Application of Frequency Analog-to-digital Converter in Frequency Measurement

摘要

This paper introduces the concept of frequency measurement using the improved method of correlative counters. We define it as frequency analog-to-digital converter. The principle of frequency A/D converter is to detect frequency with high speed and without time intervals, which can't be realized by general correlative counters. Firstly, a general counter counts in a time interval, but in two adjacent time intervals dead time exists, during which data reading and clearing are performed. So the frequency of continuous time of the input signal can't be derived completely by general counters. Secondly, there is a quantization error of "± 1" caused by a general counter, which prevents it from achieving high frequency resolution. As an improved method, the frequency A/D converter applies techniques such as "zero-dead-time (ZDT)"; "interpolation" and "fast sampling" to solve aforementioned problems and introduces a frequency measurement method which has desirable characteristics of high speed of frequency detecting and good frequency resolution capability. The explanation and application of these techniques are also contained in this paper.