DIGITAL CONTROLLED XTAL OSC

摘要

According to the present invention, an unlimited number of steps or increments of given size are obtained in a delay line for phase alignment of, for instance, the signal from a crystal oscillator (XO) by momentarily switching between two parallel delay lines. One delay line operates as an active or enabled delay line while the other line is disabled or inactive. It is ensured at the same time that the inactive delay line produces a signal which has the same relative phase as the active delay line, this absolute phase differing by N x 2 pi , where N is a positive or a negative integer other than zero. The inventive method and the inventive device enable the active delay line to operate constantly within its regulation range and the phase of the local oscillator can be kept continuously locked to the phase of the reference signal. The inventive device also includes an oscillator (2), a phase comparator (5) and counter logic (4) and a further phase comparator (7) and a selection circuit (6) for signal selection from that one of the two parallel delay lines (10, 11) that has been placed in its active mode.