A fully parallel CMOS analog median filter

A fully integrated CMOS implementation of a continuous-time analog median filter is presented. The array median filter uses two compact analog circuits as building blocks to implement the variable delay and median detection. Median detectors are based on transconductance comparators to speed their time response, while the time delay is implemented using all-pass filters. Both circuits allow modular expansion for the implementation of large sized median filter array processors. In addition, a fast novel technique for parallel image processing is presented. It is shown that an image of 91×81 pixels is processed in less than 30 μS using an array of high-speed analog processors. Experimental results of a test chip prototype in 2 μm CMOS technology MOSIS process are presented