Analysis, Design, Modeling, and Characterization of Low-Loss Scalable On-Chip Transformers

• Published in: IEEE transactions on microwave theory and techniques Vol. 61; no. 7; pp. 2545 - 2557
• Main Authors: Tiemeijer, L. F., Pijper, R. M. T., Andrei, C., Grenados, E.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-07-2013; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Baluns; Calibration; Circuit properties; Couplers; Couplings; de-embedding; Design engineering; Design. Technologies. Operation analysis. Testing; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; Impedance; Impedance matching; Inductive coupling; Inductors; Insertion loss; Integrated circuits; Mathematical models; Microwaves; on-wafer microwave measurements; Resonant frequency; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Signal convertors; System-on-chip; Theoretical study. Circuits analysis and design; Transformations; transformer design and modeling; Transformers; Performance evaluation; Parameter estimation; Scalability; Circuit simulation; Integrated circuit design; Balun; transformer design and modeling; Compact design; Calibration; Modeling; Microwave measurement; Four port network; s parameter; Insertion loss; Equivalent circuit; Radiofrequency integrated circuits; Signal converter; Capacitive coupling; Inductive coupling; on-wafer microwave measurements; Wafer; de-embedding
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2013.2265684

A few important design choices for a low-loss scalable on-chip transformer are discussed, the most important one being that the capacitive and inductive couplings should be aligned to minimize insertion loss. The importance of these design choices is illustrated both theoretically as well as experimentally. In particular, for the first time the performance of these on-chip transformers is verified with four-port S -parameter measurements taken up to 67 GHz. With that, an insertion loss of only 0.6 dB up to 30 GHz is demonstrated. To facilitate the use of these low-loss on-chip transformers in the RF integrated-circuit design flow, a scalable compact equivalent-circuit model suitable for all pre-layout circuit simulations is described, which accurately predicts transformation ratios, transmission efficiencies and balun amplitude and phase imbalances.