified CONV1', and when the BS left-handed IF signal is selected, SW1 is switched to the Lo1 side, and the Lo frequency of Lo1, 1911 MHz, is supplied to the mixer, and the frequency band of the transmitted BS left-handed IF signal is up-converted to the original frequency band of 2224.1 MHz to 2680.87 MHz. In addition, when the 110° CS left-handed IF signal is selected, SW1 is switched to the Lo2 side, and the Lo frequency of Lo2, 2454 MHz, is supplied to the mixer, and the frequency band of the transmitted 110° CS left-handed IF signal is up-converted to the original frequency band of 2708.75 MHz to 3223.25 MHz. In this case, the frequency conversion image of the modified CONV3' is as shown in Figure 5 (b) (c).

[0028] In another modified example CONV1" (CONV3") shown in FIG. 3(b), the local oscillator is composed of a PLL (Phase Locked Loop) having a VCO (Voltage Controlled Oscillator), and the Lo frequency from the VCO supplied to the mixer can be adjusted. This is to accommodate a case where the booster (AMP4, AMP5) inserted in the common receiving equipment line 30 is configured as a U·V booster and performs amplification operation only in the VHF and UHF frequency bands, but cannot perform amplification operation in other frequency bands including the super high band. In other words, in the modified example CONV1" (CONV3"), the Lo frequency is adjusted to set a frequency band including the desired channel that can be transmitted by AMP4 and AMP5 configured as U·V boosters. An image of frequency conversion of a satellite IF signal in another modified example CONV1" is shown in Fig. 6(a)(b). As shown in Fig. 6(a), in another modified example CONV1", the Lo frequency of the VCO can be adjusted between 1754 MHz and 1911 MHz and between 2238 MHz and 2454 MHz. This makes it possible to transmit a frequency band including a desired channel in a selected BS left-handed IF signal or a 110° CS left-handed IF signal over a common receiving equipment line 30 with a U·V booster inserted. For example, Fig. 6(a) shows an example in which a frequency band including five or two channels of a 110° CS left-handed IF signal is down-converted to the UHF band of 470 MHz to 770 MHz and transmitted over a common receiving equipment line 30 with a U·V booster inserted. Furthermore, CONV3" of another modified example has the same circuit configuration as CONV1" of another modified example, and is capable of adjusting the Lo frequency from the VCO in the same frequency range as CONV1" of another modified example. In CONV3" of another modified example, the Lo frequency of the VCO is set to the same Lo frequency as the VCO of CONV1", and the frequency band of the BS left-handed circular polarization IF signal or 110° CS left-handed circular polarization IF signal including the desired channel that has been down-converted to the UHF band of 470 MHz to 770 MHz and transmitted is up-converted to the BS left-handed circular polarization IF signal or 110° CS left-handed circular polarization IF signal in the original frequency band.

[0029] Next, a functional block diagram showing a configuration of a modified example of the BPF1 in the frequency conversion device 10 is shown in Fig. 4. The modified BPF1' shown in Fig. 4 has a BPF1a that passes a BS left-handed IF signal with a passband of 2224.1MHz to 2680.87MHz, and a BPF1b that passes a 110° CS left-handed IF signal with a passband of 2708.75MHz to 3223.25MHz, arranged in parallel, and has changeover switches (SW2, SW3) provided on the input and output sides of the BPF1a and BPF1b. By switching SW2 and SW3 to the BPF1a side, the BS left-handed IF signal passes, and by switching SW2 and SW3 to the BPF1b side, the 110° CS left-handed IF signal passes. In this case, SW2 and SW3 are switched according to the selected BS left-handed or CS left-handed IF received signal. In this way, the modified BPF1' has BPF1a which passes the BS left-handed circular polarization IF signal and BPF1b which passes the 110° CS left-handed circular polarization IF signal, and by switching SW2 and SW3, the selected BS left-handed circular polarization IF signal or 110° CS left-handed circular polarization IF signal is allowed to pass.

[0030] Next, Fig. 7 shows a functional block diagram showing the configuration of a modified example of the booster (AMP4, AMP5) inserted in the common receiving facility line 30. The modified example AMP4' (AMP5') corresponds to a booster when the transmission frequency arrangement of the UHF terrestrial digital signal and the satellite IF signal transmitted through the common receiving facility line 30 is as shown in Fig. 5(b). The AMP4' (AMP5') of the modified example shown in Fig. 7 is a CATV booster for satellites, and has an AMP41 that amplifies the frequency band of satellite IF signals up to 2150MHz or 2602MHz, and an AMP42 that amplifies the CATV band, which is a frequency band of 70MHz to 770MHz that can be transmitted by cable television. Specifically, the received signal input to the input terminal IN of the AMP4' (AMP5') is split into satellite IF band and CATV band received signals by the splitter DIM41, and the satellite IF signal in the satellite IF band is amplified by the AMP41 and adjusted to a predetermined level by the ATT41. The CATV band received signal is amplified by the AMP42 and adjusted to a predetermined level by the ATT42. The satellite IF signal amplified to a predetermined level from the ATT41 and the CATV band received signal amplified to a predetermined level from the ATT42 are mixed by the MIX41 and output from the output terminal OUT as a booster output. As described above, the modified AMP4' (AMP5') operates as a satellite-compatible CATV booster with a transmission frequency arrangement in the common receiving equipment line 30 as shown in Fig. 5(b), and since the AMP42 amplifies the received signal in the CATV band, which is considered to be a wide band, it is designed as a high-output booster that can withstand the power of multiple waves. Also, the transmission frequency arrangement from the output terminal OUT is as shown in Fig. 5(b).

[0031] Next, Fig. 8 shows a functional block diagram showing the configuration of another modified example of the booster (AMP4, AMP5) inserted in the common receiving facility line 30. The other modified example AMP4" (AMP5") corresponds to a booster in which the U / V conversion unit 13 is the U / V conversion unit 13' of the modified example shown in Fig. 2, CONV1 is the CONV1" of the other modified example, and the transmission frequency arrangement of the UHF terrestrial digital signal and the satellite IF signal transmitted over the common receiving facility line 30 is as shown in Fig. 6(b). AMP4″ (AMP5″) of another modified example shown in FIG. 8 is a satellite-compatible UV booster, and includes AMP51 for amplifying the frequency band of satellite IF signals up to 2150 MHz or 2602 MHz, AMP52 for amplifying satellite IF signals down-converted to the UHF band of 470 MHz to 770 MHz, AMP53 for amplifying UHF terrestrial digital signals down-converted to the VHF-Hi band of 170 MHz to 222 MHz, and AMP54 for amplifying UHF terrestrial digital signals down-converted to the VHF-Lo band of 90 MHz to 108 MHz. Specifically, the received signal input to AMP4″ (AMP5″) of another modified example is split into satellite IF bands of BS right-handed IF signals and 110° CS right-handed IF signals by splitter DIM51, and the split satellite IF band received signals are amplified by AMP51 and adjusted to a predetermined level by ATT51. The received signal from which the satellite IF band has been split is input to the DIM52, and the BS left-handed IF signal or the 110° CS left-handed IF signal that has been down-converted to the UHF band and transmitted is split, and the split satellite IF signal that has been down-converted to the UHF band and transmitted is amplified by the AMP52 and adjusted to a predetermined level by the ATT52. The received signal from which the satellite IF band and the satellite IF signal that has been down-converted to the UHF band and transmitted is split is input to the DIM53, and the VHF-Hi band and the VHF-Lo band are split. The split UHF signal that has been down-converted to the VHF-Hi band and transmitted is amplified by the AMP53 and adjusted to a predetermined level by the ATT53, and the split UHF signal that has been down-converted to the VHF-Lo band and transmitted is amplified by the AMP54 and adjusted to a predetermined level by the ATT54. The outputs from the ATT53 and ATT54 are input to the MIX53 and mixed. The mixed output from MIX 53 and the output from ATT 52 are input to MIX 52 and mixed therein. Furthermore, the mixed output from MIX 52 and the output from ATT 51 are input to MIX 51 and mixed therein, and the mixed output is output from the output terminal OUT as a booster output. As described above, AMP4" (AMP5") in another modified example operates as a satellite-compatible U.V. booster, and AMP51 to AMP54 each amplify a received signal of a specific frequency band that is divided into multiple bands, thereby reducing the burden on each of AMP51 to AMP54. Also, the transmission frequency arrangement of the output terminal OUT is as shown in FIG. 6(b).

[0032] <Frequency conversion transmission system according to an application of the present invention> The frequency conversion transmission system 2 of the application example of the present invention is applied to, for example, an area where it is difficult to receive digital terrestrial broadcasting and where digital terrestrial broadcasting is received jointly. Fig. 10(a) shows a functional block diagram showing the configuration of the frequency conversion transmission system 2 of the application example of the present invention, and Fig. 10(b) shows an outline of the frequency arrangement of the received signals output from MIX1 and MIX2 in the frequency conversion transmission system 2. As shown in these figures, the frequency conversion transmission system 2 of the application example of the present invention is composed of a BS / CS antenna 11a, a frequency conversion device 10a, and one or more terminals 22a, 22b, ..., and the frequency conversion transmission system 2 of the application example of the present invention is installed in a house 20a. A CATV line is drawn from a community receiving facility (not shown) to the house 20a, and the frequency band that can be transmitted by the community receiving facility is at least a frequency band of 90 MHz to 222 MHz. In the community receiving facility, a UHF terrestrial digital signal is received by a UHF antenna installed at a point where the terrestrial digital broadcasting station can be seen and the frequency band of the received UHF terrestrial digital signal is down-converted to a frequency band of 90 MHz to 222 MHz and transmitted by the CATV line. This CATV line is drawn into each house in an area where it is difficult to receive the terrestrial digital broadcasting, and the pass-through (registered trademark) function of the digital broadcasting receiving device makes it possible to watch the UHF broadcasting whose frequency band has been down-converted at each house.

[0033] In the frequency conversion transmission system 2 of the application example of the present invention, the received signal output from the BS / CS antenna 11a is input to IN1 of the frequency conversion device 10a. The received signals input to IN1 are BS right-handed IF signal and 110°CS right-handed IF signal, and BS left-handed IF signal and 110°CS left-handed IF signal, and their frequency bands are shown as BS right-handed, 110°CS right-handed, BS left-handed, and 110°CS left-handed in the above-mentioned Figure 5 (a). In addition, the received signal from the CATV line is input to IN2 of the frequency conversion device 10a, and the UHF terrestrial digital signal down-converted to the frequency band of 90MHz to 222MHz is input to IN2.

[0034] The frequency converter 10a functions as the frequency converter 10 described above, and the BS left-handed IF signal or 110° CS left-handed IF signal that has been down-converted and level-adjusted is input to MIX 2. In MIX 2, the down-converted BS left-handed IF signal or 110° CS left-handed IF signal is mixed with the down-converted UHF digital terrestrial signal transmitted through the CATV line, and input to MIX 1. The frequency arrangement of the mixed output from MIX 2 is as shown in the upper part of Fig. 10(b), and the mixed output is the UHF digital terrestrial signal in the frequency band of 90 MHz to 222 MHz transmitted through the CATV line and the BS left-handed IF signal or 110° CS left-handed IF signal down-converted to the frequency band of 254.75 MHz to 770 MHz. The mixed output of MIX2 is input to MIX1, where the BS right-handed IF signal and 110° CS right-handed IF signal from ATT1 are mixed with the mixed received signal from MIX2, and output from OUT1. The frequency arrangement of the mixed output from MIX1, which is the received signal output from OUT1 of the frequency conversion device 10a, is as shown in the lower part of Fig. 10(b), and is a mixed output of the BS left-handed IF signal or 110° CS left-handed IF signal down-converted to the frequency band of 254.75 MHz to 770 MHz, and the BS right-handed IF signal and 110° CS right-handed IF signal in the frequency band of 1032 MHz to 2071 MHz or 1032 MHz to 2681 MHz. Note that the UHF terrestrial digital signal in the frequency band of 90 MHz to 222 MHz is omitted in the lower part of Fig. 10(b).

[0035] The received signal output from OUT1 of the frequency conversion device 10a is distributed to a distributor (DIV) 10 provided in the house 20a, one of the distributed outputs is input to a terminal 22a via a wall terminal 21a, and the other of the distributed outputs is input to a terminal 22b via a wall terminal 21b. Each of the other distributed outputs can also be input to each of the other terminals provided. The terminals 22a and 22b are installed on the first and second floors or in different rooms of the house 20a, and the number of terminals installed varies depending on the number of floors and rooms of the house 20a. In the example illustrated in FIG. 10, two terminals 22a and 22b are installed in the house 20a.

[0036] The terminals 22a and 22b function as the terminal 22 described above, and output a mixed signal of the BS left-handed IF signal or 110° CS left-handed IF signal up-converted to the original frequency band, and the BS right-handed IF signal and 110° CS right-handed IF signal, which are supplied to the TVs 23a and 23b, which are digital broadcasting receivers. Also, the UHF terrestrial digital signal of the frequency band transmitted through the CATV line is output and supplied to the TVs 23a and 23b. The TVs 23a and 23b can receive the BS right-handed and BS left-handed IF signals, the 110° CS right-handed and 110° CS left-handed IF signals, and can receive the UHF terrestrial digital signal of the frequency band transmitted through the CATV line by the pass-through function. That is, the TVs 23a and 23b can watch terrestrial digital broadcasting channels, BS right-handed and BS left-handed BS broadcasting channels, and 110° CS right-handed and 110° CS left-handed CS broadcasting channels. In addition, if three or more terminal units are installed in the residence 20a, it will be possible to watch terrestrial digital broadcasting channels, BS right-hand and BS left-hand BS broadcasting channels, and 110° CS right-hand and 110° CS left-hand CS broadcasting channels on the digital broadcasting receiving equipment connected to each terminal unit. [Industrial Applicability]

[0037] As described above, in the frequency conversion transmission system according to the embodiment of the present invention, even if the transmission path only supports the frequency of the BS·CS-IF right-handed received signal, the BS-IF left-handed or CS-IF left-handed received signal can be transmitted by down-converting the BS-IF left-handed or CS-IF left-handed received signal. In this case, the frequency conversion device serving as the transmitting unit down-converts the frequency band of the UHF terrestrial digital signal to a lower frequency band that can be transmitted on the transmission path, and the frequency band of the BS-IF left-handed or CS-IF left-handed received signal is down-converted to a frequency band including the frequency band of the UHF terrestrial digital signal, which is thus vacant, and transmitted to the receiving unit. In the terminal device installed in the house serving as the receiving unit, the frequency band of the down-converted BS-IF left-handed or CS-IF left-handed received signal is up-converted to the original frequency band, and the down-converted and transmitted UHF terrestrial digital signal is supplied as is to the digital receiving device. The down-converted and transmitted UHF terrestrial digital signal can be received by the pass-through function of the digital receiving device, and since multiple channels in the frequency band are down-converted (up-converted) collectively, the configuration of the frequency conversion transmission system of the present invention is simplified and can be provided at low cost. In addition, the frequency conversion transmission system of the present invention does not require a BPF with a steep cutoff characteristic to extract the frequency band for each channel, so the frequency conversion transmission system of the present invention can be provided at a lower cost. In the frequency conversion transmission system of the present invention described above, even if the configurations of the U / V conversion unit 13, the converters (CONV) 1, 3, and the bandpass filter (BPF) 1 are modified as shown in Figures 2 to 4, the simplicity of the configuration of the frequency conversion transmission system of the present invention is maintained, so that the frequency conversion transmission system of the present invention can be provided at low cost. [Explanation of symbols]

[0038] 1,2 Frequency conversion transmission system, 10,10a Frequency conversion device, 11,11a BS / CS antenna, 12 UHF antenna, 13 U / V conversion unit, 20 Apartment house, 20a House, 21,21a,21b Wall terminal, 22,22a,22b Terminal unit, 30 Community receiving equipment line, 100 Frequency conversion transmission system, 110 Frequency conversion device, 111 BS / CS antenna, 112 UHF antenna, 120 Apartment house, 122 Terminal unit

Claims

1. A frequency conversion transmission system in which a transmitter and a receiver are connected by a transmission line, The transmission unit is a first down converter that down-converts a first frequency band of a UHF terrestrial digital signal of terrestrial digital broadcasting broadcast in the UHF band to a second frequency band that is a frequency band that can be transmitted through the transmission path and is lower than the frequency band of the UHF terrestrial digital signal; a second downconverter that downconverts a third frequency band of a first IF reception signal, which is a BS left-handed circular polarization or CS left-handed circular polarization intermediate frequency signal, to a fourth frequency band including the first frequency band that has been vacated by downconversion by the first downconverter; a mixing means for transmitting a mixed reception signal obtained by mixing a UHF terrestrial digital signal down-converted to the second frequency band by the first down-converter, a first IF reception signal of the fourth frequency band down-converted by the second down-converter, and a second IF reception signal which is an intermediate frequency signal of BS right-hand rotation and CS right-hand rotation, to the transmission path; The receiving unit is an up-converter that converts the first IF received signal of the fourth frequency band transmitted through the transmission line back into the original first IF received signal of the third frequency band; A frequency conversion transmission system characterized in that a UHF terrestrial digital signal in the second frequency band transmitted over the transmission path, a first IF reception signal in the third frequency band upconverted by the upconverter, and the second IF reception signal transmitted over the transmission path are output from the receiving unit.

2. The frequency conversion transmission system according to claim 1, characterized in that one transmitting unit is installed in an apartment building, the mixed reception signal transmitted from the transmitting unit to the transmission path is drawn into each home in the apartment building, and a terminal device serving as the receiving unit installed in each home receives the mixed reception signal.

3. The frequency conversion transmission system according to claim 1, characterized in that the second downconverter has a first local oscillator and a second local oscillator having different local oscillation frequencies, and by switching to the first local oscillator, the third frequency band of BS left-hand circular polarization is selected and down-converted to the fourth frequency band, and by switching to the second local oscillator, the third frequency band of CS left-hand circular polarization is selected and down-converted to the fourth frequency band.

4. 2. The frequency conversion transmission system according to claim 1, wherein a local oscillation frequency in the second downconverter is adjustable, and the local oscillation frequency is adjusted so that a frequency band including a desired channel is downconverted to a frequency range that can be transmitted by a booster provided in the transmission path.

5. The frequency conversion transmission system according to claim 1, characterized in that the first downconverter has a plurality of first frequency conversion blocks, the first frequency band of the UHF terrestrial digital signal is divided into a plurality of frequency bands and the second frequency band is divided into a plurality of frequency bands, each divided frequency band of the first frequency band is downconverted to each divided frequency band of the second frequency band by the plurality of first frequency conversion blocks, and a guard band is provided between each divided frequency band of the second frequency band.

6. 2. The frequency conversion transmission system according to claim 1, wherein the booster provided in the transmission path has an amplifier for amplifying each of a plurality of split reception signals obtained by splitting the mixed reception signal into signals in different frequency bands.

7. The frequency conversion transmission system according to claim 1, characterized in that the output from the receiving unit is received by a digital broadcast receiving device, and the digital broadcast receiving device is capable of receiving a UHF terrestrial digital signal in the second frequency band by a pass-through function.

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