Extraction of high-frequency equivalent network parameters of HBT's by low-frequency extrapolation of microwave S-parameter data

This paper reports a comprehensive low-frequency extrapolation method for the purpose of separating the intrinsic and extrinsic or parasitic equivalent network parameters of high-frequency HBT's. The method involves measurements of the device's small-signal parameters over a wide frequency range, and low-frequency extrapolation (LFE) of various transformed two-port parameters using a range of collector bias currents. For the extraction of the equivalent network parameters, the measured S-parameters are first converted into y- and h-parameters and they are used directly or in composite fashions in order to extract the parasitic series resistance elements (r/sub bb'/, and r/sub ee'/), the shunt capacitance elements (c/sub j/e, c/sub bc/ and c/sub c/), and the intrinsic emitter-to-collector transit time after allowing for the parasitic time constant effects.<>