AN NIC-BASED NEGATIVE CAPACITANCE CIRCUIT FOR MICROWAVE ACTIVE-FILTERS

This article presents a method for synthesizing a negative capacitance in MMIC technology, and extends our earlier work (S. E. Sussman-Fort, Int. J. MIMICAE, Vol. 4, No. 2, April 1994, pp. 130-139) involving the realization of MMIC negative resistance. As before, we employ a classical negative impedance converter (NIC) that has been terminated in an RLC one port specially designed to compensate for the parasitics of the active and passive elements. We argue that, in most cases, this one port will be physically realizable, and we provide numerical results for the synthesis which supports this idea. The procedure is demonstrated in computer simulation for a four-transistor MMIC network which achieves a virtually pure capacitance of -5 pF over 1.5-2.5 GHz. Such NIC-based negative capacitance (and resistance) has potential application in the design of microwave gyrators and active filters. (C) 1995 John Wiley and Sons, Inc.