What Are Radiofrequency Integrated Circuits?

Radiofrequency integrated circuits (RFICs) are semiconductor devices that implement signal processing functions at radio frequencies, generally from a few hundred megahertz to several tens of gigahertz, on a single chip or small multichip module. They are the central hardware components of wireless communication systems, including cellular handsets, wireless local area network adapters, Bluetooth modules, satellite receivers, and radar front ends. An RFIC typically integrates the functions required to interface an antenna with a baseband digital processor: amplification, frequency translation (mixing), filtering, and in many designs, the phase-locked loop synthesizer that generates the carrier frequency reference.

The field of RFIC design grew rapidly from the 1990s onward as silicon-based CMOS technology scaled to feature sizes where the transistor transit frequency (fT) reached tens of gigahertz, enabling RF functions that previously required specialized compound semiconductor processes. As documented in Radio Frequency Integrated Circuit Design published through IEEE Xplore, RFIC design is multidisciplinary, requiring knowledge of communications theory, transceiver architectures, and analog and RF circuit design.

RFIC Design and Analog RF-CMOS

Analog RF-CMOS refers to the practice of implementing radiofrequency circuit functions in standard complementary metal-oxide-semiconductor (CMOS) silicon processes originally developed for digital logic. The principal challenge is that CMOS transistors exhibit higher noise, lower transconductance efficiency, and more substrate coupling than bipolar or compound semiconductor devices at the same frequency. Circuit techniques developed to overcome these limitations include inductive source degeneration for noise matching in low-noise amplifiers, LC tank voltage-controlled oscillators with switched capacitor tuning banks, and passive mixer topologies that avoid flicker noise from active devices. Silicon-germanium (SiGe) BiCMOS processes, which combine CMOS digital transistors with high-speed heterojunction bipolar transistors on the same wafer, offer a middle path between cost and RF performance. RFIC design methodology relies on scattering parameters (S-parameters) and noise figure models extracted from transistor test structures, combined with electromagnetic simulation of on-chip passives such as spiral inductors and transmission line interconnects.

Monolithic Microwave Integrated Circuits

Monolithic microwave integrated circuits (MMICs) are a class of RFICs fabricated in compound semiconductor processes, primarily gallium arsenide (GaAs) and gallium nitride (GaN), and are designed for frequencies extending from about 2 GHz into the millimeter-wave range above 30 GHz. The term "monolithic" indicates that active devices, passive components, and interconnects are all fabricated on the same semiconductor substrate, in contrast to hybrid circuits that assemble discrete components on a carrier substrate. GaAs high electron mobility transistors (HEMTs) and pseudomorphic HEMTs (pHEMTs) provide high electron mobility and low noise, making them the preferred devices for satellite receiver LNAs and radar front ends. GaN MMICs offer high power density and breakdown voltage, enabling compact high-power amplifiers for radar and electronic warfare. The IEEE RFIC Symposium proceedings have been a primary venue for MMIC design results since the symposium was established in 1997.

Key Circuit Blocks

An RFIC transceiver integrates several functional blocks whose performance collectively determines the system's sensitivity, dynamic range, and power consumption. The low-noise amplifier (LNA) at the receive input sets the noise figure of the entire receive chain; it must provide gain with minimal added noise while remaining linear across the full received signal range. The voltage-controlled oscillator (VCO) and phase-locked loop (PLL) synthesizer generate the local oscillator signal used by mixers to translate the RF signal to an intermediate frequency or to baseband. Power amplifiers in the transmit path consume most of the transceiver's DC power and must meet spectral mask requirements that limit out-of-band emissions. Research on millimeter-wave CMOS RFIC development has demonstrated that standard CMOS processes can realize transceivers for 5G millimeter-wave bands (24–86 GHz), enabling integration of the complete transceiver in consumer-grade silicon.

Applications

Radiofrequency integrated circuits have applications in a wide range of fields, including:

• Cellular infrastructure and handset chipsets for 4G LTE and 5G NR frequency bands
• WLAN and Bluetooth SoCs integrating multiple radios on a single silicon die
• Radiofrequency identification reader and tag ICs for supply chain, access control, and asset tracking
• Automotive radar at 77 GHz for adaptive cruise control and collision avoidance
• Satellite communications ground terminals and low-earth-orbit transponders
• Medical implants and body-area network devices requiring low-power RF links at ISM-band frequencies