JP2006148963A - Receiving system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To receive airwaves that are multiplexed by right- and left-handed circularly polarized waves for distribution to each terminal device through one IF signal cable, in a community receiving system. <P>SOLUTION: The right- and left-handed circularly polarized waves are converted into IF signals, each having different frequency by means of low-noise converters 52 and 53, and then are mixed by a mixer 54. Additionally, these signals are mixed with terrestrial television broadcast signals by a mixer 56 and are distributed to each terminal device 2 through one IF signal cable. In the terminal device 2, the signals are supplied to a receiver 61, after the terrestrial television broadcast signals have been separated by a branching filter 59. A selection circuit 60 selects the right- and left-handed circularly polarized wave components, based on the polarization switching signal supplied from the receiver 61 for supplying to the receiver 61, after performing frequency conversion, as required. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a receiving system, and more particularly to a receiving system that receives multiplexed broadcast radio waves and distributes them to a number of terminal devices.

  In order to further increase the amount of information of the broadcast radio wave transmitted via the broadcast satellite, for example, there is a method of multiplexing the left-handed polarization and right-handed polarization, or the vertical polarization and horizontal polarization of the broadcast wave. .

  In order to receive broadcast radio waves transmitted by this method, a separating device for separating left-handed polarized waves and right-handed polarized waves with respect to conventional receiving devices (devices that receive unmultiplexed radio waves) Needed to be added.

  In particular, in a joint reception system (consisting of a joint reception device and each viewer's terminal device) in an apartment house, etc., since the number of terminal devices that distribute the received broadcast waves is large, In order to be able to receive, it was necessary to add many separation devices.

  Therefore, various devices have been devised so that multiplexed broadcast radio waves can be received by adding a minimum separation device to the conventional joint reception system.

  FIG. 8 is a block diagram illustrating a configuration example of a conventional joint reception system. In this figure, the parabolic antenna 11 is an RF (Radio Frequency) band radio wave multiplexed by right-handed polarization and left-handed polarization (or vertical polarization and horizontal polarization) transmitted from a broadcasting satellite (not shown). Have been made to receive. A low noise block (LNB) converter 12 separates left-handed polarized wave and right-handed polarized wave from the radio wave in the RF band received by the parabolic antenna 11, and these signals are separated into IF (Intermediate Frequency) band signals ( (Hereinafter referred to as IF signal) and supplied to the distributors 13a and 13b.

  The distributors 13a and 13b distribute the left-hand polarized IF signal and the right-hand polarized IF signal to the multi-switches 14a and 14b, respectively. The multi-switches 14a and 14b are based on the polarization switching signals supplied from the terminal devices of the receivers (configured by the receivers 15a to 15d and the television receivers 16a to 16d). One of right-hand polarized IF signals is selected and supplied to each terminal device.

  The receivers 15a to 15d output a polarization switching signal to the multi-switch 14a or 14b based on the operation of the viewer, and input the right-hand polarized IF signal or the left-hand polarized IF signal selected as a result. Then, after processing to convert this into an RF signal of a lower frequency, it is supplied to the television receivers 16a to 16d. The television receivers 16a to 16d extract video and audio signals from signals supplied from the receivers 15a to 15d, and display and output them.

  Next, the operation of the above conventional example will be described.

  A multiplexed broadcast radio wave transmitted from a broadcast satellite (not shown) is received by the parabolic antenna 11. The LNB converter 12 separates the left-hand polarized radio wave and the right-hand polarized radio wave from the received broadcast radio waves, converts them into IF signals, and supplies them to the distributors 13a and 13b, respectively. The distributors 13a and 13b distribute the left-hand polarized IF signal and the right-hand polarized IF signal to the multi-switches 14a and 14b, respectively.

  The multi-switches 14a and 14b select one of the left-hand polarized IF signal and the right-hand polarized IF signal based on the polarization switching signals supplied from the receivers 15a to 15d, and supply them to the receivers 15a to 15d. .

  According to the above configuration, each viewer automatically selects one of these signals by designating either left-handed polarization or right-handed polarization by a predetermined operation. Thus, it is possible to view a desired broadcast (program).

  FIG. 9 is a block diagram showing another configuration example of the conventional joint reception system. In this figure, the same parts as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  The receivers 21a to 21d receive the left-hand polarization and right-hand polarization IF signals supplied from the distributors 13a and 13b through separate IF signal cables, and select them by a built-in switch (not shown). The selected IF signal is converted into an RF signal having a lower frequency and then output to the television receivers 16a to 16d.

  Other configurations are the same as those in FIG.

  Next, the operation of the conventional example shown in FIG. 9 will be described.

  The parabolic antenna 11 receives radio waves in the RF band transmitted from a broadcast satellite (not shown). The LNB converter 12 separates the left and right polarized radio waves from the received radio waves, converts them into IF signals, and supplies them to the distributors 13a and 13b, respectively.

  The distributors 13a and 13b distribute and supply the input IF signals corresponding to the left-handed and right-handed polarized waves to the respective receivers 21a to 21d through separate cables. The receivers 21a to 21d select one of the IF signals corresponding to the left-handed polarized wave and the right-handed polarized wave supplied from the distributor 13a or 13b and convert the IF signal into an RF signal having a lower frequency. Then, the data is output to the television receivers 16a to 16d.

  According to the above configuration, each viewer can select and watch a desired program included in the left-handed polarization or right-handed polarization by operating the receivers 21a to 21d.

  In the example shown in FIG. 8, two cables are required to capture IF signals for right-handed polarization and left-handed polarization into the room from the outside. Further, since the number of distributions of the multi-switches 14a and 14b is limited to some extent, there is a problem that it cannot be used for a large-scale joint reception facility. Furthermore, since the multi-switches 14a and 14b are expensive, there is a problem that the facilities are expensive.

  In the example shown in FIG. 9, since two cables for supplying IF signals from the distributors 13a and 13b to each receiver are required for each terminal device, a new cable must be installed. As a result, there has been a problem that new costs arise.

  The present invention has been made in view of the above situation, and makes it possible to receive multiplexed satellite broadcasts with simple equipment.

  A receiving system according to an aspect of the present invention includes a first receiving device that receives a plurality of broadcast radio waves multiplexed at a frequency and multiplexed on a polarization plane, and the first receiving device that receives the plurality of broadcasting radio waves. In a reception system including a selection device that selects a predetermined broadcast radio wave from a plurality of broadcast radio waves, the first reception device includes a reception unit that receives the plurality of broadcast radio waves, and the plurality of the plurality of broadcast waves received by the reception unit. Separation means for separating broadcast waves having different polarization planes from broadcast waves, and a plurality of broadcast waves separated by the separation means and having different polarization planes are multiplexed in frequency for each polarization plane The first group of IF signals corresponding to one polarization plane and the second group IF signals corresponding to the other polarization plane, which do not overlap with each other, are converted. Wave number conversion means; and output means for outputting the first group IF signals and the second group IF signals frequency-converted by the first frequency conversion means to the selection device via a common cable. The selection device includes an input means for inputting the first group of IF signals and the second group of IF signals supplied via the cable, and a polarization switching signal supplied from a second reception device. Based on this, one of the first group of IF signals and the second group of IF signals input by the input means is selected, and the selected one IF signal overlaps the frequency band of the other IF signal. To the second receiver, or based on the polarization switching signal, the first group IF signal and the second group IF signal input by the input means Any one Select comprises as a first selecting means for supplying an IF signal while the selected second reception apparatus.

  The first selecting means is arranged such that the frequency band of the first group of IF signals and the frequency band of the second group of IF signals overlap the first group of IF signals or the second group of IF signals. Based on a polarization switching signal supplied from the second receiver, and the first group of IF signals and the second group of IF signals input by the input unit. Either one of the signals is selected and supplied to the second frequency converting means and the IF signal that has been frequency converted is supplied to the second receiving device, or based on the polarization switching signal, There may be provided second selection means for selecting any one of the first group of IF signals and the second group of IF signals inputted by the input means and supplying the selected signals to the second receiving apparatus as they are.

  According to the present invention, multiplexed broadcasts can be properly received.

  In the following description, first, the outline of the configuration of the embodiment of the joint reception device and the terminal device to which the present invention is applied will be described, and then each of the joint reception device and the terminal device will be described in more detail.

  FIG. 1 is a block diagram showing a configuration of an embodiment of a joint reception device and a terminal device to which the present invention is applied.

  In this figure, the broadcast satellite 10 is configured to transmit multiplexed radio waves in the RF band toward the ground by adding different information to left-hand polarized waves and right-hand polarized waves. The joint receiving device 1 receives radio waves transmitted from the broadcasting satellite 10 and terrestrial TV radio waves, and distributes and supplies the received signals to the terminal devices 2 of each viewer (each household). . The terminal device 2 receives a signal supplied from the joint receiving device 1 and demodulates it.

  The parabolic antenna 11 of the collective receiving apparatus 1 reflects and receives radio waves transmitted from the broadcasting satellite 10 by the parabolic reflecting surface. The LNB converter 12 separates left-hand polarized waves and right-hand polarized waves from radio waves in the RF band received by the parabolic antenna 11, converts them into IF signals, and outputs them.

  Note that the polarization demultiplexer 51, the low noise converter 52, and the low noise converter 53, which will be described later, are built in the LNB converter 12 in an actual configuration, but in order to explain the state of signal processing in detail, Are shown separately.

  The polarization demultiplexer 51 is configured to separate the left-hand polarized wave component and the right-hand polarized wave component from the radio wave in the RF band received by the parabolic antenna 11. The low noise converters 52 and 53 amplify the right-handed polarized wave and left-handed polarized wave components supplied from the polarization demultiplexer 51 with a low noise amplifier, and then convert them into signals in IF bands of different frequency bands.

  The mixer 54 mixes IF signals corresponding to right-handed polarization and left-handed polarization supplied from the low-noise converters 52 and 53. The terrestrial television broadcast antenna 55 receives terrestrial television broadcast radio waves (UHF and VHF band radio waves). The mixer 56 is an IF signal obtained by mixing the right-handed polarization component and the left-handed polarization component supplied from the mixer 54, and a terrestrial wave supplied from the terrestrial television broadcast antenna 55 and input to the input unit 56a. A television broadcast signal is mixed and output via an IF signal cable. The distributors 57 and 58 distribute the signal output from the mixer 56 to each terminal device 2.

  The duplexer 59 of the terminal device 2 is installed in each viewer's home, separates the terrestrial television broadcast signal and the satellite broadcast IF signal from the signal supplied from the distributor 58, and outputs the separated signal. It is made to do.

  The selection circuit 60 receives the satellite broadcast IF signal supplied from the demultiplexer 59 and selects a right-hand polarized wave or left-hand polarized IF signal in accordance with the polarization switching signal supplied from the receiver 61. This is subjected to a predetermined frequency conversion and then output to the receiver 61.

  The receiver 61 selects any one of the terrestrial television broadcast signal, the right-hand polarized signal, or the left-hand polarized signal based on the operation of the viewer, performs a predetermined process on the signal, and then receives the television receiver. 16 is output. Further, the television receiver 16 extracts a video / audio signal from a signal supplied from the receiver 61 and displays and outputs it.

  Next, the operation of the example shown above will be described.

  A radio wave transmitted from the broadcasting satellite 10 and multiplexed with right-handed and left-handed polarized waves is received by the parabolic antenna 11 and rightward by the polarization demultiplexer 51 built in the LNB converter 12. Separated into a circular polarization component and a left polarization component. Then, the right-handed polarization component and the left-handed polarization component are respectively amplified by the low noise converters 52 and 53, converted into IF signals having different frequencies, and output to the mixer 54.

  The mixer 54 mixes the IF signals corresponding to the right-handed polarized wave and the left-handed polarized wave supplied from the low noise converters 52 and 53, and outputs them to the mixer 56. The mixer 56 receives the terrestrial television broadcast antenna 55 and receives the terrestrial television broadcast signal input to the input unit 56a and the right-hand polarized wave and left-hand polarized wave supplied from the mixer 54. The signal is mixed and output.

  The signal output from the mixer 56 is taken into the room by an IF signal cable and distributed to each terminal device 2 by distributors 57 and 58.

  The duplexer 59 separates the terrestrial television broadcast signal and the satellite broadcast IF signal from the signal supplied from the distributor 58. The terrestrial television broadcast signal is output to the receiver 61, and the satellite broadcast IF signal is output to the selection circuit 60.

  The selection circuit 60 extracts IF signals corresponding to right-handed polarization and left-handed polarization from the satellite broadcast IF signal supplied from the branching filter 59. Then, based on the polarization switching signal supplied from the receiver 61, right-handed polarization or left-handed polarization is selected, subjected to predetermined frequency conversion, and then output to the receiver 61.

  Based on the operation of the viewer, the receiver 61 selects either a terrestrial television broadcast signal, an IF signal corresponding to right-handed polarization, or an IF signal corresponding to left-handed polarization, and sends it to the television receiver 16. Output.

  When the viewer selects a program included in the terrestrial television broadcast signal, the receiver 61 supplies the terrestrial television broadcast signal supplied from the duplexer 59 to the television receiver 16.

  When the viewer selects a program included in the right-handed polarized wave, the receiver 61 supplies a polarization switching signal for selecting the right-handed polarized wave to the selection circuit 60 and is output as a result. An IF signal corresponding to the right-handed polarization signal is supplied to the television receiver 16. When a program included in the left-handed polarization is selected, a polarization switching signal for selecting the left-handed polarization is supplied to the selection circuit 60, and the IF signal corresponding to the left-handed polarization output as a result is Supplied to the television receiver 16.

  According to the configuration described above, the low-noise converters 52 and 53 convert the right-handed polarization and left-handed polarization components of the satellite broadcast into IF signals having frequencies that do not interfere with each other, and the mixers 54 and 56 convert the right-handed polarization. Since the wave, the left-handed polarized wave, and the terrestrial television signal are mixed into a single signal, three types of different signals can be supplied to each terminal device 2 arranged in the room using a single cable. it can. As a result, for example, in an apartment house where a system for distributing terrestrial TV signals and CATV broadcast signals to each home is already prepared, when changing the equipment so that satellite broadcasts can be newly received, new cables are added. Since these three types of signals can be handled together as one signal, it is not necessary to separately install distributors 57 and 58 for each signal.

  Subsequently, the configuration of the joint reception device 1 in the above joint reception system will be described in more detail.

  FIG. 2 is a block diagram showing a more detailed configuration of the joint reception apparatus 1 shown in FIG. In this figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  The circularly polarized wave generator 81 converts a right-handed polarized wave of 12.22 GHz to 12.66 GHz and a left-handed polarized wave of 12.24 GHz to 12.68 GHz contained in the radio wave received by the parabolic antenna 11 into a horizontally polarized wave. And is converted to vertical polarization. The polarization demultiplexer 51 extracts a right-hand polarization component and a left-hand polarization component from the horizontal polarization and vertical polarization supplied from the circular polarization generator 81, and converts the right-hand polarization component into a low-noise converter 52. The left-handed polarized wave component is supplied to the low noise converter 53, respectively.

  The low noise converter 52 includes a low noise amplifier 52a that amplifies the right-handed polarization component supplied from the polarization splitter 51, a local oscillator 52b having a frequency of 11.25 GHz (local frequency), an amplifier 52a, and a local portion. The multiplier 52c performs multiplication processing of the signal supplied from the transmitter 52b, and the buffer 52d amplifies the power of the output signal of the multiplier 52c.

  The low noise converter 53 includes a low noise amplifier 53a that amplifies the left-handed polarization component supplied from the polarization splitter 51, a local oscillator 53b having a local oscillation frequency of 10.675 GHz, an amplifier 53a, and a local oscillator. The multiplier 53c performs a multiplication process of the signal supplied from 53b, and the buffer 53d amplifies the power of the output signal of the multiplier 53c.

  Note that the local oscillation frequency (= 11.25 GHz) of the local transmitter 52b of the low noise converter 52 is the same frequency as in the case of individual reception (when a parabolic antenna is individually installed and received for each home). . On the other hand, the local frequency (= 10.675 GHz) of the local oscillator 53b of the low noise converter 53 is selected so as not to interfere with the local frequency of the local oscillator 52b.

  The mixer 54 includes a band-pass filter 54a that passes only signals in the 970 MHz to 1410 MHz band among the right-handed polarization components, a high-pass filter 54b that passes signals of 1565 MHz and higher among the left-handed polarization components, and a bandpass. An adder 54c that adds signals output from the filter 54a and the high-pass filter 54b is configured.

  The mixer 56 includes an input unit 56a that inputs a terrestrial television broadcast signal supplied from the terrestrial television broadcast antenna 55, and a low-pass filter 56b that passes a signal of 806 MHz or less among signals input to the input unit 56a. In addition, the adder 56c adds the signals supplied from the mixer 54 and the low-pass filter 56b.

  Next, the operation of the above embodiment will be described.

  FIG. 3 is a diagram showing the signals of the main part of the embodiment shown in FIG. 2. Hereinafter, the operation of the embodiment of FIG. 2 will be described with reference to the signals shown in FIG.

  The radio wave (FIG. 3A) transmitted from the broadcasting satellite 10 and multiplexed with right-handed polarized waves (12.22 GHz to 12.66 GHz) and left-handed polarized waves (12.24 GHz to 12.68 GHz) is parabolic. It is received by the antenna 11 and supplied to the circularly polarized wave generator 81. The circularly polarized wave generator 81 converts right-handed polarization and left-handed polarization contained in the received radio wave into horizontal polarization and vertical polarization, and supplies them to the polarization splitter 51. The polarization demultiplexer 51 separates and extracts the right-handed polarization component (FIG. 3 (b)) and the left-handed polarization component (FIG. 3 (c)) from the horizontal polarization and the vertical polarization, and generates low-noise converters 52 and 53. To supply each.

  The right-handed polarized wave component (FIG. 3B) supplied to the low noise converter 52 is amplified by the amplifier 52a. The amplified signal is multiplied by the 11.25 GHz signal supplied from the local oscillator 52b by the multiplier 52c. As a result, the right-handed polarization component (FIG. 3B) having a frequency band of 12.22 GHz to 12.66 GHz is 970 MHz = (12.22 GHz-11.25 GHz) to 1410 MHz = (12.66 GHz-11. 25 GHz) IF signal. Then, the power is amplified by the buffer 52d and then output.

  On the other hand, the left-handed polarized wave component (FIG. 3C) supplied to the low noise converter 53 is amplified by the amplifier 53a. The amplified signal is multiplied by the 10.675 GHz signal supplied from the local oscillator 53b by the multiplier 53c. As a result, the left-handed polarization component (FIG. 3C) having a frequency band of 12.24 GHz to 12.68 GHz is 1565 MHz = (12.24 GHz-10.675) to 2005 MHz = (12.68 GHz-10.675 GHz. ) IF signal. Then, the power is amplified by the buffer 53d and then output.

  The signal output from the low noise converter 52 is supplied to a bandpass filter 54a having a passband of 970 MHz to 1410 MHz, and as a result, signals other than the right-handed polarization component are removed. Further, the signal output from the low noise converter 53 is supplied to a high pass filter 54b having a cutoff frequency of 1565 MHz, and signals other than the left-handed polarized wave component are similarly removed. Then, the right-hand polarization component and the left-hand polarization component are added by the adder 54 c and output to the mixer 56.

  The terrestrial television broadcast signal received by the terrestrial television broadcast antenna 55 is input to the input unit 56a and then supplied to the low-pass filter 56b having a cutoff frequency of 806 MHz to remove signals other than the terrestrial television broadcast signal. After that, the adder 56c adds the output signal from the mixer 54, and as a result, an IF signal (FIG. 3D) is generated. The IF signal is distributed to each terminal device 2 via the IF signal cable.

  According to the above configuration, as shown in FIG. 3 (d), the right-handed polarization component of satellite broadcasting, the left-handed polarization component of satellite broadcasting, and the terrestrial television broadcasting signal are converted to frequencies that do not interfere with each other, and mixed. Since the signal is output after being transmitted, it is possible to transmit the signal with one IF signal cable.

  Next, the configuration of the terminal device 2 will be described in detail.

  FIG. 4 is a block diagram showing a more detailed configuration of the terminal device 2 shown in FIG. Hereinafter, description will be made with reference to this figure.

  In the block diagram shown in FIG. 4, the receiver 61 and the television receiver 16 are omitted for simplification, and only the block diagram of the duplexer 59 and the selection circuit 60 is shown.

  In FIG. 4, a demultiplexer 59 separates an input IF signal into a terrestrial television broadcast signal and a satellite broadcast IF signal. The terrestrial television signal output from the duplexer 59 is supplied to the receiver 61. On the other hand, the satellite broadcast IF signal is supplied to the amplifier 101.

  The amplifier 101 amplifies the satellite broadcast IF signal output from the duplexer 59 and supplies the amplified signal to the polarization switching switch 102. When the switching voltage (corresponding to the polarization switching signal) supplied from the receiver 61 is 13 V, the polarization switching switch 102 extracts an IF signal corresponding to right-handed polarization from the satellite broadcast IF signal, Supplied to the wave changeover switch 111. When the switching voltage is 18 V, the IF signal corresponding to the left-handed polarized wave is extracted from the satellite broadcast IF signal and supplied to the IF down converter 120.

  The band pass filter (BPF) 103 of the IF downconverter 120 has a pass band of 1350 MHz to 2100 MHz, and is generated in an image band (3777 (= 1565 + 2212) MHz to 4217 (= 2005 + 2212) MHz) is prevented from being converted again at the local frequency of 2212 MHz and output (generally called image removal). In addition, there is an effect of removing signal components other than the left transitional wave component.

  The multiplier 105 multiplies the output signal of the local oscillator 104 having a local oscillation frequency of 2212 MHz by the output signal of the bandpass filter 103. The low-pass filter (LPF) 106 has a cutoff frequency of 800 MHz, and outputs only a signal having a cutoff frequency or less from the output signal of the multiplier 105. The amplifier 107 amplifies the output signal of the low pass filter 106.

  The multiplier 109 multiplies the signal supplied from the local oscillator 108 having a transmission frequency of 1637 MHz and the signal output from the amplifier 107. The band pass filter 110 extracts a frequency band of 900 MHz to 1500 MHz from the signal output from the multiplier 109 and outputs the extracted frequency band to the polarization switching switch 111.

  Similarly to the polarization changeover switch 102 described above, the polarization changeover switch 111 has an IF signal corresponding to the right-handed polarization supplied from the polarization changeover switch 102 when the changeover voltage supplied from the receiver 61 is 13V. On the other hand, when the switching voltage is 18V, the IF signal corresponding to the left-handed polarized wave supplied from the IF down converter 120 is selectively output.

  The capacitor 112 blocks the direct current component included in the signal, and prevents the selection circuit 60 and the receiver 61 from affecting each other. Further, the coil 113 prevents the IF signal (high-frequency signal) corresponding to right-handed polarization and left-handed polarization from affecting the power supply unit 114. The power supply unit 114 outputs a 13V or 18V power supply voltage according to the switching voltage supplied from the receiver 61.

  FIG. 5 is a diagram showing signals of main parts of the embodiment of FIG. The operation of the embodiment of FIG. 4 will be described below with reference to this figure.

  The IF signal (FIG. 5A) supplied from the distributor 58 shown in FIG. 1 is separated into a terrestrial television broadcast signal and a satellite broadcast IF signal by the demultiplexer 59. The terrestrial television broadcast signal is output to the receiver 61 as a duplexer output signal (FIG. 5B). On the other hand, the satellite broadcast IF signal is supplied to the amplifier 101, amplified, and then supplied to the polarization switching switch 102.

  When the switching voltage supplied from the receiver 61 is 13 V, the polarization switching switch 102 extracts an IF signal corresponding to right-handed polarization from the satellite broadcast IF signal supplied from the amplifier 101, Output to the changeover switch 111. On the other hand, when the switching voltage is 18 V, the IF signal corresponding to the left-handed polarized wave is extracted from the IF signal of the satellite broadcast and supplied to the IF down converter 120.

  The band pass filter 103 of the IF down converter 120 passes a signal in a frequency band of 1350 MHz to 2100 MHz among IF signals (1565 MHz to 2005 MHz) corresponding to the left-handed polarized wave supplied from the polarization changeover switch 102, and a multiplier To 105. Thereby, as described above, output of the frequency component of the image band is prevented.

  Multiplier 105 multiplies the output signal of local oscillator 104 having a transmission frequency of 2212 MHz and the output signal of bandpass filter 103 and outputs the result. As a result of this multiplication, the frequency band of the left-hand polarized IF signal is down-converted from 1565 MHz to 2005 MHz to 207 MHz = (2212 MHz−2005 MHz) to 647 MHz = (2212 MHz−1565 MHz).

  The down-converted left-hand polarized IF signal (output signal of the multiplier 105) is input to the low-pass filter 106 having a cutoff frequency of 800 MHz, and unnecessary harmonic components are removed. Then, after being amplified by the amplifier 107, it is input to the multiplier 109.

  Multiplier 109 multiplies the output signal of local oscillator 108 having a transmission frequency of 1637 MHz and the output signal of amplifier 107 and outputs the result. As a result of this multiplication, the frequency band of the IF signal corresponding to the left-handed polarization supplied from the amplifier 107 is up-converted from 207 MHz to 647 MHz to 990 MHz = (1637 MHz−647 MHz) to 1430 = (1637 MHz−207 MHz).

  The IF signal (output signal of the multiplier 109) corresponding to the up-converted left-handed polarized wave is input to the bandpass filter 110 having a passband of 900 MHz to 1500 MHz, and unnecessary low frequency components and high frequency components are removed. Thereafter, the signal is input to the polarization switching switch 111 as an output signal of the IF down converter 120.

  When the switching voltage supplied from the receiver 61 is 13 V, the polarization switching switch 111 selects and outputs a signal (IF signal corresponding to right-handed polarization) supplied from the polarization switching switch 102 (FIG. 5 (c)). On the other hand, when the switching voltage is 18 V, the signal supplied from the IF down converter 120 (IF signal corresponding to the left-handed polarized wave) is selected and output (FIG. 5D).

  The signal output from the polarization switching switch 111 is supplied to the receiver 61 through the capacitor 112.

  According to the above configuration, the viewer selects a program included in the terrestrial television broadcast, the right-handed polarization of the satellite broadcast, or the left-handed polarization of the satellite broadcast by performing a predetermined operation with the receiver 61. This can be demodulated.

  FIG. 6A plots the outputs 2212 MHz and 1637 MHz of the local oscillators 104 and 108 of the IF down converter 120 shown in FIG. 4 on the frequency axis (horizontal axis). When these different frequency signals are modulated with each other, intermodulation distortion occurs.

  FIG. 6B shows the relationship between the left-handed polarized wave component (990 MHz to 1430 MHz) after being down-converted by the IF down converter 120 and the intermodulation distortion. Intermodulation distortion consists of frequency components of the sum and difference of integer multiples of the frequency of each signal. Accordingly, a distortion of 575 MHz, which is a difference frequency between the two local oscillation frequencies 1637 MHz and 2212 MHz, is generated. Further, as a result of mutual modulation of the local oscillation frequencies of 575 MHz and 1637 MHz, a distortion component of 1062 MHz, which is the difference frequency, is generated. Furthermore, a distortion component of 1150 MHz, which is the second harmonic of 575 MHz described above, is generated.

  These distortion components are superimposed on the left-handed polarization component. Therefore, in order not to affect the broadcast program, the local oscillation frequency of the local oscillators 104 and 108 is such that these intermodulation distortion components (1150 MHz or 1062 MHz) are counterclockwise as shown in FIG. It is desirable to set so as to be located between the channels of the polarization component (between the 1130 MHz channel and the 1160 MHz channel, or between the 1020 MHz channel and the 1080 MHz channel).

  As described above, when the terminal device 2 performs frequency conversion of a signal using two different local oscillation frequencies, the intermodulation distortion can be reduced between the channels of the broadcast signal by appropriately setting the local oscillation frequency. Can be located. As a result, the influence of intermodulation distortion on the broadcast signal can be suppressed.

  Incidentally, the intermodulation distortion of 575 MHz can be removed by the filter 54a in the LNB. Further, in the selection circuit 60, not only can the filter 103 be removed, but also the amplifier 101 functions as an attenuator of the reciprocal of the amplification gain with respect to the intermodulation distortion.

  In the IF down-converter 120 shown in FIG. 4, down-conversion is performed at a local oscillation frequency of 2212 MHz, and reverse conversion is performed at a local oscillation frequency of 1637 MHz. As a result, down-conversion at 575 MHz is performed. As described above, a method of performing frequency conversion of a signal in two steps is called double conversion, and this has the following advantages over single conversion in which the frequency of a signal is converted in one time.

  (A) In single conversion, a local frequency of 575 MHz is used, but this frequency is located within the frequency band of terrestrial television broadcasting, and the level of this signal is as large as about +10 dBm (decibel milliwatts). It is possible to influence the broadcast signal. On the other hand, in double conversion, the two local oscillation frequencies (2212 MHz and 1637 MHz) are outside the frequency band (990 MHz to 1430 MHz) of the obtained left-hand polarized signal, and thus do not affect the broadcast signal.

  (B) In the case of single conversion, it is necessary to suppress the right-handed polarization component of the basic signal by 30 dB or more with respect to the left-handed polarization component, and thus a high-pass with a steep characteristic having a cutoff frequency between 1410 MHz and 1565 MHz. It is necessary to insert a filter in the first stage of the IF down converter 120. However, it is difficult to construct a high-pass filter that is steep in this frequency band at a low cost. On the other hand, in double conversion, since it is possible to divide and configure a plurality of filters, each filter does not need to have a very steep characteristic.

  In the above embodiments, satellite broadcast radio waves multiplexed by right-handed polarized waves and left-handed polarized waves are used. However, satellite broadcast radio waves multiplexed by horizontal polarized waves and vertical polarized waves may be used, for example. Of course.

  In addition, in the selection circuit 60 shown in FIG. 4, an IF down converter 120 is provided to perform frequency conversion of left-handed polarized waves. However, if the input frequency band of the receiver 61 corresponds to the frequency band of left-handed polarized waves (1565 MHz to 2005 MHz), the IF down converter 120 can be omitted.

  FIG. 7 is a block diagram showing the configuration of another embodiment of the receiving apparatus and terminal apparatus of the present invention. In this embodiment, CATV (Cable TeleVision) cable broadcasting including terrestrial television broadcasting can be received.

  In FIG. 7, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  In FIG. 7, the mixer 56 mixes and outputs the satellite broadcast IF signal supplied from the mixer 54 and the CATV broadcast signal supplied from a cable (not shown) connected to the input unit 56a. Has been made. The low noise converters 52 and 53 are adapted to convert the frequency so that the right-hand polarized IF signal, the left-hand polarized IF signal, and the CATV broadcast signal do not interfere with each other.

  The duplexer 59 separates the satellite broadcast IF signal and the CATV broadcast signal from the IF signal supplied from the distributor 58. Then, the satellite broadcast IF signal is supplied to the selection circuit 60, and the CATV broadcast signal is supplied to the receiver 61.

  Other configurations are the same as those in FIG.

  According to the above embodiment, it is possible to receive CATV broadcasts in addition to multiplexed satellite broadcasts, and distribute them to each terminal device 2 using a single IF signal cable.

  Note that the selection circuit 60 may be built in the receiver 61.

It is a block diagram which shows the structure of one implementation of the receiver of this invention, and a terminal device. FIG. 2 is a block diagram illustrating a more detailed configuration example of the receiving device illustrated in FIG. 1. It is a figure which shows the signal of the principal part of the Example shown in FIG. It is a block diagram which shows the more detailed structural example of the terminal device shown in FIG. It is a figure which shows the signal of the principal part of the Example shown in FIG. It is a figure explaining the intermodulation distortion which generate | occur | produces in IF down converter. It is a block diagram which shows the structure of the other Example of the receiver of this invention, and a terminal device. It is a block diagram which shows the structural example of the conventional receiver and a terminal device. It is a block diagram which shows the other structural example of the conventional receiver and a terminal device.

Explanation of symbols

  11 Parabolic antenna, 51 Polarization demultiplexer, 52, 53 Low noise converter, 54 Mixer, 55 Terrestrial television broadcasting antenna, 56 Mixer, 56a Input unit, 101 Amplifier, 102 Polarization switching switch, 111 Polarization switching Switch, 120 IF down converter

Claims (2)

A first receiver that receives a plurality of broadcast radio waves that are multiplexed at a frequency and that is multiplexed on a plane of polarization; and a predetermined broadcast radio wave from the plurality of broadcast radio waves received by the first receiver. In a receiving system comprising a selection device to select,
The first receiving device is:
Receiving means for receiving the plurality of broadcast radio waves;
Separating means for separating broadcast waves having different planes of polarization from the plurality of broadcast waves received by the receiving means;
Corresponds to one polarization plane where the frequency bands do not overlap each other while maintaining the state where the plurality of broadcast radio waves separated by the separation means and having different polarization planes are multiplexed in frequency for each polarization plane First frequency converting means for converting the first group of IF signals to the second group of IF signals corresponding to the other polarization plane;
Output means for outputting the first group of IF signals and the second group of IF signals frequency-converted by the first frequency conversion means to the selection device via a common cable;
The selection device is:
An input means for inputting the first group of IF signals and the second group of IF signals supplied via the cable;
One of the first group IF signal and the second group IF signal input by the input means is selected based on the polarization switching signal supplied from the second receiver, and the selected one is selected. The IF signal is frequency-converted so as to overlap the frequency band of the other IF signal and supplied to the second receiving device, or based on the polarization switching signal, the first signal input by the input means 1. A receiving system comprising: a first selecting unit that selects one of a group of IF signals and the second group of IF signals and supplies the selected one of the IF signals to a second receiving device as it is. The first selection means includes
A second frequency for frequency-converting the IF signal of the first group or the IF signal of the second group so that the frequency band of the IF signal of the first group overlaps the frequency band of the IF signal of the second group Conversion means;
Based on the polarization switching signal supplied from the second receiver, either the first group of IF signals or the second group of IF signals input by the input means is selected and the second group is selected. And the IF signal that has been frequency-converted and supplied to the second receiver, or based on the polarization switching signal, the first group of IFs input by the input means The receiving system according to claim 1, further comprising: a second selecting unit that selects any one of the signal and the second group of IF signals and supplies the selected signal to the second receiving device as it is.

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