We propose a selective detection scheme based on pulse repetition for coherent IR-UWB (Impulse Radio-Ultra Wide Band) systems. For signal modulation and demodulation, we consider bi-phase modulation and on-off keying that are widely used in the coherent IR-UWB systems. The proposed selective detection scheme transmits the UWB signals by pulse repetition at the UWB transmitter to take system complexity into account, like conventional PRC (Pulse Repetition Coding). However, the proposed scheme performs selective detection by estimating the SNR (Signal-to-Noise Ratio) of the received pulserepeated signal to effectively improve BER (Bit Error Rate) performance at the UWB receiver, unlike the conventional PRC. Simulation results in the IEEE 802.15.4a channel models reveals that the proposed scheme effectively improves BER performance of the coherent IR-UWB systems without much increment of system complexity, as compared to the conventional PRC.
In this paper, we show the design of a rotary joint transition for the X-band channel in a rotatable microwave communication system. The transition seems complicated to make a channel between two coaxial cables through a cylindrical waveguide. To make a broad-band performance in the X-band with low insertion loss and return loss given the constraint on the length and radius of this complicated-looking cylindrical structure, Genetic Algorithm optimization is adopted to check the validity of an intensive parametric study in the design. The structure is fabricated and tested to show how valid the design method is as well as good frequency responses.
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