Oscillator design in III-V technologies
Doktorsavhandling, 2014

The thesis treats the design of low phase noise oscillators/VCOs in GaAs/InGaP HBT and GaN HEMT technologies. The covered topics are: active device modeling, noise characterization, passive structures, phase noise models, simulation/measurement tools, circuit topologies, and design techniques. The mature InGaP HBT technology is known to be good for design of low phase noise oscillators, thanks to its low flicker noise and high breakdown voltage. The emerging GaN HEMT technology with its higher breakdown voltage also indicates the potential of low phase noise oscillator design. Large signal models for both devices were extracted based on Chalmers’ in-house models. Investigation of devices’ low frequency noise (LFN) characteristics showed that GaN HEMTs have noise levels close to InGaP HBT at low power, nevertheless, noise levels are high at high bias power. The bias dependency of LFN was utilized to develop low phase noise oscillators in GaN HEMT technology. An accurate method for phase noise calculation is implemented. The method is integrated with a commercial simulator and the phase noise is calculated posteriorly based on LFN and Hajimiri’s impulse sensitivity function. The method is validated for three different InGaP HBT VCOs designed at 7 GHz using well-known topologies, i.e. balanced Colpitts, cross-coupled, and Gm-boosted balanced Colpitts. The method is also applied to a 9 GHz GaN HEMT balanced Colpitts oscillator and proven to predict phase noise accurately over a wide range of bias points. The selection of oscillator topology is a key step in VCO design. A number of different topologies, suitable for various applications have been investigated and analyzed in this work. A 9 GHz double-tuned balanced Colpitts VCO demonstrates a 14.4% tuning range and phase noise better than -102dBc/Hz@100kHz over the tuning range. A wide tuning range of 34.4% is demonstrated in a 14.3 GHz mixer-based VCO. It is shown how a pair of modified Darlington HBTs is used in a gm boosted balanced Colpitts VCO to lower phase noise. In GaN HEMT oscillator designs, biasing strategies to avoid LFN are proposed. Two designed oscillators demonstrate the-state-of-the-art low phase noise in GaN HEMT technology. A MMIC balanced Colpitts oscillator at 10 GHz demonstrates a minimum phase noise of -136dBc/Hz at 1 MHz. A hybrid negative resistance oscillator with switch mode waveform designed at 2 GHz demonstrates a phase noise of -149dBc/Hz at 1 MHz.



device model


Darlington pair




phase noise


switch mode.


Colpitts oscillator

low frequency noise

Kollektorn, Kemiväten 9
Opponent: Prof. Jean-Guy Tartarin


Szhau Lai

Chalmers, Mikroteknologi och nanovetenskap (MC2), Mikrovågselektronik

Low Phase Noise GaN HEMT Oscillators With Excellent Figures of Merit

IEEE Microwave and Wireless Components Letters,; Vol. 24(2014)p. 412-414

Artikel i vetenskaplig tidskrift

LDMOS Modeling

IEEE Microwave Magazine,; Vol. 14(2013)p. 108-116

Artikel i vetenskaplig tidskrift

A varactor model including valanche noise source for VCOs phase noise simulation

41th European Microwave Conference , Manchester, UK, Oct 10-13, 2011,; (2011)p. 591-594

Paper i proceeding

A method to lower VCO phase noise by using HBT darlington pair

IEEE MTT-S International Microwave Symposium Digest,; (2012)

Paper i proceeding

An LC VCO for High Power Millimeter-Wave Signal Generation

35th IEEE Compound Semiconductor Integrated Circuit Symposium: Integrated Circuits in GaAs, InP, SiGe, GaN and Other Compound Semiconductors, CSICS 2013, Monterey, United States, 13-16 October 2013,; (2013)

Paper i proceeding

Integrated wideband and low phase-noise signal source using two voltage-controlled oscillators and a mixer

IET Microwaves, Antennas and Propagation,; Vol. 7(2013)p. 123-130

Artikel i vetenskaplig tidskrift

Accurate Phase-Noise Prediction for a Balanced Colpitts GaN HEMT MMIC Oscillator

IEEE Transactions on Microwave Theory and Techniques,; Vol. 61(2013)p. 3916-3926

Artikel i vetenskaplig tidskrift

A 20 GHz Low Phase Noise Signal Source Using VCO and Mixer in InGaP/GaAs HBT

2012 IEEE Compound Semiconductor Integrated Circuit Symposium, CSICS 2012, La Jolla, CA, 14 - 17 October 2012,; (2012)p. Art. no. 6340056-

Paper i proceeding

Design of Low Phase-Noise Oscillators and Wideband VCOs in InGaP HBT Technology

IEEE Transactions on Microwave Theory and Techniques,; Vol. 60(2012)p. 3420-3430

Artikel i övriga tidskrifter


Informations- och kommunikationsteknik

Nanovetenskap och nanoteknik


Elektroteknik och elektronik



Kollektorn, Kemiväten 9

Opponent: Prof. Jean-Guy Tartarin