A Condition for Stable Minimum-Bandwidth Line Codes

By generalizing a concept on a power spectral zero at the Nyquist frequency, a condition for the line codes' capability to signal with the minimum bandwidth is established. From the condition, lower bounds of eyewidth are obtained for various values of a new system parameter called intersymbol interference sum variation (ISV). As an application of the condition, the nonminimum-bandwidth bipolar code is modified to a minimum-bandwidth code, which can be directly used in conventional bipolar signaling systems with increased bandwidth efficiency.