Frequency conversion device for receiving satellite broadcasts and power measurement system

Abstract

To provide a frequency converter for satellite broadcast reception, and a power measurement system provided with the frequency converter, for performing frequency conversion for a satellite broadcasting signal obtained through a satellite broadcast reception antenna.SOLUTION: A frequency converter 1 for satellite broadcast reception according to the invention includes: an interference wave reception antenna 11 having receiving gain in a predetermined image frequency band; channel under interference selection means (an interference wave detection part 12 and a frequency determination part 13 / 13a) for identifying a channel under interference in a satellite broadcasting signal from a reception signal obtained through the interference wave reception antenna 11; frequency conversion means for channel under interference (a second frequency conversion part 17 and a bandpass filter 18) for generating a second intermediate frequency signal regarding the channel under interference by performing frequency conversion for the signal of the channel under interference; and output means (a mixer 21 or the like) for transmitting a signal based on the second intermediate frequency signal regarding the channel under interference to a predetermined home distribution system with one coaxial cable.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a frequency conversion device that performs frequency conversion on a satellite broadcast signal obtained via a satellite broadcast receiving antenna, and to a power measurement system that includes the frequency conversion device. [Background technology]

[0002] Current satellite broadcasting uses radio waves in the 12 GHz band, and after receiving the 12 GHz satellite broadcast signal via a satellite broadcast receiving antenna, it is sent to a home distribution system via coaxial cable and transmitted to the receiver. In order to do this, the broadcast frequency of the satellite broadcast signal is converted to the intermediate frequency (IF) band by an LNB (Low Noise Block Converter) in the satellite broadcast receiving antenna. Such an LNB is also called a frequency conversion device.

[0003] In addition, satellite broadcasting transmitted from a geostationary orbit at 110 degrees east longitude currently includes BS digital broadcasting (hereinafter abbreviated as "BS") and broadband CS digital broadcasting (hereinafter abbreviated as "CS"), both of which use right-hand circular polarization and left-hand circular polarization.

[0004] Furthermore, since right-handed and left-handed circularly polarized waves can be used interchangeably, by using right-handed and left-handed circularly polarized waves, it is possible to transmit satellite broadcast waves of different channels on the same frequency, thereby enabling effective use of frequencies.

[0005] Therefore, the left-handed circular polarization IF frequencies of BS and CS are specified in ARIB STD-B63 (see, for example, Non-Patent Document 1). ARIB STD-B63 also cites examples of frequency conversion devices that convert the right-handed circular polarization IF frequency to 1032.23 MHz to 2070.25 MHz and the left-handed circular polarization IF frequency to 2224.41 MHz to 3223.25 MHz.

[0006] Figure 9(a) shows the frequency allocation of right-handed circularly polarized waves (right-handed) and left-handed circularly polarized waves (left-handed) as broadcast frequencies for satellite broadcast signals in the 12 GHz band satellite broadcast service (BS / CS). (BS right-handed circularly polarized waves are odd-numbered channels 1 to 23, BS left-handed circularly polarized waves are even-numbered channels 2 to 24, CS right-handed circularly polarized waves are even-numbered channels 2 to 26, and CS left-handed circularly polarized waves are odd-numbered channels 1 to 25. That is, the right-handed circularly polarized waves for BS / CS are 11.71023 GHz to 12.74825 GHz, and the left-handed circularly polarized waves for BS / CS are 11.72941 GHz to 12.72825 GHz. Hereinafter, when generalizing without distinguishing between right-handed and left-handed circularly polarized waves, the broadcast frequency band for satellite broadcast signals will be described as 11.7 GHz to 12.75 GHz for convenience.

[0007] Also, Figure 9(b) shows the IF band converted from the broadcast frequency of the satellite broadcast signal as the LNB output that is considered desirable in ARIB STD-B63 (Non-Patent Document 1). As shown in Figure 9(b), it is considered desirable for the LNB output to convert the broadcast frequency of the satellite broadcast signal to the IF band using a local oscillator frequency (LO) of 10.678 GHz for receiving right-handed circularly polarized waves (right-handed) and an LO of 9.505 GHz for receiving left-handed circularly polarized waves (left-handed). In other words, the IF band for right-handed circularly polarized waves of BS and CS is 1032.23 MHz to 2070.25 MHz, and the IF band for left-handed circularly polarized waves of BS and CS is 2224.41 MHz to 3223.25 MHz.

[0008] That is, in frequency conversion in such an LNB for receiving satellite broadcasts, the difference between the LO and the broadcast frequency band of the input satellite broadcast signal becomes the output IF band.

[0009] Incidentally, the 9 GHz band, which is the image band of right-hand circularly polarized waves, is mainly allocated to radar frequencies. Measurements of the reception characteristics of commercially available general satellite broadcast receiving antennas have reported that radio frequency (RF) signals from radars around 9 GHz cause interference with satellite broadcast reception and appear in the LNB output (see, for example, Non-Patent Document 2).

[0010] In other words, the frequency conversion in the LNB also converts interference waves around 9 GHz in the case of right-hand circular polarization (note that interference waves exist around 7 GHz in the case of left-hand circular polarization). In particular, because radar has a high equivalent isotropic radiated power (EIRP), interference waves around 9 GHz can degrade the quality of BS / CS satellite broadcast reception. For this reason, interference signals based on the interference waves around 9 GHz can be mixed into the right-hand circular polarization IF signal in satellite broadcast reception, appearing as image interference.

[0011] Figure 10 shows the frequency relationship of right-hand circular polarization image interference in 12GHz-band satellite broadcasting. The upper part of Figure 10 shows the frequency relationship between the 11.7GHz to 12.75GHz BS / CS right-hand circular polarization broadcasting frequency band for 12GHz-band satellite broadcasting, which is input to the LNB, the 10.678GHz local oscillator (LO) frequency used for right-hand circular polarization reception, and the right-hand circular polarization interference wave around 9GHz. The lower part of Figure 10 shows how the right-hand circular polarization interference wave around 9GHz is similarly frequency converted to the intermediate frequency band of 1.03223GHz to 2.07025GHz (hereinafter referred to as "BS / CS right-hand circular polarization IF") output by frequency conversion (block conversion) in the LNB, causing image interference as an interference wave signal.

[0012] To reduce the effects of such image interference, Chapter 12 of ARIB STD-B63 specifies an image interference suppression ratio of 55 dB (see, for example, Non-Patent Document 1). A conventional technique involves using a filter to suppress the image band itself before frequency conversion in the LNB. In this case, since the image band that affects right-hand circular polarization satellite broadcast signals is the 9 GHz band, the filter must pass the 12 GHz band without degradation and sufficiently suppress the 9 GHz band. LNBs for satellite broadcast receiving antennas currently on the market are already equipped with such filters and achieve the ARIB STD-B63 standard of an image interference suppression ratio of 55 dB.

[0013] However, interference waves around 9 GHz that affect right-hand circular polarization satellite broadcast signals are not sufficiently far from the 12 GHz satellite broadcast band, and there is a possibility that the image interference suppression ratio (55 dB) will degrade the received satellite broadcast signal.However, interference waves around 7 GHz that are left-hand circular polarization are sufficiently far from the 12 GHz satellite broadcast band (11.7 GHz to 12.75 GHz), even after frequency conversion by the LNB, and actual measurements have confirmed that a high image interference suppression ratio is achieved.

[0014] Incidentally, as a conventional frequency conversion device intended for receiving satellite broadcasts, a device has been disclosed that converts two IF bands (low-frequency IF and high-frequency IF) into a frequency that overlaps with the low-frequency IF by multiple frequency conversions in order to avoid interference with the high-frequency IF (see, for example, Patent Document 1).

[0015] Also disclosed is a frequency conversion device that splits a received BS left-hand circularly polarized signal, converts the frequency using a variable local oscillation frequency, and places the BS left-hand circularly polarized IF in a frequency band not used in terrestrial digital television broadcasting (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0016] [Patent Document 1] Patent No. 6242186 [Patent Document 2] Patent No. 6257191 [Non-patent literature]

[0017] [Non-Patent Document 1] “Advanced Wideband Satellite Digital Broadcasting Receiver (Desired Specifications) Standard ARIB STD-B63 Version 1.9,” [online], revised December 5, 2019, [retrieved June 28, 2022], Internet〈URL: https: / / www.arib.or.jp / kikaku / kikaku_hoso / std-b63.html〉 [Non-patent document 2] Y. Mizuki et al., "Measurement of Antenna Radiation Patterns of Commercially Available BS Antennas in the 9 GHz Band," Institute of Electronics, Information and Communication Engineers, IEICE Techniques, vol. 121, no. 128, SAT2021-23, pp. 18-23, published July 21, 2021. Summary of the Invention [Problem to be solved by the invention]

[0018] As mentioned above, the 9 GHz band, which is the image band that affects right-hand circular polarization satellite broadcast signals, is mainly allocated to radar. Since radar generally has a large output power and generates strong interference waves, the image interference suppression ratio (55 dB) specified for frequency conversion devices in ARIB STD-B63 may cause degradation of received satellite broadcast signals.

[0019] As mentioned above, it is also possible to use a large filter to suppress the image band itself before frequency conversion by the LNB of currently available satellite broadcast receiving antennas. However, this method is not desirable because it leads to signal degradation due to increased insertion loss in the 12 GHz band, as well as increased size and cost of the satellite broadcast receiving antenna.

[0020] The frequency converter disclosed in Patent Document 1 converts a high-frequency IF into a frequency that overlaps with a low-frequency IF by multiple frequency conversions, which makes it possible to avoid interference in the IF band (such as from 2.4 GHz wireless LAN), but it cannot avoid the image interference that occurs when receiving 12 GHz satellite broadcasts. Furthermore, the frequency converter disclosed in Patent Document 1 requires two coaxial cables because it has two signal outputs, and therefore cannot transmit signals in the home using a single coaxial cable, which is common in existing home distribution systems, posing a problem in terms of versatility.

[0021] Furthermore, the frequency conversion device disclosed in Patent Document 2 converts frequencies using a variable local oscillation frequency and places the BS left-hand circular polarization IF in a frequency band not used by terrestrial digital television broadcasting.Since the right-hand circular polarization has the same configuration as the frequency conversion device of ARIB STD-B63, there is a possibility that the received satellite broadcast signal will be degraded due to image interference caused by the interference wave in the 9 GHz band mentioned above.

[0022] SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a frequency conversion device for receiving satellite broadcasts that reduces the effects of image interference, and a power measurement system that includes the frequency conversion device. [Means for solving the problem]

[0023] The frequency converter of the present invention is a frequency converter for satellite broadcast reception that performs frequency conversion on satellite broadcast signals obtained via a satellite broadcast receiving antenna, and includes an interference wave receiving antenna having a reception gain in an image band of a predetermined target polarized wave that causes image interference in satellite broadcast reception, and a band-pass filter that extracts a signal in the image band from the received signal obtained via the interference wave receiving antenna as an interference wave detection signal, selects an interfered channel in satellite broadcast reception based on the interference wave detection signal having signal power equal to or greater than a predetermined threshold, and selects a signal of the interfered channel of the target polarized wave in the satellite broadcast signal within a predetermined empty band of an intermediate frequency band other than an intermediate frequency using a first local oscillation frequency specified in the standard. the second local oscillation frequency of the interfered channel is converted to a predetermined intermediate frequency of the interfered channel; the interfered channel frequency converting means converts the frequency of the interfered channel signal of the target polarization in the satellite broadcast signal using the second local oscillation frequency signal to generate a second intermediate frequency signal for the interfered channel; and the output means converts the second intermediate frequency signal for the interfered channel directly or after further frequency conversion to a predetermined new available band in another intermediate frequency band, or after further frequency conversion to replace the intermediate frequency signal using the first local oscillation frequency of the interfered channel, and transmits the converted signal to a predetermined in-home distribution system via a single coaxial cable.

[0024] In addition, in the frequency conversion device of the present invention, the output means is configured to mix the second intermediate frequency signal related to the interfered channel with intermediate frequency signals defined in the standards of the interfered channel and other channels as they are, and output the mixed signal so that it can be sent over a single coaxial cable.

[0025] In addition, in the frequency conversion device of the present invention, the satellite broadcast signal includes at least a signal of each channel of right-handed circular polarization in 12 GHz band satellite broadcasting, and the center frequency of the second intermediate frequency signal for the interfered channel is located between the intermediate frequency band of right-handed circular polarization and the intermediate frequency band of left-handed circular polarization in 12 GHz band satellite broadcasting.

[0026] Furthermore, in the frequency conversion device of the present invention, the output means is configured to generate a new second intermediate frequency signal for the interfered channel by frequency converting the second intermediate frequency signal for the interfered channel to a predetermined new available band in an intermediate frequency band other than the intermediate frequency defined in the standard, mix it with the intermediate frequency signals defined in the standard for the interfered channel and other channels, and output it so as to be transmittable over a single coaxial cable.

[0027] In addition, in the frequency conversion device of the present invention, the satellite broadcast signal includes at least a signal of each channel of right-handed circular polarization in 12 GHz band satellite broadcast, and the center frequency of the new second intermediate frequency signal for the interfered channel is located in an empty band within the intermediate frequency band of right-handed circular polarization.

[0028] In addition, in the frequency conversion device of the present invention, the output means is configured to further frequency convert the second intermediate frequency signal for the interfered channel to the band of the intermediate frequency signal of the interfered channel that uses the first local oscillation frequency defined in the standard to generate a third intermediate frequency signal for the interfered channel, replace the intermediate frequency signal of the interfered channel that uses the first local oscillation frequency with the third intermediate frequency signal for the interfered channel, mix it with intermediate frequency signals defined in the standard for channels other than the interfered channel, and output it so as to be transmittable over a single coaxial cable.

[0029] In addition, in the frequency conversion device of the present invention, the satellite broadcast signal includes at least the right-hand circularly polarized signal of each channel in 12 GHz band satellite broadcasting, and the target polarization for the image band is configured to target only right-hand circularly polarized waves in 12 GHz band satellite broadcasting.

[0030] Furthermore, a power measurement system according to the present invention is characterized by comprising the frequency conversion device according to the present invention and a power meter that measures the received power of the intermediate frequency signal of each channel obtained from the output of the frequency conversion device. [Effects of the Invention]

[0031] According to the present invention, satellite broadcast signals can be received without degradation even in the presence of strong interference waves that would cause signal degradation at the image interference suppression ratio stipulated in the standard, and this makes it easier to share the signal with other devices that use the image band (such as radar equipment that was causing image interference).

[0032] Furthermore, according to the present invention, intermediate frequency signals that avoid the effects of image interference on received satellite broadcast signals can be transmitted to receivers through an existing home distribution system using a single coaxial cable, and the output frequency of the frequency converter according to the present invention is included in the intermediate frequency band (1032 to 3224 MHz) specified in the standard (ARIB STD-B63), making it highly versatile. In other words, there is no need to modify the existing home distribution system, and it is only necessary to replace the frequency converter in the satellite broadcast receiving antenna, thereby solving the problem of image interference at low cost. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a block diagram showing a schematic configuration of a frequency conversion device for receiving satellite broadcasting according to a first embodiment of the present invention. [Figure 2] 1 is a diagram showing the relationship between right-hand circularly polarized frequencies in 12 GHz-band satellite broadcasting in relation to frequency conversion by the frequency conversion device for receiving satellite broadcasting of the first embodiment according to the present invention; [Figure 3] FIG. 10 is a block diagram showing a schematic configuration of a frequency conversion device for receiving satellite broadcasting according to a second embodiment of the present invention. [Figure 4] 10 is a diagram showing the relationship between right-hand circularly polarized frequencies in 12 GHz-band satellite broadcasting in relation to frequency conversion by a frequency conversion device for receiving satellite broadcasting according to a second embodiment of the present invention. FIG. [Figure 5] 10 is a diagram showing how intermediate frequency signals frequency-converted for an interfered channel are rearranged by frequency conversion in a down converter in a frequency conversion device for receiving satellite broadcasting according to a second embodiment of the present invention. FIG. [Figure 6] FIG. 10 is a block diagram showing a schematic configuration of a frequency conversion device for receiving satellite broadcasting according to a third embodiment of the present invention. [Figure 7] 11 is a diagram showing the relationship between right-hand circularly polarized frequencies in 12 GHz band satellite broadcasting in relation to frequency conversion by a frequency conversion device for receiving satellite broadcasting according to a third embodiment of the present invention. FIG. [Figure 8] 10 is a diagram showing how intermediate frequency signals frequency-converted for an interfered channel are rearranged by frequency conversion in a down converter in a frequency conversion device for receiving satellite broadcasting according to a third embodiment of the present invention. FIG. [Figure 9] (a) is a diagram showing the frequency allocation of the broadcasting frequencies of satellite broadcasting signals in the 12 GHz band satellite broadcasting service (BS / CS), and (b) is a diagram showing the intermediate frequency (IF) band converted from the broadcasting frequencies of satellite broadcasting signals as the LNB output considered desirable in ARIB STD-B63. [Figure 10] FIG. 1 is a diagram showing the frequency relationship of right-hand circular polarization image interference in 12 GHz band satellite broadcasting. DETAILED DESCRIPTION OF THE INVENTION

[0034] [Frequency conversion device for receiving satellite broadcasts] First, the frequency converter 1 for satellite broadcast reception according to the present invention is configured to perform frequency conversion on satellite broadcast signals received via a satellite broadcast receiving antenna 10. To reduce the effects of image interference, the frequency converter 1 identifies the interfered channel in the satellite broadcast signal by detecting interference waves in the image band of a predetermined target polarized wave that causes image interference in satellite broadcast reception via a separately provided interference wave receiving antenna 11. The frequency converter 1 according to the present invention then performs frequency conversion on the signal of the interfered channel of the target polarized wave in the satellite broadcast signal received via the satellite broadcast receiving antenna 10 using a second local oscillation frequency (LO2) that is relocated to a predetermined vacant band in the intermediate frequency band, different from the intermediate frequency using the first local oscillation frequency (LO1) specified in the standard, to generate a second intermediate frequency signal (fc2) for the interfered channel. The frequency conversion device 1 according to the present invention is configured to have an output means for transmitting the second intermediate frequency signal (fc2) relating to the interfered channel to a predetermined in-home distribution system via a single coaxial cable either directly or after frequency conversion to a predetermined new available band in another intermediate frequency band, or after further frequency conversion to replace the intermediate frequency signal of the interfered channel.

[0035] For example, in Example 1 described later, the output means in the frequency conversion device 1 according to the present invention is configured to mix the second intermediate frequency signal (fc2) relating to the interfered channel with intermediate frequency signals defined in the standard specifications of the interfered channel and other channels as they are, and output the result in a manner that allows it to be transmitted over a single coaxial cable.

[0036] Alternatively, in a second embodiment described later, the output means in the frequency conversion device 1 according to the present invention is configured to generate a new second intermediate frequency signal (fc2') for the interfered channel by frequency converting the second intermediate frequency signal (fc2) for the interfered channel into a predetermined new available band in an intermediate frequency band that is different from the intermediate frequency defined in the standard, mix it with the intermediate frequency signals defined in the standard for the interfered channel and other channels, and output it so that it can be sent over a single coaxial cable.

[0037] Alternatively, in a third embodiment described later, the output means of the frequency conversion device 1 according to the present invention is configured to further frequency convert the second intermediate frequency signal (fc2) for the interfered channel into the band of the intermediate frequency signal of the interfered channel that uses the first local oscillation frequency (LO1) defined in the standard to generate a third intermediate frequency signal (fc3) for the interfered channel, replace the intermediate frequency signal of the interfered channel that uses the first local oscillation frequency with the third intermediate frequency signal (fc3) for the interfered channel, mix it with an intermediate frequency signal defined in the standard for another channel other than the interfered channel, and output it so that it can be sent over a single coaxial cable.

[0038] In each embodiment described below, the frequencies of the second intermediate frequency signal (fc2), the new second intermediate frequency signal (fc2'), and the third intermediate frequency signal (fc3) related to this interfered channel are included in the intermediate frequency band (1032 to 3224 MHz) defined in the standard (ARIB STD-B63), as are the intermediate frequencies of other channels.

[0039] In particular, the frequency converter 1 for receiving satellite broadcasts according to the present invention detects interference waves that cause image interference in right-handed circularly polarized satellite broadcast reception via the interference wave receiving antenna 11, identifies the interfered channel of right-handed circularly polarized waves, and determines the center frequency of the interfered channel in the satellite broadcast signal that is subject to the image interference through frequency analysis.The frequency converter 1 according to the present invention then derives a second local oscillation frequency (LO2) from the determined center frequency for allocating the interfered channel in the satellite broadcast signal to a predetermined vacant band in the intermediate frequency band, and performs frequency conversion of the interfered channel using a local oscillator (second frequency converter 17, described later) that is variably set based on this local oscillation frequency (LO2), thereby generating the second intermediate frequency signal (fc2).

[0040] Hereinafter, preferred embodiments of the frequency converter 1 for receiving satellite broadcasts according to the present invention will be described in detail with reference to the drawings.

[0041] Example 1 FIG. 1 is a block diagram showing a schematic configuration of a frequency converter 1 for receiving satellite broadcasts according to a first embodiment of the present invention.

[0042] The frequency conversion device 1 of the first embodiment shown in FIG. 1 has the function of inputting the received signals of each channel of right-handed circular polarization (right-handed) and left-handed circular polarization (left-handed) after polarization separation by the polarization separation unit 10a for a 12 GHz band satellite broadcast signal received via the satellite broadcast receiving antenna 10, and performing frequency conversion to an intermediate frequency band defined by the standard to generate intermediate frequency signals for each channel for each polarization.

[0043] Current 12 GHz band satellite broadcasting (BS / CS) uses right-handed circularly polarized waves (right-handed) and left-handed circularly polarized waves (left-handed), and the frequency for satellite broadcasting is 11.7 to 12.75 GHz (12 GHz band). The frequency converter 1 of the first embodiment receives right-handed and left-handed 12 GHz band received signals as input. Since the coaxial cable used to output the frequency converter 1 for satellite broadcasting cannot transmit 12 GHz band signals, the frequency converter 1 of the first embodiment performs frequency conversion on the input right-handed and left-handed 12 GHz band received signals, converting them into signals in the intermediate frequency (IF) band of 1.0 GHz to 3.2 GHz specified in the standard ARIB STD-B63, and outputs the converted signals. The IF frequency for 12 GHz band satellite broadcasting is specified in ARIB STD-B63, and the local oscillation frequency (LO) used for frequency conversion is 10.678 GHz for right-handed and 9.505 GHz for left-handed.

[0044] However, the frequency converter 1 of the first embodiment detects signals in the image band of a predetermined target polarization (i.e., the 9 GHz band for right-hand circular polarization reception in this example) that cause image interference in satellite broadcast reception via the interference wave receiving antenna 11, and identifies the interfered channel in the satellite broadcast reception. Then, for the interfered channel in the satellite broadcast signal, the frequency converter 1 of the first embodiment separately generates a second intermediate frequency signal (fc2) by frequency conversion to a predetermined empty band (2.071 GHz to 2.224 GHz) between the right-hand circular polarization intermediate frequency band and the left-hand circular polarization intermediate frequency band (between the CS right-hand circular polarization IF and the BS left-hand circular polarization IF shown in FIG. 9), mixes the second intermediate frequency signal with the intermediate frequency signal of each channel for each polarization, and outputs the mixed signal to an external device. The output signal mixed and generated by the frequency converter 1 is configured to be transmitted to a home distribution system, which transmits the mixed signal to a receiver (not shown), using a single coaxial cable.

[0045] More specifically, the frequency conversion device 1 of Example 1 shown in Figure 1 includes an interference wave receiving antenna 11, an interference wave detection unit 12, a frequency determination unit 13, a distributor 14, a first frequency conversion unit 15, a low-pass filter 16, a second frequency conversion unit 17, a band-pass filter 18, a third frequency conversion unit 19, a high-pass filter 20, and a mixer 21.

[0046] First, in the frequency converter 1 of the first embodiment, received signals of each channel are received as right-handed circularly polarized waves and left-handed circularly polarized waves after polarization separation by a polarization separator 10a for 12 GHz band satellite broadcast signals received via a satellite broadcast receiving antenna 10, and are input to a distributor 14. The satellite broadcast receiving antenna 10 is an antenna capable of receiving 12 GHz band satellite broadcasts, and in this example, a parabolic antenna capable of receiving both right-handed and left-handed satellite broadcasts in the 12 GHz band is exemplified. Furthermore, the satellite broadcast receiving antenna 10 and the polarization separator 10a may be configured as an integrated antenna device, or may be configured as separate entities.

[0047] The distributor 14 receives the received signals of each channel (11.7 GHz to 12.75 GHz) of right-handed circularly polarized waves in the 12 GHz band satellite broadcast signal that has been polarization-separated by the polarization separator 10a, and distributes and outputs the signals to the first frequency converter 15 and the second frequency converter 17.

[0048] The first frequency conversion unit 15 performs frequency conversion on the received signals of each channel of right-hand circularly polarized waves in the 12 GHz band satellite broadcast signal input from the distributor 14 using a signal of the first local oscillation frequency (LO1 = 10.678 GHz) for right-hand rotation according to the standard, and generates a signal in the right-hand intermediate frequency (IF) band of 1.03223 GHz to 2.07025 GHz, which is output to the low-pass filter 16.

[0049] The low-pass filter 16 performs low-pass filtering on the right-hand circular polarization IF band signal input from the first frequency converter 15 to remove unnecessary high-frequency waves and noise components, and outputs the result to the mixer 21.

[0050] Interference wave receiving antenna 11 has a receiving gain corresponding to signals in the image band of a predetermined target polarized wave that causes image interference in satellite broadcast reception (i.e., the 9 GHz band associated with right-hand circularly polarized wave reception in this example), and outputs the received signal to interference wave detection unit 12. In this example, interference wave receiving antenna 11 may be any antenna that has a receiving gain in the 9 GHz band, which corresponds to the image band of the predetermined right-hand circularly polarized wave, and can be realized by a horn antenna, microstrip antenna, or the like.

[0051] The interference wave detection unit 12 uses a bandpass filter to extract a signal in the 9 GHz band, which corresponds to the image band, from the received signal obtained via the interference wave receiving antenna 11 as an interference wave detection signal, and measures the signal power of the interference wave detection signal. If the interference wave detection signal obtained as a measurement result has signal power equal to or greater than a predetermined threshold, the interference wave detection unit 12 detects the presence of an interference wave (in this example, radio waves in the 9 GHz band radiated by a radar). The interference wave detection unit 12 then performs frequency analysis of the interference wave detection signal and outputs the obtained frequency (fi) in the 9 GHz band to the frequency determination unit 13. This interference wave detection unit 12 has the same function as a so-called spectrum analyzer, but can be made smaller because the measurement frequency is limited to the 9 GHz band.

[0052] However, since only the 9 GHz band corresponds to the image band at present, only this 9 GHz band will be described as the image band, but in order to be able to deal with other image bands that may arise in the future, it is preferable that the interference wave receiving antenna 11 be an antenna having reception sensitivity for the 8 GHz to 9 GHz bands, and that the interference wave detecting unit 12 be configured to have a variable band pass filter that is externally set to specify the image band to be extracted as an interference wave detection signal.

[0053] The frequency determination unit 13 stores a list of information on the first local oscillation frequency (i.e., LO1 for right-hand circular polarization) used for receiving satellite broadcasts of target polarization and the center frequencies of each satellite broadcast channel. The frequency determination unit 13 determines the center frequency (fc1) of the target polarization for receiving the corresponding satellite broadcasts that are subject to image interference, based on the frequency (fi) of the interference detection signal obtained from the interference wave detection unit 12. The frequency determination unit 13 then derives a second local oscillation frequency (LO2) required for frequency conversion of the signal of the interfered channel of target polarization having the center frequency (fc1) to a predetermined intermediate frequency (fc2) within a predetermined free band in the intermediate frequency band, separate from the intermediate frequency using the first local oscillation frequency (LO1) specified in the standard. In this example, the predetermined free band in the intermediate frequency band is defined as the interval between the right-hand circular polarization intermediate frequency band and the left-hand circular polarization intermediate frequency band (between the CS right-hand circular polarization IF and the BS left-hand circular polarization IF shown in FIG. 9). Then, the frequency determination unit 13 outputs information on the second local oscillation frequency (LO2) and the center frequency (fc1) of the interfered channel to the second frequency conversion unit 17. That is, the frequency determination unit 13 selects the interfered channel in receiving satellite broadcasting based on the interference wave detection signal having signal power equal to or greater than a predetermined threshold value, which is obtained via the interference wave receiving antenna 11 and the interference wave detection unit 12.

[0054] Therefore, the interference wave detection unit 12 and the frequency determination unit 13 function as an "interfered channel selection means" that uses a bandpass filter to extract the signal in the image band from the received signal obtained via the interference wave receiving antenna 11 as an interference wave detection signal, selects the interfered channel in satellite broadcast reception based on the interference wave detection signal having a signal power equal to or greater than a predetermined threshold, and derives a second local oscillation frequency (LO2) required to perform frequency conversion on the signal of the interfered channel of the target polarization in the satellite broadcast signal to a predetermined intermediate frequency within a predetermined free band in the intermediate frequency band, other than the intermediate frequency using the first local oscillation frequency (LO1) specified in the standard.

[0055] The second frequency conversion unit 17 performs frequency conversion on the received signals of each channel of right-handed circularly polarized waves in the 12 GHz band satellite broadcast signal input from the distributor 14 using the signal of the second local oscillation frequency (LO2) derived by the frequency determination unit 13, and outputs the intermediate frequency band signals of each channel of right-handed circularly polarized waves after frequency conversion to the band-pass filter 18 together with information on the center frequency (fc1) of the interfered channel.

[0056] Bandpass filter 18 performs bandpass filtering on the intermediate frequency band signals of each channel of right-handed circularly polarized waves after frequency conversion using LO2 input from second frequency converter 17, based on information about the center frequency (fc1) of the interfered channel, to extract only the intermediate frequency signal components (intermediate frequency signal components with center frequency fc2=fc1-LO2) corresponding to the interfered channel, and generates a second intermediate frequency signal for the interfered channel and outputs it to mixer 21. This second intermediate frequency signal for the interfered channel has a predetermined IF frequency (for example, center frequency fc2=2.188 GHz) within the empty band (2.071 GHz to 2.224 GHz) between the right-handed and left-handed intermediate frequency bands (between the CS right-handed IF and BS left-handed IF shown in FIG. 9).

[0057] Here, in this example, the target is one interfered channel that is affected by one image band of right-hand circular polarization 9 GHz, which is the current issue, but if multiple interfered channels may become subject to image interference in the future, multiple sets of second frequency conversion unit 17 and band-pass filter 18 will be provided to target each interfered channel individually.

[0058] In this example, for the sake of convenience, the second frequency converter 17 and the band-pass filter 18 are described as separate functional units, but they may be configured as an integrated functional unit. That is, the second frequency converter 17 and the band-pass filter 18 may be configured as an "interfered channel frequency conversion means" that performs frequency conversion on the signal of the interfered channel of the target polarization (right-handed circular polarization in this example) in the 12 GHz band satellite broadcast signal, using the signal of the second local oscillation frequency (LO2) derived by the frequency determination unit 13, and generates a second intermediate frequency signal related to the interfered channel.

[0059] The third frequency converter 19 performs frequency conversion on the received signals of each channel of the 12 GHz band left-handed circularly polarized wave input from the distributor 14 using a signal of the third local oscillation frequency for left-handed circular polarization (LO3 = 9.505 GHz) according to the standard, generates a signal in the left-handed IF band of 2.224 GHz to 3.223 GHz, and outputs it to the high-pass filter 20.

[0060] The high-pass filter 20 performs high-pass filtering on the left-handed IF band signal input from the third frequency converter 19 to remove unnecessary low-frequency waves and noise components, and outputs the result to the mixer 21.

[0061] Mixer 21 mixes (multiplexes) the right-hand circular polarization IF band signal after low-pass filtering input from low-pass filter 16, the second intermediate frequency signal (fc2) related to the interfered channel that has been input from band-pass filter 18 and that has avoided the influence of image interference, and the left-hand circular polarization IF band signal after high-pass filtering input from high-pass filter 20, and outputs the resultant signal to the outside. The output signal mixed and generated by this frequency conversion device 1 is configured to be sent to a home distribution system that transmits the signal to a receiver (not shown) using a single coaxial cable.

[0062] Therefore, the mixer 21 according to the first embodiment functions as an "output means" configured to mix the second intermediate frequency signal (fc2) relating to the interfered channel with the intermediate frequency signals defined in the standard specifications of the interfered channel and other channels, and output the result in a manner that allows it to be transmitted over a single coaxial cable.

[0063] In other words, the frequency conversion device 1 of Example 1 differs from a general frequency conversion (LNB) in the prior art in that it is equipped with an interference wave receiving antenna 11, an interference wave detection unit 12, a frequency determination unit 13, a distributor 14, a second frequency conversion unit 17, and a band-pass filter 18.

[0064] In the frequency converter 1 of the first embodiment, the problem of image interference occurs in frequency conversion of right-hand circularly rotated signals, so the configuration for left-hand circularly rotated signals is the same as that of a general frequency converter (LNB) in the prior art, and is unchanged. That is, the frequency converter 1 of the first embodiment converts and generates a channel affected by an interference wave in the 9 GHz band among right-hand circularly rotated satellite broadcast waves into a signal in a different IF band that is not affected by the interference wave, thereby making it possible to avoid image interference.

[0065] Referring to FIG. 2, the operation of the frequency conversion device 1 of the first embodiment to convert and generate a signal in another IF band that is not affected by the interference wave will be described. FIG. 2 is a diagram showing the relationship between the frequencies of right-hand circularly polarized waves in 12 GHz-band satellite broadcasting related to frequency conversion by the frequency conversion device for receiving satellite broadcasting according to the first embodiment of the present invention.

[0066] The upper part of Fig. 2 shows the frequency relationship between the 11.7 GHz to 12.75 GHz broadcasting frequency band for BS / CS right-hand circular polarization in 12 GHz-band satellite broadcasting, which is input to the frequency conversion device 1 of Example 1, the first local oscillation frequency (LO1) of 10.678 GHz used for right-hand circular polarization reception, and the frequency fi (near 9 GHz) as a right-hand circular polarization interference wave. The lower part of Fig. 2 shows how the right-hand circular polarization interference wave of fi (near 9 GHz) is similarly frequency converted to the IF band of 1.03223 GHz to 2.07025 GHz ("BS / CS right-hand circular polarization IF") output by frequency conversion (block conversion) in the frequency conversion device 1 of Example 1, and how the right-hand circular polarization interference wave of fi (near 9 GHz) is generated as an interference wave signal, and also how an interfered channel in the BS / CS right-hand circular polarization IF band that is affected by the 9 GHz-band image interference is converted and generated into a second intermediate frequency signal for the interfered channel, which is a different intermediate frequency (center frequency fc2 = 2.188 GHz) that is not affected by the interference wave.

[0067] First, the frequency conversion device 1 of the first embodiment includes an interference wave receiving antenna 11, an interference wave detection unit 12, and a frequency determination unit 13, and the interference wave receiving antenna 11 and the interference wave detection unit 12 are configured to detect interference waves of frequency (fi) in a reception system separate from the satellite broadcast receiving antenna 10. The frequency determination unit 13 stores information on the first local oscillation frequency (i.e., LO1 for right-hand rotation) used for receiving satellite broadcasts of target polarization, and a list of the center frequencies of each satellite broadcast channel, and determines the center frequency (fc1) of the target polarization in receiving the corresponding satellite broadcasts that are subject to image interference according to the frequency (fi) of the interference wave detection signal obtained from the interference wave detection unit 12.

[0068] fc1 is calculated from the frequency (fi) of the interference wave detection signal and the first local oscillation frequency (LO1) of 10.678 GHz as follows: Here, 0.0345 GHz is the occupied bandwidth of one channel. fc1-0.0345÷2 ≦ fi+(10.678-fi)×2 ≦ fc1+0.0345÷2 (unit: GHz) Therefore, 21.33875-fi ≦ fc1 ≦ 21.37325-fi (unit: GHz)

[0069] Furthermore, the frequency determination unit 13 derives a second local oscillation frequency (LO2) required for performing frequency conversion in the second frequency conversion unit 17 to a predetermined IF frequency (fc2) within the vacant band (2.071 GHz to 2.224 GHz) between the right-hand circular polarization intermediate frequency band and the left-hand circular polarization intermediate frequency band (between the CS right-hand circular polarization IF and the BS left-hand circular polarization IF shown in FIG. 9) for the signal of the interfered channel of the target polarization having the center frequency (fc1) for receiving satellite broadcasts.

[0070] Then, the second frequency conversion unit 17 and the bandpass filter 18 perform frequency conversion on the right-hand circularly polarized signal of the interfered channel in the 12 GHz band satellite broadcast signal using the second local oscillation frequency (LO2) signal derived by the frequency determination unit 13, and generate a second intermediate frequency signal (fc2) for the interfered channel.

[0071] In this example, the center frequency (fc2) of the second intermediate frequency signal is set to fc2 (=fc1-LO2) = 2.188 GHz, which is a frequency (3.224 GHz or less) that can be transmitted via a coaxial cable compatible with a typical home distribution system and does not overlap with other IF signals. Note that fc2 may be any frequency that can avoid image interference, can be transmitted via a coaxial cable in the first embodiment, and is an open band that does not overlap with IF signals related to the interfered channel and other channels; the above fc2 = 2.188 GHz is just an example. However, as described above, setting fc2 to an open band between the right-hand circular polarization intermediate frequency band and the left-hand circular polarization intermediate frequency band (between the CS right-hand circular polarization IF and the BS left-hand circular polarization IF shown in FIG. 9) is preferable because it reliably avoids image interference while maintaining the quality of signal transmission to the typical home distribution system.

[0072] Finally, the mixer 21 according to the first embodiment mixes (multiplexes) the second intermediate frequency signal (fc2) for the interfered channel, which has avoided the influence of image interference, with the standard right- and left-handed intermediate frequency (IF) band signals, and sends it to a home distribution system that transmits it to a receiver (not shown). This allows the signal of the channel that is affected by image interference to be distributed to the home in the state before the interference. In this embodiment, the receiver must be able to receive and display the channel based on the second intermediate frequency signal (fc2) for the interfered channel during the tuning operation.

[0073] Therefore, according to the frequency conversion device 1 of the first embodiment, it is possible to receive satellite broadcast signals without degradation even in the presence of strong interference waves that would cause signal degradation at the image interference suppression ratio stipulated in the standard, and it becomes easy to share the device with other devices that use the image band (such as radar equipment that was causing image interference).

[0074] Furthermore, according to the frequency conversion device 1 of the first embodiment, intermediate frequency signals that avoid the effects of image interference on received satellite broadcast signals can also be transmitted to a receiver through an existing in-home distribution system that uses a single coaxial cable, and the output frequency of the frequency conversion device 1 of the first embodiment is included in the intermediate frequency band (1032 to 3224 MHz) specified in the current standard (ARIB STD-B63), making it highly versatile.

[0075] Example 2 Some home distribution systems are only capable of receiving right-hand circular polarization IF (right-hand circular polarization IF). The upper limit frequency of a home distribution system that is only capable of receiving right-hand circular polarization IF may be 2.1 GHz, in which case the second intermediate frequency signal related to the interfered channel having a center frequency fc2 of 2.188 GHz as in the first embodiment cannot be transmitted as is.

[0076] Therefore, a configuration that solves this problem will be described as a second embodiment. Figure 3 is a block diagram showing a schematic configuration of a frequency converter 1 for receiving satellite broadcasts according to a second embodiment of the present invention. The frequency converter 1 for receiving satellite broadcasts according to the second embodiment shown in Figure 3 includes an interference wave receiving antenna 11, an interference wave detector 12, a frequency determiner 13, a distributor 14, a first frequency converter 15, a low-pass filter 16, a band-elimination filter 16a, a second frequency converter 17, a band-pass filter 18, a down-converter 18a, and a mixer 21. In Figure 3, the same components as those in Figure 1 are designated by the same reference numerals.

[0077] The frequency converter 1 for receiving satellite broadcasts according to the second embodiment shown in Fig. 3 differs from the first embodiment shown in Fig. 1 in that it further includes a band elimination filter 16a and a down converter 18a, but the other components operate in the same manner. Note that the frequency converter 1 according to the second embodiment shown in Fig. 3 is an example in which the components related to left-handed circular polarization (third frequency converter 19 and high-pass filter 20) shown in Fig. 1 are not provided, because it is assumed that the in-home distribution system supports only right-hand circular polarization. However, when the frequency converter 1 is to be applicable to both the in-home distribution systems assumed in the first and second embodiments, the components related to left-hand circular polarization (third frequency converter 19 and high-pass filter 20) shown in Fig. 1 can be provided in the frequency converter 1 shown in Fig. 3.

[0078] First, in the frequency conversion device 1 of the second embodiment, received signals of each channel are received as right-handed circularly polarized waves after polarization separation by a polarization separator 10a for 12 GHz band satellite broadcast signals received via a satellite broadcast receiving antenna 10, and are input to a distributor 14. The satellite broadcast receiving antenna 10 is an antenna capable of receiving 12 GHz band satellite broadcasts, and in this example, a parabolic antenna capable of receiving both right-handed and left-handed 12 GHz band satellite broadcasts is illustrated. Furthermore, the satellite broadcast receiving antenna 10 and the polarization separator 10a may be configured as an integrated antenna device or may be configured as separate devices. Furthermore, since this example is described as a representative example that handles only right-handed circularly polarized waves, the satellite broadcast receiving antenna 10 may also be an antenna capable of receiving only right-handed circularly polarized satellite broadcasts, or the polarization separator 10a may be omitted.

[0079] The operations of the interference wave receiving antenna 11, interference wave detection unit 12, frequency determination unit 13, distributor 14, first frequency conversion unit 15, low-pass filter 16, second frequency conversion unit 17, band-pass filter 18, and mixer 21 according to the second embodiment shown in FIG. 3 are the same as those in the first embodiment, and therefore will be briefly described.

[0080] As in the first embodiment, the distributor 14 receives the received signals of each channel (11.7 GHz to 12.75 GHz) of right-handed circular polarization in the 12 GHz band satellite broadcast signal that has been polarization-separated by the polarization separator 10a, and distributes and outputs the signals to the first frequency converter 15 and the second frequency converter 17.

[0081] As in the first embodiment, the first frequency conversion unit 15 performs frequency conversion on the received signals of each channel of right-hand circularly polarized waves in the 12 GHz band satellite broadcast signal input from the distributor 14 using a signal of the first local oscillation frequency (LO1=10.678 GHz) for right-hand rotation according to the standard, generates a signal in the right-hand intermediate frequency (IF) band of 1.03223 GHz to 2.07025 GHz, and outputs it to the low-pass filter 16.

[0082] As in the first embodiment, the low-pass filter 16 performs low-pass filtering on the right-hand circular polarization IF band signal input from the first frequency conversion unit 15 to remove unnecessary high-frequency waves and noise components, and outputs the result to the band elimination filter 16a.

[0083] The band elimination filter 16a performs band elimination filtering on the low-pass filtered right-handed IF band signal input from the low-pass filter 16, operating to remove signals (unwanted waves and noise) in a predetermined empty band within the right-handed IF band (near "fc2' = 1510.72 MHz" described later), and outputs the result to the mixer 21. By removing the unwanted waves and noise near 1510.72 MHz from the right-handed IF band signal using the band elimination filter 16a, this contributes to improving the C / N of a "new second intermediate frequency signal related to the interfered channel" (described later) that is relocated to this band. That is, in the second embodiment, which will be described in detail later, the "second intermediate frequency signal related to the interfered channel (fc2)" that was once generated by the band pass filter 18 is relocated by the down converter 18a so as to be unaffected by interference waves and to be 2.1 GHz or less, thereby generating a "new second intermediate frequency signal (fc2') related to the interfered channel."

[0084] The interference wave receiving antenna 11, the interference wave detection unit 12, and the frequency determination unit 13 are configured in the same manner as in the first embodiment, and further detailed description will be omitted. That is, the frequency determination unit 13 according to the second embodiment holds, as in the first embodiment, information on the first local oscillation frequency (i.e., LO1 for right-hand circular polarization) used for receiving satellite broadcasts of a target polarization, and a list of the center frequencies of each channel of satellite broadcasts. Based on the interference wave detection signal obtained via the interference wave receiving antenna 11 and the interference wave detection unit 12, the frequency determination unit 13 selects an interfered channel for receiving satellite broadcasts, and outputs information on the second local oscillation frequency (LO2) and the center frequency (fc1) of the interfered channel to the second frequency conversion unit 17.

[0085] As in the first embodiment, the second frequency conversion unit 17 performs frequency conversion on the received signals of each channel of right-handed circularly polarized waves in the 12 GHz band satellite broadcast signal input from the distributor 14 using the signal of the second local oscillation frequency (LO2) derived by the frequency determination unit 13, and outputs the intermediate frequency band signals of each channel of right-handed circularly polarized waves after frequency conversion to the band-pass filter 18 together with information on the center frequency (fc1) of the interfered channel.

[0086] As in the first embodiment, band-pass filter 18 performs band-pass filtering on the intermediate frequency band signal of each channel of right-handed circularly polarized waves after frequency conversion using LO2 input from second frequency converter 17, extracting only the intermediate frequency signal component (intermediate frequency signal component with center frequency fc2=fc1-LO2) corresponding to the interfered channel based on information on the center frequency (fc1) of the interfered channel, but outputs it to down-converter 18a in the second embodiment. As in the first embodiment, the second intermediate frequency signal related to the interfered channel output by band-pass filter 18 has a predetermined IF frequency (for example, center frequency fc2=2.188 GHz) within the empty band (2.071 GHz to 2.224 GHz) between the right-handed intermediate frequency band and the left-handed intermediate frequency band (between the CS right-handed IF and BS left-handed IF shown in FIG. 9).

[0087] In the second embodiment, the second frequency converter 17 and the band-pass filter 18 are described as separate functional units for the sake of convenience, but they may be configured as an integrated functional unit. That is, the second frequency converter 17 and the band-pass filter 18 may be configured as an "interfered channel frequency conversion means" that performs frequency conversion on the signal of the interfered channel of the target polarization (right-handed circular polarization in this example) in the 12 GHz band satellite broadcast signal, using the signal of the second local oscillation frequency (LO2) derived by the frequency determination unit 13, and generates a second intermediate frequency signal related to the interfered channel.

[0088] The downconverter 18a has an analog / digital converter (A / D) 181 and a digital / analog converter (D / A) 182, and converts the second intermediate frequency signal (fc2) for the interfered channel, which is input from the bandpass filter 18 and has avoided the influence of image interference, into a digital signal by the A / D 181, and then, by digital processing involving the D / A 182, downconverts the signal to a predetermined IF frequency (for example, a center frequency of 1510.72 MHz) within an empty band within the right-hand circularly rotated intermediate frequency band (the empty band of 1489 MHz to 1532 MHz between the BS right-hand circularly rotated IF and the CS right-hand circularly rotated IF shown in Figure 9) from which signals (unwanted waves and noise) have been removed by the band elimination filter 16a, and generates a new second intermediate frequency signal (fc2') for the interfered channel that has been converted back to an analog signal and outputs it to the mixer 21.

[0089] Unlike wideband frequency conversion (block conversion), this downconverter 18a can be configured to convert the frequency of only one channel with a bandwidth of 34.5 MHz. That is, the A / D 181 performs digital sampling with a bandwidth of 34.5 MHz, and the D / A 182 directly converts to the desired frequency, which can be achieved without using analog devices such as filters or mixers.

[0090] The mixer 21 mixes (multiplexes) the right-handed IF band signal input from the band elimination filter 16a after band elimination filter processing with a new second intermediate frequency signal (fc2') for the interfered channel input from the down converter 18a that has avoided the influence of image interference, and outputs the resultant signal to an external device. The output signal mixed and generated by this frequency conversion device 1 is configured to be sent to an in-home distribution system that transmits the signal to a receiver (not shown) using a single coaxial cable.

[0091] Therefore, the band elimination filter 16a, downconverter 18a and mixer 21 according to the second embodiment function as an "output means" configured to generate a new second intermediate frequency signal (fc2') for the interfered channel by performing frequency conversion on the second intermediate frequency signal (fc2) for the interfered channel to a predetermined new available band in an intermediate frequency band that is further different from the intermediate frequency defined in the standard, mix the new second intermediate frequency signal (fc2') for the interfered channel with the intermediate frequency signals defined in the standard of the interfered channel and other channels, and output the mixed signal so that it can be transmitted over a single coaxial cable.

[0092] In other words, the frequency conversion device 1 of the second embodiment converts and generates, as in the first embodiment, an interfered channel among right-hand circularly polarized satellite broadcast waves that is affected by image interference from interference waves in the 9 GHz band, into a different IF signal (a second intermediate frequency signal related to the interfered channel) that is not affected by the image interference, and in addition, in the second embodiment, in order to make it a signal in an IF band that can be received by an in-home distribution system that only supports right-hand circularly polarized IF, the converted and generated different IF signal (the second intermediate frequency signal related to the interfered channel) is down-converted to an available band of 2.1 GHz or less that does not overlap with other IF signals, and is transmitted as a new different IF signal (a new second intermediate frequency signal related to the interfered channel).

[0093] 4 and 5, the operation of the frequency conversion device 1 of the second embodiment will be described, in which the signal of the interfered channel is first converted and generated into another IF signal (second intermediate frequency signal for the interfered channel) that is not affected by the interference wave as in the first embodiment (FIG. 4), and then further down-converted to an available band of 2.1 GHz or less that does not overlap with other IF signals (FIG. 5) to generate a new another IF signal (new second intermediate frequency signal for the interfered channel).

[0094] First, Figure 4 is similar in content to Figure 2 relating to Example 1, and the upper part of Figure 4 shows the frequency relationship between the BS / CS right-hand circular polarization broadcasting frequency band of 11.7 GHz to 12.75 GHz in the 12 GHz band satellite broadcasting that is the input to the frequency conversion device 1 of Example 2, the first local oscillation frequency (LO1) of 10.678 GHz used for right-hand circular polarization reception, and the frequency fi (around 9 GHz) as a right-hand circular polarization interference wave. The lower part of Figure 4 shows how the right-hand circular polarization interference wave of the above fi (near 9 GHz) is similarly frequency converted to cause image interference as an interference wave signal for the IF band of 1.03223 GHz to 2.07025 GHz ("BS·CS right-hand circular polarization IF") output by frequency conversion (block conversion) in the frequency conversion device 1 of Example 2, and also shows how, for an interfered channel in the BS·CS right-hand circular polarization IF band that is affected by image interference in the 9 GHz band, the signal is first converted and generated into a second intermediate frequency signal for the interfered channel, which is a different intermediate frequency (center frequency fc2 = 2.188 GHz) that is not affected by the interference wave.

[0095] 4, the frequency conversion device 1 of the second embodiment includes an interference wave receiving antenna 11, an interference wave detection unit 12, and a frequency determination unit 13, similar to the first embodiment, and the interference wave receiving antenna 11 and the interference wave detection unit 12 are configured to detect interference waves in a reception system separate from the satellite broadcast receiving antenna 10. The frequency determination unit 13 holds information on the first local oscillation frequency (i.e., LO1 for right-hand rotation) used for receiving satellite broadcasts of target polarization, and a list of the center frequencies of each satellite broadcast channel, and determines the center frequency (fc1) of the target polarization in receiving the corresponding satellite broadcasts that are subject to image interference according to the frequency (fi) of the interference wave detection signal obtained from the interference wave detection unit 12.

[0096] Furthermore, similarly to the first embodiment, the frequency determination unit 13 derives a second local oscillation frequency (LO2) required for performing frequency conversion in the second frequency conversion unit 17 on the signal of the interfered channel of the target polarization having the center frequency (fc1) in satellite broadcast reception to a predetermined IF frequency (fc2) within the vacant band (2.071 GHz to 2.224 GHz) between the right-hand circular polarization intermediate frequency band and the left-hand circular polarization intermediate frequency band (between the CS right-hand circular polarization IF and the BS left-hand circular polarization IF shown in FIG. 9).

[0097] The second frequency converter 17 and band-pass filter 18 according to the second embodiment are also configured in the same manner as in the first embodiment. That is, the second frequency converter 17 and band-pass filter 18 perform frequency conversion on the right-hand circularly polarized signal of the interfered channel in the 12 GHz band satellite broadcast signal, using the signal of the second local oscillation frequency (LO2) derived by the frequency determination unit 13, and extract and generate a second intermediate frequency signal (center frequency fc2=2.188 GHz) related to the interfered channel.

[0098] However, the second intermediate frequency signal relating to the interfered channel with center frequency fc2=2.188 GHz cannot be transmitted to a home distribution system with an upper limit of 2.1 GHz.

[0099] Therefore, in the frequency conversion device 1 of the second embodiment, the downconverter 18a downconverts the second intermediate frequency signal (fc2) for the interfered channel input from the bandpass filter 18 to a frequency that is 2.1 GHz or less and does not overlap with other IF signals, thereby generating a new second intermediate frequency signal (fc2') for the interfered channel.

[0100] Here, in the second embodiment, for convenience of explanation, an example is described in which the center frequency (fc2) of the second intermediate frequency signal is the same as in the first embodiment, but in the second embodiment, the second intermediate frequency signal is not output to the outside of the frequency conversion device 1, so a band beyond the transmittable range of the coaxial cable can also be used. That is, the frequency (fc2) of the second intermediate frequency signal according to the second embodiment may be any free band that can avoid image interference and does not overlap with the IF signals related to the interfered channel and other channels, and the above fc2=2.188 GHz is one example.

[0101] FIG. 5 is a diagram showing how intermediate frequencies converted for interfered channels are rearranged by frequency conversion in a down converter 18a in a frequency conversion device 1 for receiving satellite broadcasting according to a second embodiment of the present invention.

[0102] The upper part of Fig. 5 shows a state in which an interfered channel that is affected by image interference in the 9 GHz band in the BS / CS right-hand circular polarization IF band is converted and generated into a second intermediate frequency signal for the interfered channel of another intermediate frequency (center frequency fc2 = 2.188 GHz) that is not affected by the interference wave in the frequency conversion device 1 of Example 2. The lower part of Fig. 5 shows a state in which the downconverter 18a in the frequency conversion device 1 of Example 2 converts and generates a new second intermediate frequency signal for the interfered channel with center frequency fc2' = 1510.72 MHz from the second intermediate frequency signal for the interfered channel (center frequency fc2 = 2188.00 MHz).

[0103] As can be seen from Figure 5, in the frequency conversion device 1 of Example 2, the downconverter 18a converts the second intermediate frequency signal (fc2) for the interfered channel, which has been input from the bandpass filter 18 and avoids the influence of image interference, to a predetermined IF frequency (for example, center frequency 1510.72 MHz) within the available band within the right-hand circularly rotated intermediate frequency band (the available band of 1489 MHz to 1532 MHz between the BS right-hand circularly rotated IF and the CS right-hand circularly rotated IF shown in Figure 9), and generates a new second intermediate frequency signal (fc2') for the interfered channel with center frequency fc2' = 1510.72 MHz, and outputs it to the mixer 21.

[0104] Finally, the mixer 21 according to the second embodiment mixes (combines) the new second intermediate frequency signal (fc2') for the interfered channel, which has avoided the influence of image interference, with a signal in the right-hand circular IF band according to the standard, and sends it to a home distribution system that transmits it to a receiver (not shown). This allows the signal of the channel affected by image interference to be distributed to the home in the state before the interference. In this embodiment, the receiver must be able to receive and display a channel based on the new second intermediate frequency signal (fc2') for the interfered channel during tuning operation.

[0105] In this way, the frequency conversion device 1 of the second embodiment converts the interfered channel of the right-hand circular polarization to the center frequency fc2=2.188 GHz, and then reconverts (remaps) it to a center frequency (fc2') of 2.1 GHz or less by the down converter 18a. Note that, in the above description of the second embodiment, an example in which the center frequency fc2'=1510.72 MHz is used has been described, but it is sufficient that the remap is made between the BS right-hand circular polarization IF and the CS right-hand circular polarization IF.

[0106] Therefore, according to the frequency conversion device 1 of the second embodiment, it is possible to receive satellite broadcast signals without degradation even in the presence of strong interference waves that would cause signal degradation at the image interference suppression ratio stipulated in the standard specification, and it becomes easy to share the device with other devices that use the image band (such as radar equipment that was causing image interference).

[0107] Furthermore, according to the frequency conversion device 1 of the second embodiment, intermediate frequency signals that avoid the effects of image interference on received satellite broadcast signals can also be transmitted to a receiver through an existing home distribution system that uses a single coaxial cable, and the output frequency of the frequency conversion device 1 of the second embodiment is not only included in the intermediate frequency band (1032 to 3224 MHz) specified in the current standard (ARIB STD-B63), but can also be transmitted to home distribution systems with an upper limit of the intermediate frequency band of 2.1 GHz or less, making it highly versatile.

[0108] Example 3 Some receivers receiving signals via a home distribution system cannot receive signals other than those of channels used in existing satellite broadcasting. That is, some receivers cannot directly receive intermediate frequency signals of 2188 MHz according to the first embodiment or 1510.72 MHz according to the second embodiment.

[0109] Therefore, a configuration that solves this problem will be described as a third embodiment. Figure 6 is a block diagram showing a schematic configuration of a frequency converter 1 for receiving satellite broadcasts according to a third embodiment of the present invention. The frequency converter 1 for receiving satellite broadcasts according to the third embodiment shown in Figure 6 includes an interference wave receiving antenna 11, an interference wave detector 12, a frequency determiner 13a, a distributor 14, a first frequency converter 15, a variable band-elimination filter 16b, a second frequency converter 17, a band-pass filter 18, a down-converter 18b, and a mixer 21. In Figure 6, the same components as those in Figure 3 are designated by the same reference numerals.

[0110] The frequency converter 1 for receiving satellite broadcasts of the third embodiment shown in Fig. 6 differs from the frequency converter 1 of the second embodiment shown in Fig. 3 in that it includes a frequency determination unit 13a with some additional functions instead of the frequency determination unit 13, a variable band-elimination filter 16b instead of the band-elimination filter 16a, and a down-converter 18b with some additional functions instead of the down-converter 18a, but the other components operate in the same manner. Note that the frequency converter 1 of the third embodiment shown in Fig. 6 is an example in which the components related to left-hand rotation shown in Fig. 1 (the third frequency converter 19 and the high-pass filter 20) are not provided, because it is assumed that the in-home distribution system supports only the channel frequencies used in existing right-hand rotation satellite broadcasts. However, when the frequency converter 1 is to be applicable to any of the in-home distribution systems assumed in the first, second, and third embodiments, the components related to left-hand rotation shown in Fig. 1 (the third frequency converter 19 and the high-pass filter 20) can be provided in the frequency converter 1 shown in Fig. 6.

[0111] First, in the frequency conversion device 1 of the third embodiment, the received signals of each channel are received as right-handed circularly polarized waves after polarization separation by the polarization separator 10a for 12 GHz band satellite broadcast signals received via the satellite broadcast receiving antenna 10 and input to the distributor 14. The satellite broadcast receiving antenna 10 is an antenna capable of receiving 12 GHz band satellite broadcasts, and in this example, a parabolic antenna capable of receiving both right-handed and left-handed 12 GHz band satellite broadcasts is illustrated. Furthermore, the satellite broadcast receiving antenna 10 and the polarization separator 10a may be configured as an integrated antenna device or may be configured as separate devices. Furthermore, since this example is described as a representative example that handles only right-handed circularly polarized waves, the satellite broadcast receiving antenna 10 may also be an antenna capable of receiving only right-handed circularly polarized satellite broadcasts, or the polarization separator 10a may be omitted.

[0112] The operations of the interference wave receiving antenna 11, interference wave detection unit 12, distributor 14, first frequency conversion unit 15, low-pass filter 16, second frequency conversion unit 17, band-pass filter 18, and mixer 21 according to the third embodiment shown in FIG. 6 are the same as those in the second embodiment, and therefore will be briefly described.

[0113] As in the first and second embodiments, the distributor 14 receives the received signals of each channel (11.7 GHz to 12.75 GHz) of right-handed circular polarization in the 12 GHz band satellite broadcast signal that has been polarization-separated by the polarization separator 10a, and distributes and outputs the signals to the first frequency converter 15 and the second frequency converter 17.

[0114] As in the first and second embodiments, the first frequency conversion unit 15 performs frequency conversion on the received signals of each channel of right-hand circularly polarized waves in the 12 GHz band satellite broadcast signal input from the distributor 14 using a signal of the first local oscillation frequency (LO1 = 10.678 GHz) for right-hand rotation according to the standard, and generates a signal in the right-hand intermediate frequency (IF) band of 1.03223 GHz to 2.07025 GHz, which is output to the low-pass filter 16.

[0115] As in the first and second embodiments, the low-pass filter 16 performs low-pass filtering on the right-hand circular IF band signal input from the first frequency conversion unit 15 to remove unnecessary high-frequency waves and noise components, and outputs the result to the variable band-elimination filter 16b.

[0116] The variable band-elimination filter 16b performs variable band-elimination filtering on the right-hand circular polarization IF band signal after low-pass filtering input from the low-pass filter 16 based on a frequency control signal from the frequency determination unit 13a (described later), and outputs the result to the mixer 21. The variable band-elimination filtering is variable and operates so as to eliminate signals in the intermediate frequency band (center frequency fc3=fc1-LO1) of the interfered channel using LO1.

[0117] The interference wave receiving antenna 11 and the interference wave detecting unit 12 are configured in the same manner as in the first and second embodiments, and further detailed description thereof will be omitted.

[0118] Similar to the first and second embodiments, the frequency determination unit 13a according to the third embodiment stores information on a first local oscillation frequency (i.e., LO1 for right-hand circular polarization) used for receiving satellite broadcasts of a target polarization and a list of center frequencies of each channel of the satellite broadcasts, and selects an interfered channel for receiving satellite broadcasts based on an interference wave detection signal obtained via the interference wave receiving antenna 11 and the interference wave detection unit 12, and outputs information on the local oscillation frequency (LO2) and the center frequency (fc1) of the interfered channel to the second frequency conversion unit 17. However, unlike the first and second embodiments, the frequency determination unit 13a according to the third embodiment has a function of outputting information indicating an intermediate frequency band of the interfered channel according to the standard having a center frequency fc3 (=fc1-LO1) as a frequency control signal to the variable band elimination filter 16b and the downconverter 18b.

[0119] As in the first and second embodiments, the second frequency converter 17 performs frequency conversion on the received signals of each channel of right-handed circularly polarized waves in the 12 GHz band satellite broadcast signal input from the distributor 14 using the signal of the second local oscillation frequency (LO2) derived by the frequency determination unit 13a, and outputs the intermediate frequency band signals of each channel of right-handed circularly polarized waves after frequency conversion to the band-pass filter 18 together with information on the center frequency (fc1) of the interfered channel.

[0120] As in the first and second embodiments, band-pass filter 18 performs band-pass filtering on the intermediate frequency band signal of each channel of right-handed circularly polarized waves after frequency conversion using LO2 input from second frequency converter 17, extracting only the intermediate frequency signal component (intermediate frequency signal component with center frequency fc2=fc1-LO2) corresponding to the interfered channel based on information on the center frequency (fc1) of the interfered channel, but outputs it to down-converter 18b in the third embodiment. As in the first and second embodiments, the second intermediate frequency signal related to the interfered channel output by band-pass filter 18 has a predetermined IF frequency (for example, center frequency fc2=2.188 GHz) within the empty band (2.071 GHz to 2.224 GHz) between the right-handed intermediate frequency band and the left-handed intermediate frequency band (between the CS right-handed IF and BS left-handed IF shown in FIG. 9).

[0121] In the third embodiment, the second frequency converter 17 and the band-pass filter 18 are described as separate functional units for the sake of convenience, but they may be configured as an integrated functional unit. That is, the second frequency converter 17 and the band-pass filter 18 may be configured as an "interfered channel frequency conversion means" that performs frequency conversion on the signal of the interfered channel of the target polarization (right-handed circular polarization in this example) in the 12 GHz band satellite broadcast signal, using the signal of the second local oscillation frequency (LO2) determined by the frequency determination unit 13a, and generates a second intermediate frequency signal related to the interfered channel.

[0122] The downconverter 18b has an analog-to-digital converter (A / D) 181 and a digital-to-analog converter (D / A) 182, as in the second embodiment, but in the third embodiment, the second intermediate frequency signal for the interfered channel, which has been input from the bandpass filter 18 and which has avoided the influence of image interference, is converted into a digital signal by the A / D 181, and then, based on the frequency control signal from the frequency determination unit 13a, the digital processing associated with the D / A 182 downconverts the signal to a signal in the intermediate frequency band of the interfered channel, from which the signal has been removed by the variable band-elimination filter 16b, and generates a third intermediate frequency signal (center frequency fc3=fc1-LO1) for the interfered channel which has been converted back to an analog signal, and outputs it to the mixer 21.

[0123] Unlike wideband frequency conversion (block conversion), this downconverter 18b can be configured to convert the frequency of only one channel with a bandwidth of 34.5 MHz. That is, the A / D 181 performs digital sampling with a bandwidth of 34.5 MHz, and the D / A 182 simply converts the frequency based on the frequency control signal from the frequency determination unit 13a, which can be realized without using analog devices such as filters or mixers.

[0124] The mixer 21 mixes (multiplexes) the right-handed IF band signal (from which the intermediate frequency signal of the interfered channel using LO1 has been removed) input from the variable band-elimination filter 16b with the third intermediate frequency signal (fc3) for the interfered channel from which the influence of image interference has been avoided, input from the down-converter 18b, and outputs the resultant signal to an external device. The output signal mixed and generated by this frequency conversion device 1 is configured to be sent to a home distribution system that transmits the signal to a receiver (not shown) using a single coaxial cable.

[0125] Therefore, the variable band-elimination filter 16b, downconverter 18b and mixer 21 according to the third embodiment function as an "output means" configured to further frequency convert the second intermediate frequency signal (fc2) for the interfered channel into the band of the intermediate frequency signal of the interfered channel that uses the first local oscillation frequency (LO1) as defined in the standard to generate a third intermediate frequency signal (fc3) for the interfered channel, replace the intermediate frequency signal of the interfered channel that uses the first local oscillation frequency (LO1) with the third intermediate frequency signal (fc3) for the interfered channel, mix it with intermediate frequency signals defined in the standard for other channels other than the interfered channel, and output it so that it can be transmitted over a single coaxial cable.

[0126] In other words, the frequency conversion device 1 of the third embodiment converts and generates an interfered channel, which is affected by image interference from interference waves in the 9 GHz band among right-hand circularly polarized satellite broadcast waves, into a different IF signal (a second intermediate frequency signal related to the interfered channel) that is not affected by the interference wave, as in the first and second embodiments. In addition, in the third embodiment, in order to make a signal in an IF band that can be received by an in-home distribution system that can only receive frequencies of channels used for existing satellite broadcasts, the converted and generated different IF signal (the second intermediate frequency signal related to the interfered channel) is further down-converted to convert and generate a third intermediate frequency signal related to the interfered channel, which is then transmitted in place of the original intermediate frequency signal of the interfered channel using LO1.

[0127] 7 and 8, the operation of the frequency conversion device 1 of the third embodiment will be described, in which the signal of the interfered channel is first converted and generated into another IF signal (second intermediate frequency signal related to the interfered channel) that is not affected by the interference wave as in the first and second embodiments (FIG. 7), and then, in the third embodiment, the signal is down-converted to replace the original intermediate frequency signal of the interfered channel using LO1 (FIG. 8), thereby generating a new another IF signal (third intermediate frequency signal related to the interfered channel).

[0128] First, Figure 7 is similar in content to Figures 2 and 4 relating to Examples 1 and 2, and the upper part of Figure 7 shows the frequency relationship between the BS / CS right-hand circular polarization broadcasting frequency band of 11.7 GHz to 12.75 GHz in 12 GHz band satellite broadcasting, which is the input to the frequency conversion device 1 of Example 3, the first local oscillation frequency (LO1) of 10.678 GHz used for right-hand circular polarization reception, and the frequency fi (around 9 GHz) as a right-hand circular polarization interference wave. The lower part of Figure 7 shows how the right-hand circular polarization interference wave of the above fi (near 9 GHz) is similarly frequency converted to cause image interference as an interference wave signal for the IF band of 1.03223 GHz to 2.07025 GHz ("BS·CS right-hand circular polarization IF") output by frequency conversion (block conversion) in the frequency conversion device 1 of Example 3, and also shows how, for an interfered channel in the BS·CS right-hand circular polarization IF band that is affected by image interference in the 9 GHz band, the signal is first converted and generated into a second intermediate frequency signal for the interfered channel, which is a different intermediate frequency (center frequency fc2 = 2.188 GHz) that is not affected by the interference wave.

[0129] 7, the frequency converter 1 of the third embodiment includes an interference wave receiving antenna 11 and an interference wave detecting unit 12, similar to the first and second embodiments, and the interference wave receiving antenna 11 and the interference wave detecting unit 12 detect interference waves in a reception system separate from the satellite broadcast receiving antenna 10. Similarly to the first and second embodiments, the frequency determining unit 13a of the third embodiment stores information on the first local oscillation frequency (i.e., LO1 for right-hand circular polarization) used for receiving satellite broadcasts of target polarization and a list of center frequencies of each satellite broadcast channel, and determines the center frequency (fc1) of the target polarization in receiving the corresponding satellite broadcasts that are subject to image interference according to the frequency (fi) of the interference wave detection signal obtained from the interference wave detecting unit 12.

[0130] Then, as in the first and second embodiments, the frequency determination unit 13a derives a second local oscillation frequency (LO2) required for performing frequency conversion in the second frequency conversion unit 17 on the signal of the interfered channel of the target polarization having the center frequency (fc1) for receiving satellite broadcasting to a predetermined IF frequency (fc2) within the vacant band (2.071 GHz to 2.224 GHz) between the right-hand circular polarization intermediate frequency band and the left-hand circular polarization intermediate frequency band (between the CS right-hand circular polarization IF and the BS left-hand circular polarization IF shown in FIG. 9).

[0131] The second frequency converter 17 and band-pass filter 18 are also configured in the same manner as in Examples 1 and 2. That is, the second frequency converter 17 and band-pass filter 18 perform frequency conversion on the right-hand circularly polarized signal of the interfered channel in the 12 GHz band satellite broadcast signal, using the signal of the second local oscillation frequency (LO2) derived by the frequency determination unit 13 a, and extract and generate a second intermediate frequency signal (center frequency fc2 = 2.188 GHz) related to the interfered channel.

[0132] However, the second intermediate frequency signal for the interfered channel with center frequency fc2=2.188 GHz is not compatible with receivers that can only receive frequencies of channels used in existing satellite broadcasting.

[0133] Therefore, in the frequency conversion device 1 of the third embodiment, the frequency determination unit 13a according to the third embodiment outputs information indicating the intermediate frequency band of the interfered channel according to the standard, which has a center frequency fc3 (=fc1-LO1), as a frequency control signal to the variable band-elimination filter 16b and the down-converter 18b. Then, based on the frequency control signal from the frequency determination unit 13a, the variable band-elimination filter 16b performs a variable operation to eliminate the signal of the intermediate frequency band (center frequency fc3=fc1-LO1) of the interfered channel using LO1 input from the low-pass filter 16. Furthermore, based on the frequency control signal from the frequency determination unit 13a, the down-converter 18b down-converts the second intermediate frequency signal (fc2) related to the interfered channel input from the band-pass filter 18 to the intermediate frequency band (center frequency fc3=fc1-LO1) of the interfered channel from which the signal has been eliminated by the variable band-elimination filter 16b, thereby generating a third intermediate frequency signal.

[0134] Here, in the third embodiment, for convenience of explanation, an example is described in which the center frequency (fc2) of the second intermediate frequency signal is the same as that in the first embodiment, but in the third embodiment, the second intermediate frequency signal is not output to the outside of the frequency conversion device 1, so a band beyond the transmission range of the coaxial cable can also be used. That is, the frequency (fc2) of the second intermediate frequency signal according to the third embodiment may be any free band that can avoid image interference and does not overlap with the IF signals related to the interfered channel and other channels, and the above-mentioned fc2=2.188 GHz is one example.

[0135] FIG. 8 is a diagram showing how intermediate frequencies converted for an interfered channel are rearranged by frequency conversion in down converter 18b in frequency conversion device 1 for receiving satellite broadcasting according to a third embodiment of the present invention.

[0136] The upper part of Fig. 8 shows how, in the frequency conversion device 1 of the third embodiment, an interfered channel that is affected by image interference in the 9 GHz band in the BS / CS right-hand circular polarization IF band is converted and generated into a second intermediate frequency signal for the interfered channel with a different intermediate frequency (center frequency fc2 = 2.188 GHz) that is not affected by the interference wave. The lower part of Fig. 8 shows how, by the downconverter 18b in the frequency conversion device 1 of the third embodiment, the second intermediate frequency signal for the interfered channel (center frequency fc2 = 2188.00 MHz) is converted and generated into a third intermediate frequency signal for the interfered channel with a center frequency fc3 (= fc1 - LO1). That is, the center frequency (fc3) of the third intermediate frequency signal for the interfered channel has a frequency that matches the intermediate frequency signal of the interfered channel that uses the first local oscillation frequency (LO1).

[0137] As can be seen from Figure 8, in the frequency conversion device 1 of Example 3, the downconverter 18b downconverts the second intermediate frequency signal for the interfered channel, which is input from the bandpass filter 18 and has avoided the influence of image interference, to the intermediate frequency band (center frequency fc3 = fc1 - LO1) of the interfered channel, from which the variable band-elimination filter 16b has removed the signal, to generate a third intermediate frequency signal for the interfered channel, and outputs it to the mixer 21 so as to replace the original intermediate frequency signal for the interfered channel using LO1 with the third intermediate frequency signal for the interfered channel.

[0138] Finally, the third intermediate frequency signal (fc3) for the interfered channel, which has been freed from the effects of image interference, is mixed (multiplexed) by mixer 21 with a standard right-hand circular IF band signal (the original intermediate frequency signal of the interfered channel using LO1 has been removed) and sent to a home distribution system that transmits the signal to a receiver (not shown). This allows the signal of the channel affected by image interference to be distributed to the home in the state before interference. Furthermore, even if the receiver is designed to only receive frequencies of channels used for existing satellite broadcasting, it can receive and display channels based on the third intermediate frequency signal for the interfered channel through normal tuning operations.

[0139] In this way, the frequency conversion device 1 of the third embodiment first converts the interfered right-hand circularly polarized channel to a center frequency fc2=2.188GHz, and then converts (rearranges) it by the downconverter 18b so as to replace the intermediate frequency signal of the original interfered channel using LO1.

[0140] Therefore, according to the frequency conversion device 1 of the third embodiment, it is possible to receive satellite broadcast signals without degradation even in the presence of strong interference waves that would cause signal degradation at the image interference suppression ratio stipulated in the standard specification, and it becomes easy to share the device with other devices that use the image band (such as radar equipment that was causing image interference).

[0141] Furthermore, according to the frequency conversion device 1 of the third embodiment, intermediate frequency signals that avoid the effects of image interference on received signals from satellite broadcasting can also be transmitted to a receiver through an existing home distribution system using a single coaxial cable, and the output frequency of the frequency conversion device 1 of the third embodiment is not only included in the intermediate frequency band (1032 to 3224 MHz) specified in the current standard (ARIB STD-B63), but can also be transmitted to a home distribution system at the frequency of a channel used in existing satellite broadcasting, making it highly versatile.

[0142] [Power measurement system equipped with a frequency conversion device according to the present invention] The frequency converter 1 of each of the above-described embodiments can solve the problem of image interference at low cost, without the need to modify the existing in-home distribution system, simply by replacing the existing frequency converter of the satellite broadcast receiving antenna 10. Therefore, as an application, it can also be configured as a power measurement system equipped with the frequency converter 1 of each of the embodiments, for the purpose of adjusting the orientation of the existing satellite broadcast receiving antenna 10 or inspecting the impact of image interference.

[0143] That is, although not shown, the power measurement system according to the present invention can be configured to include the frequency conversion device 1 according to each embodiment and a power meter that measures the received power of the intermediate frequency signal of each channel obtained from the output of the frequency conversion device 1. In this case, the mixer 21 in the frequency conversion device 1 according to each embodiment can be configured to output to the power meter instead of the in-home distribution system. However, it is preferable to use a distributor (not shown) as the output destination to output to both the in-home distribution system and the power meter. This allows the influence of image interference to be confirmed by the received power, and also allows the presence or absence of the influence of image interference to be confirmed on the video image at the receiver via the in-home distribution system, thereby configuring a highly convenient power measurement system.

[0144] Therefore, the power measurement system according to the present invention makes it possible to adjust the orientation of the satellite broadcast receiving antenna 10 with high precision and to easily determine whether or not there is an influence from radar or the like.

[0145] While the above-described embodiments have been described as representative examples, it will be apparent to those skilled in the art that numerous modifications and substitutions are possible within the spirit and scope of the present invention. For example, while the above-described embodiments have primarily been described as reducing the effects of image interference on right-handed circularly polarized received signals of 12 GHz-band satellite broadcasting, similar techniques can also be used to reduce the effects of image interference on left-handed circularly polarized received signals of 12 GHz-band satellite broadcasting, or to reduce the effects of image interference on both right-handed and left-handed received signals. However, in the frequency conversion device 1 according to the present invention, configuring the target polarization for the image band to target only the right-handed circularly polarized waves of 12 GHz-band satellite broadcasting has the advantages of being highly convenient from a practical standpoint and reducing device costs. Therefore, the present invention should not be construed as being limited by the above-described embodiments, but is limited only by the claims. [Industrial Applicability]

[0146] According to the present invention, the effects of image interference can be avoided even in the presence of strong interference waves that would cause signal degradation at the image interference suppression ratio stipulated in the standard for satellite broadcast reception, and therefore the present invention is useful for satellite broadcast reception. [Explanation of symbols]

[0147] 1. Frequency conversion device for receiving satellite broadcasts 10 Satellite dish 10a Polarization separation section 11 Interference wave receiving antenna 12 Interference wave detection unit 13, 13a Frequency determination unit 14 Distributor 15 First frequency conversion unit 16 Low-pass filter 16a Band-reject filter 16b Variable Band Reject Filter 17 Second frequency conversion section 18 Bandpass Filter 18a, 18b Downconverter 19 Third frequency conversion section 20 High-pass filter 21 Mixer 181 Analog-to-Digital Converter (A / D) 182 Digital-to-Analog Converter (D / A)

Claims

1. A frequency conversion device for receiving satellite broadcasts that performs frequency conversion on satellite broadcast signals obtained through a satellite broadcast receiving antenna, an interference wave receiving antenna having a receiving gain in an image band of a predetermined target polarized wave that causes image interference in satellite broadcast reception; an interfered channel selection means for extracting a signal in the image band from the received signal obtained via the interference wave receiving antenna using a band pass filter as an interference wave detection signal, selecting an interfered channel in satellite broadcast reception based on the interference wave detection signal having a signal power equal to or greater than a predetermined threshold, and deriving a second local oscillation frequency required for frequency conversion of the signal of the interfered channel of target polarization in the satellite broadcast signal to a predetermined intermediate frequency within a predetermined empty band of the intermediate frequency band, different from the intermediate frequency using the first local oscillation frequency specified in the standard; an interfered channel frequency conversion means for converting a frequency of the interfered channel signal of the target polarization in the satellite broadcast signal using the signal of the second local oscillation frequency to generate a second intermediate frequency signal for the interfered channel; an output means for transmitting the second intermediate frequency signal for the interfered channel directly or after further frequency conversion to a predetermined new vacant band in another intermediate frequency band, or after further frequency conversion so as to replace the intermediate frequency signal using the first local oscillation frequency of the interfered channel, to a predetermined in-home distribution system via a single coaxial cable; A frequency conversion device comprising:

2. 2. The frequency conversion device according to claim 1, wherein the output means is configured to mix the second intermediate frequency signal for the interfered channel with intermediate frequency signals defined by the standards of the interfered channel and other channels as they are, and output the mixed signal so that it can be transmitted over a single coaxial cable.

3. the satellite broadcast signal includes at least right-handed circularly polarized signals for each channel of a 12 GHz band satellite broadcast; 3. The frequency conversion device according to claim 2, wherein the center frequency of the second intermediate frequency signal for the interfered channel is located between the intermediate frequency band for right-handed circular polarization and the intermediate frequency band for left-handed circular polarization in 12 GHz band satellite broadcasting.

4. 2. The frequency conversion device according to claim 1, wherein the output means is configured to generate a new second intermediate frequency signal for the interfered channel by frequency-converting the second intermediate frequency signal for the interfered channel to a predetermined new available band in an intermediate frequency band other than the intermediate frequency defined by the standard, mix the new second intermediate frequency signal for the interfered channel with the intermediate frequency signals defined by the standard for the interfered channel and other channels, and output the mixed signal so as to be transmittable over a single coaxial cable.

5. the satellite broadcast signal includes at least right-handed circularly polarized signals for each channel of a 12 GHz band satellite broadcast; 5. The frequency conversion device according to claim 4, wherein the center frequency of the new second intermediate frequency signal for the interfered channel is located in an empty band within the intermediate frequency band of right-handed circularly polarized waves.

6. 2. The frequency conversion device according to claim 1, wherein the output means is configured to further frequency convert the second intermediate frequency signal for the interfered channel into a band of an intermediate frequency signal for the interfered channel that uses the first local oscillation frequency as defined by a standard to generate a third intermediate frequency signal for the interfered channel, replace the intermediate frequency signal for the interfered channel that uses the first local oscillation frequency with the third intermediate frequency signal for the interfered channel, mix it with an intermediate frequency signal defined by a standard for another channel other than the interfered channel, and output the resultant signal so as to be transmittable over a single coaxial cable.

7. the satellite broadcast signal includes at least right-handed circularly polarized signals for each channel of a 12 GHz band satellite broadcast; 2. The frequency conversion device according to claim 1, wherein the target polarization for the image band is configured to target only right-handed circularly polarized waves in 12 GHz band satellite broadcasting.

8. The frequency conversion device according to claim 1; a power meter for measuring the received power of the intermediate frequency signal of each channel obtained from the output of the frequency conversion device; A power measurement system comprising:

Images