A 6.45 GHz active bandpass filter using HBT negative resistance elements

This paper reports on a 4th order HBT active bandpass filter based on a conservative 2-/spl mu/m GaAs HBT technology which possesses f/sub T/´s and f/sub max/´s of 24 GHz and 50 GHz, respectively. The MMIC operates at a center frequency of 6.45 GHz with a +0.25 dB insertion gain and a 1100 MHz -3 dB bandwidth. A lower-out-of-band rejection of -45 to SO dB is also obtained. The measured NF and input IP3 are 15.1 dB and -7.9 dBm, respectively. The corresponding P/sub 1db/ is -5 dBm. The compact 4th order bandpass filter MMIC is only 1.6/spl times/1.2 mm/sup 2/ and consumes 208 mW of dc power. This work represents the first fully RF (NF, IP3, P/sub 1dB/) characterized HBT MMIC active filter results so far reported. We believe that the HBT active filter MMIC design demonstrates compact size and feasible RF performance suitable for monolithically integrated DDFS, ADC anti-alias, and harmonic filter applications.