Micromachined Spurline Band-stop Filter

This paper reports the design and fabrication of a membrane-supported spurline band-stop filter. The filter was fabricated using silicon bulk micromachining technique and a CMOS compatible metal/dielectric deposition RF sputtering technique. A closed-form expression of an equivalent value of dielectric constant is also derived and introduced to account for a multi-layer dielectric stack formed as a result of bulk micromachining. The proposed filter shows a better rejection performance and a wider 10-dB rejection bandwidth than the one realized on bulk silicon substrate. The proposed filter exhibits a 10-dB rejection band from 7.9-9.6 GHz with center frequency as 8.6 GHz. The measured rejection level in stop-band is better than 20 dB with maximum rejection level of 31 dB.