Abstract: A demodulation apparatus of the present invention comprises: an A/D converter for sampling and quantizing a baseband signal; a transversal filter having time-shifted tap coefficients; a decision unit for decoding the signal which has undergone the transversal filter; and a decision point estimation unit for instructing the transversal filter to select the tap coefficient to be selected based on information from the decision unit. Thus, the demodulation apparatus can operate at the same frequency as a sampling frequency of the A/D converter and can perform decision with accuracy equivalent to an arbitrary oversampling number.

Abstract: A simplified method for frequency offset estimation in a TDMA cellular PCS environment using &pgr;/4-shifted DQPSK comprises the steps of multiplying a complex conjugate of a received complex-valued symbol and a succeeding symbol to produce a comparison vector having an angle equal to the phase angle between the received complex-valued symbol and the succeeding symbol, rotating the comparison vector so that the angle thereof is between 0° and 90°, and estimating the frequency offset by determining a constant deviation of the phase angle from an ideal phase angle value of 45° by calculating an average phase angle for a plurality of successive comparison vectors or correlating the rotated comparision vector against a bank of unit vectors to determine a maximum correlation.

Abstract: Disclosed is a 16-ary QAM (Quadrature Amplitude Modulation) demodulation apparatus for receiving an input signal Rk(Xk, Yk) comprised of a kth quadrature-phase component Yk and a kth in-phase component Xk, and generating soft values &Lgr;(sk,0), &Lgr;(sk,1), &Lgr;(sk,2) and &Lgr;(sk,3) for the input signal Rk(Xk, Yk) by a soft decision means. A first calculator decides a soft value &Lgr;(sk,2) of a third demodulated symbol among 4 demodulated symbols by subtracting a distance 2a between two demodulated symbols on the same axis of a mapping table from a level |Yk| of the quadrature-phase component Yk. A second calculator decides a soft value &Lgr;(sk,3) of a fourth demodulated symbol by calculating Yk+&agr;*Zk using a first variable a determined by the soft value of the third demodulated symbol and a sign bit of the quadrature-phase component Yk.

Abstract: A demodulator includes a pair of analog mixers for incoherently demodulating modulated orthogonal signals with orthogonal local carriers to produce a pair of analog baseband signals, there being a phase rotation in the analog orthogonal baseband signals resulting from the incoherent demodulation. The analog baseband signals are converted to first and second digital signals. One of these is scaled by a gain controlled circuitry so that a difference between the average power values of the scaled first digital signal and the second digital signal is zero. The inter-channel rotating phase contained in the outputs of the gain controlled circuitry is removed by a phase shifter.

Abstract: The invention discloses a phase detection method including a quadrant determining procedure, a first comparison procedure, a second comparison procedure, a coordinate transforming procedure, and a phase computing procedure. A first and a second phase approximate values are obtained in the quadrant determining procedure and the first comparison procedure. A third phase approximate value is obtained in the second comparison procedure and the coordinate transforming procedure. A total phase is computed in the phase computing procedure. Using this method, we does not need to consult look-up tables to determine the phase, thus saving a lot of memory space. The invention also provides a phase detection device.

Abstract: A system and method for detecting the presence of a transmitted waveform in a high noise environment. The system and method can detect and classify a modulated waveform without first demodulating the single, and can detect and classify a waveform having a frequency offset without compensating for the frequency offset.

Abstract: Precision inphase/quadrature up-down converter structures generally neither requiring trimming at the time of fabrication nor calibration during use. The converters use four mixers arranged to down convert to provide Q, I, {overscore (I)}and Q baseband signals (or up convert Q, I, {overscore (I)} and Q baseband signals), the combination of which signals has a very substantially reduced unwanted image frequency content. The use of an increased number of mixers in effect shifts the primary errors from absolute gain and phase errors, to gain and phase error mismatches between elements in replicated circuits, which mismatches can be held to a minimum in circuits replicated in a single integrated circuit.

Abstract: Angle-modulated signals are transmitted in a communications system, in which coding information has been inserted into the transmitted data at regular intervals. The coding information is phase-modulated together with the transmitted data. This coding is used for pulse shaping, so that the receiver can recover the digital transmitted data with less implementation complexity and without carrier phase control by using appropriate signal processing.

Abstract: A differential FM detection of signals uses in-phase and quadrature phase signal components of a received signal in the detection process, wherein the in-phase and quadrature phase signal components are at a low intermediate frequency (IF). The in-phase and quadrature phase signal components are each amplitude limited, sampled at a prescribed sampling rate and filtered in a prescribed manner. Delayed versions of the filtered in-phase and quadrature phase signal components are generated and, then, signal products are generated of the delayed in-phase signal component and quadrature phase signal component, and the delayed quadrature phase signal component and in-phase signal component. The algebraic difference of the generated signal products is obtained to yield the desired data signal, e.g., symbols.

Abstract: A timing recovery circuit in a QAM demodulator which uses a symbol rate continuously adaptive interpolation filter. The method of interpolation used in the present invention is defined as a function of time per interpolation interval, rather than as a function of time per sampling interval as is commonly implemented in the prior art. This allows the interpolation filtering to be totally independent of the symbol rate in terms of complexity and performance and provides a better rejection of adjacent channels, since the interpolator rejects most of the signal outside the bandwidth of the received channel.

Abstract: An efficient demodulation and low pass filter structure comprises a shift-add-negate structure that effectively multiplies each received sample by a combined demodulation and filter coefficient, and an accumulator that accumulates the products. Low pass filter coefficients are selected such that the shift-add-negate structure implements multiplications by shifts, adds, and negations. In the preferred embodiment, the demodulation and low pass filter structure outputs three complex samples per symbol.

Abstract: The present invention is a method for demodulating a PSK modulated signal wherein the PSK system incorporates a transmitter generating a PSK modulated signal and wherein the transmitter is crystal based. A crystal based receiver receives the PSK modulated signal and the delta phase between the recovered PSK signal and a receiver generated reference signal is measured; the measurement is repeated with a predetermined phase shift. Voltage values are derived representing the results of each of the measurements and are applied to an analog-to-digital converter to derive digital values representing the two phases measured, and a corresponding delta phase. The digital values are applied to a look up table to derive a phase correction for the reference signal, and several methods are described to perform various types of PSK demodulation.

Abstract: A fading rate of a mobile terminal unit is estimated by a fading rate estimation unit and an optimum step constant is decided by a step constant determiner depending on the estimated fading rate. This step constant is fed back to a feedback data calculator, so that a reception level can be converged to an ideal level even under a fading environment and the like.

Abstract: Methods and devices for demodulators for continuous phase modulation waveforms. A modulated sampled signal is received. A consecutive sequence of the modulated sampled signal is buffered. The consecutive sequence is compared with all possible valid modulated sampled signals. A bit decision representing a demodulation of the consecutive sequence of the modulated sampled signal is determined based on a closest valid modulated sampled signal located closest to the consecutive sequence of the modulated sample signal in a constellation.

Abstract: A method for estimating an interference phase shift when receiving a multicarrier signal formed of a time series of symbols modulating a plurality of carrier frequencies, at least some of the carrier frequencies of at least some of the symbols bearing reference elements, whereof the value at transmission level is known by the receiver carrying out the reception. The phase variation &dgr;n between at least two symbols bearing reference elements is estimated by analysing the reference elements. Each of the reference elements in the estimation is weighted by information representing the noise affecting the carrier frequency bearing the reference element.

Abstract: A frequency-variation type demodulator and demodulating method. A start signal is received by a control signal apparatus. After a delay time, a control signal is output. The control signal, a start frequency, a frequency variation slope and a clock are received by an in-phase and quadrature-phase function generator. A phase value is output via mathematical calculation. According to the phase value, a cosine and sine values are obtain by checking a phase look-up table in a first and a second ROM units, respectively. The cosine value is multiplied by a measured digital data in a first multiplier to obtain an in-phase demodulating signal, and the sine value is multiplied by the measured digital data to obtain a quadrature-phase demodulating signal.

Abstract: The present invention is a demodulator and a method of demodulating burst communications. A demodulator (100, 200) includes a phase angle source (18), coupled to a current received burst communication, which provides a phase angle of the current received burst communication; a comparator (20), coupled to the phase angle source and a source of an estimated phase angle, which provides an output signal representing an angular difference between a phase of the current received burst communication and the estimated phase angle; and a phase lock loop (20), coupled to the output signal, which provides the estimated phase angle. The phase lock loop includes a Doppler accumulator (102) which provides a Doppler output which provides compensation in the estimated phase angle for the Doppler effect produced by relative motion between the demodulator and a source of the burst communications.

Abstract: An angular difference detector detects an angular variation according to respective signs of current xy coordinate values supplied from an FFT calculation unit and respective signs of preceding xy coordinate values. An angle calculation unit calculates an angle value of a frequency component according to respective absolute values of xy coordinate values supplied from the FFT calculation unit. Another angular difference detector classifies a difference between a current angle value and a preceding angle value supplied from a subtractor as one of a plurality of angle regions to detect an angular difference. A demapper performs demapping according to a sum of the angular variation supplied from the angular difference detector and the angular difference supplied from that another angular difference detector.

Abstract: Disclosed is a digital communication system for mobile communication, which has: a transmitter for mixing and outputting outputs from two independent and equivalently synchronized transmitting circuits in a &pgr;/4 shift QPSK modulation system; and a receiver for receiving a mixed wave transmitted from the transmitting circuits and demodulating the received signal by using information as to its phase and amplitude.

Abstract: A sequence of Quadrature Amplitude Modulated (“QAM”) data symbols is received and its' fading process estimated. The estimated fading process is then used to generate estimates of the identity of the symbols themselves. Instead of using the single, received sequence to complete the fading process estimates, multiple offset sequences are used. For a given signal-to-noise ratio, the resulting fading process estimates and data symbol estimates provide for reduced bit error rates.

Abstract: To keep the power consumption in the modulator-demodulator of a mobile radio as low as possible, the modulator-demodulator has a voltage-controlled oscillator. Downstream of which a divider chain having a plurality of series-connected dividers each with an even-numbered division factor is connected. Each of the dividers produces a carrier signal and a carrier signal that is orthogonal with respect thereto. A quadrature modulator for the received signal is connected to a divider of the divider chain that produces the carrier signal at the required carrier frequency. In addition, a first vector modulator is provided whose mixers are connected to the dividers of the divider chain that produce the carrier signals at the required carrier frequencies. Connected downstream of the first vector modulator is a further divider with an even-numbered division factor, and connected downstream of this is a second vector modulator for producing a transmitted signal.

Abstract: A method and apparatus to efficiently calculate log-likelihood ratios for each bit within M-ary QAM modulated symbols transmitted in a communication system. The method and apparatus utilize characteristics of square Karnaugh mapping of the QAM symbol constellation in order to reduce the number of distance calculations needed to determine the log-likelihood ratios for each of the bits within a demodulated symbol. The reduction in the number of calculations affords significant reduction in the time needed to determine log-likelihood ratios, especially for higher order M-ary QAM systems.

Abstract: A wireless transceiver includes a Radio Frequency (RF) transceiver, a baseband transmitter section, and a baseband receiver section. The baseband receiver section receives a baseband signal from the RF transceiver, extracts data therefrom, and provides the data to a host system. The baseband receiver section includes a programmable gain amplifier, an Analog-to-Digital Converter (ADC), a symbol timing compensation section, an RF carrier compensation section, a decision feedback equalizer section, and a preamble processor. The symbol timing compensation section modifies the samples of the baseband signal to compensate for symbol timing variations between a symbol clock of the wireless device and a symbol clock of a transmitting wireless device. The RF carrier compensation section modifies the samples of the baseband signal to compensate for RF carrier variations between an RF carrier of the wireless device and an RF carrier of the transmitting wireless device.

Abstract: The invention discloses a phase detection method including a quadrant determining procedure, a first comparison procedure, a second comparison procedure, a coordinate transforming procedure, and a phase computing procedure. A first and a second phase approximate values are obtained in the quadrant determining procedure and the first comparison procedure. A third phase approximate value is obtained in the second comparison procedure and the coordinate transforming procedure. A total phase is computed in the phase computing procedure. Using this method, we does not need to consult look-up tables to determine the phase, thus saving a lot of memory space. The invention also provides a phase detection device.

Abstract: A quadrature demodulator applicable to digital communication and digital broadcast is provided, which simplifies the circuit configuration of a quadrature demodulator section and which reduces the labor or man-hours and the time required for adjusting the demodulation characteristic.

Abstract: A quadrature output oscillator device (22) includes a first voltage controlled oscillator (40) and a second voltage controlled oscillator (44). The second voltage controlled oscillator (44) generates a first output (C) and a second output (D) to drive a first amplifier (42). The second output (D) of the second voltage controlled oscillator (44) is a quadrature-phase signal component output (Q) of the quadrature output oscillator device (22). The first voltage controlled oscillator (40) generates a first output (A) and a second output (B) to drive a second amplifier (46). The second output (B) of the first voltage controlled oscillator (40) is an in-phase signal component output (I) of the quadrature output oscillator device (22). The first amplifier (42) generates feedback signals for the first output (A) and the second output (B) of the first voltage controlled oscillator (40).

Abstract: To keep the power consumption in the modulator-demodulator of a mobile radio as low as possible, the modulator-demodulator has a voltage-controlled oscillator. Downstream of which a divider chain having a plurality of series-connected dividers each with an even-numbered division factor is connected. Each of the dividers produces a carrier signal and a carrier signal that is orthogonal with respect thereto. A quadrature modulator for the received signal is connected to a divider of the divider chain that produces the carrier signal at the required carrier frequency. In addition, a first vector modulator is provided whose mixers are connected to the dividers of the divider chain that produce the carrier signals at the required carrier frequencies. Connected downstream of the first vector modulator is a further divider with an even-numbered division factor, and connected downstream of this is a second vector modulator for producing a transmitted signal.

Abstract: Left and right stereo audio information is reproduced from a compatible quadrature amplitude modulation (C-QUAM) broadcast using two separate modes of detection. In the first mode, a true C-QUAM detection is performed when the signal being received has a high level of stereo difference information. In the second mode, a synchronous detection approximation is used which avoids generating an envelope signal or calculating a cosine correction factor as in true C-QUAM decoding. The second mode is used when over-modulation is present in the received signal.

Abstract: A system for demodulating narrowband signals from a received signal is disclosed. The system includes a downconverter that is operative to downconvert the received signal. Furthermore, the system includes a baseband processor that is configured to decode the narrowband signal from the received signal, as well as decode wideband signals. In this respect, the system is operative to demodulate both narrowband and wideband signals without the use of separate demodulation paths.

Abstract: In a cellular telephone having a receiving circuit of a direct conversion type using an even harmonic orthogonal mixer, high-pass filters for removing a DC offset component are arranged before and after a variable gain amplifier in a base band circuit. The DC offset component occurred in the even harmonic orthogonal mixer is always constant, and the DC offset component occurred in the variable gain amplifier frequently varies so that a cutoff frequency of the front high-pass filter is set to be lower than a cutoff frequency of the rear high-pass filter, and the frequencies are set to achieve a fast transition response.

Abstract: A fast algorithm for performing maximum likelihood detection of data symbols transmitted as phases of a carrier signal.

Abstract: A system and method for demodulating slots having a mixed slot formation including differential and coherently encoded slots is disclosed. The method includes pre-phase encoding data and a predetermined sequence in a slot at a transmitter such that the encoded data and the predetermined sequence have equal reference phases from a reference symbol of a previous slot having a reference phase. Another method includes pre-phase encoding the predetermined sequence with a phase determined from a reference symbol from the previous slot at the transmitter. Yet another method includes differentially phase encoding the predetermined sequence according to IS-136A standards using a reference phase of π 4 . In another method pre-phase encoding data includes phase shifting data using one of a group of different phase angles, each of the different phase angles an integer multiple of π 2 .

Abstract: A system is provided which facilitates a single-channel signal processing system. The system includes a single mixing stage, wherein an RF input signal is mixed with an In-Phase and a Quadrature-Phase signal. The mixing stage generates a multiplexed output signal for subsequent signal processing.

Abstract: A digital demodulator (100) includes a differentiate and cross multiply stage (102) and a plurality of filter/decimator stages (106, 112, 118 and 108, 114, 120 and 110, 116, 122) that accept both multiple baud rates and multiple modulation deviation frequencies, and that provide a common frequency data stream at their respective outputs. One of said filter/decimator stages is coupled to a primary filter (124) which is followed by a box filter (134). The box filter (134) improves the overall filter response and provides notches at a specified frequency (e.g., 4800 Hz) and its harmonics. Demodulator (100) provides improved sensitivity without the need for any circuit trimming. The filter stages (e.g., 106, 112, 118; 108, 114, 120; and 110, 116, 122) used in demodulator (100) have been optimized to eliminate the need for costly multipliers.

Abstract: A communication system (10) includes a transmitter (12) which induces in a communication signal (16), a first component of in-phase to quadrature phase (I-Q) imbalance and a receiver (14) which adds a second component of I-Q imbalance. A digital, intermediate frequency (IF) I-Q balancer (38) compensates for the receiver-induced I-Q imbalance so that total distortion is sufficiently diminished and a data directed carrier tracking loop (60) may then perform carrier synchronization to generate a baseband signal (70). An adaptive equalizer (64) within the carrier tracking loop (60) may then effectively operate to compensate for additional distortions, such as the transmitter-induced I-Q imbalance.

Abstract: A demodulation circuit for recovering frequency redundant quadrature amplitude modulated data comprises an A/D converter generating digitized carrier signal. A mixer receives the digitized carrier and generates a frequency shifted I-signal and a frequency shifted Q-signal. A bank of filters includes a narrow band filter centered at each one of a plurality frequency shifted sub-spectra to generate a digital data signal for each sub-spectrum. A selection circuit determines which one of the sub-spectrum data signals is the strongest and a receiver circuit recovers the transmitted data in response to the strongest sub spectrum data signal.

Abstract: A compensation circuit for phase modulation systems, such as QPSK and QAM systems, which compensates for phase errors in the I and Q components of the QPSK or QAM signals to minimize carry over of such phase errors in analog up and down conversions of such signals. In particular, the invention relates to a relatively simple circuit, which compensates for channel phase errors by providing a direct correction of one of the channels based on the measured correlation between the I and Q components, which should ideally be 0. As such, cross talk between I-Q channels is minimized, which improves the signal-to-noise ratio of transmitted and received QPSK or QAM signals.

Abstract: A variable-rate QAM (Quadrature Amplitude Modulation) transceiver of the present invention facilitates data interfacing between a number of bands having different transmission rates by using a number of transmitters and receivers in downstream and upstream, respectively, to provide a symmetric service in which data transmission rate in upstream is equal to that in downstream even under environment of serious channel attenuation of a signal for high frequency. That is, the variable-rate QAM transceiver of the present invention comprises a number of transmitter blocks for providing various transmission rates to the transmitters and a number of receiver blocks for providing various transmission rates to the receivers, for properly adjusting bandwidth allocation of the passband signal bandwidth of a number of transmitters and receivers to enable high speed symmetric data transmission.

Abstract: A GMSK timing recovery loop in a receiver of a Gaussian Minimum Shift Keying (GMSK) link with a low channel Bit Signal-to-Noise Ratio (BSNR) and a small bandwidth-bit period BT product in a high bandwidth efficiency channel, includes a hard limiter for converting at baseband a GMSK demodulated received signal into a hard clocking signal clocking a conventional digital tracking transition loop generating the bit timing signal in closed loop control for stable time tracking performance for coherent demodulation of GMSK signals. The hard limiter provides the hard clocking signal at baseband having transitions at multiple bit periods adjusted by the bit timing error signal from the digital tracking transition loop for providing reduced jitter of the bit timing signal for accurate timing recovery and detection of communicated data.

Abstract: The invention relates to a multi-standard digital receiver, in a digital video transmission system.

Abstract: A distortion compensating apparatus for use in IQ modulation and demodulation techniques wherein a first distortion arrangement distorts the I-signal by adding to the I-signal a first weighted function of the I-signal and a first weighted function of the Q-signal and a second distortion arrangement distorts for Q-signal by adding to the Q-signal a second weighted function of the I-signal and a second weighted function of the Q-signal, such that the weighted functions of the I-signal are independent of the Q-signal and the weighted functions of the Q-signal are independent of the I-signal. This enable distortions to be compensated in both sidebands of the IQ modulated signal.

Abstract: In a receiver supporting multiple data rates, a sweep control range is calculated on the basis of the data rate of the carrier of the channel to be selected and sweep control is executed on the oscillated frequency by VCO 8 within the sweeping frequency range so that synchronization locking to the carrier is attained and thereby an erroneous channel selection is prevented.

Abstract: A receiver for receiving an analog signal that is digitally modulated using differential binary phase shift keying (DBPSK) and demodulated by a quadrature demodulator into two signals. The receiver converts the two signals into two digital signals using 2-bit analog-to-digital converters. Samples of these digital signals are then encoded according to a maximum likelihood criteria algorithm and decisions are made based on the signal constellation, which identifies the original data transmitted.

Abstract: The present invention relates to a method and a device for the I/Q demodulation of modulated RF signals. The I/Q demodulator (60) has a first input for the RF signal (61) to be demodulated and a second input for a RF signal (62) originating from a local oscillator (20). The demodulator (60) combines the two RF signals (61,62) to generate three output signals supplied to three power detectors. In a combination unit (70) the three power signals of the power detectors are merged in two signal branches wherein after passing an A/D converting (72) and digital processing unit (73) one signal is the I component and the other one is the Q component of the received modulated RF signal (61).

Abstract: An apparatus for receiving signals includes a low noise amplifier (LNA) configured to receive a radio frequency (RF) signal. An I/Q direct down converter is coupled to the LNA. The I/Q direct down converter is configured to split the RF signal into real and imaginary components and to down convert the real and imaginary components directly to baseband signals. A local oscillator (LO) is coupled to the I/Q direct down converter and is configured to drive the I/Q direct down converter. First and second filters are coupled to the I/Q direct down converter. The first and second filters are configured to filter the down converted real and imaginary components, respectively. First and second analog-to-digital converters (ADCs) are coupled to the first and second filters, respectively. The first and second ADCs are configured to convert the real and imaginary components into digital signals.

Abstract: In a transmission side, a k-bit parallel signal is divided into n signals, which are respectively encoded and then phase-shifted so as to causing a mutual phase difference of &pgr;/2n. Spectrum spreading is performed on the phase-shifted encoded signals which are combined together to produce a transmission digital signal. In a receiving side, reverse spreading is performed on a receiving signal to produce reverse-spread signals, which are given the phase difference to cancel the phase shift of the transmission side, and then decoded. Thus, the original k-bit parallel signal is reproduced in the receiving side.

Abstract: A demodulator circuit including: a signal generating circuit for generating a sine-wave signal and a cosine-wave signal whose frequencies are same as that of the carrier wave of a modulated signal, a multiplying circuit for multiplying the modulated signal by the sine-wave signal and the cosine-wave signal generated by the signal generating circuit, and a filtering circuit for eliminating the frequency twice as high as that of the carrier wave from each of the results of the computation conducted by the multiplying circuit. Due to this, no restriction is imposed by the frequency of the system clock signal in configuring the system as a whole.

Abstract: In a frequency adjusting circuit, an oscillator outputs cosine and sine waves. A quadrature demodulator extracts and outputs the baseband signal of an in-phase component from a carrier wave input from an antenna using the cosine wave and the baseband signal of a quadrature component from the carrier wave using the sine wave. First and second A/D converters convert the baseband signals into digital signals. First and second despreaders despread the digital signals. A frequency error detection section detects the error between the frequency of the carrier wave and the frequency of the cosine and sine waves from the values of the signals output from the despreaders. A reference oscillator outputs the value of an oscillation frequency as the frequency of the cosine and sine waves and changes the value of the oscillation frequency to cancel the detected frequency error.

Abstract: When it is detected that a carrier reproduction in a demodulator (6) loop is locked and that frame synchronization cannot be established in data from the demodulator (6), a detection signal c representing occurrence of a pseudo locked state is output. In accordance with the detection signal c, the timer (22) is activated to count up. When the timer (22) counts a predetermined value, an address counter (23) is made to count up, and correction data in accordance with an address signal is read from a correction data memory (24). The correction data is added up with channel selection data and is input to a programmable divider (15) where a local oscillation frequency is subjected to fine adjustment. The address signal remains updated until the pseudo locked state is released.

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.