Analog median filtering

The basic nonlinear operation in median filtering is a sorting of the input data vector. An analog structure for this filtering operation is presented. The sorting operation is embedded in a matrix-valued ordinary differential equation (ODE). The data to be sorted serve as initial values for the ODE. To induce the dynamics of the system a small perturbation is necessary. The circuit structure for the analog median filter consists of basic processing cells containing multipliers, integrators, and adders, arranged in an one-dimensional array. All connections are local only and no external control is necessary