DUAL-LOOP AUTOMATIC FREQUENCY CONTROL FOR WIRELESS COMMUNICATION

摘要

Techniques for performing frequency control using dual-loop automatic frequency control (AFC) are described. The dual-loop AFC includes an inner loop that corrects short-term frequency variations (e.g., due to Doppler effect) and an outer loop that corrects long-term frequency variations (e.g., due to component tolerances and temperature variations). In one design, a first inner loop is implemented for frequency control of a first system (e.g., a broadcast system), a second inner loop is implemented for frequency control of a second system (e.g., a cellular system), and at least one outer loop is implemented for adjusting a reference frequency used to receive the first and second systems. Each inner loop estimates and corrects the frequency error in an input signal for the associated system and may be enabled when receiving the system. The reference frequency may be used for frequency downconversion, sampling and/or other purposes.