Tunable High-Q N-Path Band-Pass Filters: Modeling and Verification

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Ghaffari, Amir and Klumperink, Eric A.M. and Soer, Michiel C.M. and Nauta, Bram (2011) Tunable High-Q N-Path Band-Pass Filters: Modeling and Verification. IEEE Journal of Solid-State Circuits, 46 (5). pp. 998-1010. ISSN 0018-9200

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Abstract:Abstract—A differential single-port switched-RC N-path filter with band-pass characteristic is proposed. The switching frequency defines the center frequency, while the RC-time and duty cycle of the clock define the bandwidth. This allows for high-Q highly tunable filters which can for instance be useful for cognitive radio. Using a linear periodically time-variant (LPTV) model, exact expressions for the filter transfer function are derived. The behavior of the circuit including non-idealities such as maximum rejection, spectral aliasing, noise and effects due to mismatch in the paths is modeled and verified via measurements. A simple RLC equivalent circuit is provided, modeling bandwidth, quality factor and insertion loss of the filter. A 4-path architecture is realized in 65 nm CMOS. An off-chip transformer acts as a balun,improves filter-Q and realizes impedance matching. The differential architecture reduces clock-leakage and suppresses selectivity around even harmonics of the clock. The filter has a constant 3 dB bandwidth of 35 MHz and can be tuned from 100 MHz up to 1 GHz. Over the whole band, IIP3 is better than 14 dBm, dBm and the noise figure is 3–5 dB, while the power dissipation increases from 2 mW to 16 mW (only clocking power).
Item Type:Article
Copyright:© 2011 IEEE
Faculty:
Electrical Engineering, Mathematics and Computer Science (EEMCS)
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Link to this item:http://purl.utwente.nl/publications/77956
Official URL:http://dx.doi.org/10.1109/JSSC.2011.2117010
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