RF Signal Multiplexer Embedded Into Multifunctional Composite Structure

This article describes the design and fabrication of an active four-port microwave switching network embedded into a multilayer aerospace composite structure. The multifunctional design is based on three broadband Integrated Device Technology (IDT) F2972 single-pole-double-throw (SP2T) RF switches and also includes a control and power supply circuit. The composite structure has been developed using a preimpregnated structural glass (S-Glass) material (Hexcel HexPly 914E). The conductive tracks of the switch and its ground plane have been fabricated using a nonwoven carbon-nickel-copper (CNC) veil material and a semiflexible conducting silver ink. This article contains an analysis of the electrical properties of both materials at microwave frequencies. The equivalent electrical conductivities of materials were determined using a curve fitting method that was then used to verify the computational modeling of the switching network. The RF switching network was developed based on a hybrid manufacturing approach. The RF transmission lines and a component of the control circuitry were transferred onto uncured pre-preg material using a laser to ablate select regions of the CNC veil material. Postcuring, flexible silver ink was additively printed onto the surface to create the remaining control circuits. The RF performance of the design has been evaluated, and it indicates that the overall performance was consistent with the measured S-parameters of the same circuit fabricated on Rogers 5880 substrate.