About Castelion

Castelion is bringing a new approach to defense development and production: one that focuses on short, iterative design cycles, rapid testing in development, and modern commercial manufacturing strategies for production at scale. We're designing, building, and testing next generation long range strike weapons systems to give America and its Allies a definitive edge and deter future conflicts.

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

All employees are granted long-term stock incentives as part of their employment as Castelion. All employees receive access to comprehensive medical, vision, and dental insurance, and the company offers three weeks of paid time off per year.

Leadership Qualities

Bias to Action and Creative Problem Solving. Desire and experience questioning assumptions in ways that lead to break through ideas that are ultimately implemented. Successfully bring in applicable processes/concepts/materials from other industries to achieve efficiency gains. Ability to personally resolve minor issues in development without requiring significant support.

High Commitment, High Initiative. A successful candidate will have a genuine passion for Castelion's mission and consistently look for ways to contribute to the company's technical goals and prevent hardware blockers. Ability to work in a fast paced, autonomously driven, and demanding atmosphere. Strong sense of accountability and integrity.

Clear Communicator. Proactively communicates blockers. Trusted in previous roles to be voice of company with regulators, suppliers, gate keepers and customers. Capable of tactfully managing relationships with stakeholders to achieve company-desired outcomes without compromising relationships. Emails, IMs and verbal interactions are logical, drive clarity, and detailed enough to eliminate ambiguity.

ITAR Requirements:

• To conform to U.S. Government export regulations, applicant must be a (i) U.S. citizen or national, (ii) U.S. lawful, permanent resident (aka green card holder), (iii) Refugee under 8 U.S.C. § 1157, or (iv) Asylee under 8 U.S.C. § 1158, or be eligible to obtain the required authorizations from the U.S. Department of State.

Employment with Castelion is governed on the basis of competence and qualifications and will not be influenced in any manner by race, color, religion, gender, national origin/ethnicity, veteran status, disability status, age, sexual orientation, gender identity, marital status, mental or physical disability or any other legally protected status.