| 摘要 |
In one preferred embodiment, apparatus for determining values of a periodic function by interpolation receives signals A, B, C, D from the periodic function which are nominally in phase quadrature with each other. These are combined to produce sine and cosine functions (SN, CS) from which interpolation is performed by a computer (25). In known such apparatus, accuracy substantially depends on the actual phase separation of the signals being very close to the nominal quadrature separation. In the present embodiment, this dependence is reduced by deriving each function SN, CS from at least three of the signals A, B, C, D, e.g. in the forms 2B-A-D and 2C-A-B. Other such formulae for deriving the functions SN, CS are disclosed. In one further embodiment there are three input signals A1, B1, C1 which have a nominal phase separation of 120 DEG , rather than quadrature separation; and in another embodiment there are five input signals. |
