Frequency conversion transmission system

Abstract

To make it possible to transmit an advanced wide band satellite digital broadcasting signal exceeding a transmittable frequency band of existing reception equipment without renovating the existing reception equipment.SOLUTION: A target IF reception signal of at least one channel in a BS left-handed IF signal or a CS left-handed IF signal is down-converted into a band from 2071 MHz, which is the upper limit of a frequency band of a 110°CS right-handed IF signal, to 2150 MHz, which is the upper limit of a transmittable frequency band, by a converter unit 13 and is transmitted through a common reception equipment line 30. The transmitted down-converted target IF reception signal is up-converted into the original frequency and supplied to a TV23 by a terminal device 22. Thereby, an advanced wide band satellite digital broadcasting signal can be viewed without renovating existing reception equipment.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a frequency conversion transmission system that enables transmission of advanced wideband satellite digital broadcasting 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, and the corresponding transmission frequency bands were successively updated, with the maximum transmission frequency expanding from 1335MHz to 1550MHz to 2150MHz to 2602MHz. Furthermore, full-scale broadcasting of advanced wideband digital satellite broadcasting (ISDB-S3, 4K / 8K broadcasting, BS / CS left-hand circular polarization broadcasting) began on December 1, 2018. Advanced wideband digital satellite broadcasting adds a BS / 110°CS left-hand circular polarization intermediate frequency signal (hereinafter referred to as "BS / 110°CS left-hand circular polarization IF signal") in the frequency band of 2224 MHz to 3224 MHz. Therefore, in order to transmit the BS / 110°CS left-hand circular polarization IF signal of advanced wideband digital satellite broadcasting in a shared receiving facility or other in-building TV signal receiving equipment, all receiving equipment, including coaxial cables, amplifiers, splitters / distributors, receiver terminals, and serial units, must be modified to be capable of transmitting the 2224 MHz to 3224 MHz transmission frequency band.

[0003] Thus, to provide BS / 110°CS left-hand circular polarization broadcasting services over the existing 2150MHz transmission band, it would be necessary to carry out modifications to extend the upper frequency limit of the transmission line to 3224MHz. Alternatively, it would be possible to temporarily downconvert the satellite left-hand circular polarization channel using vacant bands such as CATV bands, and then upconvert it back to the original frequency at the transmission destination. For example, Patent Document 1 proposes a CATV system that enables the transmission of BS intermediate frequency signals (BS-IF signals), which have higher frequencies than terrestrial television broadcast signals, even in existing CATV systems designed to transmit terrestrial television broadcast signals. The transmission frequency arrangement of this CATV system is shown in Figures 13(a) and 13(b). As shown in Figure 13(a), the transmittable band of the existing CATV system is 90 MHz to 770 MHz, which includes television broadcast signals in the VHF band (90 to 222 MHz) and the UHF band (470 to 770 MHz). The BS-IF signals are eight channels ranging from 1030 to 1337 MHz, which is higher than the transmittable band. Therefore, a downconverter is provided at the headend to downconvert four of the eight BS-IF signals from 1030 to 1337 MHz to the frequency band of the television broadcast signals. Specifically, as shown in Figure 13(b), the downconverter downconverts channels 1 and 3 of the BS-IF signal from 1030 to 1107 MHz to 330 to 407 MHz within the transmittable band, and downconverts channels 13 and 15 of the BS-IF signal from 1260 to 1337 MHz to 253 to 330 MHz within the transmittable band. In this case, the band from 253 to 407 MHz is considered an available band within the transmittable band.

[0004] Signals in the transmittable band, including the BS-IF signal downconverted by the downconverter, are transmitted from the headend to the terminal. An upconverter is installed on the terminal side, which converts channels 1 and 3 of the BS-IF signal, which are 330 to 407 MHz, back to their original frequencies of 1030 to 1107 MHz, and channels 13 and 15 of the BS-IF signal, which are 253 to 407 MHz, back to their original frequencies of 1260 to 1337 MHz, before supplying them to TV receivers, etc. This makes it possible to transmit BS-IF signals in addition to terrestrial television broadcast signals in existing CATV systems. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-86477 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to provide BS / 110°CS left-hand circular polarization broadcasting services on existing transmission lines, which have a transmission bandwidth of up to 2150 MHz, it is necessary to carry out modification work to expand the upper frequency limit of the transmission line to 3224 MHz. However, the cost of modification work can be high, and depending on the equipment, modification work can be impossible or difficult. Additionally, since the VHF band in the CATV band is currently vacant, it is conceivable to temporarily downconvert the BS·110°CS left-hand circular polarization channel using the vacant CATV band, and then upconvert it to the original frequency at the transmission destination. However, in order to do this, it would be necessary to replace (modify) the booster in the shared receiving equipment with a CATV booster in order to transmit the BS·110°CS left-hand circular polarization channel in the CATV band, and this could be difficult to implement in facilities where CATV has been introduced, as the frequency band is already almost entirely occupied by CATV channels.

[0007] Therefore, an object of the present invention is to provide a frequency conversion transmission system that can transmit advanced wideband satellite digital broadcasting signals that exceed the transmittable frequency band of existing receiving equipment lines without modifying the existing receiving equipment lines. [Means for solving the problem]

[0008] The frequency conversion transmission system of the present invention comprises a frequency conversion device that uses a downconverter to downconvert at least one channel of a target IF reception signal from among BS left-hand circular polarization IF signals or CS left-hand circular polarization IF signals, which are satellite broadcast intermediate frequency signals that exceed the upper limit of the transmittable frequency band of a transmission line, to a frequency within the transmittable frequency band that is lower than the original frequency, and transmits the target IF reception signal downconverted by the downconverter and other broadcast signals to a transmission line, and a terminal device that includes an upconverter that returns the downconverted target IF reception signal transmitted over the transmission line to the frequency of the original target IF reception signal, in which the downconverter downconverts the at least one channel of the target IF reception signal to a band that exceeds the frequency band of the CS right-hand circular polarization IF signal and is up to the upper limit of the transmittable frequency band, and the upconverter upconverts the downconverted target IF reception signal to the target IF reception signal at the original frequency. is its most important feature.

[0009] Another frequency conversion transmission system of the present invention is a frequency conversion transmission system comprising a frequency conversion device that uses a downconverter to downconvert two-channel target IF received signals of either BS left-hand circular polarization IF signals or CS left-hand circular polarization IF signals, which are satellite broadcast intermediate frequency signals that exceed the upper limit of the transmittable frequency band of a transmission path, to a frequency within the transmittable frequency band that is lower than the original frequency, and transmits the target IF received signals downconverted by the downconverter and other broadcast signals to a transmission path, and a terminal device including an upconverter that restores the frequency of the downconverted target IF received signals transmitted over the transmission path to the original target IF received signals, in which the downconverter downconverts the two-channel target IF received signals to a band that exceeds the frequency band of the CS right-hand circular polarization IF signals and is upconverts the downconverted two-channel target IF received signals to a band that is higher than the frequency band of the CS right-hand circular polarization IF signals and is upconverts the downconverted target IF received signals to the target IF received signals at the original frequency. is its most important feature.

[0010] Furthermore, in the frequency conversion transmission system of the present invention, two adjacent channels are set as target IF reception signals of the two channels, and the downconverter and the upconverter are configured to perform frequency conversion on the target IF reception signals of the two channels collectively, and the downconverter downconverts the target IF reception signals of the two channels using a single local oscillator signal to a band that exceeds the frequency band of the CS right-hand circular polarization IF signal and is up to the upper limit of the transmittable frequency band, and the upconverter upconverts the downconverted target IF reception signals of the two channels using a single local oscillator signal to adjacent target IF reception signals of the original frequency. Furthermore, in the frequency conversion transmission system of the present invention, the downconverter may be configured to perform double frequency conversion, and in the downconverter, the target IF reception signals of the two channels may be frequency converted by a first local oscillator signal, and the frequency-converted target IF reception signals of the two channels may be extracted by two surface acoustic wave filters having the bands of the frequency-converted target IF reception signals of the two channels as their passbands, respectively, and the target IF reception signals of the two channels extracted by the two surface acoustic wave filters may be frequency converted by a second local oscillator signal to a band exceeding the frequency band of the CS right-hand circular polarization IF signal and up to the upper limit of the transmittable frequency band. Furthermore, in the frequency conversion transmission system of the present invention, any two channels may be selected as target IF reception signals for the two channels, and the downconverter may use a local oscillator signal prepared for each channel to downconvert the target IF reception signals for the two channels to a band that exceeds the frequency band of the CS right-hand circular polarization IF signal and is up to the upper limit of the transmittable frequency band, and the upconverter may use a local oscillator signal prepared for each channel to upconvert the downconverted target IF reception signals for the any two channels to target IF reception signals of the original frequency. Furthermore, in the frequency conversion transmission system of the present invention, the downconverter may be configured to perform frequency conversion of each channel of the target IF reception signals of the two channels using a first converter and a second converter arranged in parallel, and the target IF reception signals of any two channels may be frequency converted in the first converter and the second converter so that they have the same frequency in the first converter and the second converter, and the frequency-converted target IF reception signals of any two channels may be extracted in the first converter and the second converter using surface acoustic wave filters having the same passband, and the extracted target IF reception signals of any two channels may be frequency-converted in the first converter and the second converter to a band beyond the frequency band of the CS right-hand circular polarization IF signal up to the upper limit of the transmittable frequency band so that the target IF reception signals of the any two channels do not overlap. Furthermore, in the frequency conversion transmission system of the present invention, the first downconverter and the second converter may be configured to perform double frequency conversion, and in the first converter, one of the two channels of target IF reception signals may be frequency converted by a third local oscillator signal, the target IF reception signal of the frequency-converted channel may be extracted by a surface acoustic wave filter having a passband equal to the band of the target IF reception signal of the frequency-converted channel, and the target IF reception signal of the channel extracted by the surface acoustic wave filter may be frequency converted by a fourth local oscillator signal to a band exceeding the frequency band of CS right-hand circular polarization IF signals and up to the upper limit of the transmittable frequency band; and in the second converter, the other of the two channels of target IF reception signals may be frequency converted by a fifth local oscillator signal, the target IF reception signal of the frequency-converted channel may be extracted by a surface acoustic wave filter having a passband equal to the band of the target IF reception signal of the frequency-converted channel, and the target IF reception signal of the channel extracted by the surface acoustic wave filter may be frequency converted by a sixth local oscillator signal to a band exceeding the frequency band of CS right-hand circular polarization IF signals and up to the upper limit of the transmittable frequency band.

[0011] Yet another frequency conversion transmission system of the present invention is a frequency conversion transmission system comprising a frequency conversion device that uses a downconverter to frequency convert target IF reception signals of up to four channels out of BS left-hand circular polarization IF signals or CS left-hand circular polarization IF signals, which are satellite broadcast intermediate frequency signals that exceed the upper limit of the transmittable frequency band of a transmission line, to a frequency within the transmittable frequency band that is lower than the original frequency, and transmits the target IF reception signals downconverted by the downconverter and other broadcast signals to a transmission line, and a terminal device that includes at least an upconverter that returns the frequency-converted target IF reception signals transmitted over the transmission line to the frequency of the original target IF reception signals, The most important feature of this system is that it downconverts the target IF reception signal to a band exceeding the frequency band of the CS right-hand circular polarization IF signal and up to the upper limit of the transmittable frequency band, and downconverts the target IF reception signal of two channels or less to within the guard band between the BS right-hand circular polarization IF signal and the CS right-hand circular polarization IF signal, and the upconverter upconverts the target IF reception signal of two channels or less that has been downconverted to a band exceeding the frequency band of the CS right-hand circular polarization IF signal and up to the upper limit of the transmittable frequency band, to the target IF reception signal of the original frequency, and upconverts the target IF reception signal of two channels or less that has been downconverted to within the guard band between the BS right-hand circular polarization IF signal and the CS right-hand circular polarization IF signal, to the target IF reception signal of the original frequency. [Effects of the Invention]

[0012] The frequency conversion transmission system of the present invention down-converts one or more target IF received signals of an advanced wideband satellite digital broadcasting signal that exceeds the upper limit of the transmittable frequency band of the transmission line to a band that exceeds the frequency band of the CS right-hand circular polarization IF signal and is up to the upper limit of the transmittable frequency band, and transmits the down-converted signals.Therefore, it is possible to transmit an advanced wideband satellite digital broadcasting signal that exceeds the transmittable frequency band of an existing receiving equipment line without modifying the existing receiving equipment line. Furthermore, by down-converting and transmitting one or more target IF received signals of advanced wideband satellite digital broadcasting signals that exceed the upper limit of the transmittable frequency band of the transmission line within the guard band between the BS right-hand circular polarization IF signal and the CS right-hand circular polarization IF signal, it is possible to transmit multiple channels of advanced wideband satellite digital broadcasting signals that exceed the transmittable frequency band of the existing receiving equipment line without modifying the existing receiving equipment line. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a functional block diagram showing the configuration of a frequency conversion transmission system according to a first embodiment of the present invention. [Figure 2] 1 is a circuit block diagram showing the configuration of a converter unit in a frequency conversion device of a frequency conversion transmission system according to a first embodiment of the present invention. [Figure 3] 1 is a circuit block diagram showing the configuration of a terminal device of a frequency conversion transmission system according to a first embodiment of the present invention. [Figure 4] FIG. 2 is a diagram showing a transmission frequency arrangement in the frequency conversion transmission system according to the first embodiment of the present invention. [Figure 5] FIG. 2 is a circuit block diagram showing the configuration of a first modified example of a converter unit in a frequency conversion device of the frequency conversion transmission system according to the first embodiment of the present invention. [Figure 6] 10A and 10B are circuit block diagrams showing configurations of second and third modified examples of the converter unit in the frequency conversion device of the frequency conversion transmission system according to the first embodiment of the present invention. [Figure 7] FIG. 10 is a circuit block diagram showing a configuration of a modified example of the converter unit in the terminal device of the frequency conversion transmission system according to the first embodiment of the present invention. [Figure 8] 1 is a circuit block diagram showing a configuration of an example of an application that can be applied to a converter unit in a frequency conversion transmission system according to an embodiment of the present invention. [Figure 9] 1 is a diagram showing an example of a transmission frequency arrangement in the case of conversion by 1Lo and 2Lo in a frequency conversion device of a frequency conversion transmission system according to a first embodiment of the present invention. FIG. [Figure 10]10 is an enlarged view of a portion of the example of the transmission frequency arrangement of FIG. 9. FIG. [Figure 11] FIG. 2 is a diagram showing an example of a transmission frequency arrangement in the case of conversion by 1Lo and 2Lo in the frequency conversion transmission system according to the first embodiment of the present invention. [Figure 12] FIG. 10 is a diagram showing a transmission frequency arrangement in a frequency conversion transmission system according to a second embodiment of the present invention. [Figure 13] FIG. 1 is a diagram showing a transmission frequency arrangement of a conventional CATV system. DETAILED DESCRIPTION OF THE INVENTION

[0014] In the frequency conversion transmission system of the present invention, the object of the present invention is achieved by down-converting the target IF received signals of at least one channel of an advanced wideband satellite digital broadcasting signal that exceeds the upper limit of the transmittable frequency band of the transmission path to a band that exceeds the frequency band of the CS right-hand circular polarization IF signal and is up to the upper limit of the transmittable frequency band, and transmitting the down-converted signals. [Example]

[0015] <First Example> The frequency conversion transmission system 1 of the first embodiment of the present invention can transmit broadcast channels in BS·110°CS left-hand circular polarization intermediate frequency signals (hereinafter referred to as "BS·110°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 2150 MHz. FIG. 1 shows a functional block diagram showing the configuration of the frequency conversion transmission system 1 of the first embodiment of the present invention, FIG. 2 shows a circuit block diagram showing the configuration of the converter unit 13 in the frequency conversion device 10 of the frequency conversion transmission system 1 shown in FIG. 1, FIG. 3 shows a circuit block diagram showing the configuration of the terminal device 22, and FIGS. 4(a), (b), and (c) show the transmission frequency arrangement. As shown in these figures, the frequency conversion transmission system 1 of the first embodiment of the present invention is composed of a BS / CS antenna 11, a UHF antenna 12, a frequency conversion device 10 serving as a downconverter, a community receiving facility line 30 serving as a transmission path, and a terminal device 22. The frequency conversion device 10 is the sending side, and the terminal device 22 is the receiving side. The community receiving facility line 30 is an existing transmission path, and the upper limit frequency of the frequency band that can be transmitted over the community receiving facility line 30 is set to 2150 MHz, and the terminal device 22 is installed in each home of the apartment building 20. The received signals output from the BS / CS antenna 11 are a BS right-hand circular polarization intermediate frequency signal (hereinafter referred to as the "BS right-hand circular polarization IF signal"), a 110°CS right-hand circular polarization intermediate frequency signal (hereinafter referred to as the "110°CS right-hand circular polarization IF signal"), a BS left-hand circular polarization intermediate frequency signal (hereinafter referred to as the "BS left-hand circular polarization IF signal"), and a 110°CS left-hand circular polarization intermediate frequency signal (hereinafter referred to as the "110°CS left-hand circular polarization IF signal"), and their frequency bands are shown in FIG. 4(a) as BS right-hand circular polarization, 110°CS right-hand circular polarization, BS left-hand circular polarization, and 110°CS left-hand circular polarization. FIG. 4(a) also shows the frequency arrangement of the received signals input to the frequency conversion device 10. The received signals output from the UHF antenna 12 are UHF terrestrial digital signals, and their frequency bands are shown in FIG. 4(a) as CATV or UHF. Note that the CATV frequency band is shown when CATV is installed in the frequency conversion transmission system 1, but if CATV is not installed, the CATV frequency band is not shown. The frequency band of UHF terrestrial digital signals (UHF band) is 470 MHz to 770 MHz, and the frequency band of CATV or UHF is 90 MHz to 770 MHz, which are frequency bands that can be transmitted over the community receiving facility line 30. A received signal output from the BS / CS antenna 11 is input to a first input terminal (IN) 1 of the frequency converter 10, and a UHF terrestrial digital signal output from the UHF antenna 12 is input to a second input terminal (IN) 2 of the frequency converter 10.

[0016] In frequency conversion device 10, a signal received by BS / CS antenna 11 input to IN1 is input to demultiplexer (DIM) 1, where it is demultiplexed into a BS right-hand circular polarization IF signal and a 110°CS right-hand circular polarization IF signal, and a BS left-hand circular polarization IF signal and a 110°CS left-hand circular polarization IF signal. The demultiplexed BS right-hand circular polarization IF signal and the 110°CS right-hand circular polarization IF signal are level-adjusted to predetermined levels by amplifier (AMP) 1 and attenuator (ATT) 1, and then input to mixer (MIX) 1. The demultiplexed BS left-hand circularly rotated IF signals in the frequency band of 2224 MHz to 2681 MHz and 110° CS left-hand circularly rotated IF signals in the frequency band of 2708 MHz to 3224 MHz are supplied to converter unit 13, which downconverts one or more channels of target IF received signals to a frequency band ranging from 2071 MHz, the upper limit of the frequency band for 110° CS right-hand circularly rotated IF signals, to 2150 MHz, the upper limit of the frequency band transmittable through shared receiving facility line 30. The target IF received signals are defined as channels desired to be transmitted that are arbitrarily selected from the BS left-hand circularly rotated IF signals and 110° CS left-hand circularly rotated IF signals. The one or more channels of BS left-hand circularly rotated IF signals or 110° CS left-hand circularly rotated IF signals downconverted by converter unit 13 are input to MIX1, where they are mixed with the BS right-hand circularly rotated IF signals and 110° CS right-hand circularly rotated IF signals from ATT1. Furthermore, the UHF terrestrial digital signal input to IN2 and output from UHF antenna 12 is level-adjusted to a predetermined level by amplifier (AMP) 2 and attenuator (ATT) 2 and then input to mixer (MIX) 2. In MIX 2, the UHF terrestrial digital signal is mixed with the BS right-hand circular polarization IF signal, the 110° CS right-hand circular polarization IF signal, and the BS left-hand circular polarization IF signal, and the 110° CS left-hand circular polarization IF signal, and the mixed received signal is transmitted from first output section terminal (OUT) 1 to community receiving facility line 30. The frequency arrangement of the mixed received signal transmitted to community receiving facility line 30 is shown in Figure 4(b).

[0017] FIG. 2 shows a detailed configuration of the converter unit 13 of the frequency conversion device 10. 2, the converter section 13 is composed of a divider (DIV) 11, a first converter and a second converter arranged in parallel and having similar circuit configurations, and a MIX 11. The first converter is composed of a cascade connection of an AMP 11, a BPF 11, a MIX a1, a BPF 12, and an ATT 11, and is equipped with a local oscillator (OSC) a1. The second converter is composed of a cascade connection of an AMP 12, a BPF 13, a MIX a2, a BPF 14, and an ATT 12, and is equipped with a local oscillator (OSC) a2. AMP11 and AMP12 are amplifiers for adjusting the level, BPF11 and BPF13 are bandpass filters that extract one channel of the target IF received signal, local oscillator (OSC) a1 is an oscillator that oscillates local oscillator signal f1, local oscillator (OSC) a2 is an oscillator that oscillates local oscillator signal f2, MIX a1 is a mixer that converts the frequency using the local oscillator signal f1 from local oscillator (OSC) a1, MIX a2 is a mixer that converts the frequency using the local oscillator signal f2 from local oscillator (OSC) a2, BPF12 and BPF14 are bandpass filters that extract one of the sidebands frequency-converted by MIX a1 and MIX a2, and ATT11 and ATT12 are attenuators that adjust the level. Converter unit 13 receives the BS·110°CS left-handed IF signal (BS left-handed IF signal and 110°CS left-handed IF signal) demultiplexed by DIM1, and divides it into two signals by divider (DIV) 11, which are input to the first and second converters, respectively. In the first converter, the BS·110°CS left-handed IF signal is amplified by AMP11 and input to BPF11, where, for example, the channel BS8 signal from the BS left-handed IF signal is extracted and input to MIXa1. A local oscillator signal f1 from OSCa1 is supplied to MIXa1, and the channel BS8 signal is frequency-converted by MIXa1. BPF 12 extracts the lower sideband of the frequency-converted channel BS8 signal, thereby down-converting the channel BS8 signal using the local oscillator signal f1. The down-converted channel BS8 signal is level-adjusted by ATT11 and input to MIX11.

[0018] The second converter also operates in a similar manner, where the BS·110°CS left-hand circularly polarized IF signal is amplified by AMP12 and input to BPF13, where, for example, the channel BS14 signal is extracted from the BS left-hand circularly polarized IF signal and input to MIXa2. A local oscillator signal f2 from OSCa2 is supplied to MIXa2, and the channel BS14 signal is frequency-converted by MIXa2. BPF14 extracts the lower sideband of the frequency-converted channel BS14 signal, thereby down-converting the channel BS14 signal using the local oscillator signal f2. The down-converted channel BS14 signal has its level adjusted by ATT12 and is input to MIX11. Then, the down-converted channel BS8 signal from ATT11 and the down-converted channel BS14 signal from ATT12 are mixed in MIX11 and output to MIX1. Note that the first and second converters down-convert, for example, the channel BS8 signal and the channel BS14 signal to a band ranging from 2071 MHz, which is the upper limit of the frequency band of the 110° CS right-hand circular polarization IF signal, to 2150 MHz, which is the upper limit of the frequency band that can be transmitted through the community receiving facility line 30. The above explanation assumes that channels BS8 and BS14 are selected as the target IF reception signal from among the BS·110°CS left-handed IF signals, and converter unit 13 performs frequency conversion using two local-oscillating signals (2Lo) prepared for channels BS8 and BS14, which are local-oscillating signals f1 from OSCa1 and f2 from OSCa2. Furthermore, down-converted channels BS8 and BS14 are placed in the band from 2071 MHz to 2150 MHz so that their bands do not overlap. If the channel selected as the target IF reception signal is changed, the passbands of BPF11 and BPF13, and local-oscillating signals f1 and f2, are also changed to correspond to the selected channel.

[0019] Returning to Figure 1, the received signal transmitted over the community receiving facility line 30 is amplified by booster (AMP) 3 and then distributed to multiple signals by distributor (DIV) 1, and one of the distributed received signals is amplified by booster (AMP) 4 and then distributed sequentially by cascaded DIV2 and DIV3, with one of the distributed outputs of DIV3 being further distributed by DIV4, and one of the distributed outputs of DIV4 being brought into the apartment building 20. AMP3, AMP4, and DIV1 to DIV4 only need to be compatible with bands up to 2150 MHz. Each home in apartment building 20 is provided with a wall terminal 21 to which the distributed output of DIV4 is input, and wall terminal 21 is connected to a television (TV) 23 via a terminal device 22 that is an upconverter. Wall terminal 21 and a third input terminal (IN) 3 of terminal device 22 are connected by a cable, and a received signal with the transmission frequency arrangement shown in Fig. 4(b) that is brought into the home is input to IN3. Fig. 4(b) shows a case in which any two channels of a BS left-hand circular polarization IF signal and a 110° CS left-hand circular polarization IF signal are selected as target IF received signals for Ach and Bch to be downconverted by the first converter and the second converter in converter section 13 of frequency conversion device 10.

[0020] In the terminal device 22, the downconverted target IF received signals Ach and Bch of the received signal having the transmission frequency arrangement shown in Figure 4(b) input from IN3 are upconverted to the frequencies of the original BS left-hand circular polarization IF signal and 110°CS left-hand circular polarization IF signal. Furthermore, the terminal device 22 outputs the UHF terrestrial digital signal of the received signal having the transmission frequency arrangement shown in Figure 4(b) input from IN3 as is from the third output terminal (OUT) 3, and also adjusts the level of the BS·110°CS right-hand circular polarization signal (BS right-hand circular polarization IF signal and 110°CS right-hand circular polarization IF signal), mixes it with the target IF received signals Ach and Bch upconverted to the band of the original BS·110°CS left-hand circular polarization IF signal, and outputs it from the second output terminal (OUT) 2. A circuit block diagram showing the configuration of the terminal device 22 is shown in Figure 3.

[0021] In terminal device 22 shown in Figure 3, the received signal input from IN3, which has the transmission frequency arrangement shown in Figure 4(b), is input to splitter (DIM) 21 and split into a BS·110°CS right-hand circularly rotated signal, down-converted target IF received signals for channels A and B, and a UHF terrestrial digital signal. The split BS·110°CS right-hand circularly rotated signal and down-converted target IF received signals for channels A and B are split into two by splitter (DIV) 21, and the BS·110°CS right-hand circularly rotated signal of one of the split signals is amplified to a predetermined level by AMP 21 and input to MIX 21. The other split signal is input to converter unit 221, where the down-converted target IF received signals for channels A and B are up-converted to the band of the original BS·110°CS left-hand circularly rotated IF signal, input to MIX 21, mixed with the BS·110°CS right-hand circularly rotated signal, and output from OUT2. Furthermore, the demultiplexed UHF terrestrial digital signal is output as is from OUT3.

[0022] The converter section 221 is configured with a third converter, a fourth converter, and a MIX 22, which are arranged in parallel with the DIV 22 and have the same circuit configuration. The third converter is configured with an AMP 22, a BPF 21, a MIX b1, and a BPF 22 connected in cascade, and includes a local oscillator (OSC) b1. The fourth converter is configured with an AMP 23, a BPF 23, a MIX b2, and a BPF 24 connected in cascade, and includes a local oscillator (OSC) b2. AMP22 and AMP23 are level adjustment amplifiers, BPF21 and BPF23 are bandpass filters that extract one channel from the downconverted target IF received signal, OSCb1 is an oscillator that oscillates local oscillator signal f10, OSCb2 is an oscillator that oscillates local oscillator signal f11, MIXb1 is a mixer that performs frequency conversion using local oscillator signal f10 from OSCb1, MIXb2 is a mixer that performs frequency conversion using local oscillator signal f11 from OSCb2, and BPF22 and BPF24 are bandpass filters that extract one of the sidebands frequency-converted by MIXb1 and MIXb2. Converter unit 221 receives a BS·110°CS right-hand circularly polarized signal including the down-converted target IF received signals of Ach and Bch divided by DIV21, which is then divided into two by DIV22 and input to the third and fourth converters, respectively. In the third converter, the BS·110°CS right-hand circularly polarized signal including the down-converted target IF received signals of Ach and Bch is amplified by AMP22 and input to BPF21, where, for example, the down-converted target IF received signal of Ach is extracted and input to MIXb1. A local oscillator signal f10 from OSCb1 is supplied to MIXb1, and the target IF received signal of Ach is frequency-converted in MIXb1. In BPF22, the upper sideband of the frequency-converted target IF received signal of Ach is extracted, thereby up-converting the target IF received signal of Ach using the local oscillator signal f10. As a result, the target IF received signal of Ach is up-converted to the band of the original BS·110° CS left-handed circular polarization IF signal and input to MIX 22.

[0023] The fourth converter operates in a similar manner. In the fourth converter, the BS·110°CS right-hand circular polarization signal containing the down-converted target IF received signals of Ach and Bch is amplified by AMP23 and input to BPF23. For example, the down-converted target IF received signal of Bch is extracted and input to MIXb2. A local oscillator signal f11 from OSCb2 is supplied to MIXb2, and the target IF received signal of Bch is frequency-converted in MIXb2. BPF24 extracts the upper sideband of the frequency-converted target IF received signal of Bch, thereby up-converting the target IF received signal of Bch using the local oscillator signal f11. This up-converts the target IF received signal of Bch to the band of the original BS·110°CS left-hand circular polarization IF signal and inputs it to MIX22. In MIX22, the target IF received signals of Ach and Bch, up-converted to the band of the original BS·110°CS left-hand circular polarization IF signal, are mixed and output to MIX21. As explained above, converter section 221 performs frequency conversion using two local oscillator signals (2Lo) provided on channels A and B, namely, local oscillator signal f10 from OSCb1 and local oscillator signal f11 from OSCb2. Note that the passbands of BPF22 and BPF24, and local oscillator signals f10 and f11 correspond to the channel selected as the target IF received signal, and are changed accordingly when the channel selected as the target IF received signal is changed.

[0024] Returning to Fig. 1, the signals output from OUT2 and OUT3 of terminal device 22 have the transmission frequency arrangement shown in Fig. 4(c). That is, OUT2 outputs a BS right-hand circular polarization IF signal and a 110° CS right-hand circular polarization IF signal, and target IF received signals of Ach and Bch that have been upconverted to the original frequency of the BS left-hand circular polarization IF signal or the 110° CS left-hand circular polarization IF signal, and OUT3 outputs a UHF terrestrial digital signal. Note that the CATV frequency band in Fig. 4(c) shows the case where CATV is introduced into frequency conversion transmission system 1, but if CATV is not introduced, the CATV frequency band is not shown. By connecting OUT2 and OUT3 of the terminal device 22 with the input terminal of the television (TV) 23 via a cable, the TV 23 can receive and watch the target IF received signals of Ach and Bch that have been upconverted to the original frequency of the UHF terrestrial digital signal, BS right-hand circular polarization IF signal, 110°CS right-hand circular polarization IF signal, BS left-hand circular polarization IF signal, or 110°CS left-hand circular polarization IF signal.

[0025] <First Modification of Converter Unit 13> Next, a functional block diagram showing the configuration of a converter section 13-2 according to a first modified example of the converter section 13 is shown in FIG. The converter section 13-2 of the first modified example shown in Fig. 5 is configured to perform frequency conversion using two local oscillator signals (2Lo) and also to perform double frequency conversion via an intermediate frequency. Note that a surface acoustic wave filter (SAW filter) is used, which is known as a small, high-performance filter with steep attenuation characteristics. The converter section 13-2 is composed of a DIV11, a fifth converter and a sixth converter with a similar double-conversion configuration arranged in parallel, and a MIX11. The fifth converter is composed of a cascade connection of an AMP11, a BPF11, a MIXa3, a BPF15, an AMP13, a surface acoustic wave filter (SAW)11, a MIXa4, a BPF12, an AMP14, and an ATT11, and is equipped with a local oscillator (OSC)a3 and a local oscillator (OSC)a4. The sixth converter is composed of a cascade connection of an AMP12, a BPF13, a MIXa5, a BPF16, an AMP15, a surface acoustic wave filter (SAW)12, a MIXa6, a BPF14, an AMP16, and an ATT12, and is equipped with a local oscillator (OSC)a5 and a local oscillator (OSC)a6. In the converter section 13-2, AMP11 to AMP16 are amplifiers for adjusting levels, BPF11 and BPF13 are bandpass filters for extracting one channel of the target IF reception signal, local oscillator (OSC) a3 is an oscillator that oscillates a local oscillation signal f3, local oscillator (OSC) a5 is an oscillator that oscillates a local oscillation signal f5, MIX a3 is a mixer that frequency converts the target IF reception signal using the local oscillation signal f3 from the local oscillator (OSC) a3, MIX a5 is a mixer that frequency converts the target IF reception signal using the local oscillation signal f5 from the local oscillator (OSC) a5, and BPF15 and BPF16 are bandpass filters that extract one of the sidebands frequency-converted by MIX a3 and MIX a5. SAW11 and SAW12 are filters that remove unwanted wave components from the target IF reception signal that has been converted into an intermediate frequency signal, local oscillator (OSC) a4 is an oscillator that oscillates local oscillator signal f4, local oscillator (OSC) a6 is an oscillator that oscillates local oscillator signal f6, MIX a4 is a mixer that frequency converts the target IF reception signal using local oscillator signal f4 from local oscillator (OSC) a4, MIX a6 is a mixer that frequency converts the target IF reception signal using local oscillator signal f6 from local oscillator (OSC) a6, BPF12 and BPF14 are bandpass filters that extract one of the sidebands frequency converted by MIX a4 and MIX a6, and ATT11 and ATT12 are attenuators that perform level adjustment.

[0026] The BS·110°CS left-handed circularly polarized IF signal demultiplexed by DIM1 is input to converter unit 13-2, which then divides it into two signals by DIV11 and inputs them to the fifth and sixth converters, respectively. In the fifth converter, the BS·110°CS left-handed circularly polarized IF signal is amplified by AMP11 and input to BPF11, where, for example, the channel BS8 signal from the BS left-handed circularly polarized IF signal is extracted and input to MIXa3. A local oscillator signal f3 (e.g., 2611.5 MHz) from OSCa3 is supplied to MIXa3, and the channel BS8 signal is frequency-converted by MIXa3. BPF15 extracts the lower sideband of the frequency-converted channel BS8 signal, thereby frequency-converting the channel BS8 signal to an intermediate frequency signal using the local oscillator signal f3. The channel BS8 signal, frequency-converted to an intermediate frequency signal, is amplified by AMP13 and input to SAW11, where undesired wave components are removed and input to MIXa4. MIXa4 is supplied with a local oscillator signal f4 (for example, 2347.76 MHz) from OSCa4, and the channel BS8 signal is frequency converted in MIXa4. BPF12 extracts the lower sideband of the frequency-converted channel BS8 signal, thereby frequency-converting the channel BS8 signal to a band from 2071 MHz to 2150 MHz using the local oscillator signal f4. The frequency-converted channel BS8 signal is level-adjusted by AMP14 and ATT11 and input to MIX11.

[0027] The sixth converter operates in a similar manner. In the sixth converter, the BS·110°CS left-handed circularly polarized IF signal is amplified by AMP12 and input to BPF13. For example, the channel BS14 signal is extracted from the BS left-handed circularly polarized IF signal and input to MIXa5. A local oscillator signal f5 (e.g., 2726.58 MHz) from OSCa5 is supplied to MIXa5, and the channel BS14 signal is frequency-converted by MIXa5. BPF16 extracts the lower sideband of the frequency-converted channel BS14 signal, thereby frequency-converting the channel BS14 signal to an intermediate frequency signal using the local oscillator signal f5. The channel BS14 signal, frequency-converted to an intermediate frequency signal, is amplified by AMP15 and input to SAW12, where undesired wave components are removed and the signal is input to MIXa6. A local oscillator signal f6 (e.g., 2386.12 MHz) from OSCa6 is supplied to MIXa6, and the channel BS14 signal is frequency-converted by MIXa6. The BPF 14 extracts the lower sideband of the frequency-converted channel BS14 signal, and the channel BS14 signal is frequency-converted to a band of 2071 MHz to 2150 MHz using the local oscillator signal f4. The frequency-converted channel BS14 signal is level-adjusted by the AMP 16 and the ATT 12 and then input to the MIX 11.

[0028] The frequency-converted channel BS8 signal from ATT11 and the frequency-converted channel BS14 signal from ATT12 are mixed in MIX11 and output to MIX1. Note that the fifth and sixth converters downconvert, for example, the channel BS8 signal and the channel BS14 signal from 2071 MHz, which is the upper limit of the frequency band of the 110° CS right-hand circular polarization IF signal, to 2150 MHz, which is the upper limit of the frequency band transmittable by the community receiving facility line 30. The center frequencies of the intermediate frequency signals in the fifth and sixth converters are the same, for example, 254.76 MHz. In other words, SAW filters with the same passband can be used as SAW11 and SAW12. In converter unit 13-2 of the first modification, the frequencies of channels BS8 and BS14 selected from the BS·110°CS left-handed circular polarization IF signal are down-converted to a band of 2071 MHz to 2150 MHz using 2Lo and a double conversion configuration. Furthermore, the down-converted channels BS8 and BS14 are placed in the band of 2071 MHz to 2150 MHz so that their bands do not overlap. The above explanation assumes that channels BS8 and BS14 are selected as the target IF reception signals from among the BS·110°CS left-handed IF signals. If the channel selected as the target IF reception signal is changed, the passbands of BPF11 and BPF13, and local oscillator signals f3 and f5 are changed to correspond to the selected channel.

[0029] <Second Modification of Converter Unit 13> Next, a functional block diagram showing the configuration of a converter section 13-3 according to a second modification of the converter section 13 is shown in FIG. 6(a). The converter unit 13-3 of the second modified example shown in Fig. 6(a) performs frequency conversion using one local oscillator signal (1Lo) and also performs frequency conversion using double conversion via an intermediate frequency, with a double converter configuration using a surface acoustic wave filter (SAW filter). In this case, two adjacent channels are selected as target IF received signals and are down-converted collectively by the converter unit 13-3 of the second modified example. The converter section 13-3 of the second modification is configured by cascading an AMP12, a BPF13', a MIXa5, a BPF16', an AMP16, a DIV12, a SAW11 arranged in parallel with a SAW12, a MIXa5, a MIXa6, a BPF14', an AMP16, and an ATT12, and is also provided with a local oscillator (OSC) a5 and a local oscillator (OSC) a6. Each section is as described above, but BPF13' is a bandpass filter that extracts two adjacent channels that are the target IF received signal, BPF16' is a bandpass filter that extracts one of the sidebands frequency-converted by MIXa5 to extract the two adjacent channels, and BPF14' is a bandpass filter that extracts one of the sidebands frequency-converted by MIXa6 to extract the two adjacent channels. DIV12 is a distributor that inputs the two divided signals to SAW11 and SAW12 that are arranged in parallel, and MIX12 is a mixer that mixes the signals extracted by SAW11 and SAW12.

[0030] In the second modified example, converter unit 13-3 receives the BS·110°CS left-hand circularly polarized IF signal demultiplexed by DIM1, which is amplified by AMP12 and input to BPF13'. For example, the signals of adjacent channels BS12 and BS14 are extracted from the BS left-hand circularly polarized IF signal and input to MIXa5. Local oscillator signal f5 (e.g., 2726.58 MHz) from OSCa5 is supplied to MIXa5, and the signals of adjacent channels BS12 and BS14 are frequency-converted by MIXa5. BPF16' extracts the lower sideband of the frequency-converted signals of adjacent channels BS12 and BS14, thereby converting the signals of adjacent channels BS12 and BS14 to intermediate frequency signals using local oscillator signal f5. The frequency-converted signals of adjacent channels BS12 and BS14 are amplified by AMP16, split into two by DIV12, and input to SAW11 and SAW13, which are arranged in parallel. The center frequency of the passband of SAW11 is the center frequency of frequency-converted channel BS14, and the center frequency of the passband of SAW13 is the center frequency of frequency-converted channel BS12. The channel BS14 signal extracted by removing unwanted wave components in SAW11 and the channel BS12 signal extracted by removing unwanted wave components in SAW13 are input to MIX12, mixed, and input to MIXa6. MIXa6 is supplied with a local oscillator signal f6 (e.g., 2386.12 MHz) from OSCa6, and the signals of adjacent channels BS12 and BS14 are frequency-converted in MIXa6. BPF14' extracts the lower sidebands of the frequency-converted signals of adjacent channels BS12 and BS14, thereby frequency-converting the signals of adjacent channels BS12 and BS14 collectively to a band from 2071 MHz to 2150 MHz using local oscillator signal f6. The frequency-converted adjacent channel BS12 and BS14 signals are level-adjusted by AMP16 and ATT12 and output to MIX1. In converter unit 13-3 of the second modified example, the frequencies of adjacent channels BS12 and BS14 selected from the BS·110°CS left-handed circular polarization IF signal are down-converted together to a band from 2071 MHz to 2150 MHz using 1Lo. Note that since channels BS12 and BS14 are adjacent and down-converted together, the bands of the down-converted channels BS12 and BS14 do not overlap each other. The above explanation is based on the case where adjacent channels BS12 and BS14 are selected as the target IF reception signal from among the BS·110°CS left-handed circular polarization IF signals. If the two adjacent channels selected as the target IF reception signal are changed, the passband of BPF13′ and the local oscillator signal f5 are changed to correspond to the two selected adjacent channels.

[0031] <Third Modification of Converter Unit 13> Next, a functional block diagram showing the configuration of a converter section 13-4 according to a third modification of the converter section 13 is shown in FIG. 6(b). The converter unit 13-4 of the third modified example shown in Figure 6(b) is configured to perform frequency conversion using one local oscillator signal (1Lo), and two adjacent channels are selected as target IF received signals and are downconverted collectively. The converter section 13-4 of the third modified example is configured by cascading an AMP11, a BPF11', a MIX a7, a BPF12', an AMP14, and an ATT11, and is equipped with a local oscillator (OSC) a7. Each section is as described above, but the BPF11' is a bandpass filter that extracts two adjacent channels that are the target IF received signal, the local oscillator (OSC) a7 is an oscillator that oscillates a local oscillator signal f7, the MIX a7 is a mixer that performs frequency conversion using a local oscillator signal f12 from the local oscillator (OSC) a7, and the BPF12' is a bandpass filter that extracts one of the sidebands frequency-converted by the MIX a7 to extract the two adjacent channels.

[0032] In the third modified example, converter unit 13-4 receives the BS·110°CS left-hand circularly polarized IF signal demultiplexed by DIM1, which is amplified by AMP11 and input to BPF11'. For example, the signals of adjacent channels BS12 and BS14 are extracted from the BS left-hand circularly polarized IF signal and input to MIXa7. Local oscillator signal f7 (e.g., 4564.82 MHz) from OSCa7 is supplied to MIXa7, and the signals of adjacent channels BS12 and BS14 are frequency-converted by MIXa7. BPF12' extracts the lower sideband of the frequency-converted signals of adjacent channels BS12 and BS14, thereby down-converting the signals of adjacent channels BS12 and BS14 collectively to a band from 2071 MHz to 2150 MHz using local oscillator signal f7. The down-converted signals of adjacent channels BS12 and BS14 are level-adjusted by AMP14 and ATT11 and output to MIX1. In converter unit 13-4 of the third modified example, the frequencies of adjacent channels BS12 and BS14 selected from the BS·110°CS left-handed circular polarization IF signal are down-converted together to a band from 2071 MHz to 2150 MHz using 1Lo. Note that since channels BS12 and BS14 are adjacent and down-converted together, the bands of the down-converted channels BS12 and BS14 do not overlap each other. The above explanation is based on the case where adjacent channels BS12 and BS14 are selected as the target IF reception signal from among the BS·110°CS left-handed circular polarization IF signals. If the two adjacent channels selected as the target IF reception signal are changed, the passband of BPF11′ and local oscillator signal f7 are changed to correspond to the two selected adjacent channels.

[0033] <Modifications of the converter section 221> Next, a functional block diagram showing the configuration of converter section 222, which is a modified example of converter section 221 in terminal device 22, is shown in FIG. The converter unit 222 of the modified example shown in FIG. 7 performs upconversion using one local oscillator signal (1Lo), and the downconverted target IF received signals of two channels that are used as target IF received signals are upconverted collectively. The converter unit 222 of the modified example is configured by cascading an AMP22, a BPF21', a MIXb3, and a BPF22', and is equipped with a local oscillator (OSC) b3. The BPF21' is a bandpass filter that extracts the downconverted two-channel target IF received signals, the local oscillator (OSC) b3 is an oscillator that oscillates a local oscillator signal f12, the MIXb3 is a mixer that performs frequency conversion using the local oscillator signal f12 from the local oscillator (OSC) b3, and the BPF22' is a bandpass filter that extracts one of the sidebands frequency-converted by the MIXb3 to extract the two-channel target IF received signals. Converter unit 222 of the modified example receives a BS·110°CS right-hand circular polarization signal including the down-converted target IF received signals of Ach and Bch distributed by DIV21, amplified by AMP22, and input to BPF21', where the down-converted target IF received signals of Ach and Bch are extracted and input to MIXb3. Local oscillator signal f12 from OSCb3 is supplied to MIXb3, and the target IF received signals of Ach and Bch are frequency-converted in MIXb3. BPF22' extracts the upper sideband of the frequency-converted target IF received signals of Ach and Bch, thereby up-converting the target IF received signals of Ach and Bch using local oscillator signal f12. As a result, the target IF received signals of Ach and Bch are collectively up-converted to the band of the original BS·110°CS left-hand circular polarization IF signal and output to MIX21. The passband of BPF22' and the local oscillator signal f12 correspond to the two adjacent channels selected as the target IF received signal, and are changed accordingly when the channel selected as the target IF received signal is changed.

[0034] <Converter application example> Next, a functional block diagram showing the configuration of a converter section 40 that can be applied to the converter section 13 of the frequency conversion device 10 or the converter section 221 in the terminal device 22 is shown in FIG. The converter unit 40 shown in Fig. 8 is configured with an LSI (Large-Scale Integration). A complete set of computer functions can be implemented in the LSI, and the computer can have the functions of an AD converter (ADC) 41, a filter processing / converter processing unit 42, and a DA converter (DAC) 43. The BS·110°CS left-handed IF signal, which is an analog signal input to the LSI, is converted into a digital signal by the ADC 41 and digitally processed by the filter processing / converter processing unit 42. The filter processing / converter processing unit 42 digitally performs the functions previously performed by the filters and frequency conversion in the converter unit 13 and converter unit 221. The digital signal digitally processed by the filter processing / converter processing unit 42 is converted into an analog signal by the DAC 43 and output. The converter section 40 described above may be used as the converter section 13 of the frequency conversion device 10 or the converter section 221 in the terminal device 22.

[0035] <Transmission frequency arrangement for 1Lo and 2Lo conversion> Here, the transmission frequency arrangements for down-conversion performed by the converter unit 13 shown in Fig. 2 and the converter unit 13-4 of the third modified example shown in Fig. 6(b) are shown in Fig. 9. Note that the converter unit 13 shown in Fig. 2 performs down-conversion using two local oscillator signals (2Lo), while the converter unit 13-4 of the third modified example shown in Fig. 6(b) performs down-conversion using one local oscillator signal (1Lo). For example, consider the case of 2Lo frequency conversion by converter unit 13 shown in FIG. 2. Assume that channels BS8 and BS14 of the BS·110°CS left-handed IF signal are selected as target IF reception signals. The center frequency of channel BS8 of the target IF reception signal is 2356.74 MHz. The frequency spacing between BS channels is 38.3 MHz, the frequency spacing between 110°CS channels is 40 MHz, and the channel bandwidth is the same for BS and 110°CS, 34.5 MHz. Channel BS8 of the target IF reception signal is frequency-converted using a local oscillator signal f1 of 4449.74 MHz and down-converted to channel A with a center frequency of 2093 MHz. Channel BS14 of the target IF reception signal has a center frequency of 2471.82 MHz and is frequency-converted using a local oscillator signal f2 of 4603.18 MHz and down-converted to channel B with a center frequency of 2131.36 MHz. In this case, the frequency spacing between Ach and Bch is 38.36 MHz, and the frequency spacing between 110°CS right-hand circular polarization channel ND24 and Ach is 40 MHz. The upper limit of the down-converted bandwidth of Ach and Bch is 2148.61 MHz, and the down-converted bandwidth of Ach and Bch is within the 2150 MHz transmission bandwidth of community receiving facility line 30. Note that the bandwidths of Ach and Bch are down-converted so that they do not overlap.

[0036] Next, let us consider the case of 1Lo batch block conversion by converter unit 13-4 of the third modified example shown in FIG. 6(b). Assume that two adjacent channels, channel BS12 and channel BS14, of the BS·110°CS left-handed circularly rotated IF signal are selected as the target IF received signal. The center frequency of channel BS12 of the target IF received signal is set to 2433.46 MHz. Channels BS12 and BS14 of the target IF received signal are frequency-converted using a local oscillator signal f7 of 4564.82 MHz, with channel BS14 down-converted to channel A with a center frequency of 2093 MHz and channel BS12 down-converted to channel B with a center frequency of 2131.36 MHz. In this case, the frequency spacing between channels A and B is 38.36 MHz, and the frequency spacing between channel ND24 of the 110°CS right-handed circularly rotated IF signal and channel A is 40 MHz. The upper limit of the bandwidth of the down-converted Ach and Bch is 2148.61 MHz, and the bandwidth of the down-converted Ach and Bch is within the transmission bandwidth of the community receiving facility line 30, 2150 MHz.

[0037] As shown in Figure 9 above, when down-converting two-channel target IF received signals from BS left-hand circular polarization IF signals to Ach and Bch, Ach is arranged above ND24 at the same frequency interval (40 MHz) as CS, and Bch is arranged above Ach at the same frequency interval of 38.36 MHz as BS, making it possible to transmit two new channels within the 2150 MHz transmission band. Here, as shown in Figure 10(a), the frequency spacing Fw between BS channels is 38.3 MHz, and the frequency spacing Fw between 110°CS channels is 40 MHz, and the channel bandwidth is the same 34.5 MHz for both BS and 110°CS. Figure 10(b) shows a case where the target IF received signals for two channels are replaced with BS left-hand circular polarization IF signals and down-converted from 110° CS left-hand circular polarization IF signals to Ach and Bch. Figure 10(b) is an enlarged view of a portion of the example transmission frequency arrangement shown in Figure 9. When down-converting two-channel target IF received signals from 110°CS left-hand circular polarization IF signals to Ach and Bch, the upper frequency limit can be kept within 2150 MHz by setting the frequency spacing between Ach and ND24 to 38.36 MHz, the same as BS, and the frequency spacing between Ach and Bch to the same as CS frequency spacing (40 MHz), as shown in Figure 10(b). Furthermore, by setting the frequency spacing between Ach and Bch to 40 MHz, it becomes possible to simultaneously down-convert 110°CS left-hand circular polarization IF signals of two adjacent channels using 1Lo.

[0038] <Other transmission frequency arrangements for 1Lo and 2Lo conversion> Here, Figures 11(a) and 11(b) show transmission frequency arrangements of down-conversion performed by converter unit 13-2 of the first modified example shown in Figure 5 and converter unit 13-3 of the second modified example shown in Figure 6(a), and frequency arrangements of up-conversion performed by converter unit 221 of terminal device 22 shown in Figure 3 and converter unit 222 of the modified example shown in Figure 7. Note that converter unit 13-2 of the first modified example shown in Figure 5 performs down-conversion using two local oscillator signals (2Lo) and has a double conversion configuration, while converter unit 221 shown in Figure 3 performs up-conversion using two local oscillator signals (2Lo). Also, converter unit 13-3 of the second modified example shown in Figure 6(a) performs down-conversion using one local oscillator signal (1Lo) and has a double conversion configuration, while converter unit 222 of the modified example shown in Figure 7 performs up-conversion using one local oscillator signal (1Lo).

[0039] 11(a), the case of 2Lo downconversion in converter unit 13-2 of the first modified example shown in FIG. 5 will be described. Assume that channels BS8 and BS14 of the BS·110°CS left-handed circular polarization IF signal are selected as target IF reception signals. The center frequency of channel BS8 of the target IF reception signal is 2356.74 MHz. The frequency spacing between BS channels is 38.3 MHz, the frequency spacing between 110°CS channels is 40 MHz, and the channel bandwidth is the same 34.5 MHz for both BS and 110°CS. Channel BS8 of the target IF reception signal is frequency-converted using a local oscillator signal f3 (Lo1) of 2611.5 MHz to an intermediate frequency signal with a center frequency of 254.76 MHz. Furthermore, the center frequency of channel BS14 of the target IF reception signal is set to 2471.82 MHz, and is frequency-converted by a 2726.58 MHz local oscillator signal f5 (Lo2) to the same intermediate frequency signal with a center frequency of 254.76 MHz. Unwanted wave components are removed from channel BS8, which has been frequency-converted to an intermediate frequency signal, by SAW11, and unwanted wave components are removed from channel BS14, which has been frequency-converted to an intermediate frequency signal, by SAW12. The intermediate frequency signal of channel BS8 output from SAW11 is frequency-converted by a 2347.76 MHz local oscillator signal f4 (Lo1'), to Ach, which has a center frequency of 2093 MHz. Furthermore, the intermediate frequency signal of channel BS14 output from SAW12 is frequency-converted by a 2386.12 MHz local oscillator signal f6 (Lo2'), to Bch, which has a center frequency of 2131.36 MHz. As a result, in converter unit 13-2 of the first modified example, the frequencies of channels BS8 and BS14 selected from the BS·110°CS left-handed circular polarization IF signal are down-converted to the bands from 2071 MHz to 2150 MHz using 2Lo, respectively. Note that the bands of channels BS8 and BS14 are down-converted so as not to overlap.

[0040] Next, referring to FIG. 11(a), the case of up-conversion using two local oscillator signals (2Lo) performed in converter unit 221 shown in FIG. 3 will be explained. Channel BS8 down-converted to Ach with a center frequency of 2093 MHz is frequency-converted by local oscillator signal f10 (Lo1") with a center frequency of 263.7 MHz and up-converted to the frequency of the original channel BS8 with a center frequency of 2356.74 MHz. Also, channel BS14 down-converted to Bch with a center frequency of 2131.36 MHz is frequency-converted by local oscillator signal f11 (Lo2") with a center frequency of 340.46 MHz and up-converted to the frequency of the original channel BS14 with a center frequency of 2471.82 MHz. As a result, the target IF received signals of Ach and Bch are each up-converted by 2Lo to the band of the original BS·110°CS left-hand circular polarization IF signal.

[0041] 11(b), the case of 1Lo downconversion by converter unit 13-3 of the second modified example shown in FIG. 6(a) will be described. Assume that two adjacent channels, channel BS12 and channel BS14, of the BS·110°CS left-handed circular polarization IF signal are selected as target IF received signals. The two adjacent channels, channel BS12 and channel BS14, of the target IF received signal are frequency-converted using a 2726.58 MHz local oscillator signal f5(Lo2). Channel BS14 is frequency-converted to an intermediate frequency signal with a center frequency of 254.76 MHz, and channel BS12 is frequency-converted to an intermediate frequency signal with a center frequency of 293.12 MHz, 38.36 MHz higher than the 254.76 MHz intermediate frequency. Unwanted wave components are removed from channel BS14, which has been frequency-converted to an intermediate frequency signal, by SAW 11, and unwanted wave components are removed from channel BS12, which has been frequency-converted to an intermediate frequency signal, by SAW 13. The center frequency of the passband of SAW 13 is set to the center frequency of frequency-converted channel BS12. The intermediate frequency signal, which is a mixture of channels BS12 and BS14 output from SAW 11 and SAW 13, is frequency-converted by a local oscillator signal f6 (Lo2') of 2386.12 MHz, with channel BS12 being frequency-converted to Ach with a center frequency of 2093 MHz and channel BS14 being frequency-converted to Bch with a center frequency of 2131.36 MHz. As a result, in the converter unit 13-3 of the second variant, the frequencies of two adjacent channels BS12 and BS14 selected from the BS·110°CS left-hand circular polarization IF signal are downconverted in one go to the band from 2071 MHz to 2150 MHz using 1Lo.

[0042] Next, referring to FIG. 11(b), the case of upconversion using one local oscillator signal (1Lo) performed in converter unit 222 of the modified example shown in FIG. 7 will be described. Channel BS12 downconverted to Ach with a center frequency of 2093 MHz and channel BS14 downconverted to Bch with a center frequency of 2131.36 MHz are frequency converted by local oscillator signal f12(Lo2") of 340.46 MHz and upconverted to the frequency of the original channel BS12, and are also upconverted to the frequency of the original channel BS14 with a center frequency of 2471.82 MHz. As a result, the target IF received signals of Ach and Bch are upconverted collectively by 1Lo to the band of the original BS·110°CS left-hand circular polarization IF signal.

[0043] As described above, the frequency conversion transmission system 1 of the present invention takes advantage of the available band from 2071 MHz, the upper limit of the frequency band for 110° CS right-hand circularly rotated IF signals, to 2150 MHz, the upper limit of the frequency band that can be transmitted by the community receiving facility line 30, and transmits any two channels of BS left-hand circularly rotated IF signals and 110° CS left-hand circularly rotated IF signals in this band. Therefore, the frequency conversion transmission system 1 of the present invention makes it possible to transmit up to any two desired channels of BS left-hand circularly rotated IF signals and 110° CS left-hand circularly rotated IF signals without modifying the existing community receiving facility line 30.

[0044] <Second Example> The frequency conversion transmission system of the second embodiment of the present invention can transmit broadcast channels in BS / 110°CS left-hand circular polarization IF signals even if the upper limit frequency of the frequency band that can be transmitted on the common receiving facility line 30, which is the transmission path, is 2150 MHz. The configuration of the frequency conversion transmission system of the second embodiment of the present invention is not shown, but it is similar to the configuration of the frequency conversion transmission system 1 of the first embodiment of the present invention. However, frequency conversion device 10 is frequency conversion device 10', converter unit 13 is converter unit 13', terminal device 22 is terminal device 22', and converter unit 221 is converter unit 221'. The transmission frequency arrangement of the frequency conversion transmission system of the second embodiment of the present invention is shown in Figures 12(a), (b), and (c), and the frequency conversion transmission system of the second embodiment of the present invention will be described with reference to Figures 12(a), (b), and (c). Figure 12(a) shows the frequency arrangement of received signals input to frequency conversion device 10' in a frequency conversion transmission system according to a second embodiment of the present invention. In Figure 12(a), the CATV or UHF band refers to the band of UHF terrestrial digital signals received by UHF antenna 12 input to frequency conversion device 10' and the band of CATV signals input from CATV. The BS right-hand circular polarization, 110°CS right-hand circular polarization, BS left-hand circular polarization, and 110°CS left-hand circular polarization bands refer to the bands of BS right-hand circular polarization IF signals and 110°CS right-hand circular polarization IF signals, and BS left-hand circular polarization IF signals and 110°CS left-hand circular polarization IF signals received by BS / CS antenna 11 input to frequency conversion device 10'.

[0045] 12(b) shows a case where four arbitrary channels, Ach, Bch and Cch, Dch, are selected from the BS left-handed circularly rotated IF signal and the 110° CS left-handed circularly rotated IF signal as target IF received signals to be down-converted by converter unit 13' of frequency conversion device 10'. In this case, the target IF received signals of Ach and Bch are down-converted to a band from 2071 MHz, the upper limit of the frequency band of the 110° CS right-handed circularly rotated IF signal, to 2150 MHz, the upper limit of the frequency band transmittable by community receiving facility line 30, by using a configuration similar to that of converter unit 13 of frequency conversion device 10 described above. Furthermore, the target IF received signals of Cch and Dch are down-converted to fall within the guard band between the BS right-handed circularly rotated IF signal and the 110° CS right-handed circularly rotated IF signal by using a configuration in which the frequency of the local oscillator signal is changed in converter unit 13 of frequency conversion device 10 described above. This allows target IF received signals of any four channels Ach, Bch and Cch, Dch, selected from the BS left-hand circular polarization IF signal and the 110°CS left-hand circular polarization IF signal, to be transmitted over the community receiving facility line 30, which has an upper limit frequency of 2150 MHz in the transmittable frequency band. In this way, the frequency arrangement shown in Figure 12(b) is the frequency arrangement of the transmission signal transmitted from the frequency conversion device 10' of the frequency conversion transmission system of the second embodiment to the community receiving facility line 30, and this transmission signal is input to the terminal device 22'. As described above, the converter section 13' includes a converter section 13 that down-converts the target IF received signals of Ach and Bch, and a converter section 13 configured to change the frequency of the local oscillator signal.

[0046] Figure 12(c) shows a frequency arrangement illustrating upconversion in terminal device 22'. As shown in Figure 12(c), the target IF received signals of channels A and B, which have been downconverted to the upper limit of the frequency band of the CS right-hand circularly rotated IF signal, from 2071 MHz to 2150 MHz, and transmitted over the common receiving facility line 30, are upconverted to the frequencies of the original channels of the BS left-hand circularly rotated IF signal and the 110° CS left-hand circularly rotated IF signal, as shown in Figure 12(c), by converter unit 221' configured similarly to converter unit 221 of terminal device 22 described above. Furthermore, the target IF received signals of channels C and D, which have been downconverted to the guard band between the BS right-hand circularly rotated IF signal and the 110° CS right-hand circularly rotated IF signal and transmitted over the common receiving facility line 30, are upconverted to the frequencies of the original channels of the BS left-hand circularly rotated IF signal and the 110° CS left-hand circularly rotated IF signal, as shown in Figure 12(c), by converter unit 221' configured by changing the frequency of the local oscillator signal of converter unit 221 of terminal device 22 described above. As described above, the converter section 221' includes a converter section 221 that up-converts the target IF received signals of Ach and Bch, and a converter section 221 configured to change the frequency of the local oscillator signal. Figure 12(c) shows a case in which two channels, Ach and Bch, are selected from the BS left-handed circularly rotated IF signal and two channels, Cch and Dch, are selected from the 110°CS left-handed circularly rotated IF signal as target IF received signals to be down-converted in converter unit 13' of frequency conversion device 10', and converter unit 221' up-converts the four channels, Ach, Bch and Cch, and Dch, to the original channels of the BS left-handed circularly rotated IF signal and the 110°CS left-handed circularly rotated IF signal. [Industrial Applicability]

[0047] As described above, the frequency conversion transmission system according to an embodiment of the present invention enables transmission of a BS·110°CS left-handed circularly rotated IF signal by down-converting a desired channel of the BS·110°CS left-handed circularly rotated IF signal, even over a transmission path where the upper frequency limit for transmitting a BS·110°CS right-handed circularly rotated IF signal is 2150 MHz. In this case, one or two channels of the BS·110°CS right-handed circularly rotated IF signal are selected and down-converted to a frequency band ranging from 2071 MHz, the upper limit of the frequency band for the 110°CS right-handed circularly rotated IF signal, to 2150 MHz, the upper limit of the transmittable frequency band. This enables transmission of the BS·110°CS left-handed circularly rotated IF signal or 110°CS left-handed circularly rotated IF signal of the selected desired channel, allowing reception of the transmitted signal by a terminal device. Furthermore, by selecting one or two channels of the BS·110°CS right-hand circular polarization IF signal and down-converting them to the guard band between the BS right-hand circular polarization IF signal and the 110°CS right-hand circular polarization IF signal, it becomes possible to transmit BS left-hand circular polarization IF signals or 110°CS left-hand circular polarization IF signals of up to four desired channels, and the transmitted BS·110°CS left-hand circular polarization IF signals can be received by the terminal device. In this way, in the frequency conversion transmission system of an embodiment of the present invention, the BS·110°CS left-hand circular polarization IF signal, which exceeds the upper limit of the transmittable frequency on a transmission path up to 2150 MHz, which is the maximum frequency that can be transmitted for BS·110°CS right-hand circular polarization IF signals in satellite broadcasting, is down-converted to a frequency band of 2071 MHz to 2150 MHz, which is the upper limit of the frequency band for 110°CS right-hand circular polarization IF signals that can be transmitted on that transmission path, and sent out to the transmission path, and the frequency of the down-converted BS·110°CS left-hand circular polarization IF signal transmitted from the transmission path is up-converted to return it to the original frequency. Furthermore, in the frequency conversion transmission system according to the embodiment of the present invention, the BS·110°CS left-hand circular polarization IF signal is down-converted to the guard band between the BS right-hand circular polarization IF signal and the 110°CS right-hand circular polarization IF signal and sent to the transmission path, and the frequency of the down-converted BS·110°CS left-hand circular polarization IF signal transmitted from the transmission path is up-converted back to the original frequency. In the embodiment of the present invention, a SAW (surface acoustic wave filter) is used as a filter to extract channels, but this is not limited to this and any filter that can extract channels may be used, for example a digital filter. [Explanation of symbols]

[0048] 1 frequency conversion transmission system, 3 converter section, 10 frequency conversion device, 11 BS / CS antenna, 12 UHF antenna, 13 converter section, 20 apartment building, 21 wall terminal, 22 terminal device, 30 shared receiving equipment line, 40 converter section, 41 ADC, 42 filter processing / converter processing section, 43 DA, 221 converter section, 222 converter section

Claims

1. A frequency conversion transmission system comprising: a frequency conversion device that uses a downconverter to downconvert at least one channel of a target IF reception signal from among a BS left-hand circular polarization IF signal or a CS left-hand circular polarization IF signal, which is a satellite broadcast intermediate frequency signal exceeding the upper limit of the transmittable frequency band of a transmission line, to a frequency within the transmittable frequency band that is lower than the original frequency, and transmits the target IF reception signal downconverted by the downconverter and other broadcast signals to a transmission line; and a terminal device including an upconverter that returns the downconverted target IF reception signal transmitted over the transmission line to the frequency of the original target IF reception signal, A frequency conversion transmission system characterized in that the downconverter downconverts the target IF received signal of at least one channel to a band exceeding the frequency band of the CS right-hand circular polarization IF signal up to the upper limit of the transmittable frequency band, and the upconverter upconverts the downconverted target IF received signal to a target IF received signal of the original frequency.

2. A frequency conversion transmission system comprising: a frequency conversion device that uses a downconverter to downconvert two channels of target IF reception signals, either BS left-hand circular polarization IF signals or CS left-hand circular polarization IF signals, which are satellite broadcast intermediate frequency signals that exceed the upper limit of the transmittable frequency band of a transmission line, to frequencies within the transmittable frequency band that are lower than the original frequencies, and transmits the target IF reception signals downconverted by the downconverter and other broadcast signals to a transmission line; and a terminal device including an upconverter that returns the downconverted target IF reception signals transmitted over the transmission line to the frequency of the original target IF reception signals, A frequency conversion transmission system characterized in that the downconverter downconverts the two-channel target IF reception signals to a band exceeding the frequency band of the CS right-hand circular polarization IF signal up to the upper limit of the transmittable frequency band, and the upconverter upconverts the downconverted two-channel target IF reception signals to target IF reception signals of the original frequency.

3. 3. The frequency conversion transmission system according to claim 2, wherein two adjacent channels are used as target IF reception signals for the two channels, and the downconverter and the upconverter perform frequency conversion on the target IF reception signals for the two channels collectively, the downconverter downconverts the target IF reception signals for the two channels using a single local oscillator signal to a band that exceeds the frequency band of a CS right-hand circular polarization IF signal and is up to the upper limit of the transmittable frequency band, and the upconverter upconverts the downconverted target IF reception signals for the two channels to adjacent target IF reception signals of the original frequency using a single local oscillator signal.

4. 4. The frequency conversion transmission system according to claim 3, wherein the downconverter is configured to perform frequency conversion by double conversion, wherein the two-channel target IF reception signals are frequency converted by a first local oscillator signal in the downconverter, and the frequency-converted two-channel target IF reception signals are extracted by two surface acoustic wave filters, each of which has as its passband the bands of the frequency-converted two-channel target IF reception signals, and the two-channel target IF reception signals extracted by the two surface acoustic wave filters are frequency converted by a second local oscillator signal to a band exceeding the frequency band of a CS right-hand circular polarization IF signal and up to an upper limit of the transmittable frequency band.

5. 3. The frequency conversion transmission system according to claim 2, wherein any two channels are selected as target IF reception signals for the two channels, the downconverter uses a local oscillator signal prepared for each channel to downconvert the target IF reception signals for the two channels to a band exceeding the frequency band of the CS right-hand circular polarization IF signal and up to the upper limit of the transmittable frequency band, and the upconverter uses a local oscillator signal prepared for each channel to upconvert the downconverted target IF reception signals for the any two channels to target IF reception signals of the original frequency.

6. 6. The frequency conversion transmission system according to claim 5, wherein the downconverter uses a first converter and a second converter arranged in parallel to perform frequency conversion of each channel of the target IF reception signals of the two channels, the first converter and the second converter frequency convert the target IF reception signals of any two channels so that they have the same frequency, the first converter and the second converter extract the frequency-converted target IF reception signals of any two channels using surface acoustic wave filters having the same passband in the first converter and the second converter, and the first converter and the second converter frequency convert the extracted target IF reception signals of any two channels to a band exceeding the frequency band of a CS right-hand circular polarization IF signal up to the upper limit of the transmittable frequency band so that the target IF reception signals of the any two channels do not overlap.

7. 7. The frequency conversion transmission system according to claim 6, wherein the first converter and the second converter are configured to perform double frequency conversion, wherein in the first converter, one channel of the two-channel target IF reception signals is frequency converted by a third local oscillator signal, the target IF reception signal of the frequency-converted channel is extracted by a surface acoustic wave filter having a passband equal to the band of the target IF reception signal of the frequency-converted channel, and the target IF reception signal of the channel extracted by the surface acoustic wave filter is frequency converted by a fourth local oscillator signal to a band exceeding the frequency band of the CS right-hand circular polarization IF signal and up to an upper limit of the transmittable frequency band, and wherein in the second converter, the other channel of the two-channel target IF reception signals is frequency converted by a fifth local oscillator signal, the target IF reception signal of the frequency-converted channel is extracted by a surface acoustic wave filter having a passband equal to the band of the target IF reception signal of the frequency-converted channel, and the target IF reception signal of the channel extracted by the surface acoustic wave filter is frequency converted by a sixth local oscillator signal to a band exceeding the frequency band of the CS right-hand circular polarization IF signal and up to an upper limit of the transmittable frequency band.

8. A frequency conversion transmission system comprising: a frequency conversion device that uses a downconverter to frequency convert target IF reception signals of up to four channels of BS left-hand circular polarization IF signals or CS left-hand circular polarization IF signals, which are satellite broadcast intermediate frequency signals that exceed the upper limit of the transmittable frequency band of a transmission line, to a frequency within the transmittable frequency band that is lower than the original frequency, and transmits the target IF reception signals downconverted by the downconverter and other broadcast signals to a transmission line; and a terminal device that includes at least an upconverter that returns the frequency-converted target IF reception signals transmitted over the transmission line to the frequency of the original target IF reception signals, the downconverter downconverts the target IF reception signal within two channels to a band exceeding the frequency band of the CS right-hand circular polarization IF signal up to an upper limit of the transmittable frequency band, and downconverts the target IF reception signal within two channels to a band within a guard band between the BS right-hand circular polarization IF signal and the CS right-hand circular polarization IF signal; The upconverter upconverts target IF received signals within two channels that have been downconverted to a band exceeding the frequency band of the CS right-hand circular polarization IF signal up to the upper limit of the transmittable frequency band, to target IF received signals of the original frequency, and also upconverts target IF received signals within two channels that have been downconverted to a guard band between the BS right-hand circular polarization IF signal and the CS right-hand circular polarization IF signal, to target IF received signals of the original frequency.

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