The field of monolithic microwave integrated circuits (MMICs) emerged in the late 1970s and early 1980s with the development of the first GaAs MESFET and pseudomorphic high electron mobility transistor (p-HEMT) IC technologies and started to thrive in the mid-to-late 1990s once the performance of silicon transistors became adequate for radio frequency (RF) applications above 1GHz. Since then, CMOS, SiGe BiCMOS, and III-V HEMT, and heterojunction bipolar transistor (HBT) technology scaling to nanometer dimensions and THz cutoff (fT) and oscillation frequencies (fMAX) has continued unabated. Despite the increasing dominance of CMOS, each of these technologies has carved its own niche in the high-speed, RF, microwave, and mm-wave IC universe. Today’s nanoscale 3-D tri-gate MOSFET is a marvel of atomic-layer and mechanical strain engineering with more “exotic” materials, heterojunctions, and compounds than any SiGe HBT or III-V device. Indeed, InGaAs and Ge are expected to displace silicon channels in “standard” digital CMOS technology sometime in the next five to ten years. More so than in the past, it is very important that high-frequency circuit designers be familiar with all these high-frequency device technologies.

Apart from the general acceptance of CMOS as a credible RF technology, during the last decade “digital-RF” has radically changed the manner in which high-frequency (HF) circuit design is conducted. Traditional RF building blocks such as low-noise amplifiers (LNAs), voltage-controlled oscillators (VCOs), power amplifiers (PAs), phase shifters, and modulators have greatly benefited from this marriage of digital and microwave techniques and continue to play a significant role well into the upper mm-wave frequencies. New, digital-rich, radio transceiver architectures have emerged based on direct RF modulators and IQ power DACs, fully digital PLLs, and digitally calibrated phased arrays.