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

Abstract

In this paper, we demonstrate a comprehensive analysis of the temperature effect (from −25°C to 175°C) on the quality-factors (Q1 and Q2), magnetic-coupling factor (KIm), resistive-coupling factor (KRe), maximum available power gain (GA max), and minimum noise figure (NFmin) performances of RF bifilar and stacked transformers for RFIC applications. Excellent GA max of 0.713 and 0.806 (that is, NFmin 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 KIm and KRe. In addition, for the 1:1 bifilar transformer at room temperature, though its KIm and KRe are low, good GA max of 0.636 and 0.631 (that is, NFmin of 1.965 and 2.0 dB) were still achieved at 5 and 7 GHz, respectively, mainly due to its high Q1 and Q2. 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