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This paper provides a channel select low-pass filter with automatic cut-off frequency tuning circuit for low-IF conversion digital audio broadcasting (DAB) and terrestrial-digital multimedia broadcasting (T-DMB) tuner IC. This filter has 1.58MHz cut-off frequency, 20dB and 65dB stop band attenuation at 1.9MHz and 2.4MHz, respectively. The in-band IIP3 is -8.4dBV and 1dB desensitization is satisfied for 490mVpp interferer at 1.7MHz frequency offset. By using simple automatic tuning technique, less than +/-1.5% cut-off frequency error and more than 40dB adjacent channel rejection (ACR) are obtained. The low-pass filter is fabricated in 0.18μm CMOS technology and consumes about 4.5mA with 1.8V power supply.
Date of Conference: 12-16 Sept. 2005