Circuit Design and Device Modeling
Circuits for frequencies up to X-band are realized using the FBH coplanar GaN-HEMT MMIC process. The focus is on power amplifiers (PAs), both the conventional topologies and novel circuits such as digital power switches as required for class-D and class-S architectures.
Beyond the modeling of the active device, the description of the passive elements is a key issue. Therefore, a library for coplanar elements has been developed, which covers the common discontinuities (T-junction, air bridges, ...). The models are derived by means of electromagnetic simulation and verified by measurements.
InP-DHBT MMICs for mm-wave and sub-THz frequencies
Circuits for frequencies from W-band up to 250 GHz are developed based on the InP-DHBT transferred-substrate process at FBH. Two versions of this process are available and employed for circuit realization, one on an AlN substrate, the other as an InP-on-BiCMOS variant, which offers integration of InP-HBT circuits with BiCMOS on the same chip. Activities target mainly power amplifiers, multipliers, and oscillators.
The accurate description of the active element is a prerequisite for successful circuit design. FBH research on transistor models covers all types needed for the design of integrated circuits and discretes outlined above:
- A GaN-HEMT large-signal model for MMICs up to X-band as well as for discrete power transistors in the 1…3 GHz range. The latter comprises a full electro-thermal large-signal description of a powerbar in package, as needed when analyzing multi-cell high-power transistors.
- A HBT model for the W-band InP-DHBT process. The basic formulation of this model was developed for GaAs HBTs and has been in routine use also by external partners. For details, see HBT modeling.