Generalized Scattering Matrix Formulation and its Relationship with TARC and Maximum Power Transfer Theorem

Abstract: In this paper, we present a rigorous framework for analyzing arbitrary passive matching networks using a generalized Thevenin-Helmholtz equivalent circuit. Unlike prior formulations, which often impose restrictive assumptions such as diagonal matching impedance matrices, our approach accommodates fully passive and interconnected multiport matching networks in their most general form. We first establish the mathematical conditions that any Linear Time Invarient, LTI, passive matching network must satisfy, starting from a $N \times N$ impedance matrix and continuing to $2N \times 2N$ and modified to follow the Thevenin-Helmholtz equivalent network. Using the Maximum Power Transfer Theorem (MPTT), we derive the scattering matrix $\mathbf{S}$ explicitly, showing its general applicability to arbitrary impedance configurations. Furthermore, we demonstrate the connection between the Total Active Reflection Coefficient (TARC) and the MPTT, proving that the TARC is inherently tied to the power conservation principle of the MPTT. This formulation not only unifies existing approaches, but also broadens the scope of applicability to encompass arbitrary physical passive systems. The equations and relationships derived provide a robust mathematical foundation for analyzing complex multiport systems, including interconnected phased arrays and passive antenna networks.