Abstract: A digital demodulator which will need no absolute phasing circuit is provided.

Abstract: After receiving a time division multiplex signal including a plurality of digital data signals transmitted in accordance with different transmission schemes, the received time division multiplex signal is demodulated by a demodulation circuit, and it is judged by a detection circuit whether each of the demodulated digital data signals is received correctly or not. When it is detected that a digital data signal transmitted by any one of the plurality of different transmission schemes is not received correctly, the relevant digital data signal is replaced by a suitable signal such as a null packet signal which does not affect a correct reception of the remaining digital data signals transmitted by the remaining transmission schemes to form a corrected time division multiplexed signal even if a digital data signal is not received correctly.

Abstract: A carrier reproduction circuit which can perform stable carrier reproduction even when reception takes place with low C/N values is provided. The reception phase of the demodulated known-pattern reception signal is detected with a frame synchronizing timing circuit (4), and based on the detected reception phase, either the phase difference table of absolute phase having one convergence point or the phase difference table of the phase rotated from the absolute phase by 180°, which are included in a carrier reproduction phase difference detecting circuit (8), is selected, and from the selected phase difference table the output based on the phase difference between the phase obtained from the signal point position of the reception signal and the phase convergence point is obtained, and thus carrier reproduction is implemented by undergoing the reproduced carrier frequency control via an AFC circuit (10) so that the phase obtained from the signal point position coincides with the phase convergence point.

Abstract: A digital demodulator that eliminates the need for an absolute phase circuit is provided. In a digital demodulator for a digital broadcasting receiver that receives digital time-division multiplexed signals of different types of modulation, the demodulated baseband signal is selectively inverted by an inverter (7) according to an inversion command signal “0” or “1” that is output from an inversion decision circuit (6) depending on a BPSK signal of a known pattern. A phase error detector (8) for carrier reproduction determines the phase error voltage based on the phase difference between the absolute phase and the phase of the signal point of the demodulated baseband signal output from the inverter (7). The phase error voltage is passed through a carrier filter (9), including a low-pass filter, to control the carrier frequency so that carrier reproduction can be carried out with the phase at the signal point being coincident with the point of phase convergence.

Abstract: Stabilized carrier recovery is achieved even at the time of a low C/N ratio by measuring the phase of a signal and controlling VCO or NCO (Numerical Controlled Oscillator) using only a period having few constellation points. At this time, false lock phenomenon is avoided as follows. That is, relatively short SYNC modulated by an already-known pattern is entered into a modulation wave, VCO or NCO oscillation frequency is swept in a wide range and sweep is stopped at a frequency in which the SYNC can be received, thereby carrying out coarse control AFC. Further, a period having long to some extent, having few constellation points is provided in the modulation wave and then, a difference between the frequency of a received modulated signal and a local oscillation signal of VCO or NCO is obtained in this period.