Method for communicating binary data using modified frequency shift

Abstract

A method for communicating binary data using modified frequency shift keying techniques generally includes the steps of selecting a first bit count representative of a first untranslated frequency denoting a data signal at a first logic state, selecting a second bit count representative of a second untranslated frequency denoting a data signal at a second logic state and computing a mean bit count intermediate the first and second bit counts. A signal is detected which has a first component at a first translated frequency and a second component at a second translated frequency and defines a first interval of time having boundaries identifiable as T0 and T1, a second interval of time having boundaries identifiable as T1 and T2, a third interval of time having boundaries identifiable as T2 and T3 and a fourth interval of time having boundaries identifiable as T3 and T4. A base bit count is generated which is representative of the sum of said second and third time intervals and the first component is decoded as a data signal at said first logic state if the base bit count is equal to or greater than the mean bit count. If the base bit count is less than the mean bit count, other bit counts are generated and a bit clock initiation time is selected as that time identifiable as T1 if the base bit count is equal to or less than a fore bit count. Other times may be selected as the bit clock initiation time, depending upon the outcome of disclosed bit count comparisons.