A Phase-Shift Data-Transmission System for Analog to Digital or Digital to Analog Conversion

A block diagram of the basic building blocks of phase-shift data-transmission systems is outlined in Figure 1. These basic blocks establish a reference time base in one or more synchro receivers to which phase signals may be compared. A pulse source generates a train of pulses which provide this time base for the system. This chain of pulses is divided down in the reference counter and provides two 400-cycle (chosen for convenience) square-wave signals which are 90° out of phase. These signals are filtered and amplified in the synchro exciter and appear as outputs of the exciter in the form of two sinusoidal, 400-cycle signals 90° out of phase. The two sinusoids are used to excite the two stator windings of one or more synchro resolvers. The voltage induced in the rotor of each synchro resolver is a constant-amplitude, 400-cycle sinusoid whose phase angle with respect to the reference is equal to the mechanical angle of the rotor.