JP7084838B2 - Multiple signal change device and multiple signal change method - Google Patents

Description

The present invention relates to a multiplex signal changing device and a multiplex signal changing method.

To watch television broadcasts, there are methods such as receiving broadcast waves directly from a broadcasting station or subscribing to cable television. Of these, in cable television, a plurality of video signals frequency-multiplexed by the head-end station are received at home via a transmission medium such as a coaxial cable or an optical fiber cable.

FIG. 3 is a configuration diagram of a broadcasting system. The figure shows a general distribution configuration of cable television using an optical fiber cable. The transmission equipment 1 includes a broadcasting equipment 10 and an optical transmitter 11. The broadcasting equipment 10 includes a VHF / UHF band video signal in the 90 MHz to 770 MHz band and a BS / CS 110 ° satellite right-handed circularly polarized intermediate frequency band video signal in the 1 GHz to 2.1 GHz band (hereinafter, BS / CS). A right-handed IF signal) is transmitted to the optical transmitter 11. The broadcasting equipment 10 may transmit video signals of signals other than these, but they are omitted in this figure. In the following, the video signal of each channel is also described as a channel signal.

As the video signal of the VHF / UHF band, specifically, in addition to the rebroadcast signal of terrestrial broadcasting, the video signal of the channel supplied from the video content production company, or the cable TV operator owns it for the service providing area. There is a video signal of a channel produced by a station (hereinafter referred to as a regional production channel).

The optical transmitter 11 converts these video signals into optical signals, and each subscriber's house 2-1 to 2-n (n is 1 or more) via an optical network 3 configured by using an optical fiber cable. It is distributed to the optical receivers 20-1 to 20-n installed in (the integer of). In the figure, the subscriber's homes 2-1 to 2-n are collectively referred to as the subscriber's home 2. Further, although omitted in the figure, the optical network 3 is composed of an optical amplifier, an optical branching device, an optical transmission line, and the like for expanding the transmission distance or distributing to a plurality of subscribers.

As an optical signal transmission method, there are an intensity modulation method and an FM batch conversion method (see, for example, Non-Patent Document 1), each of which has been put into practical use. In the intensity modulation method, a frequency-multiplexed video signal is converted into an optical intensity-modulated signal and transmitted. In the FM batch conversion method, frequency-multiplexed signals are collectively converted into one FM signal (hereinafter referred to as FM batch conversion signal), and the FM batch conversion signal is converted into an optical intensity modulation signal. The FM batch conversion method has a more complicated configuration of an optical transmitter and an optical receiver than the intensity modulation method, but is less susceptible to noise and can transmit video signals of the same quality over a longer distance. ..

"Transmission equipment for transferring multi-channel television signals over optical access networks by frequency modulation conversion," Recommendation ITU-T J.185, 2012

In recent years, with the background of optical or digitization technology of transmission lines, it has become possible to transmit an optical signal from one transmission equipment to an area conventionally covered by a plurality of transmission equipments. FIG. 4 shows a configuration of a broadcasting system in which one centralized station transmitting equipment 4 covers an area of a plurality of regional station equipments 9-1, 9-2, ... (collectively referred to as regional station equipment 9). An example is shown. In the figure, the same parts as those of the broadcasting system shown in FIG. 3 are designated by the same reference numerals. The area covered by each regional station equipment 9-1, 9-2, ... Corresponds to the area covered by one transmission equipment 1 in FIG. The optical transmitter 41 of the central station transmission facility 4 and the regional station facilities 9-1 and 9-2 are connected via the optical networks 6-1 and 6-2, respectively. The regional station equipment 9-1 is equipped with an optical relay transmitter 90 that relays and transmits an optical signal transmitted from the optical transmitter 41 of the central station transmission equipment 4. The same applies to other regional station equipment 9-2, ..., but omitted in the figure. Further, the optical relay transmitter 90 of the regional station equipment 9-1 and the optical receivers 20-1 to 20-n installed in each of the subscriber's homes 2-1 to 2-n are connected by the optical network 3. ..

Here, for example, there are the following two methods for distributing the video signal output by the broadcasting equipment 10 of the central station transmission equipment 4 to the subscriber's house 2 via the regional station equipment 9. One is that after the video signal is distributed as a digital baseband signal from the central station transmission equipment 4 to the regional station equipment 9, the digital baseband signal is converted into a frequency-multiplexed signal in the regional station equipment 9 and the subscriber's house. It is a method of delivering to 2. The other is a method of delivering a frequency-multiplexed signal of the video signal of each channel from the aggregation station transmission equipment 4 to the subscriber's house 2. The frequency used is different for each channel. Hereinafter, the latter case of these two cases will be described.

When applying the configuration of FIG. 4, it is necessary to add the video signal of the regional production channel previously produced by the regional station equipment 9 to the signal transmitted from the central station transmission equipment 4. As this additional method, the one performed by the configuration shown in FIGS. 5 and 6 can be considered.

FIG. 5 is a schematic configuration diagram of a broadcasting system in which a video signal of a regional production channel is inserted in an aggregation station transmission facility. In the figure, the same parts as those of the broadcasting system shown in FIG. 4 are designated by the same reference numerals. In the broadcasting system shown in the figure, the centralized station transmitting equipment 4a and the broadcasting station equipment 9a-1, 9a-2 are replaced with the centralized station transmitting equipment 4 and the broadcasting station equipment 9-1, 9-2, ... , ... (collectively described as broadcasting station equipment 9a). The broadcasting station equipment 9a-2, ... Has the same configuration as the broadcasting station equipment 9a-1. The transmitter 92 of the regional station equipment 9a-1 transmits the video signal (regional production channel signal source) of the regional production channel output by the broadcasting equipment 91. The receiver 42 of the aggregation station transmission equipment 4a receives this video signal via the network 7. The transmission signal flowing through the network 7 is an optical signal or an electric signal. The broadcasting equipment 40 of the central station transmission equipment 4a frequency-multiplexes the video signal input from the receiver 42 to the VHF / UHF band video signal and the BS / CS right-handed IF signal, and then distributes the video signal from the optical transmitter 41.

FIG. 6 is a schematic configuration diagram of a broadcasting system in which a video signal of a regional production channel is inserted in a regional station facility. In the figure, the same parts as those of the broadcasting system shown in FIG. 4 are designated by the same reference numerals. The broadcasting system shown in the figure is described as broadcasting station equipment 9b-1, 9b-2, ... (collectively referred to as broadcasting station equipment 9b) instead of broadcasting station equipment 9-1, 9-2, ... Shown in FIG. ). The broadcasting station equipment 9b-2, ... Has the same configuration as the broadcasting station equipment 9b-1. In the case of this method, the regional station equipment 9b-1 returns the optical signal received from the central station transmission equipment 4 to a video signal (electrical signal) by the optical receiver 93. The mixer 94 mixes the video signal (regionally produced channel signal source) output from the broadcasting equipment 91 by using the free frequency band of the electric signal returned by the optical receiver 93. The optical transmitter 95 outputs the video signal mixed by the mixer 94 again as an optical signal. The optical signal output from the optical transmitter 95 may be further relayed / transmitted via the optical relay transmitter.

In the case of the method shown in FIG. 5, it is necessary to prepare transmission equipment from each regional station equipment 9a to the centralized station transmission equipment 4a, and there are problems in terms of equipment cost and maintenance as compared with the method shown in FIG. As another issue, in the rebroadcast signal of terrestrial broadcasting included in the signal from the broadcasting equipment 40, the re-transmission agreement has been obtained for the distribution area of the regional station equipment 9a-1, but the regional station equipment If the distribution area of 9a-2 contains a channel signal for which retransmission consent has not been obtained, it may be necessary to delete the channel signal in the regional station equipment 9a-2, which may cause a further increase in equipment cost. can give. Therefore, the method of FIG. 6 is superior in terms of equipment cost and maintenance.

Here, when the transmission method is an intensity modulation method, the optical receiver 93 and the optical transmitter 95 may have a highly linear optical-electric conversion function and an electro-optical conversion function. FIG. 7 is a schematic diagram of the structure of the optical receiver 93a and the optical transmitter 95a used as the optical receiver 93 and the optical transmitter 95 of FIG. 6 when the transmission method is the intensity modulation method. The optical signal 81 is converted into a video signal 82 of the electric signal by the optical-electric conversion unit of the optical receiver 93a. The converted video signal 82 is amplified by the electric signal amplification unit and mixed with the video signal 83 of the regional production channel by the mixer 94 to become the video signal 84. The video signal 84 is converted into an optical signal 85 by the electric optical conversion unit of the optical transmitter 95a, amplified by the optical signal amplification unit, and output.

On the other hand, FIG. 8 is a schematic diagram of the structure of the optical receiver 93b and the optical transmitter 95b used as the optical receiver 93 and the optical transmitter 95 of FIG. 6 when the transmission method is the FM batch conversion method. The optical signal 86 is converted into an FM batch conversion signal 87 by the optical / electrical conversion unit of the optical receiver 93b, and then demodulated to the video signal 82 by the FM demodulation unit. Further, the video signal 82 is amplified by the electric signal amplification unit. As in the case of FIG. 7, the video signal 84, which is a mixture of the video signal 82 and the video signal 83 of the regional production channel by the mixer 94, is re-modulated to the FM batch conversion signal 88 by the FM modulation unit of the optical transmitter 95b. Will be done. The FM batch conversion signal 88 is converted into an optical signal 89 by an electric optical conversion unit, and then amplified and output by an optical signal amplification unit. Therefore, when the transmission method is the FM batch conversion method, the FM demodulation function is required for the optical receiver 93b and the FM modulation function is required for the optical transmitter 95b, as compared with the case of the intensity modulation method. In particular, when performing FM modulation, as described in Non-Patent Document 1, it is necessary to prepare an FM modulator having a center frequency of 3 GHz and a modulation signal of up to about 2.1 GHz. This method can enjoy the advantage of being less susceptible to noise, which is a feature of the FM batch conversion method, but has a problem that the equipment cost is high. It should be noted that FIGS. 7 and 8 are basic configuration diagrams, and although the actual device may have a function not included in this figure, it is omitted because the flow of signal processing does not change.

In view of the above circumstances, the present invention provides a multiplex signal changing device and a multiplex signal changing method capable of changing the multiplexed video signal at low cost for the video signal using the FM batch conversion method. It is an object.

In one aspect of the present invention, the FM batch conversion signal obtained by collectively FM-modulating a signal in which channel signals, which are video signals of each channel, are frequency-multiplexed, is a first signal having a phase different from each other by 90 degrees and a first signal. A branch portion that branches into two signals and a signal that uses the same frequency band as a part of the channel signal to be erased and is multiplexed with the FM batch conversion signal and has no correlation with the channel signal to be erased. , A frequency mixing unit that outputs a mixed signal obtained by mixing a third signal including either or both of a channel signal added to an empty frequency band in the FM batch conversion signal and the first signal, and the mixing. It is a multiplex signal changing device including a combiner portion that combines a signal and the second signal.

In one aspect of the present invention, the FM batch conversion signal obtained by collectively FM-modulating a signal in which channel signals, which are video signals of each channel, are frequency-multiplexed, is a first signal having a phase different from each other by 90 degrees and a first signal. A branch step that branches into two signals and a signal that uses the same frequency band as the channel signal to be erased and is not correlated with the channel signal to be erased, which is partially multiplexed with the FM batch conversion signal. , A mixing step of generating a mixed signal in which a third signal including either or both of a channel signal added to an empty frequency band in the FM batch conversion signal and the first signal is generated, and the mixed signal. It is a method of changing a multiplex signal having a combined wave step for combining the second signal and the second signal.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to change a video signal to be multiplexed with respect to a video signal using the FM batch conversion method at low cost.

It is a schematic block diagram of the broadcasting system by one Embodiment of this invention. It is a block diagram of the multiplex signal changing apparatus by the same embodiment. It is a schematic block diagram of the broadcasting system of the prior art. It is a schematic block diagram of the broadcasting system of the prior art. It is a schematic block diagram of the broadcasting system of the system which inserts the regional production channel of the prior art in the centralized station transmission equipment. It is a schematic block diagram of the broadcasting system of the system which inserts the regional production channel of the prior art in the regional station equipment. It is a schematic diagram of the internal structure of an optical receiver and an optical transmitter when the intensity modulation method of the prior art is used. It is a schematic diagram of the internal structure of an optical receiver and an optical transmitter when the FM batch conversion method of the prior art is used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First Embodiment)
FIG. 1 is a schematic configuration diagram of a broadcasting system 100 according to an embodiment of the present invention. In the figure, the same parts as those of the broadcasting system shown in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted. The figure shows a system from the centralized station transmission equipment 4 to the subscriber's house 2. The difference between the broadcasting system 100 shown in the figure and the broadcasting system shown in FIG. 6 is that instead of the regional station equipment 9b-1, 9b-2, ..., The regional station equipment 5-1, 5-2, ... The point is that it is equipped with regional bureau equipment 5). The regional station equipment 5-2, ... Has the same configuration as the regional station equipment 5-1.

The regional station equipment 5-1 includes an optical relay transmitter 50, a broadcasting equipment 51, and a multiplex signal changing device 52. The same optical relay transmitter 90 as shown in FIGS. 4 and 5 can be used for the optical relay transmitter 50, and the same broadcasting equipment 91 shown in FIGS. 5 and 6 can be used for the broadcasting equipment 51. be able to. Therefore, in the present embodiment, the multiplex signal changing device 52 and the optical relay transmitter 50 are used instead of the optical receiver 93, the mixer 94, and the optical transmitter 95 of the regional station equipment 9b-1 in the broadcasting system shown in FIG. It can be configured to be provided.

In the present embodiment, the multiplex signal changing device 52 operates as a channel insertion device. That is, the multiplex signal changing device 52 receives both the optical signal transmitted from the optical transmitter 41 of the central station transmission equipment 4 and the video signal (regional production channel signal source) 83 of the regional production channel output by the broadcasting equipment 51. These are input, combined, and output as an optical signal to the optical relay transmitter 50. The optical signal output from the optical relay transmitter 50 may be relayed and transmitted to the subscriber's house 2 via another optical relay transmitter.

FIG. 2 is a schematic diagram of the internal configuration of the multiplex signal changing device 52. The multiplex signal changing device 52 includes an optical / electric conversion unit 521, a 90 ° hybrid unit 522, a level adjustment unit 523, a frequency mixing unit 524, a synthesis unit 525, and an electric / optical conversion unit 526. The optical input signal is, for example, an optical signal received from the optical transmitter 41 of the aggregation station transmission equipment 4. As described in Non-Patent Document 1, the optical input signal is an optical signal intensity-modulated by the FM signal by the FM batch conversion method.

The opto-electric conversion unit 521 converts an optical input signal into an electric signal. The 90 ° hybrid unit 522 splits the converted electrical signal into two signals. Since the 90 ° hybrid unit 522 branches so that the phases of the two outputs differ from each other by 90 °, the two turnouts and the 90 ° inserted into one of the two branches of the two turnouts. It is also possible to substitute it with a phase shifter.

The level adjusting unit 523 adjusts one of the electric signals branched into two by the 90 ° hybrid unit 522 to an appropriate level as needed. The frequency mixing unit 524 generates a mixed wave of an electric signal whose level has been adjusted by the level adjusting unit 523 and an external signal which is an electric signal from the outside. The external signal input to the frequency mixing unit 524 is a channel signal to be additionally inserted in the regional station equipment 5-i (i is an integer of 1 or more) provided with the multiplex signal changing device 52, that is, a video signal (regional production channel signal). Source) 83. The channel into which the channel signal is inserted is not limited to one channel. That is, the external signal may be a signal obtained by frequency-multiplexing channel signals of a plurality of channels as long as the optical input signal has a free band and does not affect the signal quality received at the subscriber's house 2. The synthesis unit 525 frequency-multiplexes the output from the frequency mixing unit 524 and the other output from the 90 ° hybrid unit 522. The electric light conversion unit 526 converts an electric signal frequency-multiplexed by the synthesis unit 525 into an optical signal, and then sends it out as an optical output signal.

The multiplex signal changing device 52 of the present embodiment can be connected in multiple stages as long as it does not affect the signal quality received at the subscriber's house 2.

The configuration from the 90 ° hybrid section 522 to the synthesis section 525 in the multiplex signal changing device 52 is the same as that of the Armstrong FM modulator which is one of the FM modulators. The Armstrong FM modulator is described in, for example, the literature "Yuya Ito, Akira Fujii," Easy-to-understand FM technology ", Kosaido Sanpo Publishing".

The Armstrong modulator applies a carrier wave as an input signal and a signal after passing through the integrator of the modulated signal as an input signal to the frequency mixing unit 524. Specifically, when the angular frequency of the carrier wave is ω _c and the angular frequency of the modulated signal is ω _s , the carrier wave _fc (t) is given by Eq. (1) and the modulated signal f _s (t) is given by Eq. (2). ).

However, _Ac is the amplitude of the carrier wave and t is the time. At this time, the output signal f _fm (t) is given by the following equation (3).

However, m _f represents the FM modulation degree. The above equation (3) can be approximated to the following FM modulated signal equation (4).

Therefore, the Armstrong modulator can be used as an FM modulator.

In the present embodiment, the FM batch-converted signal is used as the input signal instead of the equation (1) as the carrier wave, and the channel signal to be inserted as the modulation signal of the equation (2) is used, and the frequency mixing unit is directly used without going through the integrator. It is input to 524. It is not necessary to go through the integrator because the effect on the signal quality received without going through the integrator if the ratio of the lowest frequency to the highest frequency of the band of one channel signal to be inserted can be approximated to 1. It utilizes the fact that there is almost no.

By using the FM batch conversion signal instead of the carrier wave, an unnecessary strain component may be generated and the quality may be deteriorated. However, in an actual system, even if an error occurs in the transmission line due to quality deterioration, there is no problem as long as it can be corrected by the error correction code (Reed-Solomon code) used as the standard method for channel signals. It doesn't become.

By using the technique of the Armstrong FM modulator for the transmission line of the optical signal, it becomes possible to add another FM signal without demodulating the FM batch conversion signal, which has not been performed in the past.

(Second embodiment)
In the first embodiment, the channel signal is added to the video signal received from the centralized station transmission equipment in the regional station equipment, but in the present embodiment, some channel signals multiplexed with the received video signal are added. Disable viewing. In this embodiment, the difference from the first embodiment will be mainly described. The configuration of the broadcasting system and the configuration of the multiplex signal changing device of the present embodiment are the same as those of the first embodiment. In the present embodiment, the multiplex signal changing device 52 is a channel erasing device that gives noise to the video signals of some channels among the video signals of each channel multiplexed with the FM batch conversion signal so that they cannot be viewed. Operate.

In the present embodiment, a channel erasing signal is input as an external signal to the frequency mixing unit 524 of the multiplex signal changing device 52 shown in FIG. The channel erasing signal fits in the same 6 MHz bandwidth as a part of the channel signals to be erased (hereinafter referred to as the channel signal to be erased) among the plurality of channel signals transmitted from the aggregation station transmission equipment 4 as FM batch conversion signals. Moreover, it is a signal that does not have a correlation with the channel signal to be erased. The uncorrelated signal is, for example, an OFDM (Orthogonal Frequency Division Multiplexing) signal, a multi-level QAM (Quadrature Amplitude Modulation) signal, or a noise signal modulated by a random pattern. That is, the external signal of the present embodiment acts as noise on the channel signal to be erased. By setting the signal level of this external signal to a level that does not satisfy the required S / N (Signal to Noise) ratio of the channel signal to be erased, it is impossible to demodulate the channel signal to be erased, and erasure is realized. .. The multiplex signal changing device 52 mixes such an external signal with one of the signals branched into two by the 90 ° hybrid unit 522, and is delivered from, for example, the aggregation station transmission equipment 4 shown in FIG. 1 to a regional station. Only video signals that are delivered to equipment 5-2 but cannot be delivered to regional station equipment 5-1 can be erased.

The number of channel signals to be erased is not limited to one, and a plurality of channel signals can be erased as long as the signals delivered from the regional station equipment 5 are not affected. Further, the multiplex signal changing device 52 of the present embodiment can be connected in multiple stages as long as it does not affect the signal quality received at the subscriber's house 2.

(Third embodiment)
In the first embodiment, a channel signal is added to the video signal received by the regional station equipment, and in the second embodiment, some channel signals multiplexed with the video signal received by the regional station equipment are erased. However, in this embodiment, both are performed. In this embodiment, the difference from the first embodiment will be mainly described. The configuration of the broadcasting system and the configuration of the multiplex signal changing device of the present embodiment are the same as those of the first embodiment.

When the external signal to be inserted into the frequency mixing unit 524 of the multiplex signal changing device 52 shown in FIG. 2 is a signal of a plurality of channels, a part of the signal is used as one or more channel signals to be newly inserted, and the other one. The signal of the unit can be used in combination with one or more channel erasing signals which are signals having no correlation with the channel signal to be erased. By doing so, it is possible to simultaneously insert the channel signal into the video signal and erase the channel signal by one multiplex signal changing device 52.

Further, the multiplex signal changing device 52 of the present embodiment can be connected in multiple stages as long as it does not affect the signal quality received at the subscriber's house 2.

According to the embodiment described above, the multiplex signal changing device includes a branch portion, a frequency mixing portion, and a combine section. The branch portion is, for example, a 90 ° hybrid portion 522. The branch portion converts the FM batch conversion signal obtained by collectively FM-modulating the channel signal, which is the video signal of each channel, into the first signal and the second signal whose phases are different from each other by 90 degrees. Branch. The first signal is output to the frequency mixing unit, and the second signal is output to the compositing unit. The frequency mixing unit outputs a mixed signal in which the first signal and the third signal are mixed. The third signal is, for example, an external signal input to the frequency mixing unit 524. The third signal is one or more channel signals to be added to the free frequency band in the FM batch conversion signal when adding channels, and when erasing a part of the channel signals multiplexed with the FM batch conversion signal, the third signal is It is a signal that uses the same frequency band as the channel signal to be erased and has no correlation with the channel signal to be erased. The third signal may include both of these signals. The combined wave section combines the mixed signal and the second signal.

According to the embodiment described above, the video is distributed from the central station transmission equipment by the FM batch conversion method, and the video signal of the regional production channel is inserted without performing FM demodulation and FM remodulation in the regional station equipment in the middle. Or, it is possible to restrict the viewing of video signals of channels for which re-transmission has not been agreed to the distribution area of the regional station. Therefore, it is not necessary to prepare a transmission facility for transmitting the video signal of the regional production channel from each regional station facility to the central station transmission facility, and it is not necessary to prepare an FM demodulator and an FM modulator in each regional station facility. .. Therefore, it is possible to reduce the equipment cost of the broadcasting system using the FM batch conversion method.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and the design and the like within a range not deviating from the gist of the present invention are also included.

1 ... Transmission equipment, 2, 2-1 to 2-n ... Subscriber's house, 3, 6-1, 6-2 ... Optical network, 4, 4a ... Aggregate station transmission equipment, 5, 5-1 and 5-2 , 9, 9-1, 9-2, 9a, 9a-1, 9a-2, 9b, 9b-1, 9b-2 ... Regional station equipment, 7 ... Network, 10, 51, 91 ... Broadcasting equipment, 11, 41 ... Optical transmitter, 20-1 to 20-n ... Optical receiver, 42 ... Receiver, 50, 90 ... Optical relay transmitter, 52 ... Multiple signal changer, 92 ... Transmitter, 93, 93a, 93b ... Optical receiver, 94 ... Mixer, 95, 95a, 95b ... Optical transmitter, 100 ... Broadcast system, 521 ... Optical electrical conversion unit, 522 ... 90 ° hybrid unit, 523 ... Level adjustment unit, 524 ... Frequency mixing unit, 525 ... Synthesis unit, 526 ... Electric light conversion unit

Claims (2)

A branching part that branches an FM batch conversion signal obtained by collectively FM-modulating a channel signal that is a video signal of each channel into a first signal and a second signal that are 90 degrees out of phase with each other. When,
A signal that uses the same frequency band as a part of the channel signal to be erased that is multiplexed with the FM batch conversion signal and has no correlation with the channel signal to be erased, and an empty frequency in the FM batch conversion signal. A frequency mixing unit that outputs a mixed signal obtained by mixing either or both of the channel signals to be added to the band and the first signal.
A combined wave section that combines the mixed signal and the second signal,
A multi-signal changing device. A branching step in which an FM batch conversion signal obtained by collectively FM-modulating a channel signal that is a video signal of each channel and having frequency-multiplexed signals is branched into a first signal and a second signal whose phases are 90 degrees different from each other. When,
A signal that uses the same frequency band as a part of the channel signal to be erased that is multiplexed with the FM batch conversion signal and has no correlation with the channel signal to be erased, and an empty frequency in the FM batch conversion signal. A mixing step of generating a mixed signal in which a third signal including either or both of the channel signals to be added to the band and the first signal are mixed.
A combined wave step that combines the mixed signal and the second signal,
Multiple signal change method having.

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