Abstract: A cross polarization interference canceler includes a digital conversion circuit for subjecting a demodulated signal of one channel to an analog-to-digital conversion out of two channels which are independently formed using carriers having the same frequency but having planes of polarization which are mutually orthogonal. An interference cancelling circuit cancels interference caused by the other channel out of the two channels, with respect to the demodulated signal which is digitally converted by the digital conversion circuit. An integrator circuit performs an integration process with respect to the demodulated signal which is digitally converted by the digital conversion circuit so as to provide negative feedback to the digital conversion circuit.

Abstract: A fractionally spaced cross-polarization interference canceller, wherein a compensation signal is generated through an adaptive filter operating in a frequency that is an integer multiple of a transmission data frequency. The cross-polarization interference canceller includes a mechanism for generating an error signal used to control coefficients of the adaptive filter in the integer multiple frequency. The mechanism is realized, for example, by using a waveform generator generating an estimate of a baseband signal in the integer multiple frequency using a plurality of estimates of transmission data and coefficients determined by an impulse response of a transmission path.

Abstract: A digital demodulation apparatus which has a detector (11) for receiving transmission signals (S.sub.in) modulated under a multivalue quadrature amplitude modulation method in accordance with a honeycomb signal structure point arrangement. The detector produces I channel and Q channel demodulation signals. The apparatus also includes a discriminator (13) which converts the analog demodulation signals (Sa) to digital demodulation signals (Sd), a memory (21) which successively receives said digital demodulation signals (Sd) and reproduces corresponding original data. The read only memory (21) stores data representatives of the honeycomb signal structure point arrangement, and stores polarity bits (P) and error bits (.epsilon.) of the signal points.

Abstract: The present invention relates to a circuit which controls the decision timing for deciding multi-level signal to the optimum decision timing. The control is carried out in such a manner as reducing deviation of phase of decision clock by deciding slope of multi-level signal at the center decision timing from the decision data at least continuous three decision timings and deciding deviation of decision timing from the slope and error signal at the center decision timing. Moreover, two kinds of slope decision are realized and the desired slope decision can be selected in accordance with the line condition.

Abstract: A digital communication system using a QAM signal and a honeycomb constellation multilevel signal. The digital communication system includes a modulator having a unit for transforming in-phase and quadrature-phase data arranged in a quadrature lattice constellation into two data arranged in a honeycomb constellation, and a unit for amplitude-modulating the transformed data. A demodulator demodulates a transmitted signal output from the modulator.

Abstract: The present invention relates to a radio transmission system. The system includes a transversal type automatic equalizer which controls tap weight based on bit error rate (BER) from a pseudo error pulse. In the equalizer, the threshold value (BER1) which defines the mode change for tap weighting control from normal to reset is different from the threshold value (BER2) from reset to normal. Therefore, the mode change is carried out by a simple circuit properly and stably.

Abstract: A coordinate reading apparatus for reading positions on a tablet, having magnetic-field generating coils, with a magnetic-field detector. The magnetic-field detector produces an analog electric signal corresponding to a desired position to be read on the tablet in response to the magnetic fields induced by the magnetic-field generating coils. The analog electric signal generated by the detector is composed of both a fundamental wave component signal and an n-th order harmonic wave component signal (n being an integer equal to or larger than 2). A processing unit for receiving the analog electric signal from the magnetic-field detector and produces coordinate data corresponding to the desired position to beread on the tablet by analyzing a first rotating magnetic-field vector induced by the fundamental wave component signal and a second rotating magnetic-field vector induced by the n-th order harmonic wave component signal.