In this letter, an ultrawideband (UWB) antipodal tapered slot antenna with reflectionless notched band is proposed and investigated. The proposed antenna uses an integrated absorptive bandstop filter, consisting of two quarter-wavelength open-circuit stubs and a 50 Ω resistor, to form a reflectionless notched band. Consequently, the input energy at the notched frequency is absorbed by the resistor rather than reflected. An antenna prototype is designed and fabricated to validate the design. Both simulated and measured results present that the realized gain drops over 40 dB at 5.5 GHz, and the reflection coefficient is below –10 dB from 3.1 to 10.6 GHz. Besides, a low ringing level of –23.4 dB of the measured reception pulse shows a good time-domain performance. Therefore, the proposed antenna could be applied in UWB short-pulse system to inhibit the 5 GHz WLAN interference.

A time-domain design method for networks with an arbitrary time-domain response is proposed and applied to design a short-pulse differentiator. The proposed method is termed as WAM because it is actually a waveform approach method (WAM) based on the normalized Euclid distance (NED). The NED could naturally characterize the difference between the desired and actual time-domain signals, including their waveforms and amplitudes. The WAM enables the NED to approach zero by tuning the network parameter for the given network topology and thus the actual time-domain response approaches the desired time-domain response. Also, the WAM is utilized to design a short-pulse differentiator with both magnitude and phase responses. Both the theoretical and experimental results verify the feasibility and validity of the WAM.

In this letter, a postwall-slotline stepped impedance resonator (PWS-SIR) is proposed and applied to a bandpass filter (BPF) with a wide stopband. The proposed PWS-SIR-BPF comprises three U-shaped PWS-SIRs and two microstrip-slot feeding transitions. A PWS has a much lower impendence which a conventional slotline (CSL) cannot reach, so a much smaller impendence ratio of the PWS-SIR can be achieved. Consequently, a wider stopband simultaneously can be realized for the proposed filter. The designed PWS-SIR-BPF, as well as a CSL-BPF, have been fabricated, measured, and compared to verify the features of the PWS-SIR. The measured results are consistent with the simulation ones. The PWS-SIR is 7.3 mm (0.22λ₀) long, 67% of 11.1 mm (0.34λ₀) of the CSL resonator. The first spurious resonance frequency of the PWS-SIR-BPF is extended from 9.8 GHz (2f₀) to 23 GHz (4.7f₀).