Miniature Microstrip Bandpass Filter Using Resonator-Embedded Dual-Mode Resonator Based on Source-Load Coupling

A novel miniature microstrip bandpass filter (BPF) using resonator-embedded dual-mode resonator is proposed. Two transmission zeros are created to improve the selectivity of the filter. Furthermore, source-load capacitive coupling is introduced to create a transmission zero above the passband. A 2.28 GHz BPF with 300 MHz bandwidth is designed and measured, the measured result agrees well with the simulation. The size of the filter is less than 0.21 ¿ × 0.15 ¿, where ¿ is guided wavelength at the central frequency.