A HEMT large‐signal model for use in the design of microwave switching circuits

Abstract

The nonlinear sources of switch-HEMTs have been well analyzed by using the measured data. The small signal intrinsic capacitances (under both positive and negative V ds operation) have been extracted by an extended small signal model. one-dimension capacitance model has been effectively applied to model the small signal incremental capacitances directly extracted from the key operation region, which has also automatically taken into account the surface trapping effects. A new capacitance model has been effectively proposed to well fit the key nonlinear source (the deep subthreshold capacitance) of switch-HEMTs. Simple switching function and additional voltage dependence have been applied to model the wide linear-region (from high-V gs region to deep subthreshold region) of channel current. On/off state small signal insertion loss, small signal isolation, weak harmonics, and power carrying capabilities are accurately predicted by the large signal model. The model shows very good convergence of circuit simulation. Meanwhile, the simple equations and distinguishing among the capacitances accurately make the scaling rules simple and accurate. K E Y W O R D Sharmonic, high electron-mobility transistor (HEMT) switch, large signal model, microwave switch, monolithic microwave integrated circuit (MMIC), small signal model

A new extraction flow of the s mall‐signal s witch‐HEMT model based on the parasitic resistance scanning algorithm

“…[15][16][17][18] However, switch-HEMT modeling remains challenging as only a few works studied its pitfalls. [19][20][21][22][23][24][25][26] In practice, switch-HEMTs usually operate in the common-gate (CG) configuration. A large-valued resistor is connected to the gate of the switch-HEMT to prevent RF leakage to the bias circuitry.…”

“…Later the same research group developed a largesignal model for microwave switching circuit design relying on the proposed small-signal modeling techniques. 25,26 As will be considered further, despite the robust determination of the parasitic capacitance shell, suggested by Tao et al, 24 the mainstream extraction techniques tend to overestimate parasitic resistances, which result in negative intrinsic resistance (conductance) of the common-gate switch-HEMT equivalent circuit (EC). In addition, practical implementation of the commongate switch-HEMT structures may include a complex gate network with microstrip lines and via-holes that should be properly de-embedded before extracting the model parameters.…”

“…Lots of models were proposed for common‐source devices manufactured by various process technologies 15–18 . However, switch‐HEMT modeling remains challenging as only a few works studied its pitfalls 19–26 …”

“…As opposed to previous papers, they suggest using a new test structure (a CG switch‐HEMT with the gate directly grounded) to extract parasitic resistance, inductance, and intrinsic parameters. Later the same research group developed a large‐signal model for microwave switching circuit design relying on the proposed small‐signal modeling techniques 25,26 …”

Experimental insight into the temperature effects on DC and microwave characteristics for a GaAs pHEMT in multilayer 3‐D MMIC technology

“…It is worth underlying that the small-signal equivalent circuit can be used as cornerstone for building both large-signal and noise microwave models. [34][35][36][37][38][39][40][41][42] RFIC circuit designers use complicated large-signal models for designing RF circuits however, in cases when this is not available or when straightforward hand calculations are required, it is helpful to utilize a devoted small-signal model based on linear network. As will be shown, the S-parameter measurements are accurately reproduced by the extracted equivalent circuit, whose elements are analyzed vs temperature to understand the impact of the thermal effects on device microwave performance.…”