An analysis of layout and temperature effects on magnetic‐coupling factor, resistive‐coupling factor, and power gain performances of RF transformers for RFIC applications

In this paper, we demonstrate a comprehensive analysis of the temperature effect (from −25°C to 175°C) on the quality‐factors (Q 1 and Q 2 ), magnetic‐coupling factor (K Im ), resistive‐coupling factor (K Re ), maximum available power gain (G A max ), and minimum noise figure (NF min ) performances of RF bifilar and stacked transformers for RFIC applications. Excellent G A max of 0.713 and 0.806 (that is, NF min of 1.469 and 0.937 dB) were achieved at 5 and 7 GHz, respectively, at room temperature, for a 1:1 stacked transformer mainly due to its high K Im and K Re . In addition, for the 1:1 bifilar transformer at room temperature, though its K Im and K Re are low, good G A max of 0.636 and 0.631 (that is, NF min of 1.965 and 2.0 dB) were still achieved at 5 and 7 GHz, respectively, mainly due to its high Q 1 and Q 2 . The present analysis is helpful for RF engineers to design temperature‐insensitive ultra‐low‐voltage high‐performance transformer‐feedback low‐noise‐amplifiers (LNAs) and voltage‐controlled‐oscillators (VCOs), and other radio‐frequency integrated circuits (RF‐ICs) which include transformers. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1460–1466, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21732