Several methodologies for active filter design at microwaves

This article presents several directions for the development of active filter structures in both hybrid and monolithic technology. The first direction generally used consists in compensating intrinsic losses of classical passive structures due to active components. We apply this methodology to the design of a three‐pole dielectric resonator structure (DR), a dual HEM11δDR mode two‐pole filter, and a planar microstrip resonator. For all these filters, an active loop, composed of an amplifier and a phase shifter, performs the appropriate gain and phase values to tune the response and to compensate for the intrinsic losses of the different resonators. Using the same approach, a microstrip active resonator is developed with losses compensated for by the help of a negative resistance MMIC circuit. With the increasing development of MMIC technology, a second direction, which appears to be quite promising, focuses on new original structures fully integrable in MMIC technology. Following this, we present the design of recursive and transversal filters which well meet the requirements for realization as MMICs for broadband and narrowband applications. © 1997 John Wiley & Sons, Inc. Int J Microwave Millimeter‐Wave CAE 7: 250–267, 1997