Coplanar MMIC active bandpass filters using negative resistance circuits

Several active bandpass filters for 1.8 and 5.5 GHz have been developed with the coplanar line technique using negative resistance circuits. For example, a first-order active bandpass filter at 5.5 GHz and two second-order bandpass filters at 1.8 GHz are presented, where one of the 1.8 GHz filters is a fixed center frequency filter and the other a tunable one. These 1.8 GHz filters have a 3 dB bandwidth of 110 MHz. The tuning range of the center frequency is 200 MHz.>