Abstract: A receiving device that converts, to a digital signal, a signal in which signal light from an optical transmission path and local oscillation light are mixed, so as to perform digital signal processing, the optical communication receiving device comprising: a frequency offset compensation unit configured to calculate a frequency offset of the digital signal and to, based on the frequency offset, compensate for a phase of the digital signal; a carrier phase recovery unit configured to calculate a carrier phase of the digital signal whose phase is compensated for in the frequency offset compensation unit; and a residual frequency offset detection unit configured to calculate an average of differences in the carrier phase, and to output the average as a residual frequency offset, wherein the frequency offset compensation unit is configured to correct the frequency offset using the residual frequency offset output by the residual frequency offset detection unit.

Abstract: A loop filter include: a register that stores a result of arithmetic operation performed on a complex signal and outputs the stored complex signal; a first multiplier that multiplies the complex signal output from the register and a predetermined coefficient; an absolute value judging unit that outputs a multiplier coefficient used to control such that the amplitude of the complex signal output from the register is held in a predetermined range; a multiplier that multiplies an output from the first multiplier and the multiplier coefficient; a second multiplier that multiplies an input signal and a value (1?the predetermined coefficient); and an adder that adds an output from the multiplier to an output from the second multiplier and inputs a result of addition into the register.

Abstract: A method of tap coefficient correction includes: obtaining a synchronization symbol difference between a first polarization and a second polarization orthogonal to the first polarization; obtaining a delay amount of each of the first polarization and the second polarization in an adaptive equalizer; calculating, in a case where a horizontal axis represents a tap number and a vertical axis represents a tap coefficient and a tap number or a nearest tap number with which an area of a drawn figure is halved is set as a gravity center of tap coefficients, a correction reference gravity center of the tap coefficients set in the adaptive equalizer, based on the synchronization symbol difference and the delay amount; and performing a correction of shifting an entire tap coefficients in units of symbol to cause the correction reference gravity center to be closest to a tap center.

Abstract: An adaptive equalizer includes a finite impulse response filter with a predetermined number of taps; and a tap coefficient adaptive controller having a register to hold tap coefficients for the filter, a weighted center calculator to calculate a weighted center of the tap coefficients, and a tap coefficient shifter to shift the tap coefficients based on a calculation result of the weighted center. During an initial training period, the tap coefficient shifter shifts the tap coefficients on a symbol data basis such that a difference between the calculated weighted center of the tap coefficients and a tap center defined by the number of taps is minimized.

Abstract: A digital coherent receiving apparatus includes a first oscillator for outputting a local light signal of a fixed frequency, a hybrid unit mixing the local light signal with a light signal received by a receiver, a second oscillator for outputting a sampling signal of a sampling frequency, a converter for converting the mixed light signal into digital signal synchronizing with the sampling signal, a waveform adjuster for adjusting a waveform distortion of the converted digital signal, a phase adjustor for adjusting a phase of the digital signal adjusted by the waveform adjustor, a demodulator for demodulating the digital signal adjusted by the phase adjuster, and a phase detector for detecting a phase of the digital signal adjusted by the phase adjuster, and a control signal output unit for outputting a frequency control signal on the basis of the detected phase signal to the second oscillator.

Abstract: A digital coherent receiving apparatus includes a first oscillator for outputting a local light signal of a fixed frequency, a hybrid unit mixing the local light signal with a light signal received by a receiver, a second oscillator for outputting a sampling signal of a sampling frequency, a converter for converting the mixed light signal into digital signal synchronizing with the sampling signal, a waveform adjuster for adjusting a waveform distortion of the converted digital signal, a phase adjustor for adjusting a phase of the digital signal adjusted by the waveform adjustor, a demodulator for demodulating the digital signal adjusted by the phase adjuster, and a phase detector for detecting a phase of the digital signal adjusted by the phase adjuster, and a control signal output unit for outputting a frequency control signal on the basis of the detected phase signal to the second oscillator.

Abstract: An ALC processing unit to adjust the signal level of outputs from an adaptive equalizer to a target value is provided in a stage later than the adaptive equalizer and earlier than a frequency offset estimation/compensation unit in an optical digital coherent receiver. The ALC processing unit generates a histogram that counts the number of samples for discrete monitored values corresponding to amplitude values of outputs from the adaptive equalizer, and determines a level adjustment coefficient that is to be multiplied by an output from the adaptive equalizer so as to multiply the determined coefficient by the output from the adaptive equalizer so that the monitored value of the peak value of the histogram is the target value.

Abstract: A simulation method includes obtaining an execution log generated while a predetermined processing is executed by simulating a series of operations in a test model that is a modeled version of a test target device by causing a predetermined processing to be executed in the test model, extracting a processing unit log constituted by a predetermined processing unit from the execution log obtained in the obtaining, and simulating an operation in which processing corresponding to the processing unit log extracted in the extracting is executed in a test model in which a part of function of the test target device is modified, the operation being simulated on the basis of a setting condition set by a user.

Abstract: A memory control method that carries out first-in first-out access control for a memory having a plurality of storage areas, including: selecting, as write positions, an address of a storage area in a storage block having at least one or more storage areas and an address of a storage area in any one of a plurality of redundant blocks that are made redundant with respect to the storage block and have at least one or more storage areas when the write positions are selected to write data to the memory; and selecting, as read positions, an address of a storage area of the storage block and an address selected by the selecting of the write position from among the addresses of a plurality of the redundant blocks when the read positions are selected to read data written by the writing of the data to the memory.

Abstract: A performance evaluation simulation apparatus divides a process into basic process units based on an execution log, calculates a throughput of each basic process unit from information held in the execution log, changes an arrangement structure so that a basic process unit with the calculated throughput exceeding a predetermined threshold is disposed in a hardware model, and performs a performance evaluation simulation on the hardware model and a software model to generate statistical information on which performance evaluation is based.

Abstract: A loop filter include: a register that stores a result of arithmetic operation performed on a complex signal and outputs the stored complex signal; a first multiplier that multiplies the complex signal output from the register and a predetermined coefficient; an absolute value judging unit that outputs a multiplier coefficient used to control such that the amplitude of the complex signal output from the register is held in a predetermined range; a multiplier that multiplies an output from the first multiplier and the multiplier coefficient; a second multiplier that multiplies an input signal and a value (1?the predetermined coefficient); and an adder that adds an output from the multiplier to an output from the second multiplier and inputs a result of addition into the register.

Abstract: An adaptive equalizer includes a finite impulse response filter with a predetermined number of taps; and a tap coefficient adaptive controller having a register to hold tap coefficients for the filter, a weighted center calculator to calculate a weighted center of the tap coefficients, and a tap coefficient shifter to shift the tap coefficients based on a calculation result of the weighted center. During an initial training period, the tap coefficient shifter shifts the tap coefficients on a symbol data basis such that a difference between the calculated weighted center of the tap coefficients and a tap center defined by the number of taps is minimized.

Abstract: An ALC processing unit to adjust the signal level of outputs from an adaptive equalizer to a target value is provided in a stage later than the adaptive equalizer and earlier than a frequency offset estimation/compensation unit in an optical digital coherent receiver. The ALC processing unit generates a histogram that counts the number of samples for discrete monitored values corresponding to amplitude values of outputs from the adaptive equalizer, and determines a level adjustment coefficient that is to be multiplied by an output from the adaptive equalizer so as to multiply the determined coefficient by the output from the adaptive equalizer so that the monitored value of the peak value of the histogram is the target value.

Abstract: A digital coherent receiving apparatus includes a first oscillator for outputting a local light signal of a fixed frequency, a hybrid unit mixing the local light signal with a light signal received by a receiver, a second oscillator for outputting a sampling signal of a sampling frequency, a converter for converting the mixed light signal into digital signal synchronizing with the sampling signal, a waveform adjuster for adjusting a waveform distortion of the converted digital signal, a phase adjustor for adjusting a phase of the digital signal adjusted by the waveform adjustor, a demodulator for demodulating the digital signal adjusted by the phase adjuster, and a phase detector for detecting a phase of the digital signal adjusted by the phase adjuster, and a control signal output unit for outputting a frequency control signal on the basis of the detected phase signal to the second oscillator.

Abstract: A digital signal processing apparatus includes a frame generator configured to generate a plurality of frames from a row of sample data of a time-domain, a part of each frame overlapping with adjoining frames, a Fourier transform unit configured to transform at least one of the generated frames into a frequency domain by Fourier transformation, an addition unit configured to add predetermined frequency characteristic to the transformed frame, and an inverse Fourier transform unit configured to transform the added frame into the time-domain by inverse Fourier transformation and to delete the overlap of the frame of the time-domain transformed.

Abstract: A memory control method that carries out first-in first-out access control for a memory having a plurality of storage areas, including: selecting, as write positions, an address of a storage area in a storage block having at least one or more storage areas and an address of a storage area in any one of a plurality of redundant blocks that are made redundant with respect to the storage block and have at least one or more storage areas when the write positions are selected to write data to the memory; and selecting, as read positions, an address of a storage area of the storage block and an address selected by the selecting of the write position from among the addresses of a plurality of the redundant blocks when the read positions are selected to read data written by the writing of the data to the memory.

Abstract: A simulation method includes obtaining an execution log generated while a predetermined processing is executed by simulating a series of operations in a test model that is a modeled version of a test target device by causing a predetermined processing to be executed in the test model, extracting a processing unit log constituted by a predetermined processing unit from the execution log obtained in the obtaining, and simulating an operation in which processing corresponding to the processing unit log extracted in the extracting is executed in a test model in which a part of function of the test target device is modified, the operation being simulated on the basis of a setting condition set by a user.

Abstract: A performance evaluation simulation apparatus divides a process into basic process units based on an execution log, calculates a throughput of each basic process unit from information held in the execution log, changes an arrangement structure so that a basic process unit with the calculated throughput exceeding a predetermined threshold is disposed in a hardware model, and performs a performance evaluation simulation on the hardware model and a software model to generate statistical information on which performance evaluation is based.

Abstract: A digital subscriber line communicating system having a central office and a remote terminal connected through a telephone line, the transmitting side comprising a sliding window transmitting unit for transmitting DMT symbols according to the sliding window through the telephone line to the receiving side, and the receiving side comprising a sliding window receiving unit for receiving DMT symbols according to the sliding window from the transmitting side, the sliding window indicating the phase of cross-talk condition due to a TCM-ISDN transmission at the receiving side, whereby TCM cross-talk can be reduced without largely departing from the standard system.

Abstract: This printed wiring board manufacturing method comprises the steps of providing a large number of through holes (for a through-hole) in a substrate made of an insulating material of which both sides are coated with a copper foil; making the inside of the through holes electrically conductive, coating the substrate with a photosensitive dry film, and developing and hardening the photosensitive dry film as a plating resist; and copper-plating the inside of the through holes and the opening periphery thereof. The manufacturing method further comprises the steps of coating the copper-plated area with a metal protective film, eliminating the photosensitive dry film; forming a circuit pattern; and conducting an overlaying treatment as a post-processing step.