JP4940222B2 - Signal receiving apparatus and method - Google Patents

Description

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

Conventionally, in a radio receiver in a communication system using a single carrier, a received signal is subjected to Fourier transform, each frequency spectrum component is extracted and equalized, and then a time signal is obtained by inverse Fourier transform and demodulated. (For example, refer nonpatent literature 1).
D. Falconer, SL Ariyavisitakul, A. Benyamin-Seeyar, and B. Eidson, “Frequency domain equalization for single-carrier broadband wireless systems,” IEEE Commun. Mag., Vol. 40, no. 4, pp. 58−66 , Apr. 2002.

  When a plurality of signals are multiplexed and transmitted at a frequency, and the reception side tries to demodulate the received signal by performing equalization in the frequency domain, the signal of the adjacent channel will be lost if the signal of the adjacent channel is not synchronized. There was a problem that the characteristics were greatly deteriorated.

  The present invention has been made in consideration of such circumstances, and its object is to remove a high-quality broadband using a single carrier that can remove interference components of adjacent channel signals and improve transmission efficiency. A signal receiving apparatus and method capable of transmission are provided.

In order to solve the above-described problem, the present invention is a signal receiving apparatus that receives and demodulates a single carrier signal including a transmission signal, and a branching unit that branches the received single carrier signal, each of which includes the single carrier signal A plurality of processing units that demodulate transmission signals of channels corresponding to the channels, and a parallel-serial conversion unit that converts the transmission signals demodulated by the plurality of processing units into serial signals and outputs them. Then, each of the processing units uses a bandpass filter for extracting a frequency region corresponding to the own channel from a single carrier signal branched by the branching unit, and a signal extracted by the bandpass filter is used by the own channel. A frequency conversion unit that performs frequency conversion so as to be the center frequency of the frequency band, and the frequency conversion unit performs frequency conversion An analog-to-digital converter that performs analog-to-digital conversion on a digital signal that is oversampled and synchronized with a digital signal that is output by another processing unit, and a digital signal that is converted by the analog-to-digital converter A Fourier transform unit that performs Fourier transform so that a predetermined number overlaps the end of the immediately preceding Fourier transform window, and a digital signal that is predetermined as a demodulation target in its own channel from a digital signal that has undergone Fourier transform by the Fourier transform unit A first signal selection unit that extracts the frequency domain of the digital signal extracted by the first signal selection unit, and an inverse Fourier transform of the digital signal that is equalized in frequency domain by the equalization unit The inverse Fourier transform unit for transforming and the transform by the inverse Fourier transform unit A second signal selection unit that extracts a digital signal obtained by removing a predetermined number of leading end portions and termination portions from the digital signal; a demodulation unit that demodulates the digital signal extracted by the second signal selection unit according to a predetermined demodulation method; The parallel-serial conversion unit converts the transmission signal for each channel demodulated by the plurality of demodulation units into a serial signal, and the processing units are digital signals extracted by the second signal selection unit, respectively. A signal receiving apparatus comprising: a guard interval removing unit that removes a guard interval from a signal, wherein the demodulating unit demodulates the digital signal from which the guard interval has been removed by a predetermined demodulation method. It is.

The present invention is also a signal receiving method for receiving and demodulating a single carrier signal including a transmission signal, the branching process of branching the received single carrier signal, and the transmission signal of each channel of the single carrier signal A signal processing process for demodulating the signal, and a parallel-serial conversion process for converting the transmission signal demodulated in the signal processing process into a serial signal and outputting the serial signal. An extraction process for extracting a frequency region corresponding to the own channel from the single carrier signal branched in the branching process, and a signal extracted in the extraction process to be a center frequency of a frequency band used by the own channel A frequency conversion process for performing frequency conversion in the frequency conversion, and frequency conversion in the frequency conversion process. An analog-to-digital conversion process in which the signal is over-sampled and converted into a digital signal synchronized with the digital signal output in the demodulation process of the transmission signal of another channel, and the digital signal converted in the analog-to-digital conversion process A Fourier transform process in which Fourier transform is performed so that a predetermined number of Fourier transform windows overlap the end portion of the immediately preceding Fourier transform window, and a digital signal Fourier-transformed in the Fourier transform process is used as a demodulation target in its own channel. A first signal selection process for extracting a predetermined digital signal, an equalization process for equalizing the frequency domain of the digital signal extracted in the first signal selection process, and a frequency domain in the equalization process, etc. Inverse Fourierize digitized digital signal An inverse Fourier transform process for converting, a second signal selection process for extracting a digital signal obtained by removing a predetermined number of leading and trailing ends from the digital signal transformed in the inverse Fourier transform process, and the second signal selecting process. a demodulating step of demodulating the extracted digital signals by a predetermined demodulation method, and the in the parallel-serial conversion process, converts the transmission signal for each respective channel demodulated in the demodulating step to a serial signal, the The demodulating process of the transmission signal of each channel in the signal processing process includes a guard interval removing process for removing a guard interval from the digital signal extracted in the second signal selecting process, and the guard interval removing process is performed in the demodulating process. The digital signal from which the guard interval was removed during the process A signal receiving method is characterized in that demodulation is performed by a demodulation method .

  According to the present invention, the signal receiving apparatus performs Fourier transform, frequency domain equalization, and inverse Fourier transform on the received signal, then cuts the head and tail of the obtained signal, and selects only the remaining signal. Therefore, the interference component of the adjacent channel signal can be removed.

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

<Signal transmitter>
FIG. 1 is a block diagram illustrating an example of a configuration of a signal transmission device that transmits a signal to a signal reception device according to an embodiment of the present invention. In the figure, a signal transmission apparatus 100 includes a signal generation circuit 101 that modulates binary data into an output signal having a wideband frequency, a signal light source 103 that generates an optical carrier having a frequency fc, and an optical carrier that the signal light source 103 generates. An optical intensity modulator 104 is provided 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 signal generation circuit 101.

FIG. 2 is a block diagram showing a detailed configuration of the signal generation circuit 101 shown in FIG.
In the figure, an S / P (serial parallel) conversion circuit 111 converts an input signal of binary data input to the signal generation circuit 101 into a parallel signal and outputs the parallel signal to the modulation circuits 112-1 to 112-k.

  Each of the modulation circuits 112-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 111 for each channel by a predetermined modulation method. At this time, each of the modulation circuits 112-i (i = 1 to k) modulates the signal input from the S / P conversion circuit 111 for each channel by a predetermined single carrier modulation method corresponding to the channel of the single carrier signal. To do. Hereinafter, the channels corresponding to the respective modulation circuits 112-i are referred to as channels i.

  The Fourier transform circuit 113-i (i = 1 to k) performs Fourier transform on the signal modulated by the modulation circuit 112-i. The 0 insertion circuit 114-i (i = 1 to k) inserts a frequency component of 0 in a frequency band outside the signal transmission frequency band of the signal subjected to the Fourier transform by the Fourier transform circuit 113-i. At this time, the 0 insertion circuit 114-i (i = 1 to k) is a frequency band outside the signal transmission frequency band of the signal Fourier-transformed by the Fourier transform circuit 113-i, and is adjacent to the signal transmission frequency band. A frequency component of 0 is inserted into the frequency band to be used. Here, the same effect can be obtained by performing processing such as oversampling in the subsequent stage without using the zero insertion circuit 114-i and without performing zero insertion. Further, by using a band limiting filter such as a root Nyquist filter instead of the 0 insertion circuit 114-i (i = 1 to k), interference with an adjacent channel can be reduced.

  The inverse Fourier transform circuit 115-i (i = 1 to k) performs inverse Fourier transform on the signal in which the 0 frequency component is inserted by the 0 insertion circuit 114-i. The GI (guard interval) insertion circuit 116-i (i = 1 to k) inserts a guard interval into the signal subjected to inverse Fourier transform by the inverse Fourier transform circuit 115-i. The GI insertion circuit 116-i (i = 1 to k) can be omitted depending on the configuration of the transmitter. The smoothing circuit 117-i (i = 1 to k) smoothes the joints between the Fourier transform blocks by digital signal processing. The D / A conversion circuit 118-i (i = 1 to k) converts the digital signal into a synchronized analog signal using the clock by the common clock 122.

  The frequency conversion circuit 119-i (i = 1 to k) converts the frequency of the analog signal using the oscillation signal from the local oscillator 123. At this time, the center frequency in the frequency band of the analog signal output from the D / A conversion circuit 118-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 120-i (i = 1 to k) extracts a frequency band signal used by the channel from the frequency-converted signal. The synthesizing circuit 121 synthesizes the channels i output from the BPFs 120-i (i = 1 to k), generates a baseband signal of a broadband single carrier signal, and outputs it as an output A.

  The Fourier transform circuit 113-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 115-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. Thus, by using the fast Fourier transform for the Fourier transform circuit 113-i (i = 1 to k) and by using the inverse fast Fourier transform for the inverse Fourier transform circuit 115-i (i = 1 to k). The calculation load and calculation time for each channel are further reduced.

Next, signal processing by the signal transmission apparatus described above will be described.
First, the S / P conversion circuit 111 converts the binary signal input to the signal generation circuit 101 from a serial signal into a parallel signal having a predetermined data length, and outputs the parallel signal to the modulation circuits 112-1 to 112-k. The modulation circuit 112-i (i = 1 to k) has a predetermined modulation scheme, for example, 16QAM (Quadrature Amplitude Modulation), 64QAM, QPSK (Quadrature Phase Shift Keying), etc. Data input from the S / P conversion circuit 111 is modulated by the carrier modulation method, mapped to a channel, and output to the Fourier transform circuit 113-i (i = 1 to k). Specifically, the Fourier transform circuit 113-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. 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 111 converts, for example, serial signal data to be transmitted through the channel i (i = 1 to k) out of the serial signals into a parallel signal having a predetermined data length. Output to the modulation circuit 112-i (i = 1 to k) corresponding to i.

  The Fourier transform circuit 113-i (i = 1 to k) performs Fourier transform on the signal modulated by the modulation circuit 112-i, and outputs it to the 0 insertion circuit 114-i (i = 1 to k). The 0 insertion circuit 114-i (i = 1 to k) inserts a frequency component of 0 in the adjacent frequency band outside the signal transmission frequency band of the signal subjected to Fourier transform by the Fourier transform circuit 113-i. And output to the inverse Fourier transform circuit 115-i. FIG. 3 is a diagram illustrating an output of the 0 insertion circuit 114-i when a signal is not assigned to a 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 channel i from the modulation circuit 112-i. Also, by designating 0 for all channels in advance and outputting a signal to the corresponding channel by the modulation circuit 112-i, the same effect can be obtained without going through the 0 insertion circuit 114-i. .

  The inverse Fourier transform circuit 115-i (i = 1 to k) performs inverse Fourier transform on the data input from the 0 insertion circuit 114-i, thereby converting the transmission signal mapped in the frequency domain into a time domain signal. Convert to a single carrier signal. Thereby, in each 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 113-i (i = 1 to k), the 0 insertion circuit 114-i (i = 1 to k), and the inverse Fourier transform circuit 115-i (i = 1 to k). When the signal modulated by the circuit 112-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.

The GI (guard interval) insertion circuit 116-i (i = 1 to k) inserts a guard interval into the signal input from the inverse Fourier transform circuit 115-i.
FIG. 4 is a diagram illustrating a guard interval insertion method in the GI insertion circuit 116-i. The GI insertion circuit 116-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.

The smoothing circuit 117-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 116-i, and the D / A conversion circuit 118. Output to -i.
FIG. 5 is a diagram illustrating a smoothing process in the smoothing circuit 117-i. If the Fourier transform blocks are simply arranged continuously, the signal becomes discontinuous between the Fourier transform blocks. Therefore, the smoothing circuit 117-i performs processing so that the joints between the Fourier transform blocks change smoothly, and removes the presence of steep frequency components.

  The D / A conversion circuit 118-i (i = 1 to k) uses the clock by the common clock 122 to convert the digital signal input from the smoothing circuit 117-i to the other D / A conversion circuit 118-i. The signal is converted into an analog signal synchronized with the signal and output to the frequency conversion circuit 119-i. The frequency conversion circuit 119-i (i = 1 to k) uses the oscillation signal from the local oscillator 123 to change the frequency band of the analog signal of the channel i input from the D / A conversion circuit 118-i to the frequency band. The frequency is converted to fi and output to the BPF 120-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 119-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. 6 is a diagram illustrating frequency conversion in the frequency conversion circuit 119-1. In the figure, the frequency conversion circuit 119-1 frequency-converts the signal output from the D / A conversion circuit 118-1 to 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.

The BPF 120-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, and at this time, the BPF 120-i is adjacent to the frequency band Δfi. A signal for the frequency band δfi is also extracted.
FIG. 7 is a diagram showing processing in the BPF 120-1. In the figure, the BPF 120-1 extracts the signal of the frequency band Δf1 from the signal of the frequency band f1, but when the BPF 120-1 extracts the frequency band Δf1, the frequency band adjacent to 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 114-1, the channel i can be used without using a steep BPF (δf1 is close to 0) 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.

The combining circuit 121 combines the channels i output from the BPFs 120-i (i = 1 to k), generates an output A, and outputs the output A.
FIG. 8 is a diagram illustrating the output A output from the synthesis circuit 121. As shown in the figure, the synthesis circuit 121 synthesizes the channels 1 to k in the frequency bands f1 to fk output from the BPFs 120-i (i = 1 to k), respectively, and generates an electrical ultra-wideband single carrier signal. Output A is generated.

For example, a Mach-Zehnder type modulator is used as the light intensity modulator 104. By inputting the output A of the signal generation circuit 101 to this Mach-Zehnder type modulator, an optical carrier having a frequency fc emitted from the signal light source 103 is used. DSB (double sideband) optical single carrier signal is generated. FIG. 9 is a diagram showing a spectrum of an optical single carrier signal output from the optical intensity modulator 104. As shown in the figure, the optical single carrier signal output from the optical intensity modulator 104 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 104 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 centering on the frequency fc, but in order to increase the use efficiency of the band, an optical BPF (band pass filter) is provided after the optical intensity modulator 104. The single carrier signal output from the light intensity modulator 104 may be converted into an SSB (single sideband) by the optical BPF.
Also, 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, SSB can be realized without using the optical BPF.

  Next, a signal receiving apparatus according to an embodiment of the present invention will be described.

<First Embodiment>
FIG. 10 is a block diagram showing a configuration of the optical receiver 200 according to the first embodiment of the present invention. The optical receiver 200 receives the broadband optical single carrier signal transmitted from the signal transmission apparatus 100 and divided into a plurality of channels including transmission data, and demodulates the transmission data from the received broadband optical single carrier signal. Output as binary data.

The optical receiver 200 includes a local oscillation light source 202, a coupler 203, a balance receiver 204, and a signal receiving device 205. The broadband optical single carrier signal carrying the signal on the optical carrier having the frequency fc is combined with the optical signal having the frequency f _L0 from the local oscillation light source 202 by the coupler 203. Next, it is optical / electrically converted by the balance receiver 204 and output to the signal receiving device 205 as a broadband electric single carrier signal. Instead of the balanced receiver 204, a single-ended receiver may be used.

The balance receiver 204 optically / electrically converts the optical signal combined by the coupler 203 by, for example, heterodyne detection or homodyne detection. In this balanced receiver 204, not only optical / electrical conversion but also a wideband electric single carrier signal output from the balanced receiver 204 is the difference between the frequency fc of the optical carrier and the frequency f _L0 of the local oscillation light source 202. Frequency conversion to IF (Intermediate Frequency) band.

  The broadband electric single carrier signal output from the balance receiver 204 is input to the signal receiving device 205 and demodulated into binary data by the signal receiving device 205.

<Configuration of Signal Receiver 205>
Next, the configuration of the signal receiving apparatus 205 shown in FIG. 10 will be described with reference to FIG. The branch circuit 250 branches the broadband electric single carrier signal output from the balance receiver 204 to the BPFs 251-1 to 251-k and outputs the signals. The BPF 251-i (i = 1 to k) is a predetermined frequency band used by each channel corresponding to the BPF 251-i (i = 1 to k) from the broadband electric single carrier signal input by the branch circuit 250. Are extracted and output. In the following, the channels corresponding to the BPFs 251-i (i = 1 to k) are respectively referred to as channels i. Further, the center frequency fi of the frequency band extracted by the BPF 251-i (i = 1 to k) is set as the center frequency fi.

  The frequency conversion circuit 252-i (i = 1 to k) uses the oscillation signal from the local oscillation light source 202 to extract the frequency of the broadband electric single carrier signal output by the BPF 251-i, that is, the frequency of the analog signal. Convert. In this case, the frequency conversion circuit 252-i (i = 1 to k) has the center frequency of the frequency band of the broadband electric single carrier signal extracted and output by the BPF 251-i approximately at the center of the frequency band used by the channel. The frequency conversion is performed so that the frequency becomes.

  The A / D conversion circuit 253-i (i = 1 to k) converts the analog signal frequency-converted by the frequency conversion circuit 252-i into a digital signal synchronized with the clock signal from the common clock 271. Accordingly, the digital signals output from the A / D conversion circuit 253-i (i = 1 to k) are synchronized with each other. The A / D conversion circuit 253-i performs oversampling and converts it into a digital signal synchronized with the clock signal from the common clock 271. For example, the A / D conversion circuit 253-i oversamples a 64 sample received signal as 256 times transmission information of 256 samples.

  The digital signal obtained by the A / D conversion circuit 253-i (i = 1 to k) is stored in the buffer 254-i. The signal sequence stored in the first buffer 254-i (i = 1 to k) is Fourier transformed while shifting the head position by S so that a part of the signal sequence overlaps with the Fourier transform window read immediately before. The window is set and read out to the Fourier transform circuit 255-i. The Fourier transform circuit 255-i (i = 1 to k) performs Fourier transform on the read digital signal. The first signal selection circuit 256-i (i = 1 to k) selects (extracts) a digital signal predetermined as a demodulation target in the channel i from the digital signal Fourier-transformed by the Fourier transform circuit 255-i. And output. The equalization circuit 257-i (i = 1 to k) equalizes and outputs the digital signal selected by the first signal selection circuit 256-i.

Here, the equalization circuit 257-i performs frequency domain equalization on the received signal (see Non-Patent Document 1). As weights used in frequency domain equalization, weights of a mean square error minimum (MMSE) norm that minimizes an error between a transmission signal and a reception signal after equalization, a zero forcing (ZF) weight, and the like are conventionally used. Although there are similar weights, they are used to equalize the received signal.
In order to estimate the weight, a conventional weight calculation method such as a method of calculating a transfer function of a propagation path using a pilot signal inserted at the head and calculating a weight using the function can be used.

  The inverse Fourier transform circuit 258-i (i = 1 to k) performs an inverse Fourier transform on the signal input from the equalization circuit 257-i. The second signal selection circuit 259-i (i = 1 to k) is a signal at the center portion of the block that is predetermined as a demodulation target in the channel i with respect to the signal input from the inverse Fourier transform circuit 258-i. Select (extract) a digital signal. The GI removal circuit 260-i (i = 1 to k) removes the guard interval from the digital signal of each block selected by the second signal selection circuit 259-i. When the GI is not given to the transmission signal, the GI removal circuit 260-i (i = 1 to k) can be omitted. The demodulating circuit 261-i (i = 1 to k) converts the digital signal from which the guard interval has been removed by the GI removing circuit 260-i to a predetermined method corresponding to a modulation method used in a signal transmission device such as 16QAM, 64QAM, or QPSK. Is demodulated into binary data by the demodulation method.

A P / S (parallel / serial) conversion circuit 262 receives binary data modulated by the demodulation circuits 261-1 to 261-k in parallel for each channel i, and converts the input parallel binary data into serial data. Convert to and output.
Note that the GI removal circuit 260-i (i = 1 to k) can be installed immediately before the Fourier transform circuit 255-i.

<Operation of Optical Receiver 200>
Next, the operation of the optical receiver 200 described with reference to FIGS. 10 and 11 will be described. First, the coupler 203 of the optical receiver 200 that has received a broadband optical single carrier signal in which a single carrier signal is carried on an optical carrier having a frequency fc, receives the received broadband optical single carrier signal and the frequency f _L0 from the local oscillation light source 202. Combines with optical signal.

  FIG. 12 shows a waveform as an example of a broadband optical single carrier signal received by the coupler 203 of the optical receiver 200. As shown in FIG. 12, the broadband optical single carrier signal has a waveform centered on the frequency fc of the optical carrier, and the signal is distorted as it propagates through the transmission line. The spectrum is In the figure, the frequency band extracted later by BPF 251-i (i = 1 to k) and the center frequency fi (i = 1 to k) are shown.

Next, the balance receiver 204 optically / electrically converts the optical signal combined by the coupler 203 by, for example, heterodyne detection, and the difference between the frequency fc of the optical carrier and the frequency f _L0 of the local oscillation light source 2 is calculated. Frequency conversion is performed up to an IF (Intermediate Frequency) band, and the result is output to the signal receiving device 205 as a broadband electric single carrier signal.
FIG. 13 shows a waveform as an example of a wideband electric single carrier signal frequency-converted up to the IF band output from the balance receiver 204 to the signal receiver 205.

  Next, the branch circuit 250 of the signal receiving device 205 to which the broadband electric single carrier signal output from the balance receiver 204 is input, converts the broadband electric single carrier signal output from the balance receiver 204 into the BPFs 251-1 to 251. Branch to -k and output.

Next, the BPF 251-i (i = 1 to k) is determined in advance from the broadband electric single carrier signal input by the branch circuit 250 to be used by the channel i corresponding to the BPF 251-i (i = 1 to k). The frequency band signal is extracted and output to the frequency conversion circuit 252-i (i = 1 to k).
FIG. 14 shows an example of a frequency band that BPF 251-i (i = 1 to k) extracts from a broadband electric single carrier signal.

Next, the frequency conversion circuit 252-i (i = 1 to k) uses the oscillation signal from the local oscillator 270 to extract the frequency of the broadband electric single carrier signal output by the BPF 251-i, that is, an analog signal. Frequency is converted so that it becomes the center frequency of the frequency band used by the channel i, and is output to the A / D conversion circuit 253-i (i = 1 to k).
FIG. 15 shows frequency conversion as an example by the frequency conversion circuit 252-i (i = 1 to k).

  Next, the A / D conversion circuit 253-i (i = 1 to k) oversamples the analog signal frequency-converted by the frequency conversion circuit 252-i into a digital signal synchronized with the clock signal from the common clock 271. Then, the data is converted and output to the buffer 254-i.

  Next, as shown in FIG. 16, the Fourier transform circuit 255-i (i = 1 to k) starts from the buffer 254-i so as to overlap the end of the Fourier transform window read immediately before by the S position at the top. The digital signal is read out by setting the Fourier transform window while shifting. That is, the digital signal is converted so that the head of the Fourier transform window m overlaps the end of the previous Fourier transform window (m−1) and the end of the Fourier transform window m overlaps the head of the next Fourier transform window (m + 1). Read and perform Fourier transform. The first signal selection circuit 256-i (i = 1 to k) selects a signal predetermined as a demodulation target in the channel i from the signal Fourier-transformed by the Fourier transform circuit 255-i for each Fourier transform window. Then, the equalization circuit 257-i (i = 1 to k) equalizes and outputs the frequency domain of the signal selected by the first signal selection circuit 256-i.

  The inverse Fourier transform circuit 258-i (i = 1 to k) performs an inverse Fourier transform on the signal of each block input from the equalization circuit 257-i. As shown in FIG. 16, the second signal selection circuit 259-i (i = 1 to k) affects the influence of inter-block interference on each block of the time-series signal subjected to inverse Fourier transform by the inverse Fourier transform circuit 258-i. A predetermined number of signals at the beginning and end having a large value are deleted, and the remaining digital signal at the center having a small influence of interference, which is predetermined as a demodulation target in channel i, is selected (extracted). The GI removal circuit 260-i (i = 1 to k) removes the guard interval from the signal of each block selected by the second signal selection circuit 259-i.

Next, the demodulation circuit 261-i (i = 1 to k) demodulates the digital signal from which the guard interval has been removed by the GI removal circuit 260-i into binary data by a predetermined demodulation method, and performs P / S conversion. Output to the circuit 262.
Next, binary data modulated by the demodulation circuits 261-1 to 261-k is input to the P / S conversion circuit 262 in parallel for each channel i, and the input parallel binary data is converted into serial data. Convert and output.

<Adjustment of Local Oscillation Light Source 202>
Next, adjustment of an optical signal output from the local oscillation light source 202 will be described. A demodulation circuit 261-i (i = 1 to k) detects a frequency deviation from the demodulated digital signal, and has a local oscillator adjustment unit that adjusts an optical signal output from the local oscillation light source 202 based on the detected frequency deviation. Like that. By applying feedback to the local oscillation light source 202 by this local oscillator adjustment unit, the signal quality of a signal detected by the balance receiver 204 by heterodyne detection or homodyne detection is improved.

Here, a plurality of blocks (frequency band blocks) in which a single carrier signal is divided by a bandpass filter of BPF 251-i (i = 1 to k) will be described with reference to FIG.
The optical receiver 200 demodulates the single carrier signal by dividing it into a plurality of blocks i (i = 1 to k) using a band pass filter of BPF 251-i (i = 1 to k). At this time, the pass band of BPF 251-i (i = 1 to k) is set wider than the band of the block to be demodulated. Since the passband of the BPF 251-i (i = 1 to k) is set wide, unnecessary frequency components are included. Therefore, only the symbols of the necessary frequency components are extracted by the first signal selection circuit 256-i and demodulated. Data is demodulated by the circuit 261-i (i = 1 to k).

  Here, Δfi (i = 1 to k) indicates a frequency band to be demodulated in the broadband optical single carrier signal. Further, by setting the pass band wider than the desired frequency band of Δfi + 2δfi (i = 1 to k), the channel of Δfi (i = 1 to k) is not distorted by the filter.

  Then, the frequency conversion circuit 252-i (i = 1 to k) performs frequency conversion to the baseband, and the A / D conversion circuit 253-i (i = 1 to k) exceeds Δfi + 2δfi (i = 1 to k) or more. By oversampling at the sampling frequency, the data symbol of the channel to be demodulated is demodulated by the demodulation circuit 261-i (i = 1 to k) without being affected by the filtering by the BPF 251-i (i = 1 to k). .

<Second Embodiment>
A signal receiving apparatus according to the second embodiment of the present invention will be described. The signal receiving apparatus according to the present embodiment is obtained by replacing the signal receiving apparatus 205 according to the first embodiment with the configuration shown in FIG. In the figure, the same parts as those of the signal receiving apparatus 205 according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The apparatus shown in this figure is different from the signal receiving apparatus 205 according to the first embodiment in that the buffer 254-i (i = 1 to k) is not provided, and the Fourier transform circuit 255-i and the first signal selection circuit 256-are provided. i, instead of the equalization circuit 257-i and the inverse Fourier transform circuit 258-i, the Fourier transform circuit 255a-i, the first signal selection circuit 256a-i, the equalization circuit 257a-i, and the inverse Fourier transform Two systems of a set of circuits 258a-i and a set of Fourier transform circuit 255b-i, first signal selection circuit 256b-i, equalization circuit 257b-i, and inverse Fourier transform circuit 258b-i are provided. It is. Thereby, a plurality of operations after the Fourier transform are performed in parallel, and real-time processing becomes possible.
That is, if the signal of the Fourier transform window (m−1) in FIG. 16 is input to the Fourier transform circuit 255a-i, the signal of the next Fourier transform window m is input to the Fourier transform circuit 255b-i, and then the next Fourier transform circuit 255b-i. The signal of the conversion window (m + 1) is input to the Fourier transform circuit 255a-i.

<Third Embodiment>
Next, a signal receiving apparatus according to the third embodiment will be described with reference to FIG. Here, the signal receiving apparatus according to the third embodiment will be described as a signal receiving system.

  This signal receiving system has a plurality of optical receivers 200 which are the signal receivers 200 described in the first embodiment or the signal receivers described in the second embodiment. In FIG. 19, the signal reception system has n optical receivers 201. This optical receiver 201 is described as an optical receiver 201-i (i = 1 to n). The plurality of optical receivers 201-i (i = 1 to n) are set in advance so as to demodulate wideband single carrier signals of different frequency bands.

  In addition, this signal receiving system demultiplexes the received optical single carrier signal into channels in a frequency band demodulated by a plurality of optical receivers 201-i (i = 1 to n), and the demultiplexed optical single carrier signal. An optical demultiplexing unit 280 that outputs to the optical receiver 201-i (i = 1 to n) corresponding to the frequency band is included.

Each of the plurality of optical receivers 201-i (i = 1 to n) demodulates the signal input from the optical demultiplexing unit 280.
The optical demultiplexing unit 280 receives the received optical single carrier so that the frequency band of the demultiplexed channel is wider than at least the frequency band demodulated by the corresponding optical receiver 201-i (i = 1 to n). The signal is demultiplexed into a frequency band signal demodulated by a plurality of optical receivers 201-i (i = 1 to n).

  In this way, the pass band of the optical demultiplexing unit 280 is set wider than the signal to be demodulated, and the light is demultiplexed and demodulated by the optical receiver 201-i (i = 1 to n). As a result, the optical receiver 201-i (i = 1 to n) demodulates only symbols of frequency components necessary for demodulation.

According to the third embodiment, the block division by the BPF, which has been performed in the electrical domain in the first and second embodiments, is also performed in the frequency domain of light using the optical demultiplexing unit 280. As a result, the requirements for circuit speed can be relaxed. In other words, it is possible to demodulate a wider-band optical single carrier signal than when the optical receiver 201-i (i = 1 to n) is used alone.
Note that the GI removal circuit 260-i (i = 1 to k) can be installed immediately before the Fourier transform circuit 255-i.

<Configuration not using GI>
In the above description, the case where a signal with a GI inserted is transmitted and received, but the GI may not be used. In this case, the GI insertion circuits 116-1 to 116-k and the smoothing circuits 117-1 to 117-k shown in FIG. 2 and the GI removal circuits 260-1 to 260-k shown in FIGS. . Thereby, transmission efficiency can be improved. In the first to third embodiments, the Fourier transform circuits 255-1 to 255-k, 255a-1 to 255a-k, and 255b-1 to 255b-k are before performing the Fourier transform on the input signal. Can be multiplied by window functions such as Hann window, Hamming window, Blackman window, Kaiser window.

As described above, the signal receiving apparatus according to the present embodiment performs frequency domain equalization by performing Fourier transform and equalization and inverse Fourier transform on the received signal, and then displays the beginning and end of the obtained signal. By deleting like 16 and selecting only the remaining signals and demodulating, it is possible to remove the interference components of the signals of the adjacent channels.
Also, circuits that perform digital data processing, such as Fourier transform circuits, GI removal circuits, and demodulation circuits, perform data processing in parallel on data divided into channels, and therefore, when processing data without dividing into channels In contrast, it is possible to operate the data processing with a slow clock, and therefore, it is possible to realize signal processing for an ultra-wideband input signal in real time.

It is a block diagram which shows the structure of the signal transmitter which transmits a signal to the signal receiver of this invention. It is a block diagram which shows the structure of the signal generation circuit in FIG. It is a figure which shows the output of the 0 insertion circuit in FIG. It is a figure which shows the output of the GI insertion circuit in FIG. It is a figure which shows the output of the smoothing circuit in FIG. It is a figure which shows the output of the frequency converter circuit in FIG. It is a figure which shows the process of BPF in FIG. It is a figure which shows the output of the synthetic | combination circuit in FIG. It is a figure which shows the output from the light intensity modulator in FIG. It is a block diagram which shows the structure of the signal receiver in the 1st Embodiment of this invention. It is a block diagram which shows the structure of the demodulator by the same embodiment. It is a figure which shows the waveform as an example of the broadband optical single carrier signal input into the embodiment. It is a figure which shows the waveform as an example of the broadband electric single carrier signal frequency-converted to IF band which the balance receiver by the same embodiment outputs to a demodulator. It is a figure which shows the frequency band as an example which BPF by the embodiment extracts from a broadband electric single carrier signal. It is a figure which shows the frequency conversion as an example by the frequency conversion circuit by the embodiment. It is a figure for demonstrating the duplication equalization method by the same embodiment. It is a figure which shows the some block which divides the single carrier signal by the same embodiment by BPF It is a block diagram which shows the structure of the demodulator in the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the signal receiver in the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100, 100a ... Signal transmitter 101 ... Signal generation circuit 103 ... Signal light source 104 ... Light intensity modulator 105 ... Optical BPF
111 ... S / P conversion circuits 112-1 to 112-k ... modulation circuits 113-1 to 113-k ... Fourier transform circuits 114-1 to 114-k ... 0 insertion circuits 115-1 to 115-k ... inverse Fourier transform Circuits 116-1 to 116-k GI insertion circuits 117-1 to 117-k Smoothing circuits 118-1 to 118-k D / A conversion circuits 119-1 to 119-k Frequency conversion circuits 120-1 to 120-1 120-k ... BPF
121 ... Synthesizing circuit 122 ... Common clock 123 ... Local oscillator 200, 201 ... Optical receiver 202 ... Local oscillation light source 203 ... Coupler 204 ... Balance receiver 205 ... Signal receiving device 250 ... Branch circuits 251-1 to 251-k ... BPF (Band pass filter)
252-1 to 252-k... Frequency conversion circuit (frequency conversion unit)
253-1 to 253-k ... A / D conversion circuit (analog / digital conversion unit)
254-1 to 254-k... Buffers 255-1 to 255-k, 255a-1 to 255a-k, 255b-1 to 255b-k... Fourier transform circuit (Fourier transform unit)
256-1 to 256 -k, 256 a-1 to 256 a -k, 256 b-1 to 256 b -k... First signal selection circuits 257-1 to 257 -k, 257 a-1 to 257 a -k, 257 b-1 to 257 b -K, ... Equalization circuit (equalization unit)
258-1 to 258-k, 258 a-1 to 258 a-k, 258 b-1 to 258 b-k,..., Inverse Fourier transform circuit (inverse Fourier transform unit)
259-1 to 259-k... Second signal selection circuit (second signal selection unit)
260-1 to 260-k... GI removal circuit (guard interval removal unit)
261-1-261-k .. Demodulator circuit (demodulator)
262... P / S conversion circuit (parallel-serial conversion unit)
270 ... Local oscillator 271 ... Common clock 280 ... Optical demultiplexing part

Claims (2)

A signal receiving apparatus that receives and demodulates a single carrier signal including a transmission signal,
A branching unit for branching the received single carrier signal;
A plurality of processing units each corresponding to a channel of the single carrier signal and demodulating a transmission signal of a channel corresponding to the channel;
A parallel-serial conversion unit that converts the transmission signal demodulated by the plurality of processing units into a serial signal and outputs the serial signal;
Have
The processing units are respectively
A bandpass filter for extracting a frequency region corresponding to the own channel from the single carrier signal branched by the branching unit;
A frequency conversion unit that performs frequency conversion so that the signal extracted by the bandpass filter becomes the center frequency of the frequency band used by the own channel;
The analog-to-digital conversion unit that performs analog-to-digital conversion to a digital signal that is over-sampled and synchronized with the digital signal that is output by the other processing unit, the frequency converted by the frequency conversion unit,
A Fourier transform unit that performs a Fourier transform on the digital signal converted by the analog-to-digital conversion unit, so that a predetermined number of end portions of the Fourier transform window overlap a terminal portion of the immediately preceding Fourier transform window;
A first signal selection unit that extracts a digital signal predetermined as a demodulation target in the own channel from the digital signal Fourier-transformed by the Fourier transform unit;
An equalization unit for equalizing the frequency domain of the digital signal extracted by the first signal selection unit;
An inverse Fourier transform unit for performing an inverse Fourier transform on the digital signal equalized in the frequency domain by the equalization unit;
A second signal selection unit that extracts a digital signal obtained by removing a predetermined number of leading end portions and terminal end portions from the digital signal converted by the inverse Fourier transform unit;
A demodulator that demodulates the digital signal extracted by the second signal selector by a predetermined demodulation method;
Have
The parallel serial converter is
The transmission signal for each channel demodulated by the plurality of demodulation units is converted into a serial signal,
The processing units are respectively
A guard interval removing unit for removing a guard interval from the digital signal extracted by the second signal selecting unit;
The demodulator
The guard interval removing unit demodulates the digital signal from which the guard interval is removed by a predetermined demodulation method,
A signal receiving device. A signal reception method for receiving and demodulating a single carrier signal including a transmission signal,
A branching process for branching the received single carrier signal;
A signal processing step of demodulating the transmission signal of each channel of the single carrier signal;
A parallel-serial conversion process in which the transmission signal demodulated in the signal processing process is converted into a serial signal and output;
Have
The demodulation processing of the transmission signal of each channel in the signal processing process,
An extraction process for extracting a frequency region corresponding to the own channel from the single carrier signal branched in the branching process;
A frequency conversion process for performing frequency conversion on the signal extracted in the extraction process so as to be a center frequency of a frequency band used by the own channel;
An analog-to-digital conversion process in which the frequency-converted signal in the frequency conversion process is oversampled and analog-to-digital converted into a digital signal synchronized with a digital signal output in a demodulation process of a transmission signal of another channel;
A Fourier transform process in which the digital signal converted in the analog-to-digital conversion process is Fourier transformed so that a predetermined number of Fourier transform window end portions overlap with a terminal portion of the immediately preceding Fourier transform window;
A first signal selection process for extracting a digital signal predetermined as a demodulation target in the own channel from the digital signal Fourier-transformed in the Fourier transform process;
An equalization process for equalizing the frequency domain of the digital signal extracted in the first signal selection process;
An inverse Fourier transform process for performing an inverse Fourier transform on the digital signal equalized in the frequency domain in the equalization process;
A second signal selection step of extracting a digital signal obtained by removing a predetermined number of leading end portions and terminal end portions from the digital signal converted in the inverse Fourier transform step;
A demodulation process for demodulating the digital signal extracted in the second signal selection process according to a predetermined demodulation method;
Have
In the parallel-serial conversion process,
The transmission signal for each channel demodulated in the demodulation process is converted into a serial signal,
The demodulation processing of the transmission signal of each channel in the signal processing process,
A guard interval removing step of removing a guard interval from the digital signal extracted in the second signal selection step;
In the demodulation process,
Demodulating the digital signal from which the guard interval has been removed in the guard interval removing process using a predetermined demodulation method;
And a signal receiving method.

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