Abstract: A transmission device outputs a modulated signal based on amplitude information and phase information respectively indicating an amplitude and a phase of a transmission symbol. The transmission device includes: an oscillation signal generation circuit configured to generate an oscillation signal based on the phase information; a laser light source configured to be driven by the oscillation signal; a bias controller configured to control a bias current of the laser light source based on the amplitude information; a photo detector configured to convert an output light of the laser light source into an electric signal; and a bandpass filter configured to filter an output signal of the photo detector so as to output the modulated signal.

Abstract: A distortion compensating device includes: a filter that receives input of a transmitting signal including a plurality of subcarrier signals assigned to respective frequencies and that superimposes filter coefficients on the respective subcarrier signals; a first signal converting unit that converts the subcarrier signals, on which the respective filter coefficients are superimposed, from a frequency domain into a time domain to obtain an input signal; a distortion compensating unit that superimposes a distortion compensation coefficient on the input signal to obtain an output signal; a power amplifier that amplifies and outputs the output signal; and a control unit that generates the filter coefficients according to an arithmetic equation using the subcarrier signals and a feedback signal from the power amplifier, and outputs the filter coefficients to the filter.

Abstract: A transmission device outputs a modulated signal based on amplitude information and phase information respectively indicating an amplitude and a phase of a transmission symbol. The transmission device includes: an oscillation signal generation circuit configured to generate an oscillation signal based on the phase information; a laser light source configured to be driven by the oscillation signal; a bias controller configured to control a bias current of the laser light source based on the amplitude information; a photo detector configured to convert an output light of the laser light source into an electric signal; and a bandpass filter configured to filter an output signal of the photo detector so as to output the modulated signal.

Abstract: A transmission device outputs a modulated signal based on amplitude information and phase information respectively indicating an amplitude and a phase of a transmission symbol. The transmission device includes: an amplitude corrector configured to correct the amplitude information based on a specified carrier frequency; a phase corrector configured to correct the phase information based on the carrier frequency; a D/A converter configured to convert the corrected amplitude information into an analog signal so as to generate an amplitude information signal; an oscillator circuit configured to generate an oscillation signal that has a phase corresponding to the corrected phase information; a comparator configured to generate a pulse width modulated signal based on a comparison between the amplitude information signal and the oscillation signal; and a bandpass filter configured to filter the pulse width modulated signal so as to output the modulated signal.

Abstract: A communication device includes: a signal generator configured to generate a plurality of intermediate frequency signals; a combiner configured to combine the plurality of intermediate frequency signals to generate a multichannel signal; a reduction unit configured to reduce a peak-to-average power ratio of the multichannel signal; and a converter configured to convert the multichannel signal whose peak-to-average power ratio is reduced by the reduction unit into an optical signal. The reduction unit reduces a power of the multichannel signal using supplemental signals, frequencies of the supplemental signals being different from frequencies of the intermediate frequency signals, when the power of the multichannel signal is higher than a specified threshold level.

Abstract: A communication device includes: a converter circuit configured to convert an optical signal that carries an oscillator signal of a radio frequency and transmission signals generated in a signal processing device into an electric signal; an extractor configured to extract the oscillator signal from the electric signal; a recovery circuit configured to recover the transmission signals from the electric signal; a radio frequency signal generator configured to generate radio frequency signals that respectively carry the transmission signals recovered by the recovery circuit using the oscillator signal; amplifiers respectively configured to amplify the radio frequency signals; antennas respectively configured to output the amplified radio frequency signals; a feedback circuit configured to generate a feedback signal from the amplified radio frequency signals; and a transmitter configured to convert the feedback signal into an optical signal and transmit it to the signal processing device.

Abstract: An optical transmitter includes: an amplitude control circuit, an E/O (Electrical-to-Optical) circuit, a detector and an optical power control circuit. The amplitude control circuit controls an amplitude of an input electric signal to generate a constant amplitude electric signal. The E/O circuit generates a modulated optical signal from the constant amplitude electric signal by a direct modulation. The detector detects an amplitude modulation component of the input electric signal. The optical power control circuit controls a power of the modulated optical signal based on the amplitude modulation component detected by the detector.

Abstract: A wireless transmission system includes a first device and a second device that are connected by an optical transmission line. The first device includes: a generating unit that generates a transmission signal; and a first attenuation unit that attenuates the transmission signal generated by the generating unit and that inputs the transmission signal to the optical transmission line. The second device includes: a second attenuation unit that attenuates the transmission signal output from the optical transmission line; an amplifying unit that amplifies the transmission signal attenuated by the second attenuation unit; and a transmitting unit that wirelessly transmits the transmission signal amplified by the amplifying unit. The first device or the second device further includes a control unit that controls attenuation in each of the first attenuation unit and the second attenuation unit.

Abstract: A communication device includes: a signal generator configured to generate a plurality of intermediate frequency signals; a combiner configured to combine the plurality of intermediate frequency signals to generate a multichannel signal; a reduction unit configured to reduce a peak-to-average power ratio of the multichannel signal; and a converter configured to convert the multichannel signal whose peak-to-average power ratio is reduced by the reduction unit into an optical signal. The reduction unit reduces a power of the multichannel signal using supplemental signals, frequencies of the supplemental signals being different from frequencies of the intermediate frequency signals, when the power of the multichannel signal is higher than a specified threshold level.

Abstract: A communication device includes: a converter circuit configured to convert an optical signal that carries an oscillator signal of a radio frequency and transmission signals generated in a signal processing device into an electric signal; an extractor configured to extract the oscillator signal from the electric signal; a recovery circuit configured to recover the transmission signals from the electric signal; a radio frequency signal generator configured to generate radio frequency signals that respectively carry the transmission signals recovered by the recovery circuit using the oscillator signal; amplifiers respectively configured to amplify the radio frequency signals; antennas respectively configured to output the amplified radio frequency signals; a feedback circuit configured to generate a feedback signal from the amplified radio frequency signals; and a transmitter configured to convert the feedback signal into an optical signal and transmit it to the signal processing device.

Abstract: A base station device includes: a converting unit that converts a transmission signal with a multi-bit quantization bit rate to a signal with a quantization bit rate smaller than the quantization bit rate of the transmission signal; a first amplifier that amplifies the signal; an extracting unit that extracts a noise component generated in the signal due to the conversion; a second amplifier that amplifies the noise component; a combining unit that combines the signal amplified by the first amplifier with the noise component amplified by the second amplifier to remove a noise component included in the amplified signal; and an adding unit that adds, based on an error between the signal from which the noise component has been removed and the transmission signal, distortion to the signal that is input to the first amplifier or the noise component that is input to the second amplifier.

Abstract: A distortion compensation apparatus includes a calculation unit that acquires, from calculation performed by using a factor and an output signal from the amplifier, a distortion component that is associated with the distortion generated in the amplifier, and a comparing unit that compares a signal that is obtained by giving the distortion component acquired by the calculation unit to an output signal output from the amplifier, with an input signal input to the amplifier, to which a distortion component is previously given. The calculation unit adjusts, on the basis of a comparison result obtained by the comparing unit, the factor that is used for the calculation.

Abstract: A wireless transmission system includes a first device and a second device that are connected by an optical transmission line. The first device includes: a generating unit that generates a transmission signal; and a first attenuation unit that attenuates the transmission signal generated by the generating unit and that inputs the transmission signal to the optical transmission line. The second device includes: a second attenuation unit that attenuates the transmission signal output from the optical transmission line; an amplifying unit that amplifies the transmission signal attenuated by the second attenuation unit; and a transmitting unit that wirelessly transmits the transmission signal amplified by the amplifying unit. The first device or the second device further includes a control unit that controls attenuation in each of the first attenuation unit and the second attenuation unit.

Abstract: A wireless transmission system includes a base station device connected to a wireless device by an optical transmission member. The base station device includes an acquiring unit that acquires a distortion component that corresponds to a level of a transmission signal, an amplifying unit that amplifies the distortion component at a predetermined gain, and a transmitting unit that transmits the transmission signal and the amplified distortion component in a separable manner. The wireless device includes a receiving unit that receives the transmission signal and the distortion component, a filtering unit that filters the transmission signal, an attenuating unit that attenuates the distortion component at a gain inverse of the predetermined gain, a combining unit that combines the filtered transmission signal with the attenuated distortion component to obtain a combined signal, and an amplifier that amplifies the combined signal.

Abstract: A base station device includes: a converting unit that converts a transmission signal with a multi-bit quantization bit rate to a signal with a quantization bit rate smaller than the quantization bit rate of the transmission signal; a first amplifier that amplifies the signal; an extracting unit that extracts a noise component generated in the signal due to the conversion; a second amplifier that amplifies the noise component; a combining unit that combines the signal amplified by the first amplifier with the noise component amplified by the second amplifier to remove a noise component included in the amplified signal; and an adding unit that adds, based on an error between the signal from which the noise component has been removed and the transmission signal, distortion to the signal that is input to the first amplifier or the noise component that is input to the second amplifier.

Abstract: An amplification device includes at least two amplifiers. The amplification device further includes: a switching unit that switches an amplification mode to one of a first amplification mode and a second amplification mode based on power of a signal before or after amplification by the amplifiers; a separating unit that separates an input signal to two signals having a constant amplitude and different phases from each other when switched to the first amplification mode by the switching unit; a modulation unit that modulates an input signal into a signal having a constant amplitude when switched to the second amplification mode by the switching unit; an amplification unit that amplifies the two signals obtained by the separating unit or two signals obtained by the modulation unit by using the amplifiers; and a combining unit that combines the two signals amplified by the amplifiers.

Abstract: A distortion compensation apparatus includes a pre-distorter, a gain control unit, and a learning unit. The pre-distorter adds distortion according to compensation coefficients to individual input signals prior to the input signals being input to a power amplifier. The gain control unit applies gain control to individual feedback signals fed back from the power amplifier according to a maximum level of the feedback signals within a time frame. The learning unit updates the compensation coefficients used by the pre-distorter, using the feedback signals subjected to the gain control by the gain control unit.

Abstract: A predistorter gives an input signal inputted to a power amplifier distortion corresponding to a compensation coefficient. A band limiter limits components in a second frequency band other than a first frequency band of a feedback signal fed back from the power amplifier, and distorts components in the first frequency band according to the limited components in the second frequency band. A learner updates the compensation coefficient on the basis of the distorted feedback signal.

Abstract: An amplification device includes at least two amplifiers. The amplification device further includes: a switching unit that switches an amplification mode to one of a first amplification mode and a second amplification mode based on power of a signal before or after amplification by the amplifiers; a separating unit that separates an input signal to two signals having a constant amplitude and different phases from each other when switched to the first amplification mode by the switching unit; a modulation unit that modulates an input signal into a signal having a constant amplitude when switched to the second amplification mode by the switching unit; an amplification unit that amplifies the two signals obtained by the separating unit or two signals obtained by the modulation unit by using the amplifiers; and a combining unit that combines the two signals amplified by the amplifiers.

Abstract: A transmitter includes: first and second IFFT units that respectively generate first and second time domain signals from first and second modulated signals generated in first and second modulation schemes; a clipping noise signal generator that generates a clipping noise signal representing a difference between a combined signal of the first and second time domain signals and a specified threshold in a time period in which the power of the combined signal is higher than the threshold; first and second calculators that respectively subtract the clipping noise signals to which first and second coefficients are multiplied from the first and second time domain signals; first and second frequency filters that respectively filter output signals of the first and second calculators; and a combiner that generates a transmission signal including an output signal of the first frequency filter and an output signal of the second frequency filter.