This paper deals with study results on the effect of nonlinear amplification in the CDMA system using offset-QPSK signals bandlimited with a square-root cosine roll-off filter. As a result of the study, it is shown that the nonlinear amplification does not affect bit error rate performance with reasonable out-of-band emission characteristics when the roll-off factor of the transmit filter is one.

It has been reported that the efficiency of a low voltage power supply is improved by replacing diodes in an output-stage with synchronous rectifiers (SR). A SR consists of a bipolar junction transistor with a low-saturation voltage and a current transformer. Although the SR has low offset-voltage, its reverse recovery characteristic is usually poor. In this paper, an RCD circuit which improves the reverse recovery characteristic of the SR is proposed. This circuit is simple, and it is composed of a diode, a capacitor and a resistor. The analysis and the experimental results of the SR with the proposed RCD circuit are presented. The optimum design of the RCD to improve the reverse recovery characteristic of SR is discussed.

A novel coupling configuration consisting of a tapered slab waveguide with a wedge-shaped nonlinear cladding is proposed. Coupling characteristics for TE waves are analyzed by means of the beam propagation method. The proposed configuration is less sensitive to the offset between coupled waveguides than is the configuration with a homogeneous non-linear cladding.