Senior RF Systems Engineer

Why Castelion, Why Now Castelion is moving incredibly fast to develop and deliver advanced defense systems at a time when execution matters more than ever. We believe focus, ownership, and excellence are decisive advantages - and we're building a world-class team to turn bold ideas into real capability. This is a rare opportunity to join at an early stage, where you'll have significant ownership, collaborate with exceptional teammates, and make a direct, measurable impact on our mission and the future of the company - regardless of your function. Senior RF Systems Engineer Castelion is building next-generation, high-performance systems where cost, scale, and speed matter as much as technical excellence. We are looking for an RF Systems Engineer to lead the design and development of a multi-channel exciter/receiver subsystem that interfaces between RF hardware and digital baseband systems. In this role, you will own the subsystem end-to-end (from architecture and design through production) ensuring it is performant, affordable, and producible at scale. You will not be starting from scratch. You will work within an existing system architecture, leveraging established concepts, infrastructure, and a high-performing team to rapidly iterate and improve the design. Success in this role requires someone who can build on what exists, make it better, and deliver without reinventing for the sake of it. This is not a lone-wolf role. You will be the missing piece in a tightly integrated team of engineers across software/firmware, power, manufacturing, and test. You will operate as a technical leader within that team, collaborating closely, making trade-offs, and driving the subsystem to production readiness. Responsibilities • Own the exciter/receiver subsystem end-to-end as both systems engineer and RF design lead, driving architecture, design, integration, and production readiness • Design and deliver a multi-channel RF system bridging RF front-end and digital baseband, optimizing for performance, cost, and manufacturability • Lead RF system modeling and analysis, including phase noise, spur analysis, gain, noise figure, compression, and dynamic range • Execute hands-on design validation and debugging in the lab, using RF test equipment to ensure performance and reliability • Partner cross-functionally with software, firmware, power, manufacturing, and test teams to ensure seamless system integration and scalable production • Collaborate with suppliers and fabrication partners to optimize RF PCB designs, improve technical performance, and reduce cost • Develop and influence test strategies and infrastructure that achieve lower cost and higher throughput than traditional approaches without sacrificing screening effectiveness • Drive design decisions that enable aggressive production goals and ensure resilience to supply chain disruptions • Deliver a solution that meets a target cost, significantly improving on traditional system costs • Establish a production-first standard for the subsystem, improving design quality, reducing preventable errors, and minimizing the need for day-to-day oversight • Strengthen supplier relationships and technical engagement, enabling better responsiveness, more sourcing flexibility, and improved design-for-manufacturing outcomes • Consistently balance and deliver strong technical performance within real-world constraints such as cost, schedule, and manufacturability\ Basic Qualifications • Bachelor's or Master's degree in Electrical Engineering, RF Engineering, or related field • Experience with high-frequency RF PCB design • Proficiency in RF system modeling and analysis • Hands-on experience with RF lab equipment and testing • Ability to design and analyze complex RF systems from architecture through implementation Preferred Skills and Experience • Experience designing RF systems including phase noise budgeting, spur analysis, RF system synthesis, and performance modeling • Experience working with PCB fabrication houses to realize RF structures, including understanding fabrication limits and cost drivers • Experience with RF simulation tools such as ADS, HFSS, or CST, including design verification and iteration • Familiarity with supplier capabilities and constraints across RF components and fabrication • Experience developing or supporting production test strategies Castelion offers a generous benefits package. Please refer to the bottom of our Careers page for more details. Other Duties Please note this job description is not designed to cover or contain a comprehensive listing of activities, duties or responsibilities that are required of the employee for this job. Duties, responsibilities and activities may change at any time with or without notice. Additional Eligibility Requirements This position may require access to classified information or restricted U.S. Government sites, systems, or information, as determined by the Company and/or applicable U.S. Government requirements. If the position is so designated, your employment in the role may be contingent upon your ability to obtain and maintain the required U.S. Government security clearance or other government authorization, and to satisfy any citizenship or other eligibility requirements imposed by applicable law, regulation, executive order, or government contract requirements. You will be notified if and when such requirements apply. Affirmative Action/EEO Statement Castelion is an Equal Opportunity Employer. We are committed to providing equal employment opportunities to all applicants and employees without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, age, disability, genetic information, protected veteran status, or any other characteristic protected by applicable federal, state, or local law. Castelion is committed to providing reasonable accommodations to qualified individuals with disabilities throughout the application and hiring process. If you require a reasonable accommodation to complete an application, participate in the interview process, or otherwise participate in the hiring process, please contact hr@castelion.com. Requests for accommodation will be considered on an individual basis and handled in accordance with applicable law. Castelion is committed to fostering a workplace where employment decisions are based on qualifications, business needs, and the ability to perform the essential functions of the role, with or without reasonable accommodation. EAR/ITAR Requirements This position requires access to export-controlled information, and as such, employment (or hiring of a contractor) is contingent upon the candidate’s ability to access all applicable export-controlled information without additional export licensing being required by the Bureau of Industry and Security and/or the Directorate of Defense Trade Controls.