Takahide Matsuo

A ZCZ-CDMA system with high tolerance to frequency selective fading

A Quasi-synchronous CDMA system using a ZCZ code called a ZCZ-CDMA system can remove co-channel interferences, simplify hardware design, and achieve fast (less latency) transmission, due to enhancement in Frame synchronization techniques. Inter-symbol interference and co-channel interference appearing in frequency-selective Rayleigh fading channels influence the bit error rate performance. This paper proposes a ZCZ-CDMA system with block coding and channel estimation techniques to improve the performance.

Voltage distribution in multi-cascaded transformer

The voltage distribution for lightning surges in multicascaded transformers that will be used for converter transformers in self-excited dc transmission was studied using model transformers. There was good agreement between measured data and calculated results. It was shown that our calculation program has sufficient accuracy for estimating voltage distribution. Maximum voltages in high-voltage windings for lightning surges were below 120% and transfer voltages to the converting circuit were below about 5%. Therefore, there were no serious problems in cascaded transformers for lightning surges. However, their voltage distribution was not satisfactory when the same transformers were connected in cascade. We determined by a simulation that the distribution could be improved by modifying transformer structures according to their position in the cascade connection.