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We present an artificial neural network (ANN) model that predicts high-frequency, large-signal hetero-junction bipolar transistor (HBT) performance as a function of the load reflection coefficient and input power trained on a set of load—pull (LP) data that include delivered source power, output power, power-added efficiency (PAE), gain compression, input voltage, and output current. The ANN models are trained with data measured using a novel $D$ -band vector LP test bench at 130, 135, and 140 GHz. We analyze common-base (CB) and common-emitter (CE) indium phosphide (InP) HBTs and show that the CE HBT provides the highest impedance margin that maximizes PAE across a 10% bandwidth centered at 140 GHz. We fabricate CE HBT power cells and demonstrate state-of-the-art measured performance (36.2% PAE at 135 GHz at 4-dB compressed gain and 13.6 dBm). Using the ANN model trained at 130 GHz, transfer learning is accomplished for 135 GHz, 140 GHz, and prematched device datasets. The size of the ANN training sets is varied from 25% to 1% of the data collected, showing that our models are capable of predicting performance with an average rms error below 1.5% across sets. To our knowledge, this is the first demonstration of transfer learning within ANNs for transistor nonlinear modeling.

A 1310-nm (O-band) coherent optical Link is demonstrated for short-range optical interconnects that operate to 56-GBd symbol rate (SR) (112 Gbps) with FEC-acceptable BER. The coherent optical receiver (CORX) leverages a monolithic 45-nm CMOS SOI photonic-enabled process to realize an energy-efficient quadrature phase shift keying (QPSK) demodulation. Co-design of the optical and electronic circuit elements supports high-speed operation and low-power consumption. The coherent link is demonstrated with an optical transmitter photonic IC (PIC) fabricated in silicon photonic (SiPh) process with laser diodes wirebonded to a 90-nm SiGe driver electronic RFIC. The transmitter operates at 5.9-pJ/bit energy efficiency (EE) while the receiver achieves 0.73 pJ/bit and, to our knowledge, is the best EE reported for a coherent optical receiver.

Source degeneration and neutralization techniques are investigated at millimeter-wave (mm-Wave) in gallium nitride (GaN) high-electron-mobility transistors (HEMTs). The role of thru-substrate vias for inductive source degeneration (ISD) is analyzed and modeled. A series of 40-nm GaN HEMTs with ISD are measured under small-signal, pulsed I–V and 94-GHz load pull. The ISD HEMTs demonstrate a 3-dB improvement in available gain at 83 GHz but also an unanticipated up to 75% increase in power density at 94 GHz with respect to the baseline devices. We discuss possible reasons for the performance enhancement. Device characterization to 200 GHz is presented.