JP5874432B2 - RF signal transmission system, signal output device, reception system, RF signal transmission method, broadcast system, broadcast machine, broadcast facility, and broadcast method - Google Patents

Description

  The present invention relates to an RF signal transmission system, a signal output device, a reception system, an RF signal transmission method, a broadcasting system, a broadcasting machine, broadcasting equipment, and a broadcasting method.

Wireless broadcast receivers such as television receivers or radio receivers are widespread throughout the world. For this reason, wireless broadcasting such as television broadcasting is very attractive as a means for transmitting information.
However, in order to provide a wireless broadcast service that can be received by a wireless broadcast receiver, a large-scale wireless broadcast facility is required.

In general, broadcasting equipment requires a broadcasting machine (broadcasting transmitter) and a transmission antenna. The broadcaster puts a video signal or an audio signal on a carrier wave to generate an RF (Radio Frequency) signal. The RF signal is output by a high-power amplifier and radiated as a radio wave from the transmitting antenna.
An RF signal radiated into space as a radio wave is received by a wireless broadcast receiver such as a television receiver via a receiving antenna.

Takao Wabo and Akira Yasuda (original author Richard Schreier, Gabor C. Temes) Introduction to ΔΣ analog / digital converters (Understanding Delta-Sigma Data Converters), Maruzen Co., Ltd., 2007

Broadcasting equipment is configured as a large-scale system for reasons such as being configured in a duplex system for stable operation.
In order to provide a broadcasting service in many regions / countries, it is necessary to install such a large-scale broadcasting facility in each region / country, which requires enormous costs. In addition, the maintenance and management of broadcasting facilities will be expensive.

  Conventional broadcasting services have a problem that a large amount of money is required to provide the services.

The inventor has realized that this problem is caused by handling a high-frequency analog signal called an RF signal.
Therefore, an object of the present invention is to perform transmission or broadcasting of an RF signal in a manner different from the conventional one.

(1) The present invention viewed from one viewpoint includes a first device that transmits a signal to a signal transmission path, and a second device that receives a signal from the signal transmission path, and the first device includes an RF signal. The second apparatus, comprising: a delta-sigma modulator that performs delta-sigma modulation and outputs a quantized signal; and a transmission unit that transmits the quantized signal output from the delta-sigma modulator to the signal transmission path. A receiving unit that receives the quantized signal from the signal transmission path, a buffer that stores the quantized signal received by the receiving unit, an output unit that outputs the quantized signal stored in the buffer, An RF signal transmission system comprising:

  According to the present invention relating to the above RF signal transmission system, the RF signal is converted into a quantized signal by ΔΣ modulation. Therefore, the RF signal that has become the quantized signal can be transmitted as a digital signal through the signal transmission path. In addition, since the second device that receives the quantized signal includes the buffer, the quantized signal can be output at a necessary speed regardless of the transmission speed in the signal transmission path.

(2) The transmission unit is configured to be capable of transmitting information, and the information transmitted by the transmission unit is used in the second device to reproduce the signal waveform of the quantized signal output from the ΔΣ modulator. Preferably included. In this case, since the second device can acquire information used to reproduce the signal waveform of the quantized signal output from the ΔΣ modulator, it is not necessary to know the information in advance.

(3) It is preferable that the transmitting unit packetizes the quantized signal and outputs the packet to the signal transmission path, and the receiving unit receives the packetized quantized signal and depackets it. When the quantized signal is packetized, the signal can be transmitted via a signal transmission path (for example, the Internet) through which packet communication is performed.

(4) The signal transmission path is preferably a wired signal transmission path. Although the RF signal is handled, the signal transmission path is wired so that it is not subject to legal restrictions regarding radio waves.

(5) The output unit preferably outputs the quantized signal to a receiver that receives an RF signal. In this case, the quantized signal is given to the receiver as an RF signal.

(6) The second device further includes an antenna that radiates an RF signal to the space as a radio wave, and the second device radiates the quantized signal output from the output unit as a radio wave by the antenna. It is preferably used as an RF signal. In this case, the second device can radiate the RF signal transmitted through the signal transmission path as a radio wave.

(7) It is preferable that the RF signal includes an RF signal of a video signal.

(8) The RF signal is preferably an RF signal for digital television broadcasting.

(9) The ΔΣ modulator is preferably a bandpass ΔΣ modulator.

(10) From another viewpoint, the present invention saves a quantized signal obtained by ΔΣ modulation of an RF signal from a signal transmission path, and a quantized signal received by the receiving unit. A signal output device comprising: a buffer; and an output unit that outputs the quantized signal stored in the buffer as a signal including an RF signal.

(11) The present invention viewed from still another viewpoint includes a receiver that receives an RF signal, and the signal output device according to (10), wherein the signal output device is A reception system that outputs the quantized signal.

(12) The present invention viewed from still another aspect is an RF signal transmission method, comprising: transmitting a quantized signal obtained by ΔΣ modulation of an RF signal to a signal transmission path; and Receiving from the signal transmission path, storing the received quantized signal in a buffer, and outputting the quantized signal stored in the buffer to a receiver that receives an RF signal; It is the transmission method of RF signal characterized by including.

(13) The present invention viewed from still another viewpoint includes a transmission device that transmits a signal to a signal transmission path and one or a plurality of broadcasting facilities, and the transmission device performs ΔΣ modulation on the broadcast RF signal. And a first transmission unit that transmits the quantized signal output from the ΔΣ modulator to the signal transmission path, and the broadcasting facility is for broadcasting An antenna that radiates an RF signal to a space as a radio wave, and a broadcaster that outputs a broadcast RF signal to the antenna, the broadcaster receiving the quantized signal from the signal transmission path; A second transmission unit that outputs the quantized signal received by the reception unit as the broadcast RF signal to the antenna.

According to the present invention relating to the above broadcasting system, the RF signal for broadcasting is converted into a quantized signal by ΔΣ modulation. Therefore, the broadcast RF signal that has become the quantized signal can be transmitted as a digital signal through the signal transmission path.
In the broadcasting machine, the received quantized signal can be radiated from the antenna as a radio wave signal for broadcasting.

(14) The broadcaster further includes a buffer that stores the quantized signal received by the receiving unit, and the second transmitting unit converts the quantized signal stored in the buffer to the broadcast RF The signal is preferably output to the antenna. Since the broadcaster includes a buffer, the broadcaster can output the quantized signal at a necessary speed regardless of the transmission speed in the signal transmission path.

(15) The first transmission unit is configured to be capable of transmitting information, and the information transmitted by the first transmission unit is configured to reproduce the signal waveform of the quantized signal output from the ΔΣ modulator. It preferably contains information used in the machine.
In this case, since the broadcaster can acquire information used to reproduce the signal waveform of the quantized signal output from the ΔΣ modulator, it is not necessary to know the information in advance.

(16) It is preferable that the first transmitting unit packetizes the quantized signal and transmits the packet to the signal transmission path, and the receiving unit receives the packetized quantized signal and depackets it. When the quantized signal is packetized, the signal can be transmitted via a signal transmission path (for example, the Internet) through which packet communication is performed.

(17) The ΔΣ modulator is preferably a bandpass ΔΣ modulator.

(18) From another viewpoint, the present invention provides a reception unit that receives a quantized signal obtained by ΔΣ modulation of a broadcast RF signal from a signal transmission path, and the quantization received by the reception unit. And a transmitter that outputs a signal to the antenna as the broadcast RF signal.

(19) The present invention viewed from still another aspect includes the broadcasting device according to the above (16), and an antenna that radiates the quantized signal output from the transmission unit of the transmitter to space. It is a broadcasting facility characterized by

(20) According to still another aspect of the present invention, a broadcast RF signal is ΔΣ-modulated to obtain a quantized signal, the quantized signal is transmitted to a broadcaster, and the broadcaster receives And outputting the quantized signal as an RF signal for broadcasting to an antenna.

1 is a configuration diagram of a broadcasting system according to an embodiment. It is a block diagram of broadcasting equipment (parent equipment). It is a block diagram of a signal output device. It is a block diagram of broadcasting equipment (child equipment). It is a block diagram of a ΔΣ modulator. This is a primary low-pass type ΔΣ modulator. (A) is an output spectrum of the low pass type ΔΣ modulator, and (b) is an output spectrum of the band pass type ΔΣ modulator. (A) is an output spectrum of the low pass type ΔΣ modulator, and (b) is an output spectrum of the band pass type ΔΣ modulator. (A) is an output spectrum of the low pass type ΔΣ modulator, and (b) is an output spectrum of the band pass type ΔΣ modulator. (A) is a polar coordinate indicating the operation of the low-pass ΔΣ modulator, and (b) is a polar coordinate indicating the operation of the bandpass ΔΣ modulator. This is a secondary band-pass ΔΣ modulator obtained by converting from a primary low-pass ΔΣ modulator. This is a low-pass ΔΣ modulator having a CRFB structure. This is a bandpass type ΔΣ modulator obtained by conversion from a low pass type ΔΣ modulator having a CRFB structure. FIG. 6 is an output spectrum waveform diagram of a bandpass ΔΣ modulator for θ ₀ = π / 4. It is an output spectrum waveform diagram of a band pass type ΔΣ modulator for θ ₀ = 3π / 4. It is an output spectrum waveform diagram of a band pass type ΔΣ modulator for θ ₀ = 5π / 4. It is an output spectrum waveform diagram of a band pass type ΔΣ modulator for θ ₀ = 7π / 4. It is a block diagram of the broadcast facility which has a zone | band extension part. It is explanatory drawing of the extended signal band. It is a figure which shows the pass characteristic of the extended signal band and a band pass filter. It is a figure which shows a main signal component and a harmonic component.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[1. RF signal transmission system (broadcasting system)]
FIG. 1 shows a broadcasting system. This broadcasting system uses an RF signal transmission system 1 that transmits an RF signal for wireless broadcasting service via a signal transmission path 4.
The RF signal transmission system 1 is used for providing a broadcasting service to a viewer (television receiver). The RF signal transmission system 1 is used to transmit an RF signal for broadcasting service to the broadcasting facilities 5 and 5 at remote locations.

[2. Provision of broadcasting services to viewers]
The broadcast system (RF signal transmission system 1) shown in FIG. 1 includes a broadcast facility (first device) 2 that transmits a broadcast RF signal for digital terrestrial television broadcasting. The broadcast system (RF signal transmission system 1) includes a signal output device (second device) 3 as a viewer-side device.

  The broadcasting facility 2 has the same function as the broadcasting facility of a conventional television broadcasting station. That is, the broadcast facility 2 modulates the video signal / audio signal of the broadcast content (the content photographed by the television studio 2a or the broadcast content stored in the content storage unit) with the carrier wave and converts it into an RF signal. The RF signal is radiated as a radio wave from the antenna 2c.

  Radio waves (RF signals) radiated from the antenna 2c can be received by the television receivers 7A and 7A in the area A where the antenna 2c is installed. In other words, the broadcasting facility 2 can provide a wireless broadcasting service to viewers in the area A by transmitting RF signals as radio waves in the area A.

  The broadcasting facility 2 has not only functions similar to those of the conventional broadcasting facility, but also the signal transmission path 4 (outside the area where the radio wave of the antenna 2c reaches) outside the area A using the RF signal transmission system 1. 4a, 4b, 4c, 4d) can transmit RF signals.

  As shown in FIG. 2, the broadcasting facility 2 includes a transmission device (first device) for the RF signal transmission system 1. The transmission device (first device) includes a digital signal processing unit 21. The broadcasting facility 2 includes a wireless transmitter 60 for performing the same wireless broadcasting as the conventional broadcasting facility.

  The digital signal processing unit 21 performs processing for expressing the RF signal with a quantized signal (packetized quantized signal) that is a digital signal, and outputs the generated quantized signal. The quantized signal output from the digital signal processing unit 21 is output to the optical transmission line 4a by an electro-optical converter (optical link) 22 that is an output unit of the quantized signal.

In the RF signal transmission system 1 of the present embodiment, a quantized signal as a digitized RF signal is transmitted to the optical transmission line 4a. When digitizing an RF signal, it is generally necessary to sample at a frequency sufficiently higher than the frequency (carrier frequency) of the RF signal. For example, if the frequency of the RF signal is several hundred MHz, a very high sampling speed of about several tens of GS / s is required.
For this reason, when an RF signal is digitized and transmitted, a very high transmission rate is required, or the amount of information becomes very large. For this reason, conventionally, it was theoretically impossible to digitize and transmit a very high frequency RF signal, but it was not practical.

  However, in the RF signal transmission system 1 of the present embodiment, ΔΣ modulation (particularly, bandpass type ΔΣ modulation) is performed on the RF signal, so the RF signal is digitized and transmitted regardless of the frequency of the RF signal. It is practically possible to do this. The ΔΣ modulation will be described later.

  The digital signal processing unit 21 includes a baseband unit 23 that outputs a baseband signal (IQ signal) that is a transmission signal, a modulator (orthogonal modulator) 24a that modulates the baseband signal, a processing unit 24b, a bandpass A type ΔΣ modulator 25 and a transmission unit (first transmission unit) 26 are provided.

  The baseband unit 23 acquires the video signal and audio signal of the content acquired from the television studio 2a or the storage unit 2b. The baseband unit 23 outputs IQ baseband signals (I signal and Q signal) of the acquired video signal and audio signal as digital data.

The modulator 24a converts the IQ baseband signal into an intermediate frequency signal. The modulator 24a is configured as a digital quadrature modulator that performs quadrature modulation by digital signal processing. Therefore, a signal (digital IF signal) in a digital signal format expressed by multi-bit digital data (discrete values) is output from the quadrature modulator 24a.
Note that the modulator 24a that generates the modulated wave is not limited to the quadrature modulator, and may be a modulator of another type for generating the modulated wave.

  The IF signal output from the modulator 24 a is given to the processing unit 24 b in the digital signal processing unit 21. The IF signal output from the modulator 24 a is also given to the wireless transmitter 60.

The processing unit 24b performs various digital signal processing such as DPD (Digital Pre-distortion), CFR (Crest Factor Reduction), and DUC (Digital Up Conversion) on the IF signal. The processing unit 24b outputs an RF signal generated by digital signal processing.
The frequency of the carrier wave of the RF signal is set to the frequency of the channel in the terrestrial digital television broadcast if the RF signal is for terrestrial digital television broadcast.
The radio transmitter 60 may be provided with an RF signal output from the processing unit 24b.

  The digital RF signal output from the processing unit 24 b is given to the ΔΣ modulator 25. The ΔΣ modulator 25 of the present embodiment is configured as a bandpass type ΔΣ modulator, but may be a low pass type ΔΣ modulator.

The ΔΣ modulator 25 performs ΔΣ modulation on the RF signal and outputs a 1-bit quantized signal (pulse signal). The bandpass type ΔΣ modulator 25 is set so that its center frequency matches the frequency of the carrier wave.
Note that the quantized signal output from the ΔΣ modulator 25 does not have to be 1 bit. The quantized signal output from the ΔΣ modulator 25 may be smaller than the number of bits of digital data input to the ΔΣ modulator 25.

The quantized signal (ΔΣ modulated signal) output from the ΔΣ modulator 25 is transmitted by the transmitter 26 to the signal transmission optical transmission line 4a (4).
The transmission unit (first transmission unit) 26 packetizes the quantized signal (ΔΣ modulation signal) as a digitized RF signal, and transmits the packetized data. The transmission unit 26 performs processing necessary for packet communication such as packet retransmission.

  The transmission unit 26 also transmits necessary information to the reception side (the signal output device 3 or the broadcaster 5 described later) in the packet data. The information transmitted by the transmission unit 26 includes the quantized signal (pulse-like) output from the ΔΣ modulator 25 by the device (the signal output device 3 or the broadcasting device 5) that has received the quantized signal. Information (reproduction information) to be reproduced as a signal having the same waveform (pulse waveform) as (ΔΣ modulation signal).

  The ΔΣ modulator 25 outputs a pulsed quantized signal (ΔΣ modulation signal) at a rate corresponding to the sampling frequency fs. If only the quantized value indicated by such a quantized signal is simply converted into packet data, the bit data indicating the quantized value is only included in the packet data, and information regarding the rate of the quantized signal is lost. Therefore, the transmitting unit 26 receives the pulsed ΔΣ modulation output from the Σ modulator 25 from the bit string indicating the quantized value on the reception side (the signal output device 3 or the broadcasting device 5) of the packetized quantized signal. The packet data is transmitted including the reproduction information so that the signal can be reproduced.

The reproduction information includes, for example, information (sampling rate information) indicating a sampling rate (sampling frequency) in the ΔΣ modulator 25. If the quantized value indicated by the quantized signal is pulsed at a speed corresponding to the sampling speed, the pulsed ΔΣ modulated signal output from the Σ modulator 25 can be reproduced.
When the quantized signal is multi-bit, the reproduction information may include information indicating the number of bits of the quantized signal.

Note that. When the reproduction information is already known on the receiving side (the signal output device 3 or the broadcaster 5), the transmission unit 26 does not need to transmit the reproduction information.
Further, when a quantized signal as a digitized RF signal is transmitted to the optical transmission line 4a while maintaining a signal waveform as a 1-bit or multi-bit pulse signal, the receiving side (the signal output device 3 or Since it is not necessary for the broadcaster 5) to reproduce the signal, transmission of reproduction information is not required.

The packet data output from the transmission unit 26 is converted into an optical signal by the electro-optical converter (optical link) 22 and transmitted to the optical transmission line 4a. The optical transmission line 4a is connected to the Internet. That is, the packet data is transmitted via the Internet 4 that is a signal transmission path.
The electro-optical converter (optical link) 22 may be provided as a device different from the transmission device in the broadcasting facility 2.

  In the RF signal transmission system 1 of the present embodiment, the quantized signal as a digitized RF signal is packetized, so that a communication network that performs packet communication such as the Internet 4 can be used as a signal transmission path.

The digitized RF signal may be transmitted by a signal transmission path configured as a dedicated line or by a circuit switching type signal transmission path. Occupying communication is performed, so it tends to be expensive.
On the other hand, a communication network that performs packet communication such as the Internet 4 can be used as a signal transmission path, and the cost can be reduced.
In addition, since the RF signal is digitized by ΔΣ modulation (particularly, band-pass ΔΣ modulation), the amount of information is relatively small, so that it is suitable for packet communication.
When a signal transmission path (such as a dedicated line) that does not require packetization is used, the packetization function in the transmission unit 26 can be omitted.

In the case of packet communication, since the transmission speed of the signal transmission path 4 is not guaranteed, it is not possible to transmit the quantized signal output from the ΔΣ modulator 25 to the signal transmission path 4 while maintaining the signal waveform as a pulse signal. However, by exchanging the reproduction information described above, the receiving side (signal output device 3 or broadcaster 5) can receive the pulsed ΔΣ modulation signal output from the Σ modulator 25 even from the packetized quantized signal. It is easy to reproduce.
Even if the communication is not packet communication but occupies the signal transmission path, the transmission speed of the signal transmission path 4 is not sufficient to transmit the quantized signal output from the ΔΣ modulator 25 as it is (ΔΣ When the transmission speed of the signal transmission path 4 is lower than the sampling speed (1 / fs) of the modulator 25), it is necessary to convert the quantized signal into a signal that is low enough to be transmitted by the signal transmission path 4. Even in this case, the receiving side (the signal output device 3 or the broadcasting device 5) can continue to output the Σ modulator 25 from the quantized signal converted to low speed by exchanging the reproduction information described above. It is easy to reproduce the quantized signal.

Here, the wireless transmitter 60 in the broadcasting facility 2 shown in FIG. 2 includes a DA converter (DAC) 61, a frequency converter 62, and a power amplifier 63. The DA converter 61 converts the digital signal (IF signal) output from the digital modulator into an analog signal. The frequency converter 62 performs frequency conversion for converting the analog IF signal into an RF signal. The power amplifier 63 amplifies the RF signal and outputs it to the antenna 2 c of the broadcasting facility 2. When the RF signal is supplied to the DA converter 61, the frequency converter 62 can be omitted.
Further, when the broadcasting facility 2 does not perform wireless broadcasting, the wireless transmitter 60 and the antenna 2c may be omitted. In this case, the broadcasting facility 2 does not substantially have an analog circuit that causes an increase in cost, and most of the broadcasting facility 2 is configured by the digital signal processing unit 21, so that the cost of the broadcasting facility 2 can be reduced. .
Further, in the case where an additional transmission device (first device) 2 for the RF signal transmission system 1 is additionally provided in the existing broadcasting equipment 2 capable of wireless broadcasting, it is sufficient to provide the digital signal processing unit 21 and the like. Low cost.

The radio wave radiated from the antenna 2c of the broadcasting facility 2 can be received only by the receiver 7A within the range (area A) where the radio wave reaches.
On the other hand, the quantized signal transmitted from the broadcasting facility 2 to the signal transmission path (Internet) 4 can be received not only in the region A but also in all regions / countries in the world that can be connected to the Internet.

  FIG. 1 shows a state where a quantized signal (a digitized RF signal) transmitted from the broadcasting equipment (first device) 2 in the area A is received by the television receiver 7B installed in the area B. It was. The quantized signals transmitted from the signal transmission paths 4 and 4B are received by the signal output device (second device) 3 and output to the television receiver 7B.

As shown in FIG. 3, the signal output device (second device) 3 includes an optical-electrical converter (optical link) 31, a receiving unit 32, a buffer 33, an output unit 34, and a switch unit 35. I have.
Note that the photoelectric converter 31 may be provided as a separate device from the signal output device 3.

  An optical-electrical converter (optical link) 31 converts an optical signal (packet data; packetized quantized signal) transmitted from an optical transmission line 4b connected to the Internet 4 into an electrical signal and outputs it. To do.

The receiving unit 32 depackets the packet data converted into the electrical signal, and extracts a quantized signal (quantized value of the quantized signal) and other information (reproduction information) from the packet data. The receiving unit 32 performs processing necessary for packet communication such as a packet retransmission request.
When the quantized signal is not packetized, the depacketizing function of the receiving unit 32 can be omitted.

  The quantized signal received by the receiving unit 32 is temporarily stored in a (FIFO; First In First Out) type buffer 33. Further, the reproduction information (sampling speed information) received by the receiving unit 32 is given to the output unit 34.

  By temporarily storing the received quantized signal in the buffer 33 and outputting it, the quantized signal can be obtained even if the transmission speed of the signal transmission path is not constant or the packet is lost. It is possible to output continuously at a predetermined rate (a rate corresponding to the sampling speed indicated by the reproduction information) without any breaks. That is, by providing the buffer 33, it is possible to cope with a case where a quantized signal is transmitted by packet communication or a case where the signal transmission path 4 has no speed guarantee. If the transmission speed of the signal transmission path 4 is sufficiently high, the buffer 33 can be omitted.

The output unit 34 outputs the quantized signal (quantized value of the quantized signal) stored in the buffer 33 as a pulse signal at a predetermined rate (a rate corresponding to the sampling rate indicated by the reproduction information).
That is, the quantized signal output from the output unit 34 reproduces the signal waveform of the quantized signal output from the ΔΣ modulator 25.
Note that it is not necessary to use the reproduction information received by the receiving unit 32, and the reproduction information may be set in advance in the signal output device 3.

The quantized signal output from the ΔΣ modulator (bandpass type ΔΣ modulator) 25 holds information as an RF signal in the vicinity of the carrier frequency of the RF signal. Therefore, the quantized signal output from the output unit 34 also holds information as an RF signal.
For this reason, when the quantized signal output from the output unit 34 is given as an RF signal input of the television receiver 7B, the television receiver 7B can receive the quantized signal as an RF signal. That is, the television receiver 7B can receive the RF signal transmitted via the RF signal transmission system 1 in the same manner as the RF signal transmitted as a wireless broadcast.

Note that the quantized signal has quantized noise that is noise-shaped in the ΔΣ modulator 25, and when it is desired to remove the quantized noise and extract the RF signal, the frequency near the carrier frequency of the RF signal. It is necessary to use a band-pass filter that passes. However, if a radio broadcast receiver such as the television receiver 7B has a bandpass filter that cuts signals of unnecessary frequencies, it is not necessary to provide a bandpass filter in the signal output device 3.
Of course, a band pass filter may be provided. In this case, the output unit 34 may output the quantized signal to the television receiver 7B via the band pass filter.

The switch unit 35 selectively transmits the quantized signal (RF signal) output from the output unit 34 and the RF signal received by the antenna 38 (radio waves broadcast from the broadcasting equipment in the area B) to the television set. This is given to the receiver 7B.
The signal output device 3 has an antenna terminal 36 (for example, a terminal for a coaxial cable) to which the antenna 38 is connected, and an RF signal received by the antenna 38 can be input to the signal output device 3. Yes. When an RF signal having the same channel (frequency) as the RF signal received by the antenna 38 is output from the output unit 34, the switch unit 35 receives only one of the RF signals from the television receiver in order to avoid interference. 7B.

Whether the switch unit 35 is connected to the antenna 38 side or the output unit 34 side is appropriately set by the viewer (user) depending on which of the broadcasts is desired to be received.
When there is no fear of interference, both the RF signal from the antenna 38 and the RF signal from the output unit 34 may be given to the television receiver 7B.
Note that the antenna 38 may not be connected to the signal output device 3.

In FIG. 3, the signal output device 3 is configured as a separate device from the television receiver 7B. An RF signal output terminal 37 (for example, a terminal for a coaxial cable) in the signal output device 3 and an antenna terminal 7B-1 (for example, a terminal for a coaxial cable) of the television receiver 7 are connected by a cable such as a coaxial cable. By being connected, the signal output device 3 and the television receiver 7B constitute one reception system.
On the other hand, the signal output device 3 may be configured as an integrated reception system built in the television receiver 7B. That is, you may comprise as a receiving system which has the function as a television receiver, and the function as the signal output device 3 integrally.
By configuring it as an integrated reception system, it is possible to achieve high functionality with the same handling as a conventional television, and it does not burden the viewer for introducing technology.

When the signal output device 3 according to the present embodiment is used, a broadcasting service provided by the broadcasting facility 2 can be received via the Internet even in a region / country far from the broadcasting facility 2.
In addition, the signal output device 3 can be used as a countermeasure for difficult viewing areas. That is, in an area where radio waves from the broadcast facility 2 cannot be received, the broadcast service can be received via the Internet 4 by using the signal output device 3.

  Furthermore, in the RF signal transmission system 1 of the present embodiment, the transmission of the RF signal from the area A to the area B is transmitted not by radio waves but by the wired signal transmission path 4, which is subject to legal regulations regarding radio waves. Absent.

[3. Transmission to remote broadcasting equipment]
In the broadcasting system (RF signal transmission system 1) shown in FIG. 1, the broadcasting facility 2 is digitized with respect to the broadcasting facilities 5 and 5 installed in other regions / countries (regions C and D in FIG. 1). It is also used for transmitting broadcast RF signals. For this reason, the broadcasting system (RF signal transmission system 1) includes broadcasting facilities 5 and 5 for other areas C and D.

The broadcasting facilities 5 and 5 in the regions C and D receive the RF signal transmitted from the broadcasting facility 2 in the region A, and radiate the received RF signal from the antenna 55 as radio waves. Thereby, the broadcasting equipment 5 and 5 can make the television receivers 7C and 7D in the areas C and D receive the RF signal transmitted from the broadcasting equipment 2.
That is, if the broadcasting facility 2 in the region A is a parent facility for broadcasting service, the broadcasting facilities 5 and 5 in the regions C and D can be said to be child facilities.

The broadcasting facilities 5 and 5 that are sub-equipment include a broadcasting device (hereinafter referred to as “broadcasting device 5”) and an antenna 55.
As shown in FIG. 4, the broadcaster (second device) 5 includes an optical-electrical converter (optical link) 51, a receiving unit 52, a buffer 53, and a transmitting unit (second transmitting unit) 54. I have.
Note that the photoelectric converter 51 may be provided as a separate device from the broadcaster 5.

  The optical-electrical converter (optical link) 51 converts an optical signal (packet data; packetized quantized signal) transmitted from the optical transmission lines 4c and 4d connected to the Internet 4 into an electrical signal. Output.

The receiving unit 52 depackets the packet data converted into the electrical signal, and extracts a quantized signal (quantized value of the quantized signal) and other information (reproduction information) from the packet data. The receiving unit 52 performs processing necessary for packet communication such as a packet retransmission request.
When the quantized signal is not packetized, the depacketizing function of the receiving unit 52 can be omitted.

  The quantized signal received by the receiving unit 52 is temporarily stored in a (FIFO; First In First Out) type buffer 53. The reproduction information (sampling speed information) received by the receiving unit 52 is given to the output unit 54 a of the transmitting unit 54.

  By temporarily storing the received quantized signal in the buffer 53 and outputting it, even if the transmission speed of the signal transmission path is not constant or there is a packet loss, the quantized signal is It is possible to output continuously at a predetermined rate (a rate corresponding to the sampling speed indicated by the reproduction information) without any breaks. In other words, the provision of the buffer 53 can cope with a case where a quantized signal is transmitted by packet communication or a case where the signal transmission path 4 has no speed guarantee. If the transmission speed of the signal transmission path 4 is sufficiently high, the buffer 53 can be omitted.

  The transmission unit 54 includes an output unit 54a, an analog filter (bandpass filter) 54b, and an amplifier (power amplifier 54) c.

The output unit 54a outputs the quantized signal (quantized value of the quantized signal) stored in the buffer 53 as a pulse signal at a predetermined rate (a rate corresponding to the sampling rate indicated by the reproduction information).
That is, the quantized signal output from the output unit 54a is a reproduction of the signal waveform of the quantized signal output from the ΔΣ modulator 25.
Note that it is not necessary to use the reproduction information received by the receiving unit 52, and the reproduction information may be set in advance in the broadcasting device 5.

  The bandpass filter (analog bandpass filter) 54b is a bandpass filter that passes frequencies near the carrier frequency of the RF signal. When the quantized signal output from the output unit 54a passes through the band-pass filter 54b, the quantization noise noise-shaped in the Σ modulator 25 is removed. That is, an analog RF signal is output from the bandpass filter 54b.

  The power amplifier 54 c amplifies the RF signal output from the band pass filter 54 b and outputs it to the antenna 55. Thereby, the broadcasting equipment 5 and 5 can make the television receivers 7C and 7D in the areas C and D receive the RF signal transmitted from the broadcasting equipment 2.

When the antenna 55 has a characteristic as a band pass filter, the band pass filter 54b may be omitted.
Further, the amplifier 54c may be provided not only in the subsequent stage of the filter 54b but also in the previous stage of the filter 54b. A digital amplifier can be adopted as the amplifier 54c provided in front of the filter 54b. Since the digital amplifier operates in a saturated state, it is highly efficient. When the amplifier 54c is provided before the filter 54b, the amplifier 54c after the filter 54b may be omitted.

When the broadcasting device (second device) 5 according to the present embodiment is used, even in a region / country far from the broadcasting facility (first device) 2 that is the parent facility, the signal transmission path such as the Internet 4 is used. A digitized RF signal can be obtained.
In addition, since the RF signal has already been generated in the broadcasting facility (first device) 2 that is the parent facility, the broadcasting devices (second devices) 5 and 5 that are the subsidiary facilities have the RF signal from the baseband signal. It is not necessary to perform processing (digital signal processing such as quadrature modulation, DPD, CFR, and DUC) for generating. Therefore, the configuration of the broadcasting devices (second devices) 5 and 5 that are the child facilities can be relatively simplified.
As a result, it is possible to reduce the costs of the broadcasting equipment (second devices) 5 and 5 that are the child equipment. The merit of cost reduction increases as the number of broadcasting devices (second devices) 5 and 5 that are sub-equipment increases.

  Accordingly, when a content that is wirelessly broadcast in the region A is newly provided by wireless broadcasting in the regions C and D, it is only necessary to install a low-cost broadcasting device. Can be started at low cost.

[4. Globalization of broadcasting]
By using the broadcasting system of the present embodiment, it becomes possible to provide broadcasting services globally across regions and countries.
For example, when there is a time difference between the area A and the areas C and D, since the area A is nighttime (a time zone during which no broadcast is performed), when the broadcast equipment 2 is stopped, It can be used effectively. For example, when the area A is nighttime, the broadcasting facility 2 does not pause, but transmits the RF signal to the regions C and D that are in the daytime (the time zone in which broadcasting is performed). Can be used effectively.

  In addition, since the broadcasting service can be started in the areas C and D where the RF signal is provided without installing the conventional expensive broadcasting equipment, the conventional expensive broadcasting equipment is often installed in the areas C and D. Even if this is not the case, it is possible to enhance the broadcasting service.

Further, in the regions C and D, if the broadcasting facility 2 (the wireless transmitter 60 may be omitted) which is a parent facility is installed, contents transmitted from the regions C and D can be transmitted to various regions such as the region A. Can be offered at.
Therefore, it is possible for viewers around the world to view various contents transmitted from each country.

[5. Bandpass ΔΣ modulation]
[5.1 Basic Configuration of ΔΣ Modulator]
As shown in FIG. 5, the ΔΣ modulator 25 includes a loop filter 27 and a quantizer 28 (see Non-Patent Document 1).
In the ΔΣ modulator 25 shown in FIG. 5, an input (in this embodiment, an RF signal) U is given to the loop filter 27. The output Y of the loop filter 27 is supplied to a quantizer (for example, 1-bit quantizer) 28. The output (quantized signal) V of the quantizer 28 is given as another input to the loop filter 27.

The characteristic of the delta-sigma modulator 25 can be represented by a signal transfer function (STF) and a noise transfer function (NTF; Noise Transfer Function).
That is, when the input of the ΔΣ modulator 25 is U, the output of the ΔΣ modulator 25 is V, and the quantization noise is E, the characteristics of the ΔΣ modulator 25 are expressed in the z region as follows. is there.

  Therefore, given the desired NTF and STF, the transfer function of the loop filter 27 can be obtained.

Such ΔΣ modulation is a kind of oversampling modulation, and is generally a technique used for AD conversion or DA conversion.
In ΔΣ modulation, noise shaping (Noise Shaping) is performed in which the quantization noise in the signal band is moved outside the signal band to greatly reduce the quantization noise in the signal band.

FIG. 6 shows a block diagram of a linear z-domain model of the first-order low-pass type ΔΣ modulator 125. Reference numeral 127 represents a loop filter portion, and reference numeral 128 represents a quantizer. When the input to the ΔΣ modulator 125 is U (z), the output is V (z), and the quantization noise is E (z), the characteristics of the ΔΣ modulator 125 are expressed in the z region. It is as follows.
V (z) = U (z) + (1-z ⁻¹ ) E (z)

That is, in the primary low-pass ΔΣ modulator 125 shown in FIG. 6, a signal transfer function STF (z) = 1, the noise transfer function ^{NTF (z) = 1-z} -1.

[5.2 Low-pass ΔΣ modulation and bandpass ΔΣ modulation]
In general, the term “ΔΣ modulation” refers to low-pass ΔΣ modulation.
In the low-pass ΔΣ modulation, as shown in FIG. 7A, the noise shaping is performed so that the low-frequency quantization noise moves to the higher frequency side and the low-frequency quantization noise is attenuated. That is, in the low-pass type Δ modulation, the noise transfer function (NTF) has a characteristic of blocking passing noise at a low frequency (near 0 Hz).

  In order to perform oversampling, the frequency of the signal subjected to ΔΣ modulation needs to be sufficiently smaller than the sampling frequency fs of the low-pass ΔΣ modulator. In other words, a sufficiently high sampling frequency fs is required for the signal frequency. For example, a sampling frequency fs of about 128 times the signal frequency is required.

  On the other hand, in the bandpass type ΔΣ modulation, as shown in FIG. 7B, the noise transfer function (NTF) blocks the passing noise at a frequency higher than 0 Hz.

In the band-pass ΔΣ modulation, not the signal frequency f ₀ but the signal bandwidth f _B should be sufficiently smaller than the sampling frequency fs.
Therefore, in the bandpass type ΔΣ modulation, the frequency (center frequency) f ₀ of the signal subjected to ΔΣ modulation may be equal to or lower than the sampling frequency fs.
In other words, in the band-pass ΔΣ modulation, the sampling frequency fs may be sufficiently larger than the signal bandwidth f _B. For example, a sufficiently large sampling frequency fs of about 64 times the signal bandwidth f _B is sufficient.

Here, for example, it is assumed that the carrier frequency f _{0 of} radio broadcast is 1 GHz and the signal band f _B is 20 MHz. When low-pass ΔΣ modulation is performed on a modulation wave (RF signal) of such a radio frequency, the maximum frequency of the modulation wave is about 1 GHz, so that the maximum frequency of the modulation wave is 1 GHz. A sufficiently large (about 128 times) sampling frequency fs (= about 128 GHz) is required. As described above, low-pass ΔΣ modulation is suitable for an RF signal having a relatively low carrier frequency (for example, an RF signal for radio broadcasting), but an RF signal having an extremely high carrier frequency (for example, a television signal) For the broadcast RF signal), the sampling frequency (sampling speed) is too high.

On the other hand, in the band-pass ΔΣ modulation, the sampling frequency fs may be sufficiently larger than the signal bandwidth f _B , so that if the signal band is an RF signal of 20 MHz, 20 MHz × 64 = 1. A sampling frequency fs of about 28 GHz (sampling rate = 1.28 GS / S) may be used. If the signal band is 5 MHz, a sampling frequency of 320 MHz (sampling speed = 320 MS / s) may be used.
Thus, the band-pass type ΔΣ modulation is advantageous because the sampling frequency (sampling speed) can be reduced.

[5.3 Design of bandpass type ΔΣ modulator]
[5.3.1 Conversion formula]
According to Non-Patent Document 1, a low pass type ΔΣ modulator can be converted into a band pass type ΔΣ modulator by performing the following conversion on the low pass type ΔΣ modulator.

By replacing z in the z region model of the low-pass ΔΣ modulator 125 with z ′ = − z ² in accordance with the above conversion formula, a band-pass ΔΣ modulator can be obtained.

Using the above conversion equation, an n-order low-pass ΔΣ modulator (n is an integer of 1 or more) can be converted to a 2n-order band-pass Σ modulator.
For example, the frequency characteristic of the first-order low-pass ΔΣ modulator 125 is as shown in FIG. The frequency characteristic of the secondary bandpass ΔΣ modulator obtained by converting the primary lowpass ΔΣ modulator 125 with the above conversion formula is as shown in FIG. In FIG. 8, the horizontal axis θ is the normalized frequency.

  Although the signal transfer function and noise transfer function of the bandpass ΔΣ modulator obtained by the above conversion equation have the same gain as the low-pass ΔΣ modulator 125 before conversion, the frequency characteristics shown in FIG. The frequency characteristic shown in FIG. 8A is compressed by half and folded.

  The bandpass ΔΣ modulator obtained by the above conversion formula has the same stability characteristics and SNR characteristics as the low-pass ΔΣ modulator 125 before conversion operating at the same oversampling ratio.

However, in the above conversion formula, as shown in FIG. 8B, only a band-pass ΔΣ modulator for a quarter of the sampling frequency fs (normalized frequency θ = ± π / 2) can be obtained. That is, in the above conversion formula, only a bandpass ΔΣ modulator having a quarter frequency (normalized frequency θ = ± π / 2) of the sampling frequency fs and the center frequency f ₀ of the quantization noise stop band can be obtained.

The inventor has found a conversion formula for obtaining a bandpass type ΔΣ modulator having a desired frequency f ₀ (θ = θ ₀ ) as a center frequency f ₀ from a low pass type ΔΣ modulator. The conversion formula is as shown in the following formula (3), for example.

here,
θ ₀ = 2π × (f ₀ / fs)

The conversion formula of Formula (2) relates to a specific frequency θ ₀ = π / 2, but the conversion formula of Formula (3) is generalized to an arbitrary frequency (θ ₀ ).

[5.3.2 Concept of conversion formula]
In the low-pass type ΔΣ modulator, assuming that z = e ^jωT = 1, the absolute value of z ′ for conversion to the band-pass type ΔΣ modulator should be 1 while maintaining the characteristics of the low-pass type modulator. It is.
If | z ′ | = 1, the magnitude (amplitude) of the signal that has passed through the element z changes, and the characteristics are deteriorated compared to the low-pass ΔΣ modulator before conversion.
Note that z ′ may be 1 or −1. This is because z ′ = 1 and z ′ = − 1 are merely a relationship in which the phases are reversed, and the signal magnitude is not changed.

Therefore, z ′ for obtaining a bandpass ΔΣ modulator while maintaining the characteristics of the lowpass ΔΣ modulator without deterioration is a function f _cnv (z, θ ₀ ) including z and θ _0. For any z, θ ₀ , a function f _cnv (z, θ ₀ ) in which the absolute value of f _cnv (z, θ ₀ ) is always 1 may be used.

If such a function f _cnv (z, θ ₀ ) is found, a low-pass ΔΣ modulator and a band-pass ΔΣ modulator for a desired frequency f ₀ (θ ₀ ) can be obtained.

The present inventor _finds such a function z ′ = f _cnv (z, θ ₀ ) as follows and generalizes a conversion formula z → z ′ (formula (3)) obtained by generalizing formula (2). Obtained.

First, conversion from a low pass type ΔΣ modulator to a band pass type ΔΣ modulator having a desired frequency f ₀ (θ = θ ₀ ) as a center frequency f ₀ is considered as shown in FIG. Become. FIG. 9 is a generalization of FIG. 8 at an arbitrary frequency f ₀ (θ = θ ₀ ).
As shown in FIG. 9B, the center frequency of the noise stop band of the band-pass ΔΣ modulator is f ₀ (θ ₀ = 2π × (f ₀ / fs)).

here,

Therefore, we consider in the frequency domain. T is a sampling period.

In addition, ωT in Equation (4) is

It is.

As shown in FIG. 9A, the low-pass ΔΣ modulator operates at f ₀ = 0 (θ = 0). Therefore, the present inventor considered that the following equation (6) holds in the low-pass type ΔΣ modulator with respect to the equation (4).

That is, it can be considered that the low-pass type ΔΣ modulator operates at e ^{j0 as} shown in FIG.

From the equation (6), the following equation (7) is obtained.

On the other hand, the bandpass ΔΣ modulator operates as a complex conjugate pair at θ ₀ and −θ ₀ as shown in FIGS. 9B and 10B.
Therefore, considering the fact that the bandpass type ΔΣ modulator has a complex conjugate pair based on the formula (7) in the low-pass type Δ modulator, the following formula (8) is obtained.

The present inventor obtained z ′ = f _cnv (z, θ ₀ ) using the formula (8).
That is, first, the above equation (8) is modified as follows to obtain equation (10) in which the value of the right side (one side) is 1.

Equation (10), the value of the expression of the left-hand (the other side) is, any z, the theta _0, it is clear that it is always identity as the left-hand side value = 1.
Therefore, the left side of the equation (10) is a function f _cnv (z, θ ₀ ) _whose value is always 1 for any z and θ ₀ .

From Expression (10), z ′ in the conversion expression z → z ′ for converting from the low pass type to the band pass type is as follows.

From the above equation (11), the conversion equation of equation (3) is obtained.
In the above equation (3), when θ ₀ = π / 2 (when f ₀ = fs / 4) is set, it can be seen that it is equivalent to the conversion equation of equation (2).
Further, the low-pass ΔΣ converter has θ ₀ = 0. When θ ₀ = 0, the conversion equation of Equation (3) becomes z → z, and it can be seen that Equation (3) does not deform the low-pass ΔΣ converter.

Since z ′ = f _cnv (z, θ ₀ ) may be −1 (because the absolute value is 1), z ′ may be in the following format.

Moreover, even if the denominator and the numerator of z ′ = f _cnv (z, θ ₀ ) are replaced, it becomes 1 or −1, and therefore z ′ may be in the following format.

Of course, the expression format of the expression z ′ = f _cnv (z, θ ₀ ) whose absolute value is always 1 for any z, θ ₀ is not limited to that illustrated. Regarding f _cnv (z, θ ₀ ), there are various expression formats. This means that the equation can be transformed from the equation (8) in order to obtain an identity with a value of one side of 1 or −1. It is clear that this is not the case.

[5.4 Example of Bandpass ΔΣ Modulator]
[5.4.1 First example]
FIG. 11 shows a second-order bandpass ΔΣ modulator 25 obtained by converting the first-order lowpass ΔΣ modulator 125 shown in FIG. 6 using the conversion equation (3).
In the conversion from FIG. 6 to FIG. 11, for the convenience of notation, the following conversion equation with a = cos θ ₀ in Equation (3) was used.

[5.4.2 Second example]
FIG. 12 shows a low-pass ΔΣ modulator 125 having a CRFB structure loop filter 127 described in Non-Patent Document 1. In FIG. 12, reference numeral 128 denotes a quantizer.

When the low-pass type ΔΣ modulator 125 shown in FIG. 12 is converted by the conversion formula (3), a bandpass type ΔΣ modulator 25 shown in FIG. 13 is obtained. Also here, for convenience of description, in equation (3), a = cos θ ₀ is set.

Z in (1 / (z−1)) and (z / (z−1)) in FIG. 12 is converted by a conversion formula. Expressions after conversion of (1 / (z-1)) and (z / (z-1)) are as follows, respectively.

[5.4.3 Others]
The conversion to the band-pass type ΔΣ modulator can be applied to other high-order low-pass type ΔΣ modulators (for example, the CIFB structure, the CRFF structure, the CIFF structure, etc. described in Non-Patent Document 1).

[5.5 Output results]
14 to 17 show a case where θ ₀ = π / 4 (FIG. 14) and θ ₀ = 3π / 4 in the bandpass ΔΣ modulator of the second example (FIG. 13) (FIG. 15). , Θ ₀ = 5π / 4 (FIG. 16), and θ ₀ = 7π / 4 (FIG. 17).

As shown in FIGS. 14 to 17, at each frequency of θ ₀ = π / 4, 3π / 4, 5π / 4, and 7π / 4, a signal appears at a desired θ ₀ , and θ ₀ = ± π It can be seen that bandpass ΔΣ modulators for frequencies other than / 2 are obtained.

Conventionally, a design method for a bandpass ΔΣ modulator that performs bandpass ΔΣ modulation on an arbitrary frequency f ₀ has not been established. However, by using a conversion equation such as Equation (3), the desired carrier frequency f ₀ can be set as the noise rejection band of the noise transfer function (NTF), and the bandpass ΔΣ with respect to the desired carrier frequency f ₀ . A bandpass ΔΣ modulator that performs modulation can be designed.

[6. Bandwidth expansion]
FIG. 18 shows a configuration in which a band extension unit 29 is added to the digital signal processing unit 21 of the broadcasting facility 2 of FIG. In the communication system 1 of FIG. 18, the points that are not described are the same as those of FIG.

As described above, in the band-pass ΔΣ modulation, the signal band f _B only needs to be sufficiently small with respect to the sampling frequency fs. For example, if the signal band is an RF signal having a frequency of 20 MHz, the sampling frequency fs (sampling speed = 1.28 GS / S) may be 20 MHz × 64 = 1.28 GHz.

Here, if it can increase further the aforementioned sampling frequency fs (1.28GHz), since it is a margin in the signal band _{f B,} as shown in FIG. 18, it may be provided a band spreading unit 29, a signal band _{f B} It is preferable to expand.
In the band extension unit 29, by performing upsampling, as shown in FIG. 19, zero signals are inserted on both sides of the original signal band f _B (= 20 MHz), and the signal band is doubled (f _B ′ = 40 MHz). As the signal band f _B ′ is expanded, the sampling frequency fs of the bandpass ΣΔ modulator 25 is also doubled to 2.56 GHz.

Thus, when the band f _B is expanded, the sampling frequency fs increases. Here, the carrier frequency f _0, it is possible to select the following values sampling frequency fs, the sampling frequency fs increases, also increases the range of selection of the carrier frequency f _0.

Here, for example, it is assumed that the signal band f _B = 20 MHz and the carrier frequency f ₀ is 2 GHz. In this case, if the sampling frequency fs is determined based on only the signal band f _B = 20 MHz for the band-pass ΔΣ modulation, the sampling frequency fs = 1.28 GHz = 20 MHz × 64. However, the sampling frequency fs = 1.28 GHz is inappropriate because it is smaller than the carrier frequency f ₀ = 2 GHz.

However, when the sampling frequency fs is determined based on the expanded signal band f _B ′ = 40 MHz, the sampling frequency fs = 2.56 GHz = 40 MHz × 64. In this case, the sampling frequency fs = 2.56 MHz is appropriate because it is larger than the carrier frequency f ₀ = 2 GHz.

Further, the signal band portions f _B1 and f _B2 expanded by the band extending unit 29 are substantially portions where no signal exists. Therefore, as shown in FIG. 20, the bandpass filter on the RF signal receiving side (signal output device 3 or broadcaster 5) may use the signal band f _B before the extension as the pass band, and has been expanded. The entire signal band f _B ′ may not be a pass band.
In addition, since the band-pass filter roll-off can be widened using the expanded signal band portions f _B1 and f _B2 , the design of the band-pass filter is facilitated.

[7. Use of harmonics]
Since the output of the ΔΣ modulator 25 is a quantized signal (pulse signal), a harmonic component due to aliasing exists in addition to the main signal component.
By using this harmonic component, the transmission device (first device) side receives the signal at the reception side (signal output device 3 or broadcaster 5) while keeping the carrier frequency f ₀ ′ and the sampling frequency fs low. The frequency of the modulated wave (RF signal) can be increased.

For example, it is assumed that the frequency (reception frequency) f _{0 of the} RF signal desired to be received at the receiving side (the signal output device 3 or the broadcasting device 5) is 2 GHz. When harmonics are not used, the transmission device (first device) side needs to set the carrier frequency (frequency of unmodulated wave) f ₀ to 2 GHz and the sampling frequency fs to a value larger than 2 GHz.

However, as shown in FIG. 21, when a modulated wave having a carrier frequency f ₀ ′ is input to the bandpass ΔΣ modulator 25, the output (quantized signal) of the bandpass ΔΣ modulator 25 is the carrier frequency. In addition to having a main signal component centered on f ₀ ′, it also has a harmonic component of f ₀ = n × fs + f ₀ ′ (n is an integer having an absolute value of 1 or more) by folding.
By actively receiving this harmonic component on the reception side (signal output device 3 or broadcaster 5), the transmission device (first device) side performs processing for a relatively low frequency f ₀ ′. While performing, the receiving side (the signal output device 3 or the broadcasting device 5) can receive a modulated wave with a high frequency of the carrier frequency f ₀ = n × fs + f ₀ ′.

Specifically, when the reception frequency f ₀ on the reception side (signal output device 3 or broadcaster 5) is 2 GHz, the signal passes through the analog bandpass filter 54b on the reception side (signal output device 3 or broadcaster 5). The center frequency fc of the band is also set to 2 GHz. That is, the reception side (signal output device 3, or broadcast machine 5), the center frequency _{f 0} is received 2GHz modulation wave (RF signal).
In this case, if the sampling rate fs of the bandpass type Δ modulator 25 of the transmission device (first device) is 1.5 GHz (<f ₀ ), the frequency f ₀ ′ of the carrier wave (unmodulated wave) in the modulator 24a is ,
f ₀ ′ = f ₀ −fs = 2 GHz−1.5 GHz = 500 MHz
It's okay.

Therefore, as a transmitting apparatus (first apparatus), in actuality, the center side (carrier frequency) f ₀ ′ handles a modulated wave having a frequency of 500 MHz, but is viewed from the receiving side (signal output apparatus 3 or broadcaster 5). The transmitting device (first device) can be regarded as transmitting a modulated wave having a center frequency (carrier frequency) f ₀ of 2 GHz. As a result, it is possible to transmit a modulated wave having a frequency higher than the sampling frequency in the transmission device (first device).

When the main signal component shown in FIG. 21 is transmitted as an RF signal having a frequency (reception frequency) desired by the reception side (signal output device 3 or broadcaster 5), and the harmonic component shown in FIG. When the output device 3 or the broadcasting device 5) transmits both signals as signals having a desired frequency (reception frequency), the carrier wave (unmodulated wave) used in the modulator 24a of the transmission device (first device) is summarized. The frequency f ₀ ′ satisfies the following expression.
f ₀ ′ = f ₀ −n × fs
However,
f ₀ : reception side (signal output device 3 or broadcaster 5) reception frequency fs: sampling frequency of bandpass type ΔΣ modulator 25 f ₀ ′: frequency of carrier wave (unmodulated wave) of modulator 24 a n: integer

In the above equation, when n = 0, the main signal component shown in FIG. 21 is transmitted as a signal having a frequency (reception frequency) desired by the reception side (signal output device 3 or broadcaster 5). In this case, the harmonic component shown in FIG. 21 is transmitted as a signal having a frequency (reception frequency) desired by the reception side (signal output device 3 or broadcaster 5).
As n increases, the harmonic component gradually decreases, so n = ± 1 (particularly n = 1) is preferable.

The center frequency fc of the pass band of the analog band pass filter 54b on the receiving side (the signal output device 3 or the broadcasting device 5) satisfies the following expression.
fc = f ₀ '+ n × fs
However,
fc: center frequency fs of the passband of the analog band-pass filter 54b: sampling frequency f ₀ of the bandpass ΔΣ modulator 25 ': frequency n of the carrier of the modulator 24a (continuous wave): Integer

Also in the above equation, when n = 0, the main signal component shown in FIG. 21 is transmitted as a signal of the frequency (reception frequency) desired by the reception side (signal output device 3 or broadcaster 5). A case other than the above is a case in which the harmonic component shown in FIG.
As n increases, the harmonic component gradually decreases, so n = ± 1 (particularly n = 1) is preferable.

[8. Addendum]
[8.1 Appendix 1]
In the above description, the terrestrial digital television broadcast has been described as an example of the broadcast service, but the digital television broadcast may be a satellite digital television broadcast. Also, the analog television broadcast may be used as the television broadcast. The broadcast may be a radio broadcast. Furthermore, the signal transmission system of the present embodiment can be used for transmission of RF signals other than broadcast RF signals.

[8.2 Appendix 2]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 Signal transmission system (broadcasting system)
2 Broadcasting equipment (transmitting device; first device)
3 Signal output device (second device)
4 Signal transmission path 5 Broadcaster (broadcasting equipment)
7 TV receiver 21 digital signal processing unit 23 baseband unit 24a modulator 24b processing unit 25 ΔΣ modulator 26 first transmission unit 32 reception unit 33 buffer 34 output unit 35 switch unit 38 antenna 52 reception unit 53 buffer 54 second transmission Unit 54a output unit 54b band pass filter 54c amplifier 60 wireless transmitter

Claims (19)

A first device for transmitting a signal to a signal transmission path;
A second device for receiving a signal from the signal transmission path;
With
The first device includes:
A ΔΣ modulator that performs ΔΣ modulation on the RF signal and outputs a quantized signal;
A transmission unit for transmitting the quantized signal output from the ΔΣ modulator to the signal transmission path;
With
The second device includes:
A receiver for receiving the quantized signal from the signal transmission path;
A buffer for storing the quantized signal received by the receiving unit;
An output unit for outputting the quantized signal stored in the buffer;
An RF signal transmission system comprising: The transmission unit is configured to be capable of transmitting information,
The RF signal transmission system according to claim 1, wherein the information transmitted by the transmission unit includes information used in the second device to reproduce a signal waveform of a quantized signal output from the ΔΣ modulator. The transmission unit packetizes the quantized signal and outputs the packetized signal to the signal transmission path,
The RF signal transmission system according to claim 1, wherein the receiving unit receives the packetized quantized signal and depacketizes the quantized signal. The RF signal transmission system according to claim 1, wherein the signal transmission path is a wired signal transmission path. The RF signal transmission system according to claim 1, wherein the output unit outputs the quantized signal to a receiver that receives an RF signal. The second device further includes an antenna that radiates an RF signal as a radio wave to space,
The RF signal transmission system according to any one of claims 1 to 5, wherein the second device uses the quantized signal output from the output unit as an RF signal radiated as a radio wave by the antenna. The RF signal transmission system according to claim 1, wherein the RF signal includes an RF signal of a video signal. The RF signal transmission system according to claim 1, wherein the RF signal is an RF signal for digital television broadcasting. The RF signal transmission system according to claim 1, wherein the ΔΣ modulator is a bandpass type ΔΣ modulator. A reception unit that receives a quantized signal obtained by ΔΣ modulation of an RF signal from a signal transmission path;
A buffer for storing the quantized signal received by the receiving unit;
An output unit for outputting the quantized signal stored in the buffer as a signal including an RF signal;
A signal output device comprising: A receiver for receiving an RF signal;
A signal output device according to claim 10;
With
The signal output device outputs the quantized signal to the receiver. An RF signal transmission method comprising:
Transmitting a quantized signal obtained by ΔΣ modulation of the RF signal to a signal transmission path;
Receiving the quantized signal from the signal transmission path;
Storing the received quantized signal in a buffer;
Outputting the quantized signal stored in the buffer to a receiver for receiving an RF signal;
An RF signal transmission method comprising: A transmission device for transmitting a signal to a signal transmission path;
One or more broadcasting facilities;
With
The transmitter is
A ΔΣ modulator that performs ΔΣ modulation on a broadcast RF signal and outputs a quantized signal;
A first transmitter that transmits the quantized signal output from the ΔΣ modulator to the signal transmission path;
With
The broadcasting equipment is
An antenna that radiates broadcasting RF signals into the space as radio waves;
A broadcaster for outputting a broadcast RF signal to the antenna;
With
The broadcaster is
A receiver for receiving the quantized signal from the signal transmission path;
A second transmitter that outputs the quantized signal received by the receiver as the broadcast RF signal to the antenna;
The broadcaster, a buffer for storing the quantized signal received by the receiving unit,
With
The second transmission unit outputs the quantized signal stored in the buffer to the antenna as the broadcast RF signal . The first transmission unit is configured to be capable of transmitting information,
Said information, said ΔΣ modulator output claims 1 3 Symbol placement broadcasting system contains information used in the broadcasting apparatus to reproduce the signal waveform of the quantized signal to the first transmission unit transmits . The first transmitter packetizes the quantized signal and transmits the packet to the signal transmission path;
The broadcast system according to any one of claims 13 and 14 , wherein the reception unit receives the packetized quantized signal and depackets it. ΔΣ modulator, a broadcast system according to any one of claims 13 to 15 is a band-pass ΔΣ modulator. A receiving unit that receives a quantized signal obtained by ΔΣ modulation of a broadcast RF signal from a signal transmission path;
A buffer for storing the quantized signal received by the receiving unit;
A transmitter that outputs the quantized signal stored in the buffer as an RF signal for broadcasting to an antenna;
A broadcasting machine characterized by comprising: A broadcaster according to claim 17 ;
An antenna that radiates the quantized signal output from the transmitter of the broadcaster to space;
Broadcasting equipment characterized by comprising. Obtaining a quantized signal by ΔΣ modulation of the broadcast RF signal;
Transmitting the quantized signal to a broadcaster;
The broadcaster stores the received quantized signal in a buffer;
The broadcaster outputs the quantized signal stored in the buffer as an RF signal for broadcasting to an antenna;
Broadcasting method including.