Caller-id demodulation apparatus and method using multiple thresholds

Abstract

A caller identification (ID) demodulating apparatus and method using multiple thresholds. An apparatus according to one embodiment comprises a zero crossing detector for generating pulses at points where the modulated caller ID information crosses zero and outputs each pulse as a zero crossing signal, a data extractor for computing a zero crossing interval between each output pulse of the zero crossing signal, and comparing the zero crossing interval with a plurality of thresholds to generate extracted data, and a clock generator for generating a data recovery clock signal for recovering the extracted data in response to the extracted data, wherein the data recovery clock signal is enabled at the middle point of the unit data length of the extracted data. The apparatus and method use multiple thresholds to extract data from caller ID modulated in a CPFSK format, thereby accurately extracting data at an interval where data “0” and “1” coexist. Furthermore, the clock signal for demodulating extracted data is generated about at the middle point of the unit data length of the extracted data, thereby demodulating data accurately.