microwavecircuits

Microwave circuits are electrical circuits designed to process signals in the microwave frequency range, generally from around 1 GHz to 300 GHz. At these frequencies, wavelengths are comparable to circuit dimensions, so transmission-line theory and distributed elements dominate over lumped components. Microwave circuits commonly use structures such as microstrip, stripline, coplanar waveguides, and waveguides.

Core implementations include active devices (GaAs and InP transistors, GaN HEMTs), diodes (PIN, Schottky), and mixers, along with passive components realized as transmission-line sections, filters, couplers, phase shifters, and attenuators. Many microwave circuits are fabricated as monolithic microwave integrated circuits (MMICs) on GaAs, InP, GaN, SiGe, or silicon CMOS substrates and packaged for integration with antennas and connectors.

Design relies on high-frequency network theory and S-parameter analysis, with attention to gain, input and output matching, stability, and noise figure. Designers often use distributed elements and couplers (branchline, rat-race, Lange) and electromagnetic simulation tools. Measurements employ vector network analyzers, time-domain reflectometry, and on-wafer probing to characterize impedance, gain, and intermodulation.

Applications span radar, satellite communications, microwave backhaul, and wireless systems such as 5G millimeter-wave and WiGig. Challenges include conductor and dielectric losses, thermal management, packaging parasitics, and the need for accurate device models and robust integration with antennas and photonics for agile, high-bandwidth systems.