This work presents an output matching network (OMN) design method combining analytical filter synthesis with numerical optimization, and realizes a two-stage 23–31 GHz power amplifier (PA) in a 0.1 μm GaN-on-Si process. A port impedance model (PIM) is established to characterize the optimal load, and the drain parasitics are absorbed into the filter synthesis to construct a low-pass OMN. Grounded series-resonant branches then replace the shunt capacitors to introduce transmission zeros, converting the OMN into an elliptic filter structure that suppresses the second harmonic while maintaining broadband matching. In the optimization stage, particle swarm optimization minimizes an error function that takes the optimal impedance domain (OID) as a hard constraint and the compromise optimal load as the approximation target. Simulations show a small-signal gain of 19.8 ± 0.6 dB and an output power above 32.6 dBm with a power-added efficiency (PAE) of 35.7–39.4%.

Cryogenic circuit simulation requires capacitance models for silicon carbide (SiC) Schottky barrier diodes below 77 K. We present a temperature-unified depletion-capacitance model from C–V measurements over 37–295 K up to 25 V at 1 kHz. The conventional power law is retained, with zero-bias capacitance constrained by a normalized C–V-derived effective-density ratio N_CV(T) obtained from Mott-Schottky slopes. The same trend parameterizes the low-temperature built-in-potential and grading-coefficient variations. With the extracted N_CV(T) values, six globally fitted parameters reproduce all data with a relative root-mean-square error of 1.5%. At 37 K, N_CV = 0.562, consistent with partial freeze-out, and a room-temperature-only fit accordingly deviates by 26%.

A novel interface circuit called Matrix Synchronized Switch Harvesting on Inductor (M-SSHI) is proposed. Multiple Piezoelectric Transducers (PZTs) and Thermoelectric Generators (TEGs) are arranged in an extensible matrix structure for energy harvesting with a single inductor. At the peak value of the PZT voltages, the synchronized switches are turned on so that the energy from the PZTs and TEGs can be extracted simultaneously. With the cooperation harvesting mechanism, the lowest thermoelectric harvesting voltage is as low as 20 mV. Furthermore, the self-powered diode-less designs improve conversion efficiency. The peak harvested power of the PZT can reach 3.7 times that of the standard energy harvesting circuit. The thermoelectric harvesting efficiency can reach 76% at V_oc=100 mV.