Fast Automatic Tuning of Channel Selection Filters Based on Phase Delay Calibration

An automatic tuning method for active-RC base-band filters used in direct conversion receivers is proposed. Filter calibration is realized by setting the phase delay for a reference frequency of 4.5 MHz to -360deg. The proposed method is accurate and area efficient, since it does not require a replica filter but uses the filter itself. In addition, monotonic control of the capacitor arrays makes fast tuning possible. A pair of base band filters for DVB-H receivers including this automatic tuning method was fabricated using a 0.5mum SiGe Bi-CMOS process. The accuracy of the tuning is limited by the resolution of the binary capacitor-array and is 12deg. This corresponds to a worst case cutoff frequency deviation of 300 kHz. The tuning takes 113.8musec