US 6,549,571 B1 · Circuitry and method for duty measurement

Abstract

Duty measuring circuitry of the present invention includes a pulse detecting circuit for detecting at least one of a convex pulse width and a concave pulse width included in an input data signal. A duty decision circuit determines whether or not the convex pulse width or the concave pulse width detected is smaller than a preselected value. If the detected pulse width is smaller than the preselected, the duty decision circuit determines that the pulse width is valid, and feeds it to an averaging circuit. The circuitry obviates the need for an exclusive fixed pattern, e.g., ONEs and ZEROs alternating with each other customarily used for the measurement of a duty. In addition, the circuitry is capable of accurately measuring a duty even with a random pattern based on RZ (Return-to-Zero) code or NRZ (Non-Return-to-Zero) code.

Claims52

Dependent claims

Circuitry for measuring a duty of an input data signal, wherein at least one of a peak pulse width and a trough pulse width of the input data signal is detected and is determined, when smaller than a preselected value, to be valid for a calculation of a duty value, comprising:

sampling means for sampling the input data signal with either one of N-phase (N being any integer greater than 2 inclusive) clock signals which are N clock signals sequentially shifted in phase by 360°/N and identical in frequency with the input signal and an N-times clock signal N times higher in frequency than the input signal, wherein said sampling means produces N sampled signals by sampling the input data signal with said N-phase clock signal or said N-times clock signal, and sequentially shifts said N sampled signals by M−1 periods (M being any integer greater 1 inclusive) of said N-phase clock signals or by N(M−1) periods of said N-times clock signal to thereby output N×M sampled signals.

A method of measuring a duty of an input data signal, comprising:

a detecting step for detecting at least one of a peak pulse width and a trough pulse width;
a validating step for validating, if the peak pulse width or the trough pulse width detected is smaller than a preselected value, said peak pulse width or said trough pulse width for a calculation of a duty value;
and
a sampling step for sampling the input signal with either one of N-phase (N being any integer greater than 2 inclusive) clock signals which are N clock signals sequentially shifted in phase by 360°/N and identical in frequency with the input signal and an N-times clock signal N times higher in frequency than the input signal, wherein said sampling step comprises producing N sampled signals by sampling the input signal with said N-phase clock signal or said N-times clock signal, and sequentially shifts said N sampled signals by M−1 periods (M being any integer greater than 1 inclusive) of said N-phase clock signals or by N(M−1) periods of said N-times clock signal to thereby output N×M sampled signals.

1 more element

Dependencies are inferred from the claim text.

Circuitry and method for duty measurement

Life of this patent

Circuitry and method for duty measurement

Life of this patent

Abstract

Claims52