Patent ID: 7800518

Claim:
A pulse modulation method for dividing code comprising 4N-bit data (N is a positive integer) into units configured by every 2 bits of data, the method comprising the steps of: after a pulse signal of a fixed pulse width tw has been generated, generating a code modulated signal for each unit of code by pausing between pulse pause intervals Tr for a pulse signal that has been set corresponding to value of the 2-bit data of that unit; and connecting the code modulated signals for all units, characterized in that: an optional adjusted time width of 1/2 or more and less than 1 of a fixed pulse width tw is taken to be Δt, and 4 types of pulse pause intervals Tr, in which any of the time widths 0, Δt, 2Δt, and 3Δt is added to a fixed pause period tm of time intervals nearly equivalent to the fixed pulse width tw, are set according to a corresponding one of the 4 values of the 2-bit data; if the sum total TD of the code modulated signal made from 4N-bit data is an interval of at least [(2tw+2tm+3Δt)N+Δt] or more, the pulse pause interval Tr of every unit of code is substituted by a pulse pause interval Tr in which the value of the 2-bit data of each unit is set corresponding to the inverted 2-bit data; the substituted pulse pause interval Tr is used to produce a code modulated signal from all of the units; and an inversion flag signal that expresses inversion information is added to the connected code modulated signal.