COFFEE Program to Develop Dual-Use RF Filters for Defense Systems, 6G and More

July 21, 2025

Spectrum is a limited resource, and demand is rapidly increasing. From satellites to smartphones, commercial providers are vying for more radiofrequency (RF) spectrum to support the rollout of 6G technologies. However, expanding commercial access risks interference with incumbent Department of Defense (DoD) systems, including advanced radar platforms. RF filters offer a potential solution, enabling coexistence by mitigating interference between commercial and military users. However, traditional filters lack the small form factor and versatile frequency ranges necessary for advanced radar and next-generation communication devices.

The COmpact Front-end Filters at the ElEment-level (COFFEE) program is developing a new class of ultra-compact, high-performance RF filters designed to integrate directly into the elements of advanced antenna arrays. These filters can isolate or suppress unwanted signals with exceptional precision, mitigating interference in congested environments.

In its first phase, COFFEE created breakthrough technical advances in fundamental filter technology. Now, COFFEE has launched a new technical area to integrate breakthrough filter technology into real-world systems and demonstrate next-generation performance across the defense and commercial domains. This comes at a pivotal time, as the Federal Communications Commission prepares to auction off more RF spectrum for commercial 6G and satellite communications.

“COFFEE is about more than filters, it’s about enabling our systems to adapt, avoid interference, and perform critical functions in a crowded space,” said Dr. Todd Bauer, program manager in DARPA’s Microsystems Technology Office. “By enhancing defense operations and commercial capabilities, COFFEE seeks to strengthen both national security and economic dominance.”

From Breakthrough to Demonstration

COFFEE launched in 2022 to address a core technical challenge: How to protect every element of a wideband, digitally addressable active electronically scanned array (AESA) from signal interference, without sacrificing performance, size, or power. AESAs are foundational to modern radar, communications, and electronic warfare systems, but as their bandwidth increased to accommodate more functionality, so did their exposure to jamming and interference.

In the initial technical area, COFFEE performers developed filters spanning 2–18 GHz, a particularly valuable slice of the spectrum used by both military and commercial systems for critical applications including radar, satellite communications, and wireless data transmission. The filters also surpassed the current state-of-the-art in terms of miniaturization, signal strength maintenance, and power tolerance.

Now, in the second technical area, the program is moving to system-level demonstrations. Throughout this phase, teams will integrate COFFEE filters into functional hardware to validate performance in operational settings. A key goal is to highlight COFFEE’s dual-use impact: enabling more resilient defense systems while also supporting commercial platforms, such as 6G and satellite communications.

This second stage will also demonstrate the technology’s potential for high-volume manufacturing – a critical step toward establishing a sustainable filter supply for both DoD and commercial markets after the COFFEE program concludes. Scalable production will help position the technology for deployment in next-generation infrastructure, from cellular base stations to, potentially, mobile handsets.

“We’re entering a new technical phase, where COFFEE leaves the lab and enters the real world,” said Bauer. “It’s an important step toward ensuring military and commercial technologies can safely share and maximize the spectrum we all depend on.”

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