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The prototype model of the high efficiency feed-forward amplifier using RF predistortion linearizer and the modified Doherty amplifier is developed, and the performance of the developed amplifier is examined experimentally. The efficiency of 13.6% with the output power of 45W is achieved under the condition that ACLR (Adjacent Channel Leakage Power Ratio) is -55 dBc in 3 GPP test method at room temperature of +25/spl deg/C. This is the top level performance among the previously reported feed-forward amplifiers for cellular base stations. In concerning with the modified Doherty amplifier, which is the key component to enhance the efficiency of feed-forward amplifier, the design method and its performance is described in detail.

Although application number of polymer insulators increases year by year, standard test methods for polymer insulators have not been established yet and various test methods are proposed all over the world. Generally polymer insulators have superior surface hydrophobicity and they show higher contamination withstand voltages than conventional porcelain insulators. It is reported that under some rain conditions, their contamination withstand voltages were lower than those under fog conditions. Therefore, we made contamination withstand voltage tests of polymer insulators under various simulated rain conditions in order to find out the most critical wet condition for these polymer insulators.

An IR CCD image sensor with a PtSi/p-Si Schottky-barrier detector, using three-level polysilicon and 2μm design rules, will be described. The sensor operates in the 3-5μ m spectral range.