Phase-to-Digital Converter for Positioning System Applications

• Main Authors: Ching-Jung Yang, 楊景榮
• Other Authors: Ming-Dou Ker
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/63114079910168095613

碩士 === 國立交通大學 === 電資學院學程碩士班 === 91 === Recently, because of the development of semiconductor and electronic industry, precise measurement and positioning products have been used on large scale in the process and testing equipment of electronic and semiconductor industry. Process techniques are changing; smaller line width and more precise process have been developed even scale down to nano-meter. Therefore precise measurement and positioning techniques must be improved. The typical measurement and positioning products are rotary encoder and optical scale. They require various techniques in different application. In traditional manufacture industry, the required techniques are the measurement and positioning products can work in high pollution and high temperature environment. However, in modern electronic and semiconductor industry, they need high precision and high-speed system for high driving ability. The main measurement and positioning apparatus, besides the lacer interferometer that is more high precision displacement measurement system, can be classified into two types, linear and rotary encoder. The encoder always employs sensor passing through periodic and equal distance grating and then generates periodic quadrature scaling signals for displacement measurement. The phase is relative to the movement. According to the sensor type of encoder, it can be classified into two types, optical and magnetic encoder. The optical encoder is popular in modern electronic and semiconductor industry because of the high positioning accuracy. However, its accuracy is still restricted by optical properties and mechanical assembly. To improve encoder accuracy or resolution, electronic interpolation technique had been developed. It improves encoder accuracy by subdivision the phase of quadrature scaling signals. Some of them utilizes analog-to-digital converter to digitize input quadrature scaling signals and then achieve interpolation via different algorithm. This type can achieve high-fold interpolation even ~thousands but need lots of additional component. Therefore it is hard to minimize the circuit size and it cost high to integrate into a chip because of the complex circuits. Other interpolation methods satisfy the requirement of modern electronic and semiconductor industry although its interpolation-fold is not high. In additional, its structure is simple and suitable for integrating into a chip. Not only cost down the encoder but minimize the encoder size, integrating the interpolation circuit into a chip can also improve anti-noise ability and positioning system stabilities. According to the trends, an ASIC with conditioning circuit for optical sensor and a 40-fold interpolation circuit has been fabricated and measured in UMC 0.5µm 2P2M CMOS process. Integrating the conditional circuit for optical sensor into the ASIC improve the anti-noise ability furthermore. In addition, a phase difference adjustment for quadrature signals is also proposed in the thesis to improve assembly tolerance.