Xiao-Hu Wu

Compact Differential Ultra-Wideband Bandpass Filter With Common-Mode Suppression

A compact differential ultra-wideband (UWB) bandpass filter (BPF) with planar structure is presented. The circuit of the proposed filter is analyzed, showing that the differential-mode circuit, which consists of two short-ended stubs and an open-ended parallel-coupled lines, performs as a UWB BPF. While the common-mode circuit performs as a UWB bandstop filter, and the common-mode responses are suppressed across the whole UWB differential passband. A microstrip differential UWB BPF is designed, simulated and measured. Simulated and measured results show that the proposed filter has compact size (0.35λg×0.7λg), UWB differential passband (3 dB fractional bandwidth 119%) and UWB common-mode suppression (-10 db attenuation across 2.6-12 GHz).

Quintuple-Mode UWB Bandpass Filter With Sharp Roll-Off and Super-Wide Upper Stopband

This letter presents a quintuple-mode ultra-wideband (UWB) bandpass filter (BPF), using a multiple-stub-loaded resonator, consisting of multiple loaded stubs to a uniform transmission-line resonator, i.e., two asymmetrical stepped-impedance stubs at the center and four uniform-impedance stubs at the symmetrical side locations. Six modes including two odd and four even modes are controllable, while the first five modes are allocated within the UWB band. Two transmission zeros generated by the asymmetrical stepped-impedance stub are used to improve the passband selectivity greatly. The resonant mode and transmission zero chart are given, indicating that the higher modes could be suppressed by the transmission zeros generated by the stubs and the parallel-coupled lines. A compact planar UWB BPF is simulated, fabricated and measured, and the 20 dB stopband performance is extended to 29.7 GHz.

Novel Compact Tri-Band Bandpass Filter With Controllable Bandwidths

Novel compact tri-band bandpass filter (BPF) with controllable bandwidths is presented in this letter. The tri-band performance is realized by using three sets of resonators, i.e., two sets of short-stub loaded dual-mode resonators, which are designed for the first and second passband, respectively, and half-wavelength resonators for the third passband. The three passband frequencies and bandwidths could be independently tuned and designed. The half-wavelength resonators are embedded between the two dual-mode resonators and serve as part of feed lines for the first and second passband, thus compact size is realized. The newly designed tri-band BPF is verified by circuit implementation and good agreement between the simulated and measured results can be observed.

A UWB bandpass filter with wide stopband performance using cross-shaped coupled lines

A novel coupling structure is presented for the design of an ultra-wideband (UWB) bandpass filter (BPF) with wide stopband performance. The proposed coupled structure is constructed by modifying the conventional one quarter-wavelength parallel coupled lines into cross-shaped coupled lines (CCLs), which results in size miniaturization as well as wide upper-stopband performance. The CCLs can be properly designed so that the unwanted passband is rejected and the transmission zeros can be assigned toward the harmonic resonances of the triple-mode resonator. By cooperating the proposed CCLs and the triple-mode resonator, a UWB BPF with sharp roll-off and improved out-of-band performance is then constructed. Both simulated and measured results are in good agreement to verify the predicted results.