Multilayer microwave circuit processing technology is required to develop more compact and affordable Radio-Frequency (RF) sub-assemblies for the next generation of aircraft and radar. Present microwave IC technology needs to be reengineered for its ability to increase its functionality levels with necessary concominant reduction in cost and size. The size reduction in current technology is limited because it is 2D, planar technology. Recent developments for more compact sub-assemblies extend this technology to multilayer system components. The active devices are still placed on the substrate and various circuit elements are interconnected through the upper layers to obtain shorter path lengths and in some cases, limited passive elements are also placed on the upper layers. In this resrach work, an innovative vertically interconnected multilayer monolithic microwave (M3) integrated circuit approach is presented. As shown in the figure, dielectric films sandwiched between metal layers are the building blocks for this new technology. A metal layer (ground plane) a second metal layer (circuit plane) and the third metal layer (ground plane) separated by dielectric layers constitute a subsystem-layer. Subsystem layers may share ground planes. On each subsystem-layer, various circuit elements are processed on the circuit metal layer and the subsystem layers are then interconnected by vertical posts and/or by slots.
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