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Abstract-In this paper, we present a RF directional modulation technique using a switched antenna array for physical layer secure communication. The main idea is that a switching scheme of the switched antenna array is designed according to a spreading sequence for the purpose of spreading spectrum of the transmit signal. The transmit signal is associated with the spreading sequence and the direction of the desired receiver because of information data modulated both in the baseband and the antenna level. In this way, the desired receiver with a single antenna can demodulate the receive signal as traditional spread-spectrum signal, while eavesdroppers can not extract any useful information from the receive signal even if eavesdroppers know the spreading sequence of the RF directional modulation signal.Simulation results show that the proposed technique offers a more secure transmission method for wireless communication comparison with traditional spread-spectrum signal.

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This study introduces a novel method to reduce the radar cross section (RCS) of wideband antennas. A novel wideband radar absorbing material (RAM) with frequency selective surfaces (FSSs) is proposed. The wideband RAM is used as the ground plane of a Yagi-Uda and a Vivaldi antenna for in-band RCS reduction. The measurement result shows that the radiation pattern of the antennas over the whole band is preserved when wideband RAM is used. The RCS of the Yagi-Uda and Vivaldi antenna with RAM can be reduced by more than 10 dB over the operating band with this method.

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