Micromachined filters on synthesized substrates

Effective high-frequency spectrum usage requires high-performance biters to have a sharp cutoff frequency and high stopband attenuation. Stepped-imped ance low-pass designs achieve this function best with large ratios of high- to-low-impedance values. In high-index materials, such as Si (11.7) and GaA s (12.9), however, these high-to-low-impedance ratios are around five, ther eby significantly limiting optimum filter performance. This paper character izes the use of Si micromachining for the development of synthesized substr ates, which, when utilized appropriately, can further reduce the low-impeda nce value or increase the high-impedance value. Both designs have demonstra ted high-to-low-impedance ratios that are 1.5-2 times larger than conventio nal techniques.