Compact semi-lumped two-pole DBR filter with spurious suppression

A compact second order DBR passband filter having a center frequency 1 GHz is designed, fabricated and measured. The miniaturization is achieved by capacitive loading of high impedance transmission lines. The obtained surface miniaturization percentage of the miniature filter with respect to a reference conventional one is of 95% (25 × 25 mm2). Measurement results show that by integrating miniature low-pass structures (for which the cutoff frequency is derived), the broadband response is spurious free until about eight times the center frequency.