Microwave Frequency Conversion Techniques in CMOS Technology

Microwave frequency conversion in CMOS encompasses a range of techniques for translating signals between radio-frequency (RF), intermediate-frequency (IF) and baseband domains. Core approaches include mixers, which leverage nonlinear transconductance to produce sum-and-difference frequencies, and frequency multipliers, which exploit device nonlinearity to generate harmonics at integer multiples of an input tone. Traditional diode-based and varactor-based upconverters have evolved into fully integrated CMOS solutions using differential architectures, Gilbert-cell cores and on-chip resonant filters. Injection-locked oscillators now serve as compact multiplier stages, achieving high multiplication factors in a single LC-tank topology. Cascade chains of doublers, triplers and quad­r­uplers extend reach into the D- and sub-millimetre-wave bands, while advanced process nodes such as FD-SOI and SiGe BiCMOS assist in overcoming parasitic limitations and supply-voltage constraints. Key challenges remain in balancing conversion gain, noise figure and harmonic rejection, all under tight power budgets. Practical implementations span 5G/6G transceivers, automotive radar and imaging systems, where fully monolithic CMOS frequency-conversion front ends deliver cost-effective, mass-producible solutions with bandwidths exceeding tens of gigahertz.

Research from Nature Portfolio

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Research from all publishers

Recent work in mainstream journals has demonstrated fully integrated D-band multiplier chains combining push-push doublers and Gilbert-cell triplers to achieve ×12 multiplication with over 20 dBc harmonic suppression across 117–155 GHz. Another line of research employs differential LC-tank injection-locked oscillators in 0.18 µm CMOS to realise single-stage frequency quintuplers and sixtuplers, offering compact die footprints, sub-10 mW power consumption and multi-gigahertz locking ranges. In advanced 22 nm FD-SOI CMOS, rotary traveling-wave oscillators feed four-phase-shifted signals into frequency quadruplers augmented by on-chip LC filters, yielding more than 40 dBc suppression of unwanted harmonics and milliwatt-level output power in the 32–42 GHz band. Collectively, these studies highlight the trend towards monolithic, low-power, high-multiplication-factor circuits that combine robust harmonic control with wide instantaneous bandwidth for next-generation wireless and sensing applications.

Microwave Frequency Conversion Techniques in CMOS Technology publication trend

The graph below shows the total number of articles in microwave frequency conversion techniques in cmos technology across all publications each year (not limited to Nature Index journals).

Technical terms

Frequency multiplier: A nonlinear circuit that generates output signals at integer multiples of an input frequency.

Frequency mixer: A device that combines two signals to produce sum and difference frequencies for up- or downconversion.

Injection-locked oscillator: An oscillator synchronised by an external signal to generate stable harmonics efficiently.

Harmonic rejection: The suppression of unwanted harmonic frequencies in a multiplier or mixer output.

LC tank: A resonant circuit formed by an inductor (L) and a capacitor (C) used to select or stabilise a frequency.

FD-SOI (Fully Depleted Silicon-On-Insulator): A CMOS process offering reduced parasitic capacitance and improved high-frequency performance.

Gilbert cell: A four-quadrant multiplier core commonly used in mixers and frequency-conversion circuits.

References

1. A 117.5–155-GHz SiGe ×12 Frequency Multiplier Chain With Push-Push Doublers and a Gilbert Cell-Based Tripler. IEEE Journal of Solid-State Circuits (2023).
2. A 32–42-GHz RTWO-Based Frequency Quadrupler Achieving >37 dBc Harmonic Rejection in 22-nm FD-SOI. IEEE Solid-State Circuits Letters (2021).
3. CMOS Injection-Locked Frequency Quadrupler/Quintupler. IEEE Access (2022).
4. Single-Stage Injection-Locked Frequency Sixtupler in CMOS Process. IEEE Access (2022).