Spatial Sensitivity of Capacitors in Distributed Resonators and Its Application to Fine and Wide Frequency Tuning Digital Controlled Oscillators


IEICE TRANSACTIONS on Electronics   Vol.E91-C   No.6   pp.918-927
Publication Date: 2008/06/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e91-c.6.918
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Analog Circuits and Related SoC Integration Technologies)
digital controlled oscillators,  transmission line,  frequency tuning,  

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Analysis of resonance frequency in shorted transmission lines with inserted capacitor has been made. The analysis shows a resonance frequency dependence on capacitance position on a shorted transmission line. Two analysis methods are presented to predict the resonance frequency and understand how the inserted capacitor affects the resonance frequency of the shorted transmission line. Using this knowledge we propose a new structure for digital controlled oscillators utilizing the capacitance's sensitivity dependence on position of the shorted transmission line to increase the frequency resolution. A 9 GHz transmission line based digital controlled oscillator was designed and fabricated as a proof of concept. Measured results show that more than 100 times frequency step resolution increase is possible utilizing the same tuning capacitor size located at different points on the transmission line.