AMPLITUDE AND PHASE ERROR NORMALIZATION OF SUBCARRIER GENERATOR

摘要

A subcarrier signal generator (30) includes a finite impulse response (FIR) filter (40) responsive to selected FIR coefficients from coefficient register (44). A first set of FIR coefficients represents an ideal subcarrier shape and center frequency. A calibration step performed by calibration device (34) monitors the resulting subcarrier signal and produces a new set of FIR coefficients corresponding generally to the ideal subcarrier signal shape and center frequency, but predistorted according to the complement of error detected in the actual subcarrier signal. By then loading the new set of FIR coefficients and operating the subcarrier generator (30), frequency-dependent distortions in the output stage of the subcarrier generator (30) cancel predistortion reflected in the new FIR coefficients. As a result, a high quality subcarrier signal results without use of expensive output stage devices in the subcarrier signal generator (30).