JP4871939B2 - Signal transmitting apparatus and method - Google Patents

Description

  The present invention relates to a signal transmission apparatus and method for a single carrier signal.

Conventionally, in a wireless transmission device in a communication system using a single carrier, a broadband signal is modulated and transmitted as it is (see, for example, Non-Patent Document 1).
D. Falconer, SL Ariyavisitakul, A. Benyamin-Seeyar, and B. Eidson, “Frequency domain equalization for single-carrier broadband wirelesssystems,” IEEE Commun. Mag., Vol. 40, no. 4, pp. 58-66, Apr. 2002.

  In recent years, it has been studied to use a single carrier in broadband transmission such as optical communication. However, since the signal processing is performed collectively in the conventional technology, the processing speed of the modulation circuit, inverse Fourier transform, GI (guard interval) insertion circuit, D / A (digital / analog) converter, frequency conversion circuit The data rate was limited by the operating speed, and it was not possible to perform processing faster than that in real time. Therefore, it is conceivable to divide the transmission band into a plurality of channels and generate a modulation signal using a plurality of fast Fourier transformers and inverse fast Fourier transformers. Interference with other channels will occur, leading to degradation of transmission quality. Further, in order to avoid interference, it is necessary to sufficiently separate the channel frequency intervals, and the frequency utilization efficiency is lowered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a signal transmission apparatus and method capable of real-time and high-quality broadband transmission using a single carrier.

In order to solve the above-described problems, the present invention provides a serial-parallel converter that converts an input signal into a plurality of parallel signals, each corresponding to a channel, and the plurality of parallel signals have a channel corresponding to itself. A plurality of processing units that generate signals; a combining unit that generates signals by combining the signals of the respective channels generated by the plurality of processing units; and a transmission unit that transmits the signals combined by the combining unit. Each of the plurality of processing units includes: an input signal modulation unit that modulates each parallel signal to a channel corresponding to itself; a Fourier transform unit that performs Fourier transform on the signal modulated by the input signal modulation unit; A zero insertion unit that inserts a frequency component of 0 into a frequency outside the frequency band of the signal that has undergone Fourier transform by the conversion unit, and a zero frequency component that is generated by the zero insertion unit. An inverse Fourier transform unit that performs an inverse Fourier transform on the signal inserted, and a digital analog conversion unit that converts the signal subjected to the inverse Fourier transform by the inverse Fourier transform unit into an analog signal synchronized with another processing unit; A frequency converter that converts a signal converted into an analog signal by the digital-analog converter so that a center frequency of a frequency band of the signal is a center frequency of a frequency band of a channel corresponding to the processing unit; A band-pass filter that extracts a signal in a frequency band used by a channel corresponding to the processing unit from the signal frequency-converted by the frequency conversion unit, and the synthesis unit is extracted by the band-pass filter signal combining to an generates the signal, the frequency converting unit, the center frequency of the frequency band of the group sub-carrier To a signal transmitting apparatus characterized by selecting a center frequency is the frequency band of the frequency of the subcarrier groups adjacent to each other overlap each other.

  Further, the present invention is the above-described signal transmission device, wherein each of the plurality of processing units further includes a guard interval insertion unit that inserts a guard interval into the signal subjected to inverse Fourier transform by the inverse Fourier transform unit. Features.

  Further, the present invention is the above-described signal transmission device, wherein each of the plurality of processing units performs a smoothing process at a joint between Fourier transform blocks of a signal in which a guard interval is inserted by the guard interval insertion unit Is further provided.

  In addition, the present invention is the signal transmission apparatus described above, wherein the transmission unit transmits a single carrier signal by an optical signal.

  Further, the present invention is the signal transmission device described above, wherein the transmission unit includes an optical intensity modulator that converts an electrical single carrier signal synthesized by the synthesis unit into an optical signal.

  Also, the present invention is the above-described signal transmission device, wherein the transmission unit generates an optical signal using the I component and Q component signals of the single carrier signal synthesized by the synthesis unit as drive signals. It is characterized by providing a vessel.

Further, the present invention provides a signal transmission apparatus for transmitting a single carrier signal, wherein the serial / parallel conversion unit includes a serial / parallel conversion process in which an input signal is converted into a plurality of parallel signals, and a plurality of processing units corresponding to the respective channels. A signal processing step for generating a signal of a channel corresponding to the plurality of parallel signals, and a combining unit combines the signals of the respective channels generated by the plurality of processing units in the signal processing step. A signal generating process and a transmitting unit transmitting a signal combined in the combining process, and a signal processing process by each of the plurality of processing units includes: An input signal modulation process for modulating a parallel signal into a channel, and a Fourier transform unit performs a Fourier transform on the signal modulated by the input signal modulation unit. A Fourier transform process, a zero insertion unit inserting a zero frequency component into a frequency outside the frequency band of the signal subjected to the Fourier transform by the Fourier transform unit, and an inverse Fourier transform unit An inverse Fourier transform process for performing an inverse Fourier transform on a signal in which a frequency component of 0 is inserted in the insertion process, and a digital-analog conversion unit synchronizes the signal subjected to the inverse Fourier transform in the inverse Fourier transform process with other processing units. The analog-to-analog conversion process for converting the analog signal into the analog signal, and the frequency conversion unit converts the signal converted into the analog signal in the digital-to-analog conversion process. a frequency conversion process of frequency conversion so that the center frequency of the frequency band, the band-pass filter, the An extraction process for extracting a signal in a frequency band used by a channel corresponding to the processing unit from the signal frequency-converted in the wave number conversion process, and in the synthesis process, the synthesis unit performs the extraction process in the extraction process. The extracted signals are combined to generate the signal, and in the frequency conversion process, the frequency conversion unit uses the frequency band of the subcarrier group as a center frequency of the subcarrier group outside the frequency band. The signal transmission method is characterized by selecting a center frequency at which the two frequencies overlap each other .

  According to the present invention, it is possible to realize a steep band-pass filter that is difficult to achieve with only a conventional analog filter, and to remove interference from outside the band divided for each channel. Real-time and high-quality broadband transmission can be realized by frequency-converting and synthesizing the channels. Moreover, since zero insertion, guard interval insertion, and smoothing processing are performed in parallel for each channel, it is possible to operate with a slow clock.

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

<First Embodiment>
FIG. 1 is a block diagram showing a configuration of a signal transmission apparatus according to the first embodiment of the present invention. In the figure, a signal transmission device transmits a signal to a signal generation circuit 1 that modulates binary data into an output signal of a wideband frequency, a signal light source 3 that generates an optical carrier of frequency fc, and an optical carrier generated by the signal light source 3. It comprises an optical intensity modulator 4 that generates and outputs a broadband optical single carrier signal on the output A, which is a broadband electrical single carrier signal output from the generation circuit 1.

FIG. 2 is a block diagram showing a detailed configuration of the signal generation circuit 1 shown in FIG.
In the figure, an S / P (serial parallel) conversion circuit 10 converts an input signal of binary data input to the signal generation circuit 1 into a parallel signal and outputs the parallel signal to the modulation circuit 11-i (i = 1 to k). To do.

  Each of the modulation circuits 11-i (i = 1 to k) corresponds to a channel of a single carrier signal, and modulates a signal input from the S / P conversion circuit 10 for each channel by a predetermined modulation method. Each of the modulation circuits 11-i (i = 1 to k) corresponds to a channel of a single carrier signal, and the signal input from the S / P conversion circuit 10 is converted into a channel by a predetermined single carrier modulation method. Modulate every time. Hereinafter, the channels corresponding to the respective modulation circuits 11-i are referred to as channels i.

  The Fourier transform circuit 12-i (i = 1 to k) performs Fourier transform on the signal modulated by the modulation circuit 11-i. The 0 insertion circuit 13-i (i = 1 to k) applies a frequency component of 0 to a frequency band outside the signal transmission frequency band of the signal subjected to the Fourier transform by the Fourier transform circuit 12-i (i = 1 to k). insert. The 0 insertion circuit 13-i (i = 1 to k) is a frequency band outside the signal transmission frequency band of the signal subjected to the Fourier transform by the Fourier transform circuit 12-i (i = 1 to k). The zero frequency component is inserted in the frequency band adjacent to the signal transmission frequency band.

  The inverse Fourier transform circuit 14-i (i = 1 to k) performs inverse Fourier transform on the signal in which the zero frequency component is inserted by the zero insertion circuit 13-i. The GI (guard interval) insertion circuit 15-i (i = 1 to k) inserts a guard interval into the signal subjected to inverse Fourier transform by the inverse Fourier transform 14-i. The smoothing circuit 16-i (i = 1 to k) performs smoothing by digital signal processing on the joints between the Fourier transform blocks. The D / A conversion circuit 17-i (i = 1 to k) converts the digital signal into a synchronized analog signal using the clock by the common clock 21.

  The frequency conversion circuit 18-i (i = 1 to k) converts the frequency of the analog signal using the oscillation signal from the local oscillator 22. At this time, the center frequency in the frequency band of the analog signal output from the D / A conversion circuit 17-i (hereinafter, the center frequency in the frequency band is referred to as “the center frequency of the frequency band”) depends on the channel. Frequency conversion is performed so that the center frequency of the used frequency band is obtained. The BPF 19-i (i = 1 to k) extracts a frequency band signal used by the channel from the frequency-converted signal. The combining circuit 20 combines the channels i output from the BPFs 19-i (i = 1 to k), generates a baseband signal of a single carrier signal, and outputs it as an output A.

  The Fourier transform circuit 12-i (i = 1 to k) can use Fast Fourier Transform (FFT) when discrete Fourier transform is used as Fourier transform. The inverse Fourier transform circuit 14-i (i = 1 to k) can use inverse fast Fourier transform (IFFT: Inverse FFT) when inverse discrete Fourier transform is used as inverse Fourier transform. is there. As described above, by using the fast Fourier transform for the Fourier transform circuit 12-i (i = 1 to k) and by using the inverse fast Fourier transform for the inverse Fourier transform circuit 14-i (i = 1 to k). The calculation load and calculation time for each channel are further reduced.

FIG. 3 is a diagram showing a configuration of the light intensity modulator 4 shown in FIG. As shown in the drawing, a Mach-Zehnder type modulator is used for the light intensity modulator 4, and the output A from the signal generation circuit 1 is input thereto. Thus, the light intensity modulator 4 generates a DSB (double sideband) optical single carrier signal centered on the optical carrier having the frequency fc emitted from the signal light source 3. When the intensity modulator 4 is driven, when the bias point is set to half of the half-wave voltage ( _Vπ ), the optical carrier remains, and when the bias point is set to the NULL point, the optical carrier can be suppressed.

Next, signal processing by the signal transmission apparatus described above will be described.
First, the S / P conversion circuit 10 converts the binary signal input to the signal generation circuit 1 from a serial signal to a parallel signal having a predetermined data length, and sends it to the modulation circuit 11-i (i = 1 to k). Output. Next, the modulation circuit 11-i (i = 1 to k) has a predetermined modulation scheme, for example, 16QAM (Quadrature Amplitude Modulation), 64QAM, QPSK (Quadrature Phase Shift Keying). The data input from the S / P conversion circuit 10 is modulated by a single carrier modulation method such as the above, mapped to a channel, and output to the Fourier transform circuit 12-i (i = 1 to k).

  Specifically, the modulation circuit 11-i (i = 1 to k) outputs a signal composed of an in-phase component (I component) and a quadrature component (Q component) for each channel assigned to data. Note that no signal can be assigned to any channel i. It is also possible not to assign a signal to an adjacent frequency band outside channel i.

  In the above description, the S / P conversion circuit 10 converts, for example, serial signal data transmitted through the channel i (i = 1 to k) of serial signals into a parallel signal having a predetermined data length. To the corresponding modulation circuit 11-i (i = 1 to k).

  Next, the Fourier transform circuit 12-i (i = 1 to k) performs Fourier transform on the signal modulated by the modulation circuit 11-i, and outputs it to the 0 insertion circuit 13-i (i = 1 to k). .

  Next, the 0 insertion circuit 13-i (i = 1 to k) is outside the signal transmission frequency band of the signal subjected to the Fourier transform by the Fourier transform circuit 12-i (i = 1 to k) and is adjacent thereto. A frequency component of 0 is inserted into the frequency band and output to the inverse Fourier transform circuit 14-i.

  FIG. 4 is a diagram illustrating the output of the 0 insertion circuit 13-i when no signal is assigned to the frequency band corresponding to the outside of the channel i. In the figure, 0 is inserted in the frequency band outside the transmission symbol of the channel i from the modulation circuit 11-i input through the Fourier transform circuit 12-i. Further, by designating 0 for all channels in advance and outputting a signal to the corresponding channel by the modulation circuit 11-i, the same effect can be obtained without going through the 0 insertion circuit 13-i. .

  Next, the inverse Fourier transform circuit 14-i (i = 1 to k) performs inverse Fourier transform on the data input from the 0 insertion circuit 13-i, thereby converting the transmission signal mapped in the frequency domain into the time domain. To a single carrier signal. Thereby, in the channel i, the inverse Fourier transform is operated on the signal sequence in which 0 is inserted.

  Here, modulation is performed by the Fourier transform circuit 12-i (i = 1 to k), the 0 insertion circuit 13-i (i = 1 to k), and the inverse Fourier transform circuit 14-i (i = 1 to k). When the signal modulated by the circuit 11-i (i = 1 to k) is viewed in the frequency domain, a frequency of 0 is inserted in the frequency domain outside the signal transmission frequency band. This has the effect of reducing interference between channels in the frequency domain.

Next, the GI (guard interval) insertion circuit 15-i (i = 1 to k) inserts a guard interval into the signal input from the inverse Fourier transform 14-i.
FIG. 5 is a diagram illustrating a guard interval insertion method in the GI insertion circuit 15-i. The GI insertion circuit 15-i adds the same signal as a part of the latter half of the original single carrier signal 1 Fourier transform block to the first half of the Fourier transform block as a guard interval.

Next, the smoothing circuit 16-i (i = 1 to k) performs smoothing by digital signal processing on the joint between the Fourier transform blocks of the signal input from the GI insertion circuit 15-i, and performs D / A The data is output to the conversion circuit 17-i.
FIG. 6 is a diagram illustrating a smoothing process in the smoothing circuit 16-i. If the Fourier transform blocks are simply arranged continuously, the signal becomes discontinuous between the Fourier transform blocks. Therefore, the smoothing circuit 16-i performs processing so that the joints between the Fourier transform blocks change smoothly, and removes the presence of steep frequency components.

  Next, the D / A conversion circuit 17-i (i = 1 to k) uses the clock by the common clock 21 to convert the digital signal input from the smoothing circuit 16-i into another D / A conversion circuit 17. -I is converted to an analog signal synchronized with that of -i and output to the frequency conversion circuit 18-i. The frequency conversion circuit 18-i (i = 1 to k) uses the oscillation signal from the local oscillator 22 to convert the frequency band of the analog signal of the channel i input from the D / A conversion circuit 17-i to the frequency band. The frequency is converted to fi and output to the BPF 10-i. The center frequency of the frequency band fi matches the center frequency of the frequency band used by the channel i. That is, the frequency conversion circuit 18-i has the center frequency of the frequency band of the input analog signal set to the channel i. The frequency is converted so as to be the center frequency of the frequency band.

  FIG. 7 is a diagram illustrating frequency conversion in the frequency conversion circuit 18-1. In the figure, the frequency conversion circuit 18-1 frequency-converts the signal output from the D / A conversion circuit 17-i into the frequency band f1. The frequency bands f1 to fk are continuous so that a part of the frequency band fi (a part or all of the frequency band δfi described later) overlaps with the adjacent frequency bands f (i−1) and f (i + 1). It is a frequency band.

Next, the BPF 19-i (i = 1 to k) extracts a signal of the frequency band Δfi corresponding to the frequency band of the channel i from the frequency-converted signal of the frequency band fi. At this time, the frequency band Δfi A signal for the frequency band δfi adjacent to is also extracted.
FIG. 8 is a diagram showing processing in the BPF 19-1. In the figure, the BPF 19-1 extracts the signal of the frequency band Δf1 from the signal of the frequency band f1, and the BPF 19-1 extracts the frequency band adjacent to the frequency band Δf1 when extracting the frequency band Δf1. The signal of δf1 is extracted at the same time. However, since the outer portion of the frequency band Δf1 corresponds to the frequency portion in which 0 insertion is performed by the 0 insertion circuit 13-1, the channel i can be used without using a steep (δf1 is close to 0) BPF that is difficult to achieve. It is possible to remove the interference from the outside of the frequency band and drop the operation clock of the inverse Fourier transform.

Next, the combining circuit 20 combines the channels i output from the BPFs 19-i (i = 1 to k), generates an output A, and outputs the output A.
FIG. 9 is a diagram illustrating an output A output from the synthesis circuit 20. As shown in the figure, the synthesizing circuit 20 synthesizes the channels 1 to k of the frequency bands f1 to fk output from the BPF 19-i (i = 1 to k), respectively, and generates an electrical ultra-wideband single carrier signal. Output A is generated.

Next, the optical intensity modulator 4 inputs the output A of the signal generation circuit 1 to the Mach-Zehnder type modulator, so that the optical single carrier signal of DSB centered on the optical carrier of the frequency fc emitted from the signal light source 3. Is generated.
FIG. 10 is a diagram illustrating a spectrum of an optical single carrier signal output from the optical intensity modulator 4. As shown in the figure, the optical single carrier signal output from the optical intensity modulator 4 has sidebands corresponding to the frequency fi (i = 1 to k) in the bands on both sides centered on the optical carrier frequency fc. is made of. When the light intensity modulator 4 is driven, if the bias point is set to half of the half-wave voltage ( _Vπ ), the optical carrier remains, and if the bias point is set to the NULL point, the light carrier can be suppressed.

As described above, in DSB, the same single carrier signal is generated in both bands around the frequency fc. However, in order to increase the use efficiency of the band, an optical BPF (band pass filter) 5 is used as shown in FIG. The single carrier signal output from the light intensity modulator 4 may be converted into SSB (single sideband) by the optical BPF 5.
FIG. 12 is a diagram illustrating a spectrum of a single carrier signal output from the optical BPF 5. As shown in the figure, in the single carrier signal output from the optical BPF 5, only one of the sidebands appearing in both bands centering on the optical carrier frequency fc in the optical single carrier signal output from the optical intensity modulator 4 is shown. Take out.
Although not shown in the figure, the output A can be converted to an SSB without using the optical BPF by using the output A as the Ich drive signal of the optical quadrature modulator and the Hilbert transform of the output A as the Qch drive signal.

  According to the above-described embodiment, it is possible to modulate a wideband signal in a frequency range of electricity as compared with the prior art, and therefore, it is possible to modulate a signal having a wide bandwidth and high frequency utilization efficiency for one set of light source and optical modulator. Become.

  Note that the 0 insertion circuit 13-i (i = 1 to k) inserts a frequency component of 0 in the corresponding frequency band by the modulation circuit 11-i. It is also possible to insert a frequency component having a value that does not affect the signal component at the time of conversion. Further, by using a band limiting filter such as a root Nyquist filter instead of the 0 insertion circuit 13-i (i = 1 to k), interference with adjacent channels can be reduced.

  Note that a frequency diversity effect can be obtained by dynamically mapping the signal spectrum to the entire band with respect to the signal subjected to Fourier transform by the Fourier transform circuit 12-i (i = 1 to k), It is also possible to reduce the influence of interference.

<Second Embodiment>
Next, a signal transmission apparatus according to the second embodiment of the present invention will be described. In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 13 is a block diagram showing a configuration of a signal transmission apparatus according to the second embodiment of the present invention. In the first embodiment, the signal A, which is a broadband electric single carrier signal generated by the signal generation circuit 1, is used as the drive signal for the light intensity modulator 4, but in this embodiment, the signal A is generated by the signal generation circuit 1a. The difference is that the output Ich signal and Qch signal of the output A are output to the optical quadrature modulator 6.

  FIG. 14 is a block diagram showing a configuration of the signal generation circuit 1a of the present embodiment. In the same figure, in the digital signal processing unit up to the smoothing circuit 16-i (i = 1 to k), the calculation is performed with the complex signal as in the configuration of the signal generation circuit 1 of the first embodiment shown in FIG. ing. Therefore, the D / A conversion circuits 17a-i (i = 1 to k) of the present embodiment output analog complex signals (Ich, Qch). As a result, the Ich signal and Qch signal of output A shown in FIG. 10 are output from the synthesis circuit 20a.

  FIG. 15 is a block diagram showing another configuration of the signal generation circuit 1a of the present embodiment. In the figure, the digital signal processing units up to GI insertion circuits 15-i (i = 1 to k) are the same as the configuration of the signal generation circuit 1 of the first embodiment shown in FIG. The smoothing circuits 16a-i (i = 1 to k) perform the same processing as in the first embodiment, but the output to the D / A conversion circuit is divided into Ich and Qch and is output. Qch is output to the D / A conversion circuit 17b-i, and Qch is output to the D / A conversion circuit 17c-i. Then, the D / A conversion circuit 17b-i, the frequency conversion circuit 18b-i, the BPF 19b-i, and the synthesis circuit 20b are the D / A conversion circuit 17c-i, the frequency conversion circuit 18c-i, the BPF 19c-i, The circuit 20c performs the same processing on Qch as the D / A conversion circuit 17-i, frequency conversion circuit 18-i, BPF 19-i, and synthesis circuit 20 described in the first embodiment. In this way, by processing the subsequent circuits from the smoothing circuit 16a-i separately for Ich and Qch, the number of clocks of the D / A conversion circuit can be reduced.

  FIG. 16 is a diagram illustrating a configuration of the optical quadrature modulator 6. As shown in the figure, the optical quadrature modulator 6 arranges Mach-Zehnder type modulators in parallel, and inputs an Ich drive signal and a Qch drive signal output from the signal generation circuit 1a, respectively. Then, by applying a phase shift π / 2 to one branch to which the Qch signal is input, it is possible to modulate the light sin (Qch) and cos (Ich) waves.

  FIG. 17 is a diagram illustrating a spectrum of an optical single carrier signal output from the optical quadrature modulator 7. By driving the optical quadrature modulator 6 with the output A Ich signal and Qch signal output from the signal generation circuit 1, the frequency fc of the light source is centered as shown in the spectrum transition shown in FIG. A broadband optical single carrier signal can be generated. At this time, if the bias point of the optical quadrature modulator 6 is set to a NULL point, the optical carrier can be suppressed. In the case of this configuration, the band utilization efficiency is increased as compared with the configuration using the intensity modulator. In addition, the necessary optical / electrical circuit band can be relaxed compared to a configuration using an intensity modulator.

  In the above description, the optical single carrier signal is generated and transmitted. However, the single carrier signal may be transmitted wirelessly. In this case, a radio signal is generated in the D / A conversion circuit 17-i, or the output A from the signal generation circuit 1 is placed on the carrier wave of the radio signal.

Also, the inverse Fourier transform circuit 14-i and the GI insertion circuit 15-i in FIGS. 2, 14, and 15 described above can have different numbers of inverse Fourier transform points and guard interval lengths for each channel. .
The common clock 21 and the local oscillator 22 shown in FIGS. 2, 14, and 15 are common to all channels. However, different clocks and local oscillators may be used for the respective channels. Good.
2 and 4, and 18b-i and 18c-i in FIG. 15, after frequency conversion is performed for each channel, the power common to all channels set in advance is set. The transmission quality of all channels can be made the same by adjusting the level to the target value and making the signal power of all channels constant.

  According to the present embodiment, it is possible to realize a steep band pass filter (BFP) that is difficult to realize with only a conventional analog filter, and to remove interference from outside the band divided for each channel. By combining and frequency-converting each channel from which interference has been removed, real-time and high-quality broadband transmission using a single carrier can be realized. Moreover, since zero insertion, guard interval insertion, and smoothing processing are performed in parallel for each channel, it is possible to operate with a slow clock.

1 is a signal transmission device according to a first embodiment of the present invention. It is a block diagram which shows the structure of the signal generation circuit by the embodiment. It is a block diagram which shows the structure of the light intensity modulator by the embodiment. It is a figure which shows the output of the 0 insertion circuit by the embodiment. It is a figure which shows the output of the GI insertion circuit by the embodiment. It is a figure which shows the output of the smoothing circuit by the embodiment. It is a figure which shows the output of the frequency converter circuit by the same embodiment. It is a figure which shows the process of BPF by the embodiment. It is a figure which shows the output of the synthetic | combination circuit by the embodiment. It is a figure which shows the output from the light intensity modulator by the embodiment. It is a block diagram which shows the other structure of the signal transmitter by the same embodiment. It is a figure which shows the output from the optical BPF by the embodiment. It is a signal transmission apparatus in the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the signal generation circuit by the embodiment. It is a block diagram which shows the other structure of the signal generation circuit by the embodiment. It is a block diagram which shows the structure of the optical orthogonal modulator by the embodiment. It is a figure which shows the output from the optical orthogonal modulator by the same embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a ... Signal generation circuit 10 ... S / P conversion circuit (serial parallel conversion part)
11-1 to 11-k: Fourier transform circuit (Fourier transform unit)
12-1 to 12-k ... modulation circuit (input signal modulation section)
13-1 to 13-k ... 0 insertion circuit (zero insertion section)
14-1 to 14-k: Inverse Fourier transform circuit (inverse Fourier transform unit)
15-1 to 15-k ... GI insertion circuit (guard interval insertion unit)
16-1 to 16-k, 16a-1 to 16a-k ... smoothing circuit (smoothing unit)
17-1 to 17-k, 17a-1 to 17a-k, 17b-1 to 17b-k, 17c-1 to 17c-k ... D / A conversion circuit (digital / analog conversion circuit)
18-1 to 18-k, 18b-1 to 18b-k, 18c-1 to 18c-k ... frequency conversion circuit (frequency conversion unit)
19-1 to 19-k, 19b-1 to 19b-k, 19c-1 to 19c-k ... BPF (band pass filter)
20, 20a, 20b, 20c ... synthesis circuit (synthesis unit)
21 ... Common clock 22 ... Local oscillator 3 ... Signal light source 4 ... Light intensity modulator 5 ... Optical BPF
6. Optical quadrature modulator

Claims (7)

A serial-parallel converter that converts an input signal into a plurality of parallel signals;
A plurality of processing units each corresponding to a channel and generating a signal of a channel corresponding to the plurality of parallel signals,
A synthesizing unit that synthesizes the signals of the respective channels generated by the plurality of processing units to generate a signal;
A transmission unit for transmitting the signal synthesized by the synthesis unit,
Each of the plurality of processing units is
An input signal modulator that modulates each parallel signal to a channel corresponding to the parallel signal;
A Fourier transform unit for performing a Fourier transform on the signal modulated by the input signal modulation unit;
A zero insertion unit for inserting a frequency component of 0 into a frequency outside the frequency band of the signal subjected to the Fourier transform by the Fourier transform unit;
An inverse Fourier transform unit that performs an inverse Fourier transform on the signal in which the zero frequency component is inserted by the zero insertion unit;
A digital-analog converter that converts the signal that has been subjected to the inverse Fourier transform by the inverse Fourier transform unit into an analog signal that is synchronized with another processing unit;
A frequency converter that converts the frequency of the signal converted into an analog signal by the digital analog converter so that the center frequency of the frequency band of the signal is the center frequency of the frequency band of the channel corresponding to the processing unit;
A band-pass filter that extracts a signal of a frequency band used by a channel corresponding to the processing unit from the signal frequency-converted by the frequency conversion unit;
The synthesizing unit generates the signal by synthesizing the signals extracted by the bandpass filter ,
The signal transmission apparatus , wherein the frequency converter selects a center frequency at which frequencies outside the frequency band of adjacent subcarrier groups overlap each other as a center frequency of a frequency band of the subcarrier group . Each of the plurality of processing units is
A guard interval insertion unit that inserts a guard interval into the signal that has been inverse Fourier transformed by the inverse Fourier transform unit;
The signal transmission device according to claim 1. Each of the plurality of processing units is
A smoothing unit that performs a smoothing process at a joint between Fourier transform blocks of the signal in which the guard interval is inserted by the guard interval insertion unit;
The signal transmission apparatus according to claim 2.   The signal transmission device according to claim 1, wherein the transmission unit transmits a single carrier signal using an optical signal.   The signal transmission device according to claim 4, wherein the transmission unit includes an optical intensity modulator that converts the electrical single carrier signal synthesized by the synthesis unit into an optical signal.   5. The signal according to claim 4, wherein the transmission unit includes an optical quadrature modulator that generates an optical signal using the I component and Q component signals of the single carrier signal combined by the combining unit as drive signals. Transmitter device. In a signal transmission device that transmits a single carrier signal,
A serial-parallel conversion process in which the serial-parallel converter converts the input signal into a plurality of parallel signals;
A plurality of processing units corresponding to the respective channels generate a signal of a channel corresponding to the plurality of parallel signals,
A combining unit that combines the signals of the respective channels generated by the plurality of processing units in the signal processing step to generate a signal;
A transmission unit that transmits a signal combined in the combining step,
The signal processing steps by each of the plurality of processing units are:
An input signal modulation unit that modulates each parallel signal into a channel; and
A Fourier transform process in which a Fourier transform unit performs a Fourier transform on the signal modulated by the input signal modulation unit;
A zero insertion process in which a zero insertion unit inserts a frequency component of 0 into a frequency outside the frequency band of the signal subjected to the Fourier transform by the Fourier transform unit;
An inverse Fourier transform process in which an inverse Fourier transform unit performs an inverse Fourier transform on a signal in which a zero frequency component is inserted in the zero insertion process;
A digital-analog conversion process in which the digital-analog conversion unit converts the signal subjected to the inverse Fourier transform in the inverse Fourier transform process into an analog signal synchronized with another processing unit;
The frequency conversion unit converts the frequency of the signal converted into the analog signal in the digital-analog conversion process so that the center frequency of the frequency band of the signal becomes the center frequency of the frequency band of the channel corresponding to the processing unit. and the frequency conversion process,
A band pass filter has an extraction process of extracting a signal of a frequency band used by a channel corresponding to the processing unit from the signal frequency-converted in the frequency conversion process;
In the synthesis process, the synthesis unit generates the signal by synthesizing the signals extracted in the extraction process ,
In the frequency conversion process, the frequency conversion unit selects, as a center frequency of a frequency band of the subcarrier group, a center frequency at which frequencies outside the frequency band of adjacent subcarrier groups overlap each other. Signal transmission method.

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