Circuit Group

The EmRG Circuit Group researches advanced circuit components for next-generation terrestrial and non-terrestrial communication systems. Our work focuses on power amplifier, beamforming, frequency conversion and electronically tunable circuits, as well as circuit-level linearization techniques, all targeting frequencies from GHz to sub-THz.

Past designs

A selection of circuits and modules designed and characterized in the group, from sub-6 GHz through to D band.

Die photograph of the 5G transceiver front-end prototype

5G transceiver front-end prototype, 37–41 GHz

Photograph of the sub-6 GHz front-end module board

Sub-6 front-end module, 3.2–3.8 GHz

Die photograph of the D-band frequency doubler with driver amplifier

D-band frequency doubler with driver amplifier, 112–134 GHz

Evolved power amplifier prototype, 3.2 to 4.3 GHz, on a green printed circuit board

Evolved power amplifier prototype, 3.2–4.3 GHz

Die photograph of the phase-change-material-based beamformer

Phase-change-material-based beamformer, 26–33 GHz

Die photograph of the bidirectional outphasing beamformer

Bidirectional outphasing beamformer, 24–32 GHz

Integrated circuits

Millimetre-wave integrated circuits designed in the group and fabricated in commercial silicon processes. The die photographs below cover power amplifiers, frequency doublers, vector modulators and phase shifters at 28, 40 and 60 GHz and in D band, each characterized on the group’s probe station.

Die photograph of a 28 GHz power amplifier with input balun, driver and power stages, interstage matching, output combiner and decoupling capacitors

28 GHz power amplifier with enhanced AM-PM characteristic

Die photograph of a 1.5 by 1 millimetre beamforming Doherty power amplifier with a dual vector-modulator stage and a Doherty stage

28 GHz beamforming Doherty power amplifier

Die photograph of a 28 GHz dual-mode power amplifier, approximately 700 by 300 micrometres, with balun, quad hybrid, transformer-based matching and output combiner

Dual-mode, load-resilient power amplifier and Doherty amplifier at 28 GHz

Die photograph of a digitally-assisted 28 GHz active phase shifter, cropped to the chip

Digitally-assisted 28 GHz active phase shifter

Die photograph of a digitally-assisted reflection-type phase shifter for 27 to 33 GHz, cropped to the chip and surrounded by bond pads

Digitally-assisted 27 to 33 GHz reflection-type phase shifter

Die photograph of a bidirectional variable-gain phase shifter measuring 0.51 by 0.35 millimetres

Digitally-controlled bidirectional 24 to 32 GHz variable-gain phase shifter in 45 nm SOI CMOS

Die photograph of a 40 GHz Doherty power amplifier, 0.96 by 0.95 millimetres, with main and auxiliary paths, hybrid and combiner

40 GHz Doherty power amplifier with enhanced AM-PM characteristic

Die photograph of a 40 GHz active RF vector modulator with input balun, 90 degree hybrid, variable-gain core, output combiner and output balun

40 GHz active RF vector modulator with high tuning accuracy

Die photograph of a 60 GHz power amplifier with input balun, driver stage, interstage transformer, power stage and output combiner

Two-way, two-stacked power-combining power amplifier at 60 GHz

Die photograph of a V-band beamforming front-end module measuring 0.94 by 0.24 millimetres

V-band frequency-doubler-based RF beamforming front-end module

Die photograph of the D-band frequency doubler with driver amplifier

D-band frequency doubler with driver amplifier, 112–134 GHz

Die photograph of a bidirectional variable-gain phase shifter measuring 0.51 by 0.35 millimetres
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Digitally-controlled bidirectional 24 to 32 GHz variable-gain phase shifter in 45 nm SOI CMOS

Ongoing research projects

Circuit graph evolutionary algorithms for high-performance circuit design automation

An intelligent design framework capable of synthesizing arbitrary circuit topologies from scratch.

Enables faster and more optimized circuit and system designs without manual input.

Circuit topology graphs and the matching Smith charts produced by the evolutionary design framework

Circuit topology graphs and matching Smith charts produced by the evolutionary design framework

Analog pre-distortion for linearizing wireless transmitters over wide operating conditions

A technique to linearize power amplifiers using analog circuits as the pre-distortion signal generator.

Enables scalable linearization performance across power levels and bandwidth with reduced power overhead.

Block diagram of the analog pre-distortion architecture, with a splitter, error generator and combiner placed between the up-converter and the power amplifier

Analog pre-distortion (APD) architecture

Output power spectral density before and after analog pre-distortion linearization

Output power spectral density before and after analog pre-distortion linearization

Heterogeneous technologies integration for enhanced RF circuits and systems

GaN die on multilayer PCB for compact and broadband power amplifiers.

Joint semiconductor device and circuit level design optimization for linearity- and efficiency-enhanced designs.

GaN die integrated on a multilayer printed circuit board

GaN die integrated on a multilayer printed circuit board

Experimental demonstrations

Prototypes are characterized in the EmRG laboratory under modulated signals, at the bandwidths the standards actually call for. Two representative benches and their measured spectra are shown below.

The 120 GHz frequency doubler test bench, with signal source, DC supplies, WR-6 bend, device under test and power meters

120 GHz frequency doubler testing bench

Output power spectral density of the 120 GHz frequency doubler before and after iterative learning control

120 GHz doubler driven with a 1200 MHz modulated signal, before and after linearization

The 3.7 GHz power amplifier test bench, with arbitrary waveform generator, DC supply, driver amplifiers, oscilloscope and output coupler

3.7 GHz power amplifier testing bench

Output spectrum of the 3.7 GHz power amplifier before and after digital pre-distortion, showing the ten aggregated carriers

3.7 GHz power amplifier driven with a 10 x 100 MHz modulated signal, before and after digital pre-distortion

Output power spectral density of the 120 GHz frequency doubler before and after iterative learning control
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120 GHz doubler driven with a 1200 MHz modulated signal, before and after linearization
Output spectrum of the 3.7 GHz power amplifier before and after digital pre-distortion, showing the ten aggregated carriers
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3.7 GHz power amplifier driven with a 10 x 100 MHz modulated signal, before and after digital pre-distortion

Recent publications

Journal articles

  1. Y. Chen, H. Yu, Z. J. Su, S. Boumaiza, “Automated Broadband Power Amplifier Design via Circuit-Graph Evolution and Layout-Aware Synthesis,” IEEE Transactions on Microwave Theory and Techniques, early access, Aug. 2026.
  2. M. H. Sahlabadi, H. Yu, J. Xia, S. Boumaiza, “A Digitally Controlled Bidirectional 24–32-GHz Variable Gain Phase Shifter in 45-nm SOI CMOS,” IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 71, no. 8, Aug. 2024.
  3. X. Fang, J. Xia, S. Boumaiza, “A 28-GHz Beamforming Doherty Power Amplifier With Enhanced AM-PM Characteristic,” IEEE Transactions on Microwave Theory and Techniques, vol. 68, no. 7, July 2020.
  4. J. Xia, X. Fang, A. B. Ayed, S. Boumaiza, “Millimeter Wave SOI-CMOS Power Amplifier With Enhanced AM-PM Characteristic,” IEEE Access, vol. 8, 2020.
  5. A. Jundi, S. Boumaiza, “A Series-Connected-Load Doherty Power Amplifier With Push–Pull Main and Auxiliary Amplifiers for Base Station Applications,” IEEE Transactions on Microwave Theory and Techniques, vol. 68, no. 2, Feb. 2020.
  6. M. Liu, X. Fang, H. Huang, S. Boumaiza, “Dual-Band 3-Way Doherty Power Amplifier With Extended Back-Off Power and Bandwidth,” IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 67, no. 2, Feb. 2020.
  7. Y. Li, X. Fang, A. Jundi, H. Huang, S. Boumaiza, “Two-Port Network Theory-Based Design Method for Broadband Class J Doherty Amplifiers,” IEEE Access, vol. 7, 2019.
  8. X. Fang, A. Chung, S. Boumaiza, “Linearity-Enhanced Doherty Power Amplifier Using Output Combining Network With Predefined AM–PM Characteristics,” IEEE Transactions on Microwave Theory and Techniques, vol. 67, no. 1, Jan. 2019.
  9. J. Xia, S. Boumaiza, “Digitally Assisted 28 GHz Active Phase Shifter With 0.1 dB/0.5° RMS Magnitude/Phase Errors and Enhanced Linearity,” IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 66, no. 6, June 2019.
  10. X. Fang, H. Liu, K. M. Cheng, S. Boumaiza, “Modified Doherty Amplifier With Extended Bandwidth and Back-Off Power Range Using Optimized Peak Combining Current Ratio,” IEEE Transactions on Microwave Theory and Techniques, vol. 66, no. 12, Dec. 2018.

Conference papers

  1. H. Yu, X. Zhang, S. Boumaiza, “A Compact 4-Bit PCM-Based Hybrid Phase Shifter in 0.18-μm SiGe BiCMOS for 28 GHz Phased Arrays,” 2026 IEEE MTT-S Radio Frequency Technology and Techniques Symposium (IMS RFTT), June 2026.
  2. H. Yu, M. H. Sahlabadi, S. Boumaiza, “A 28 GHz Dual-Mode Power Amplifier for Enhanced Load Resiliency or Back-Off Efficiency Enhancement in 22NM FDSOI Process,” 2025 IEEE/MTT-S International Microwave Symposium - IMS 2025, June 2025.
  3. H. Yu, M. H. Sahlabadi, S. Boumaiza, “39 GHz Transmit/Receive Front-End-Module with Back-Off Efficiency Enhancement for 5G Communication,” 2024 IEEE/MTT-S International Microwave Symposium - IMS 2024, June 2024.
  4. M. H. Sahlabadi, H. Yu, J. Xia, S. Boumaiza, “A Compact, High Tuning Accuracy and Enhanced Linearity 37-43 GHz Digitally-Controlled Vector Sum Phase Shifter,” 2024 IEEE 24th Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems (SiRF), Jan. 2024.
  5. M. Eladwy, A. B. Ayed, A. M. Darwish, S. Boumaiza, “A V-Band 16% Efficiency Frequency Doubler-Based RF Beamforming Front-End Module for Vector Modulated Signal Transmission,” 2023 53rd European Microwave Conference (EuMC), Sept. 2023.
  6. H. Yu, M. H. Sahlabadi, E. Traore, M. Eladwy, H. Ma, S. Boumaiza, “37-43 GHz Wide-Band Doherty Power Amplifier with Enhanced AM-PM Characteristic,” 2023 IEEE/MTT-S International Microwave Symposium - IMS 2023, June 2023.
  7. P. Choi, R. Fang, L. Wei, S. Boumaiza, U. Radhakrishna, E. Fitzgerald, “Design of 20-28 GHz GaAs Phase Shifter MMIC and Small Signal Validation using MVS-GaAs Model,” 2022 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS), Oct. 2022.
  8. M. Eladwy, J. Xia, A. B. Ayed, S. Boumaiza, “A 60 GHz CMOS-SOI Stacked Push-Push Frequency Doubler with 12 dBm Output Power and 20% Efficiency,” 2021 IEEE MTT-S International Microwave Symposium (IMS), June 2021.
  9. J. Xia, Y. Xu, H. Huang, S. Boumaiza, “A 0.1-5.7 GHz CMOS Phase Shifter with 0.27dB/1.8° RMS Magnitude /Phase Errors and Enhanced Linearity,” 2019 IEEE 19th Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems (SiRF), Jan. 2019.
  10. J. Xia, M. Farouk, S. Boumaiza, “Digitally-Assisted 27-33 GHz Reflection-Type Phase Shifter with Enhanced Accuracy and Low IL-Variation,” 2019 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), June 2019.