Stepped impedance hairpin resonators (SIHRs) with harmonic suppression and capability of frequency tuning are incorporated into a bandpass filter design. A tapped-in U-shaped feed structure is introduced to suppress harmonics and to reduce the passband insertion losses. The passband flexibility is accomplished by using a pair of tuning varactors. A simple method to implant a zero in the frequency response is also studied herein to further deepen the passband skirt. A 176% (4.32 GHz) stopband bandwidth is observed under more than 20-dB band rejection. A measured minimum insertion loss of 1.19 dB is observed for the circuit with absence of the tuning varactors. Using the varactors, this filter has achieved a 22% frequency tuning range with all the insertion losses less than 5 dB.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics
- Electrical and Electronic Engineering