等精度频率测量的同步门电路改进设计*

分析研究了等精度测量频率计的测量精度远低于理论值并且随被测信号频率变化而变化的原因，结果发现目前常见的等精度频率计的同步门电路在实际闸门下降沿和被测信号上升沿存在竞争冒险，产生的干扰脉冲影响了测量精度。针对此问题提出了几种同步门电路的改进设计。测试结果表明，改进后的几种同步门电路，不存在竞争冒险。采用改进后同步门电路的频率计，测量精度接近理论值，实现了等精度测量。

The Improved Design of the Synchronous Gate Circuit inEqual-Precision Frequency Measurement

In this paper, the cause, that measurement accuracy of the equal-precision frequency measurement meter is far lower than the theoretical value and it is varied with measured frequency, is analyzed. The researched results show that there is a race-hazard in the synchronous gate circuit that is used commonly and the frequency measurement precision is influenced by the resulting interference impulse. In order to solve the problem, several improved design solutions for synchronous gate circuit are brought forward. These proposed schemes are tested and the results demonstrate that there is no interference impulse. The measurement accuracy of the equal-precision frequency measurement meter with improved synchronous gate circuit is in agreement with the theoretical value very well. So the equal-precision frequency measurement can be realized.