Abstract: An OFDM receiver may include OFDM-signal receiving means for receiving an orthogonal frequency division multiplexing signal, channel-characteristic estimating means for estimating a channel characteristic, time-direction-channel estimating means used for the estimation of a channel characteristic, judging means for judging a result of the estimation of a time direction channel, switching control means for switching presence or absence of the estimation of a time direction channel in accordance with a result of the judgment on the result of the estimation of a time direction channel, and transmission-distortion compensating means for applying processing for compensating for transmission distortion to the OFDM frequency domain signal received by the OFDM-signal receiving means and subjected to the Fast Fourier Transform.

Abstract: A digital broadcast receiving apparatus for receiving a broadcast signal generated by combining sub signals modulated using a random sequence generated based on an initial value set in accordance with a frequency of a broadcast channel by a signal transmission control use signal and a main signal generated based on information source data and reproducing the information source data contained in the received broadcast signal.

Abstract: An orthogonal frequency division multiplexing (OFDM) demodulating apparatus includes a delay profile creating section, a Fourier converting section, a pilot signal extracting section, a transmission path characteristic estimating section, an inverse Fourier converting section, and a window control section. In this case, the window control section creates a delay profile for defining a calculation range by leaving a path which exists at a same position in both the delay profiles created by the delay profile creating section and the inverse Fourier converting section and the number of times of detection which is equal to or higher than a threshold value and defines a higher threshold value for the path at a predetermined position from the position of the main path within the delay profile created by the inverse Fourier converting section than for the paths at the other positions.

Abstract: A frequency interleaving circuit frequency-interleaves main signals generated according to sound data by parameters set according to frequencies of transmission channels. A sub-signal generating circuit generates sub-signals for transmission control including pilot signals. Mapping circuits modulate the sub-signals by using pseudo-random sequences generated based on initial values of random codes set according to frequencies of transmission channels. The frequency-interleaved main signals and the sub-signals modulated by the mapping circuits are OFDM-modulated. Then, they are converted to the frequencies of the transmission channels. An increase of a dynamic range of transmission signals can be suppressed by controlling the initial values of random codes set.

Abstract: A reception apparatus for OFDM signals having a short initial rise time since start of reception until outputting the sound and/or a picture. An OFDM reception apparatus 1 of the ISDB-T standard presets the TMCC information at the outset in a memory 19 in association with each broadcasting station. This TMCC information contains the information on the RF frequency and the guard interval length, time interleaving pattern information, the information on the carrier modulation scheme and the information on the code rate of the convolutional code. When a user selects a broadcasting station, a control circuit 18 reads out the TMCC information associated with the broadcasting station from the memory 19. The control circuit 18 affords the read-out TMCC information to each circuit to set e.g., the guard interval or the carrier modulation scheme.

Abstract: A demodulation method and apparatus applicable to e.g., digital broadcast in accordance with the orthogonal frequency division multiplexing system (OFDM), in which synchronization of carrier frequency correction control of OFDM signals can be maintained in stability. Based on the information indicating the demodulation reliability, such as the result of cumulative addition of CP values, supplied from the wide range fc error—CPE calculating circuit (10), or the transmission control signal detection information, supplied from the transmission control information demodulating communication (17), a holding circuit (14) verifies whether or not the wide range fc error—CPE calculating circuit (10) is making an erroneous detection operation. If the wide range fc error—CPE calculating circuit (10) is making an erroneous detection operation, the holding circuit (14) outputs the wide range fc error output in the previous symbol, without updating the information on the wide range fc error.

Abstract: A demodulation method and apparatus applicable to e.g., digital broadcast in accordance with the orthogonal frequency division multiplexing system (OFDM), in which synchronization of carrier frequency correction control of OFDM signals can be maintained in stability. Based on the information indicating the demodulation reliability, such as the result of cumulative addition of CP values, supplied from the wide range fc error—CPE calculating circuit (10), or the transmission control signal detection information, supplied from the transmission control information demodulating communication (17), a holding circuit (14) verifies whether or not the wide range fc error—CPE calculating circuit (10) is making an erroneous detection operation. If the wide range fc error—CPE calculating circuit (10) is making an erroneous detection operation, the holding circuit (14) outputs the wide range fc error output in the previous symbol, without updating the information on the wide range fc error.

Abstract: A reception apparatus for OFDM signals having a short initial rise time since start of reception until outputting the sound and/or a picture. An OFDM reception apparatus 1 of the ISDB-T standard presets the TMCC information at the outset in a memory 19 in association with each broadcasting station. This TMCC information contains the information on the RF frequency and the guard interval length, time interleaving pattern information, the information on the carrier modulation scheme and the information on the code rate of the convolutional code. When a user selects a broadcasting station, a control circuit 18 reads out the TMCC information associated with the broadcasting station from the memory 19. The control circuit 18 affords the read-out TMCC information to each circuit to set e.g., the guard interval or the carrier modulation scheme.

Abstract: An apparatus and method for receiving an OFDM signal arranged to accurately reproduce a clock signal. I channel data and Q channel data are differential-demodulated by a differential demodulation circuit and are supplied to a ROM. The ROM reads out an intersymbol phase change amount corresponding to the differential-demodulated data and supplies it to a gate circuit. The gate circuit extracts only a component corresponding to each of pilot signals in the input data, and supplies the extracted component to a sign inversion circuit and to a selector. The selector selects the output from the gate circuit if the pilot signal is a positive frequency value or the output from the sign inversion circuit if the pilot signal is a negative frequency value, and supplies the obtained value to a cumulative addition circuit. The cumulative addition circuit performs cumulative addition of values output from the selector over a symbol period, and outputs the addition result to an average circuit.

Abstract: An apparatus and method for receiving an OFDM signal arranged to reproduce correct carriers. I channel data and Q channel data decomposed into subcarrier components by FFT processing are differential-demodulated by a differential demodulation circuit to remove an FFT window phase error and a reproducing carrier phase error. In a differential demodulation circuit, a reproducing carrier frequency error and a phase error dependent on a reproducing clock frequency error are removed and only I-axis data is thereafter output to be stored in a RAM with respect each symbol. A pilot signal selecting data generation circuit supplies the RAM with data which is prepared by suitably shifting pilot signal selecting data used as a reference. Resulting Data read out is accumulated by cumulative addition performed by a cumulative addition circuit.

Abstract: An orthogonal frequency division multiplex (OFDM) demodulation apparatus which accurately reproduces a clock and accurately generates a time window for discrete Fourier transformation (DFT) for stable demodulation of an OFDM modulated signal, wherein a clock reproduction circuit of the OFDM demodulation apparatus includes a Costas computation circuit and processes a signal corresponding to the specific carrier wave signal of a predetermined single wave for each symbol out of the I and Q channel signals obtained by subjecting the OFDM modulated signal to DFT to generate a control voltage using the Costas computation circuit and low pass filters and operates a voltage control oscillator to reproduce a clock signal. The clock signal is divided to produce the time window signals used in the DFT circuit.