The impact of metallization thickness and geometry for X-band tunable microwave filters

Peter G. Lam, Zhiping Feng, Vrinda Haridasan, Angus I. Kingon, Michael B. Steer, Jon Paul Maria

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The impact of dc resistance on the performance of X-band filters with ferroelectric varactors was investigated. Two series of combline bandpass filters with specific geometries to isolate sources of conductor losses were designed and synthesized. Combining the changes in filter geometry with microwave measurements and planar filter solver (Sonnet software) simulations quantitatively identified the dependency of insertion loss on overall metallization thickness and local regions of thin metallization. The optimized 8-GHz bandpass filters exhibited insertion losses of 6.8 dB. These filters required 2.5 m of metal thickness (or 3 effective skin depths) to achieve this loss. The trend of loss with thickness indicates diminishing return with additional metal. The integration scheme requires thin regions of metal in the immediate vicinity of the varactors. It is shown through experiment and simulation that short distances (i.e., 15 m) of thin metallization can be tolerated provided that they are located in regions where the resonant microwave current is low.

Original languageEnglish (US)
Article number4976275
Pages (from-to)906-911
Number of pages6
JournalIEEE transactions on ultrasonics, ferroelectrics, and frequency control
Issue number5
StatePublished - May 2009

All Science Journal Classification (ASJC) codes

  • Instrumentation
  • Acoustics and Ultrasonics
  • Electrical and Electronic Engineering


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