Abstract
A new idea for generation of quadrature signals on chip is presented. The topology is based on a passive RC polyphase filter, where the resistive parts are made active by using inverters. The active filter combines quadrature generation, isolation, and gain without losing quadrature performance compared to a regular RC polyphase filter. The filter technique is demonstrated in a 10 GHz front-end application where a broadband VCO, having a tuning range of 1.44 GHz, drives an active polyphase filter to generate quadrature LO signals. According to simulations the quadrature phase error shows a typical tuned behavior and stays below 0.8° for the complete tuning range. Since the signal amplitude is high throughout the filter the noise is low, below 160 dBc/Hz at 10 MHz offset. The high amplitude also reduces the need for high gain tuned buffers, thereby enabling significant reductions in chip area.
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Fredrik Tillman was born in Lund, Sweden, in 1975. He received the M.S. degree in electrical engineering and the Ph.D. degree in circuit design from Lund University, Sweden, in 2000 and 2005, respectively. During his studies, he worked on wireless CMOS receiver front-ends, with particular focus on the analysis and design of low voltage LNAs and mixers. He is currently with Ericsson AB (Business Unit Mobile Platforms).
Henrik Sjöland received the M.S. degree in electrical engineering and the Ph.D. in applied electronics from Lund University, Lund, Sweden, in 1994 and 1997, respectively. He is currently an Associate Professor at Lund University. His research interests include the design and analysis of analog integrated circuits, feedback amplifiers, and RF CMOS. In 1999, he spent one year as a Fulbright Postdoctoral with the Abidi group at UCLA. He is the author of Highly Linear Integrated Wide-band Amplifiers (Boston, MA: Kluwer, 1999).
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Tillman, F., Sjöland, H. A polyphase filter based on CMOS inverters. Analog Integr Circ Sig Process 50, 7–12 (2007). https://doi.org/10.1007/s10470-006-9152-z
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DOI: https://doi.org/10.1007/s10470-006-9152-z