Electronically Switchable Dual-Band Microstrip Interdigital Bandpass Filter For Multistandard Communication Applications

This paper focuses on the design of electronically switchable microstrip interdigital filters for multistandard communication applications. The structures use PIN diodes as switching elements to operate at two different frequency bands. Two second-order bandpass filters are presented, one for which the switching achieves a "near frequency" shift, and the other one for wider switching operations. The insertion losses in the wide switching case are compensated by a MMIC negative resistance. Measurements are in good agreement with simulations.