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16 DESIGN007 MAGAZINE I FEBRUARY 2024 from phased array antennas and Ka/Ku-band radar technologies typically used in defense applications. ese robust systems have paved the way for AESA products that can dynami- cally control beam direction and target specific communication devices. However, as these technologies migrate from the defense and space sectors to commercial markets, chal- lenges arise for designers who may not have extensive experience with AESA systems. One particular concern involves managing the lim- ited surface area on PCBs while adhering to tighter routing requirements and accommo- dating a higher layer count. Fortunately, a solution exists in the form of embedded resistor copper foils. ese inno- vative materials seamlessly integrate resistors directly into the inner layers of the PCB, free- ing up valuable surface space for active compo- nents. is frees designers from the constraints of discrete SMT resistors, enabling them to create smaller, lighter, and more efficient PCBs for high-frequency applications. Beyond the immediate space savings, embed- ded resistors offer a multitude of advantages: • Simplified design and manufacturing. By eliminating the need for additional components, soldering, and routing vias, embedded resistors streamline the PCB design and manufacturing pro- cess. is translates to faster turnaround times, reduced assembly errors, and improved overall manufacturability. • Improved electrical performance. Reduction in parasitic capacitance and inductance is realized compared to surface mount components with reduced metal-to-metal transitions and elimination of vias on critical nets. • Enhanced PCB reliability. e integration of resistors within the PCB layers during lamination strengthens the entire struc- ture. is results in enhanced mechanical and electrical stability, leading to longer component lifespans and increased system reliability. • Cost optimization. Although the copper foil itself incorporates the resistors, their presence doesn't necessitate additional material and only requires a few additional processing steps. is eliminates the need for discrete SMT resistors and their associated procurement, storage, and placement costs, contributing to overall cost savings. • Reduced PCB size and weight. e thin- film nature of embedded resistors allows them to reside within existing PCB layers without increasing overall thickness or requiring internal cavities. is enables the creation of smaller, lighter boards, crucial for applications like handheld devices and satellites where every gram counts. • Resistive "blank slate." Utilizing the printed circuit board imaging process allows the foil to be customized into vari- ous structures. is enables it to be used as a radar-absorbing material, in resistive cards (R-cards) as well as high-impedance surfaces (HIS) and frequency-selective surfaces (FSS). Figure 1: An example of a flat-panel active electronically steered array (AESA) radar system.