A HIGH-Q BROAD-BAND ACTIVE INDUCTOR AND ITS APPLICATION TO A LOW-LOSSANALOG PHASE-SHIFTER

This paper demonstrates a high-Q broad-band active inductor and its ap plication to a low-loss analog phase shifter, The proposed high-Q broa d-band active inductor utilizes frequency-insensitive negative resista nce to compensate constant internal losses caused by the drain-to-sour ce conductance of the field-effect transistors (FET's), the de bias ci rcuit, and several other factors. The measured frequency range of the fabricated InAlAs/InGaAs/InP HEMT active inductor is 6 to 20 GHz for Q values greater than 100, and 7 to 15 GHz for Q values greater than 10 00, A low-loss analog phase shifter is also fabricated at C-band, This is constructed with the active inductors, the varactor diodes and the low-loss multilayer broad-side coupler in a MIC structure, Since the constant negative resistance of the active inductors also compensates the line loss of the coupler and the varactor diodes' series resistanc e, the measured results show a good insertion loss performance with a large phase shift, A phase shift of more than 225 degrees within a 0.8 dB insertion loss from 4.7 to 6.7 GHz, another of more than 180 degre es within 1.3 dB insertion loss from 3.7 to 8.5 GHz, and one more of m ore than 90 degrees within 1.4 dB insertion loss from 3.5 to 10.6 GHz were obtained.