Narrow Ka Bandpass Filters using Periodically Loaded Substrates
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High-k ceramics (TiO/sub 2/) are periodically embedded into a polymer based host material to create a filter utilizing the two-dimensional stopband of the periodic dielectric materials. The high-k ceramic rods (/spl epsiv//spl sim/90) are periodically spaced in a commercially-available Teflon-based host, to create a material that will inhibit propagation in two-dimensions. The inhibition of energy is used to create a resonance (termed a defect resonance), which in turn serves as the basis to create a filter. 2 and 4 pole filters were designed using this technology. The filter comprises a narrow passband region residing within the material stopband (12.1 GHz to 24.2 GHz). A/spl sim/1% bandwidth filter design yielded measured insertion losses of 1.13 dB and 1.69 dB @ 20.45 GHz for 2 and 4 pole filters respectively, correlating to an unloaded Q of approximately 1100. A maximal discrepancy of 2% was achieved on all measures of filter performance.
author list (cited authors)
Chappell, W. J., Gong, X., & Katehi, L.