A reconfigurable bandwidth antenna for an impulse radio-UWB (IR/UWB) system design is illustrated in this paper. By adopting a continuously tunable low-pass filter by varactor at the feed of the antenna, the proposed antenna obtains a continuous tunable bandwidth from 1.02 GHz to 2.42 GHz. To ensure the identifiability of transmitted pulses in (IR-UWB) system, the antenna is analyzed in both frequency domain and time domain. The proposed antenna is valid with a system fidelity factor (SFF) above 0.8 while the bandwidth is tuning. The compact size, low cost, and tunable bandwidth with the identifiability of the transmitted pulse makes it suitable for UWB impulse radars to improve the utility ratio of frequency, and dynamic adjustment avoids interference of the IR-UWB in other communication frequency bands.

A novel reconfigurable filter antenna with three ports for three dependent switchable states for impulse radio-ultrawideband (IR-UWB)/wireless local area network (WLAN)/worldwide interoperability for microwave access (WiMAX) applications is presented in this paper. Three positive-intrinsic-negative diodes, controlled by direct current, are employed to realize frequency reconfiguration of one ultra-wideband state and two narrowband states (2.4 GHz and 3.5 GHz). The time domain characteristic of the proposed antenna in the ultra-wideband state is studied, because of the features of the IR-UWB system. The time domain analysis shows that the reconfigurable filtering antenna in the wideband state performs similarly to the original UWB antenna. The compact size, low cost, and expanded reconfigurable filtering features make it suitable for IR-UWB systems that are integrated with WLAN/WiMAX communications.

A high-performance ultra-wideband (UWB) monocycle pulse generator is described in this paper. The pulse generator circuit is mainly composed of avalanche transistor, step recovery diode (SRD), Schottky diode (SD) and microstrip lines. The proposed circuit solution utilizes the avalanche effect of avalanche transistor to produce driver pulses with high amplitude and sharp edges, which can drive the SRD included in a universal microstrip pulse forming circuit effectively to produce high-amplitude Gaussian pulses. Monocycle pulses are then generated by an additional pulse forming network. The circuit, simulated in the radiofrequency software ADS, can generate monocycle pulse whose pulse full width is 600ps, pulse amplitude is 6.3V peak-to-peak and pulse repetition rate is 10MHz with a ringing level of -24dB and good symmetry. With the features such as high pulse amplitude and stable performance this pulse generator is applicable to UWB system.

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