0.92 and 0.85, respectively. The transmitted pulse undergoes very minimum distortion. Hence the received signal fairly retains the input pulse shape. CONCLUSIONIn this letter, a CPW-fed compact UWB antenna with tunable band-notched characteristic using a single kg/4 stub loaded with varactor diode has been successfully studied and fabricated. The proposed antennas have excellent impedance bandwidth covering the targeted UWB band. The notched bandwidth is narrow, highly selective, and continuous tunable with applied bias voltage to the varactor diode. The measured radiation pattern of the antenna is stable and consistent with frequency with fairly omnidirectional pattern in broadside plane. The system transfer function, group delay, ringing duration, and the SFF of the bandnotched UWB antenna system in face to face as well as side by side orientations are measured and discussed. The measured values indicate that the proposed band-notched UWB antenna show minimum pulse distortion and find suitable for potential application in UWB systems.

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The aim of this work is to provide practical guidelines for the design of microwave absorbers using the theory of FSS-frequency selective surfaces. The design guidelines presented here use simplified modeling to achieve numerical dimensioning which results on the designed absorbers with performance very close to the desired attenuation and bandwidth. The method, which is valid up to the frequency where high propagating Floquet mode occurs, is based on a circuital approach and takes into account the response of the FSS elements which can be represented as either series or parallel LC circuits. To provide absorption on the desired frequency the model uses the natural resonance of the HIS-high impedance surface (occurred at the parallel connection between lossy FSS impedance and the grounded dielectric slab impedance).