Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485630
Title: Active Microwave Parametric Frequency Dividers
Author: Heshmati, Zinabolhoda
ISNI:       0000 0001 3555 2874
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2007
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Abstract:
Despite the increased availability of digital frequency dividers operating up to several gigahertz, analogue dividers offer lower power consumption and higher operating frequencies. Among the different types of analogue microwave frequency dividers, parametric dividers based on passive circuits still fill a unique niche due to their simplicity and low cost. However, their major drawbacks have been their high input threshold powers and high conversion losses. Also to obtain higher division ratios, several divide-by-two circuits are usually cascaded, with the required amplitude for the input and output signals needing pre- and post-amplifiers, further complicating the circuit. In the present study, the above disadvantages are overcome by active parametric frequency dividers. This thesis presents the analysis, design and measured results of parametric frequency dividers utilizing pseudomorphic High Electron 1'1obility Transistors (pHEMTs) in place of traditional varactor diodes along with a novel circuit approach. The major advantage of using active devices is the potential for high conversion gain eliminating the need for amplification if further division is required. The active parametric frequency dividers described in this study use coupled microstrip transmission lines and two pHEMTs in a balanced configuration. A 2 GHz to 1 GHz divider is designed and fabricated, with measurements showing a 10% bandwidth, +18 dB maximum conversion gain and a lo~ input power threshold level of -14 dBm. The divider has a fundamental frequency rejection of better than 37 dBc at the output, and rejection of other harmonics of more than 22 dBc, with similar results for a lower frequency divider circuit converting 1 GHz to 0.5 GHz. A significant improvement in performance compared to previous designs is demonstrated.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.485630  DOI: Not available
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