Compact Wideband Differential Bandpass Filters Using Half-Wavelength Ring Resonator

A new compact wideband differential bandpass filters with wideband common mode suppression using half-wavelength ring resonator is presented in this letter. Five-order passband for the wideband differential mode with two transmission zeros close to the passband is realized with four open stubs. A planar wideband differential filter (3 dB fractional bandwidth 79%) with wideband common mode suppression is designed and fabricated. The theoretical and measured results agree well and show good in-band filtering performances and high selectivity.