為了實現(xiàn)鐵路道口列車接近定時報警，提出了一種基于軌道電路的列車測速系統(tǒng)設(shè)計方法。在鐵路道口的遠端設(shè)置兩段相鄰的25 m軌道電路，列車接近時，兩段軌道電路依次動作。采用單片機電路測出兩段軌道電路動作的時間間隔，即可計算出列車的行駛速度。將列車的速度信息發(fā)送給道口控制中心，確定道口合理的關(guān)閉時機。實驗結(jié)果表明，測速精度可達到0.1 m /s，能夠滿足系統(tǒng)的要求。
基于通用集成運算放大器，利用MASON公式設(shè)計了一個多功能二階通用濾波器，能同時或分別實現(xiàn)低通、高通和帶通濾波，也能設(shè)計成一個正交振蕩器。電路的極點頻率和品質(zhì)因數(shù)能夠獨立、精確地調(diào)節(jié)。電路使用4個集成運放、2個電容和11個電阻，所有集成運放的反相端虛地。利用計算機仿真電路的通用濾波功能、極點頻率和品質(zhì)因數(shù)的獨立控制和正交正弦振蕩，從而證明該濾波器正確有效。
Abstract:
A new multifunctional second-order filter based on OPs was presented by MASON formula. Functions， such as high-pass， band-pass， low-pass filtering， can be realized respectively and simultaneously， and can become a quadrature oscillator by modifying resistance ratio. Its pole angular frequency and quality factor can be tuned accurately and independently. The circuit presented contains four OPs， two capacitors， and eleven resistances， and inverting input of all OPs is virtual ground. Its general filtering， the independent control of pole frequency and quality factor and quadrature sinusoidal oscillation were simulated by computer， and the result shows that the presented circuit is valid and effective.
