Envelope constrained filter with linear interpolator

The envelope constrained (EC) filtering problem is the minimization of the noise gain of the filter while satisfying the constraint that its noiseless response to a specified input lies within a prescribed envelope. Using a hybrid filter consisting of an A/D converter, an FIR filter, and a linear interpolator, the problem is posed as a functional inequality constrained optimization problem. A technique for solving this problem is proposed by approximating it with a conventional unconstrained optimization problem that is then solved by a descent direction-based algorithm