Patent ID: 7095254
Filing Date: 2006-08-22
Classification: G01R,H03K,H03L,H04L

Abstract:
1. A frequency comparison device for producing a control signal which indicates that a frequency error between a first frequency of a useful signal and a second frequency of a reference signal exceeds a prescribed error limit value, the frequency comparison device comprising: a pulsed-signal generation device for using the useful signal and the reference signal to produce a pulsed signal having a pulse length that is proportional to a frequency difference between the first frequency of the useful signal and the second frequency of the reference signal, wherein the pulsed-signal generation device has at least two counting devices for producing the pulsed signal, and a pulse-length comparison device for comparing the pulse length with a predetermined maximum pulse length, and for one of producing the control signal and initiating production of the control signal if the pulse length exceeds the predetermined maximum pulse length, wherein the useful signal is present on a first counting device having a prescribed first maximum counter reading, the reference signal is present on a second counting device having a second maximum counter reading which matches the first maximum counter reading, the counter overflow outputs of the two counting devices are connected to a counter overflow monitoring device which monitors the two counting devices for a counter overflow and produces the pulsed signal if exclusively a single one of the two counting devices indicates a counter overflow.