A simple digital to resolver converter

A technique is described by which a digital representation of an angle is converted into a pair of ac voltages suitable for exciting a synchro or resolver, which may be used as the feedback element of a control system. The technique is quite economical of hardware, is capable of an arbitrary degree of accuracy, and is adaptable to almost any radix digital input signal. The simplicity and economy of the method depends on digitally generating two voltages that are functions of the digitally designated angle, but are not proportional to the sine and cosine per se. These functions are chosen in such a way that their ratio approximates the tangent of the designed angle with an arbitrarily small error. An example of the technique and some experimental results are given.