Silicon Laboratories Inc.
Spur canceller with multiplier-less correlator

Abstract:

A spur cancellation circuit uses low cost multipliers in a correlation circuit. Each low cost multiplier multiplies a value of a sense node by a representation of a sinusoid and supplies a multiplication result. A compare circuit compares the sinusoid to one or more threshold values and supplies a compare indication. A multiplexer selects between two or more inputs including a positive value of the sense node and a negative value of the sense node, based on the compare result. A single threshold at zero converts the sinusoid to a square wave and the multiplexer supplies either the positive value or the negative value, which is equivalent to multiplying the value at the sense node by 1 or -1 depending on the sign of the sinusoid. Two thresholds may be used to represent the sinusoid with three values, the positive value, the negative value, or zero.