In this talk we study a generalized Nevanlinna Pick interpolation problem, where transmission zero locations are imposed. Unlike in other variation of this problem considered by T.T Georgiou et al. the interpolation points are chosen one the boundary of the analyticity domain: that is, in our continuous time frame work, on the imaginary axes. We will explain how this problem is motivated by important questions in electronic and microwave system design, and how it relates to the broadband matching theories of Youla and Helton. Existence and unicity results will be presented together with a sketch of their constructive proof based on continuation techniques. Recent numerical results obtained using this techniques for microwave multiplexer and antenna design will be presented. Eventually we will discuss an open related problem concerning a matricial version of our problem with possible strong implications for the area of microwave multi-port design.