Abstract: According to one embodiment, a signal quality monitoring apparatus includes a signal processor, a comparator and a determiner. The processor obtains output signals from a first transmitter and a second transmitter which are mutually redundant and respectively reproduce digital broadcast signals based on a common origin signal, and generates a first signal based on the output signal from the first transmitter and a second signal based on the output signal from the second transmitter. The comparator compares the first signal and the second signal. The determiner determines a quality of the digital broadcast signal based on a result of the comparison.

Abstract: According to one embodiment, a signal quality monitoring apparatus includes a signal processor, a comparator and a determiner. The processor obtains output signals from a first transmitter and a second transmitter which are mutually redundant and respectively reproduce digital broadcast signals based on a common origin signal, and generates a first signal based on the output signal from the first transmitter and a second signal based on the output signal from the second transmitter. The comparator compares the first signal and the second signal. The determiner determines a quality of the digital broadcast signal based on a result of the comparison.

Abstract: According to one embodiment, a transmission device includes an insertion unit, an allocation unit, a division unit, an IFFT unit, a phase rotation unit, and a transmission unit. The phase rotation unit performs a phase rotation to reduce a PAPR characteristic for each block on which inverse fast Fourier transform has been performed. The transmission unit combines transmission signals, on each of which a phase rotation has been performed by the phase rotation unit, and transmits the combined transmission signal to an external device. In addition, the division unit includes a predetermined band and at least one pilot symbol located outside another of end of this predetermined band on an opposite side of the one end into one block.

Abstract: In some embodiments, a wireless communication apparatus may include, but is not limited to, a pilot inserter, a segment divider, a phase rotator, and a first adder. The pilot inserter inserts first and second pilot symbols into a symbol stream. The segment divider divides into a plurality of segments a plurality of subcarriers. Each of the subcarriers is allocated with a respective one of the symbols included in the symbol stream into which the first and second pilot symbols have been inserted. The phase rotator performs, for each segment, a phase rotation to all of the symbols, except for a predetermined one of the first and second pilot symbols, included in the symbol stream. The first adder adds together signals corresponding to the subcarriers included in the plurality of segments to which the phase rotation has been performed by the phase rotator to generate a transmission signal.

Abstract: In some embodiments, a wireless communication apparatus may include, but is not limited to, a segment divider, a reference symbol inserter, a phase rotator, an adder, and a peak-to-average power ratio evaluator. The reference symbol inserter inserts at least one reference symbol having a phase into at least one of the subcarrier segments. The phase rotator performs respective phase rotations to the subcarrier segments, based at least in part on a plurality of different combination patterns, each of the different combination patterns identifying a respective phase rotation to the subcarrier segments. The peak-to-average power ratio evaluator calculates, for each of the plurality of different combination patterns, a peak-to-average power ratio of the transmission signals generated. The peak-to-average power ratio evaluator selects, from the transmission signals, a transmission signal having a smallest peak-to-average power ratio among the plurality of peak-to-average power ratios calculated.

Abstract: According to one embodiment, a transmission device includes an insertion unit, an allocation unit, a division unit, an IFFT unit, a phase rotation unit, and a transmission unit. The phase rotation unit performs a phase rotation to reduce a PAPR characteristic for each block on which inverse fast Fourier transform has been performed. The transmission unit combines transmission signals, on each of which a phase rotation has been performed by the phase rotation unit, and transmits the combined transmission signal to an external device. In addition, the division unit includes a predetermined band and at least one pilot symbol located outside another of end of this predetermined band on an opposite side of the one end into one block.

Abstract: In some embodiments, a wireless communication apparatus may include, but is not limited to, a pilot inserter, a segment divider, a phase rotator, and a first adder. The pilot inserter inserts first and second pilot symbols into a symbol stream. The segment divider divides into a plurality of segments a plurality of subcarriers. Each of the subcarriers is allocated with a respective one of the symbols included in the symbol stream into which the first and second pilot symbols have been inserted. The phase rotator performs, for each segment, a phase rotation to all of the symbols, except for a predetermined one of the first and second pilot symbols, included in the symbol stream. The first adder adds together signals corresponding to the subcarriers included in the plurality of segments to which the phase rotation has been performed by the phase rotator to generate a transmission signal.

Abstract: In some embodiments, a wireless communication apparatus may include, but is not limited to, a segment divider, a reference symbol inserter, a phase rotator, an adder, and a peak-to-average power ratio evaluator. The reference symbol inserter inserts at least one reference symbol having a phase into at least one of the subcarrier segments. The phase rotator performs respective phase rotations to the subcarrier segments, based at least in part on a plurality of different combination patterns, each of the different combination patterns identifying a respective phase rotation to the subcarrier segments. The peak-to-average power ratio evaluator calculates, for each of the plurality of different combination patterns, a peak-to-average power ratio of the transmission signals generated. The peak-to-average power ratio evaluator selects, from the transmission signals, a transmission signal having a smallest peak-to-average power ratio among the plurality of peak-to-average power ratios calculated.

Abstract: A clock frequency error detecting device includes a system storage portion which stores a synchronization system based on at least one of several types of frame synchronization signals included in a received signal in which a frame synchronization signal in each frame includes a part obtained by shifting of a frame synchronization signal of another frame by a symbol by using a predetermined rule; a pattern matching portion which performs pattern matching between the received signal and the synchronization system; a symbol counter which outputs a symbol number; a timing detection portion which detects the frame synchronization signal of each frame based on a pattern matching processing result and to output the symbol number at the detection timing; and a frequency error detection portion which detects a change of the symbol number and to detect a clock frequency error of the symbol period based on the detection.

Abstract: A clock frequency error detecting device includes a system storage portion which stores a synchronization system based on at least one of several types of frame synchronization signals included in a received signal in which a frame synchronization signal in each frame includes a part obtained by shifting of a frame synchronization signal of another frame by a symbol by using a predetermined rule; a pattern matching portion which performs pattern matching between the received signal and the synchronization system; a symbol counter which outputs a symbol number; a timing detection portion which detects the frame synchronization signal of each frame based on a pattern matching processing result and to output the symbol number at the detection timing; and a frequency error detection portion which detects a change of the symbol number and to detect a clock frequency error of the symbol period based on the detection.

Abstract: In an OFDM reception apparatus, a Fourier transform unit segments a time-domain signal in an OFDM signal in accordance with a segmenting window signal and converts the time-domain signal into a frequency-domain signal. A first signal extraction unit extracts pilot signals periodically arranged in a frequency direction and in a time direction from an output from the Fourier transform unit. A second signal extraction unit extracts differential reference signals from an output from the Fourier transform unit. A delay profile detection unit performs delay profile detection using the output from the second signal extraction unit, and performs delay profile detection on the output from the first signal extraction unit within a range limited on the basis of a result of the detection. A synchronous reproduction unit generates the segmenting window signal using an output from the delay profile detection unit.

Abstract: In an OFDM reception apparatus, a Fourier transform unit segments a time-domain signal in an OFDM signal in accordance with a segmenting window signal and converts the time-domain signal into a frequency-domain signal. A first signal extraction unit extracts pilot signals periodically arranged in a frequency direction and in a time direction from an output from the Fourier transform unit. A second signal extraction unit extracts differential reference signals from an output from the Fourier transform unit. A delay profile detection unit performs delay profile detection using the output from the second signal extraction unit, and performs delay profile detection on the output from the first signal extraction unit within a range limited on the basis of a result of the detection. A synchronous reproduction unit generates the segmenting window signal using an output from the delay profile detection unit.

Abstract: A receiver includes: first and second tuners configured to select respectively different broadcast channels; first and second AGC control circuits configured to generate first and second AGC control signals configured to respectively control gains of first and second AGC amplifiers based on output signals of the respective tuners; first and second predetermined voltage generating circuits configured to generate first and second predetermined voltages configured to respectively suppress AGC gains of the first and second AGC amplifiers; and a control section configured to control to selectively apply the first AGC control signal and the first predetermined voltage to the first AGC amplifier, and control to selectively apply the second AGC control signal and the second predetermined voltage to the second AGC amplifier.

Abstract: An apparatus for receiving an OFDM modulated signal includes: an A/D converter converting the received signal to a digital signal; a quadrature demodulator performing quadrature detection of the digital signal and converting the digital signal to a base-band signal; an FFT circuit transforming the base-band signal to a signal of a frequency domain by performing a fast Fourier transformation; an equalizer equalizing the signal of the frequency domain and obtaining demodulated data; an error correcting circuit performing error correction and decoding the demodulated data obtained by the equalizer; an interference detector detecting a receiving quality for each predetermined frequency band from the demodulated data; and a synchronous sequencer assigning weights to the base-band signal and the signal of the frequency domain based on the receiving quality data, and reproducing a timing synchronized signal and a clock pulse required for the demodulation.

Abstract: The automatic gain control method with little being influenced of the unnecessary electric wave, even if strong unnecessary electric wave is near the frequency of input signal, is offered by carrying out change of the delay point level. The automatic gain control system with a scale of few circuit, having low noise property and high adjacent disturbance oppression property, is offered. When the IF AGC signal 112 is smaller than delay point level, the output agcerr of the signal level detector 614 is provided to the 1st loop filter 105. Since the IF AGC signal 112 provided to the IF AGC amplifier 608 is value responding to signal level of IF signal, output is fed back to this amplifier, and control of IF gain is performed automatically. On the other hand, when output of the 2nd loop filter 106 is “0”, output rfzero of the 2nd comparator 108 is set to 1, and “0” is provided to the 2nd loop filter 106.

Abstract: An apparatus for receiving an OFDM modulated signal includes: an A/D converter converting the received signal to a digital signal; a quadrature demodulator performing quadrature detection of the digital signal and converting the digital signal to a base-band signal; an FFT circuit transforming the base-band signal to a signal of a frequency domain by performing a fast Fourier transformation; an equalizer equalizing the signal of the frequency domain and obtaining demodulated data; an error correcting circuit performing error correction and decoding the demodulated data obtained by the equalizer; an interference detector detecting a receiving quality for each predetermined frequency band from the demodulated data; and a synchronous sequencer assigning weights to the base-band signal and the signal of the frequency domain based on the receiving quality data, and reproducing a timing synchronized signal and a clock pulse required for the demodulation.

Abstract: A phase detection circuit detects a phase of a phase detection signal output from a complex multiplication circuit. A frequency error detection circuit detects a frequency error of a phase-detected signal, with the first frequency error detection characteristic in which a first frequency domain is defined as a detection range. An average circuit converts a signal having the detected frequency error into a signal having a second frequency error detection characteristic in which a second frequency domain other than the first frequency domain is defined as a detection range. After the average circuit calculates an average of frequency error signals for each period of time, it converts an average signal into a signal having the original first frequency error detection characteristic and outputs it to an AFC loop filter.

Abstract: A transmission system is disclosed which permits the receiving end to demodulate multi-valued modulated symbols successfully under fading conditions and reduces the amount of transmitted reference data to improve data transmission efficiency. At the transmitting end, a multiplexing section, a modulating section, and a transmitting section are provided. In transmitting an OFDM transmission frame, null symbols and reference symbols are placed in the beginning portion of the frame and QPSK symbols are placed in an information symbol data region in the frame with equal spacings in time and frequency. At the receiving end, a receiving section, a demodulation section, an equalizing section, and a demultiplexing section are provided. An error detector detects amplitude and phase errors of each carrier from the reference symbols, and a variation detector detects variations in the amplitude and phase of a received signal from the QPSK symbols.

Abstract: This invention improves the frequency acquisition range and the resistance to multipath interference. In a digital signal transmission system using OFDM, on the transmission side, some or all of a plurality of equidistant carrier positions are treated as reference carrier positions. The actual transmitted carriers are arranged in a predetermined pattern non-equidistant to the frequency carrier positions to form an OFDM symbol. This OFDM symbol is periodically transmitted as frequency reference symbols. On the reception side, the carrier arrangement pattern of the frequency reference symbols is detected, a carrier frequency offset is detected from the detected pattern offset, and the carrier frequency is compensated based on the frequency offset.

Abstract: A QPSK modulated wave is inputted to an in-phase detector and an orthogonal detector. The detected components are converted to substantially a base band, and each component is digital-converted by A/D converters. Each digital component is spectrum-shaped by digital LPFs. The outputs of digital LPFs are inputted to a complex multiplier and calculated by use of first and second reproduction carriers and expressed as first and second calculation outputs, and inputted to a phase detector. The phase detector obtains phase difference data between the phase expressed by the first and second calculation outputs and a predetermined phase and quadrant data of the phase. The phase difference data is used for a PLL. The phase difference data is is inputted to a frequency error detection circuit detecting a frequency error. The frequency error output is smoothed by a filter of an AFC loop, and used as a control signal controlling the oscillation frequency of the local oscillation unit.