An adaptive array has been proposed as a canceller for both inter-symbol interference (ISI) and co-channel interference (CCI). However, it has no path-diversity gain since it selects just one signal correlated to the reference signal. In this paper, a novel interference canceller having sufficient path-diversity gain is proposed. The canceller is characterized by the combined configuration of an adaptive array and an equalizer. In the proposed system, a pre-selecting adaptive array is installed first. By employing a specific training sequence and sampling timing at the receiver during the training period, the perfect correlation between the "desired signal" and "short delayed" is achieved. Therefore, the pre-selecting adaptive array can extract the desired and ISI signals simultaneously, and the cascaded adaptive equalizer can provide the path-diversity gain without degradation by interference. The proposed system achieves a simple configuration and robustness against both ISI and CCI with a sufficient path diversity gain. In computer simulations, average BER characteristics of the proposed system were evaluated in a quasi-static Rayleigh fading channel. The simulation results showed that the system can reduce both long-delayed ISI and CCI efficiently, and that the expected path diversity gain is obtained even with strong CCI. They also showed that the degradation is not so serious when the number of antenna elements is less than that of incoming signals.

An insertion loss, branching deviation and polarization dependent loss (PDL) as to a 2 N optical splitter using silica-based planar lightwave circuits has been investigated. New key technologies such as (1) a novel wedge type Y-branch, (2) an offset waveguide at the junction between the curved input waveguide and the Y-branch, and (3) low birefringence waveguides due to the appropriate dopant concentration of a cladding, have been devised and incorporated into the splitter. As a result, 2 N optical splitters with low average insertion loss ( 13.2 dB), low branching deviation ( 0.4 dB) and low PDL ( 0.2 dB) have been successfully developed.