Patent ID: 8519784
Filing Date: 2013-08-27
Classification: H04L

Abstract:
1. A Frequency Shift Keying (FSK) demodulator comprising: a frequency detector to generate a frequency detection signal representing an amplitude value according to frequency shift of a received FSK modulation wave; a frequency offset cancellation part to cancel a frequency offset component from the frequency detection signal according to the frequency detection signal provided at a detection time point of an inflection point after detecting the inflection point of the frequency detection signal by an inflection point detector; and a data demodulation part to acquire demodulation data according to a frequency detection signal from which the frequency offset component is cancelled by the frequency offset cancellation part, and wherein the inflection point detector comprises: an inflection point extraction part to extract the inflection point according to variation of a sample value after sampling an amplitude value of the frequency detection signal at each predetermined operating clock; an amplitude determination part to determine if a size between peak values of sample values of the frequency detection signal, which are provided in front and rear of the inflection point extracted from the inflection point extraction part, is in a first predetermined range; a preamble determination part to determine if a difference between initial and final sample values of at least one of a symbol having the extracted inflection point and a symbol right before the symbol having the extracted inflection point is in a second predetermined range; and an AND circuit part to determine the inflection point, which is extracted from the inflection point extraction part, as a normal inflection point if the amplitude determination part determines that the size between the peak values is in the first predetermined range, and if the preamble determination part determines that the difference between the initial and final sample values is in the second predetermined range.