Double Planar Integrated Millimeter-Wave Filter

A double planar integrated circuit filter is introduced, which achieves significant higher stop-band attenuation against higher frequencies than the common single planar circuit, especially for designs in the near of the waveguide band end. The theory is based on field expansion into suitable eigenmodes which allows direct inclusion of both higher-order modes and finite strip thickness. Computer optimized design data for a four-resonator Ka-band metal etched double planar integrated filter prototype provide minimum passband insertion-loss of 0.43 dB (measured: 1.8 dB) at 39.04 GHz and stopband attenuations of about 53 dB (measured: 48 dB) at 40 GHz, 100 dB at 50 GHz.