Development of a Signal Flow Graph-Based De-Embedding Framework for Broadband Passive Linear Multiport RF & Microwave Networks with Applications to Power Splitters

Discrete passive components, including resistors, capacitors, inductors, and transformers, are fundamental to broadband 75-Ω radio-frequency (RF) systems, particularly in cable television (CATV) and hybrid fiber-coaxial (HFC) networks. These components are incorporated into power splitters, couplers, power inserters, and amplifiers to achieve desired frequency responses, impedance matching, and signal transmission characteristics. However, their electrical behavior becomes increasingly complex at higher frequencies due to parasitic resistance, inductance, capacitance, electromagnetic coupling, and distributed transmission-line effects. Consequently, accurate broadband characterization is essential for predicting component behavior and developing representative RF circuit models for simulation purposes.

A significant challenge arises when characterizing passive components with limited or unavailable manufacturer specifications, particularly when existing component inventories must be evaluated for broadband applications. Conventional measurement instruments, including digital multimeters, LCR meters, oscilloscopes, and function generators, generally lack the frequency range required for comprehensive RF characterization from 5 MHz to 3 GHz. Vector network analyzers (VNAs) enable complex scattering-parameter measurements across this frequency range; however, the measured response includes contributions from test fixtures, interconnections, and parasitic discontinuities that must be distinguished from the intrinsic response of the device under test (DUT).

This project investigates the development of a signal flow graph (SFG)-based de-embedding framework for broadband passive linear multiport RF networks. The methodology incorporates series-through and shunt-through DUT (CPWG) fixture configurations, conventional Open-Short and Short-Open de-embedding techniques, followed by lumped-element and distributed transmission-line representations of fixture parasitics. Scattering-parameter and ABCD-parameter analysis are employed to characterize fixture responses, while signal flow graph derivations provide a mathematical basis for analyzing interconnected multiport networks. Particular attention is given to fixture asymmetry, impedance discontinuities, and multiple signal propagation paths that complicate the extension of conventional two-port characterization methods to higher-order networks.

Experimental validation is conducted through the characterization of passive components with published impedance and quality-factor characteristics, enabling comparisons between extracted measurements, equivalent-circuit models, and manufacturer reference data. The methodology is subsequently applied to broadband power splitter networks used in CATV/HFC systems to investigate the accuracy and applicability of the proposed multiport de-embedding framework. The project aims to establish a systematic approach to broadband passive component characterization that integrates fixture modeling, network theory, and experimental measurement while reducing dependence on proprietary characterization data.