The design and development of a microstrip-based planar ultra-wideband (UWB) bandpass filter (BPF) with single/multiple interference rejection capability is presented. The proposed BPF structure is developed based on the broadside coupled mechanism of microstrip/coplanar waveguide (CPW). The BPF has microstrips and short-circuited CPW capacitively coupled through the substrate. The basic frequency response generated from this geometry covers the necessary UWB spectrum (3.1–10.6 GHz) and possesses appreciable characteristics due to dual transmission zeros at either passband boundary. Multiple resonators are embedded in the basic BPF structure to develop passband notches to circumvent unnecessary interferences. A low-pass filter is later integrated into geometry to extend the upper stopband. The proposed structure is compact and covers an area of only 14 × 11.4 mm2.

This paper presents a notched band ultra-wideband bandpass filter using a single perturbed quint-mode half-mode substrate-integrated waveguide cavity. The cavity is perturbed by loading four stubs at two corners of the magnetic walls of the single cavity. The variable parameters of stubs are selected to move down the first five resonant modes to the predetermined passband during the design process. Meanwhile, microstrip lines with a transition structure located on two loaded stubs are employed to feed the resonator. Moreover, the filter also firstly designs a notched band by introducing a complementary split-ring resonator inside the cavity to mitigate potential interference signals at 8 GHz (satellite communication). Finally, a prototype filter was implemented and measured to verify.

With quad-band-notched characteristic, a compact ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna is introduced in the paper. The UWB–MIMO system has two similar monopole elements and occupies 30 × 45 mm2. By inserting two L-shaped slots, CSRR and C-shaped stubs, four notched bands are achieved (3.25–3.9, 5.11–5.35, 5.5–6.06, and 7.18–7.88 GHz) to filter WiMAX, lower WLAN, upper WLAN, and X-band. Meanwhile, the isolation is obviously enhanced with three metal strips on the ground plane. Results indicate that the antenna covers UWB frequency band of 3.1 – 10.6 GHz except four rejected bands, isolation of better than −18 dB, envelope correlation coefficient of <0.02, and good radiation pattern, thus making it useful for UWB systems.

A novel ultra-wideband Microstrip bandpass filter using Radial Stub Loaded Resonator (RSLR) and interdigital coupled Lines is presented in this paper. The RSLR and decagonal patch form a resonator named M to create tuneable multiple notches in the passband for the suppression of Wireless Local Area Network systems’ interference. To realize sharp roll-off, two adjustable transmission nulls are located at the lower and upper frequencies out of the passband. Even and odd-mode analysis is presented to calculate modal resonance frequencies contributing to create the ultra-wide passband. Bessel function is employed to estimate the input impedance of the radial stub which is used in formulation of even and odd mode admittances. Simulated and measured results show a passband from 3.4 to 12 GHz (135% bandwidth around 6.39 GHz) with a rejection notch at 4.99 GHz is achieved with return losses better than 14 and 12 dB in the first and second passbands, respectively. The insertion loss is lower than 0.9 dB in the 90% of passband and rejection level is greater than 19 dB from 12.25 to 17.45 GHz.