Compact and high selectivity dual mode microstrip filter with source-loaded coupling

In this letter, a novel compact and high selectivity microstrip filter with source-loaded coupling is proposed using miniaturized dual-mode resonator. The resonator can generate one odd-mode and one even-mode in the desired band. Two resonant frequencies can be adjusted easily to satisfy the bandwidth of the BPF. A transmission zero is created near the lower cut-off frequency due to the main path signal counteraction. Two additional transmission zeros attributed to source-loaded coupling are generated near the upper cut-off frequency and in the upper-stopband. A dual-mode filter is simulated, fabricated and measured. The EM simulated and measured results are presented and excellent agreement is obtained.