Patent ID: 7768431

Claim:
An R/D converter converting a detection angle θ implied in a first resolver signal S 1 and a second resolver signal S 2 outputted from a resolver into a digital angle output φ, comprising: a first multiplier multipling said first resolver signal S 1 by a sine value of said digital angle output φ, where the resolver outputs said first resolver signal S 1 and said second resolver signal S 2 in response to an excitation signal, S 1 =cos θ sin ωt, S 2 =sin θ cos ωt, sin ω is the excitation signal, and ω is an angular frequency of the excitation signal; a second multiplier multipling said second resolver signal S 2 by a cosine value of said digital angle output φ; a subtracter subtracting an output of said first multiplier from an output of said second multiplier; a synchronous detection circuit performing synchronous detection of an output of said subtracter by referring to the excitation signal to output a detected output sin(θ−φ); a controller controlling said digital angle output φ to make said detected output sin(θ−φ) as a deviation zero, and outputting said digital angle output φ; a SIN ROM generating the sine value of said digital angle output φ from said digital angle output φ; and a COS ROM generating the cosine value of said digital angle output φ from said digital angle output φ; wherein the R/D converter further comprises a band elimination filter eliminating or reduces a low frequency noise superposed on said resolver signals S 1 and S 2 between said synchronous detection circuit and said controller.