Abstract-A compact dual band-notched ultra-wideband slot antenna with sharp band-notched characteristics and controllable notched bandwidths is presented. The antenna is formed by a rectangular slot with chamfered corners on a printed circuit board ground plane, a T-shaped stub and two sets of compound bandnotched structures. The compound band-notched structures are employed to generate desired lower and upper rejected bands with satisfactory skirt characteristics and sufficient rejection bandwidths. Moreover, the bandwidth of either the lower or upper rejected band can be independently adjusted by changing the size and location of the corresponding band-notched structure. Finally, a UWB slot antenna with two rejected bands at WiMAX/WLAN frequencies is successfully simulated, designed, and measured, showing good impedance matching, stable gain and near omnidirectional radiation patterns.

Photocarrier diffusion in Si at ambient temperature in the carrier density range of 4ϫ10 17 to 4 ϫ10 19 cm Ϫ3 has been characterized by the transient grating technique. Measurements show a strong density dependence in ambipolar diffusivity with a minimum of 4.7 cm 2 s Ϫ1 , a factor of 4 lower than the intrinsic value, at 10 19 cm Ϫ3 . The decrease is a result of carrier-carrier scattering at high densities. Measurements on both a Si͑111͒ surface ͑reflection geometry͒ and a Si film ͑transmission geometry͒ indicate that there is no significant surface effect in diffusivity for carriers generated near the surface.

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The design of a small printed slot antenna for ultra-wideband application is presented. The antenna is simply formed by an L-shaped slot embedded at the centre of the ground plane, a 50 Ω microstripfed line, a rectangular slit connected with the L-shaped slot and another rectangular slit at the bottom of the ground plane. The antenna has small dimensions of 16 × 28 × 0.8 mm 3. The impedance bandwidth with 10 dB return loss of the antenna is from 3.1 to 10.6 GHz, in which there is two rejected bands which cover 3.3-3.73 and 5.15-5.9 GHz.

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