A high-Q broad-band active inductor and its application to a low-loss analog phase shifter

This paper demonstrates a high-Q broad-band active inductor and its application to a low-loss analog phase shifter, The proposed high-Q broad-band active inductor utilizes frequency-insensitive negative resistance to compensate constant internal losses caused by the drain-to-source conductance of the field-effect transistors (FET's), the de bias circuit, 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 1000, 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 resistance, 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 degrees within 1.3 dB insertion loss from 3.7 to 8.5 GHz, and one more of more than 90 degrees within 1.4 dB insertion loss from 3.5 to 10.6 GHz were obtained.