Creating a Digital Gateway for RF Domain Will Advance Designs That Meet DoD Initiatives

June 1, 2023

As the Department of Defense (DoD) prepares the military for the evolving needs of the 21st century battlefield, its focus is on emerging technologies that enable all domain operations, from cyber to the electromagnetic spectrum. In parallel, the DoD continues to pay close attention to the fundamental supply-chain building blocks of future weapons systems ranging from open standards and smaller form factors to cost controls and supply chain strengthening.

Fundamentally, controlling the battlefield starts with managing the electromagnetic spectrum, whether for communications, guided munitions, or electronic warfare (EW). Successful platforms will require technological innovation and smaller, more cost-effective solutions that can be developed and produced rapidly.

Defense contractors are looking for RF miniaturization and integrated RF and digital control in the same compact package (figure 1). Smaller RF packages and more densification opens up the capacity to add more transmit/receive channels or additional systems. It also adds complexity and creates design challenges.

To meet these obstacles, RF suppliers must make dramatic evolutionary steps in design, materials, packaging, and manufacturing processes. And all of this must come together and integrate into the digital weapons systems of the future. Traditional Integrated Microwave Assemblies (IMAs) with chip-and-wire-in-metal packaging have physical constraints and do not have digital control circuitry due to isolation issues.

A new approach must be imagined; one that integrates RF and digital engineering teams and breaks down the old silos. Where these teams once operated independently, they must come together to create truly unified solutions.

RF and Digital Silos

Many RF suppliers have few, if any, digital engineers. When RF and digital teams coexist in a company they are typically organized into different groups with little or no systems engineering function. Lack of collaboration in the past had as much to do with mindset than any other factor.

There are two distinct thought processes between RF and digital design teams. Digital engineers are concerned with specifications, such as clock rates, speed of internal devices, storage, memory, and most importantly, software. Conversely, RF designers focus on other functions, including impedance traces, VSWR matching, and noise created by system components based on the board layout. RF engineers also are concerned with voltage, high slew rates, noise, and other factors associated with digital circuitry that can degrade RF performance.

Compounding the differing mindsets is that each design team wears virtual blinders. Both engineering groups are so focused on their responsibilities and concerns that they have a blind spot towards each other. Their eyes only become open when the RF and digital elements need to be integrated into the component or module. The result is a design nightmare.

Often, engineering teams must design a “back-door” late in the process to overcome calibration and overall compatibility issues. This added step leads to multimonth delays in development schedules and days to every single device that is tested. Subsequently, design costs increase.

The Solution – Integrated Systems Engineering

As outlined above, addressing the DoD initiatives is about more than technology. A new engineering approach and mindset are required. Every aspect of the system design must be considered initially, prior to beginning the RF design. Digital engineering teams must work side-by-side with RF engineers, so digital controls with RF functions can be developed synergistically.

The result is implementing advanced technologies to create a digital gateway into the RF domain. It will streamline the process, while creating an efficient design path for Sensor Open Systems Architecture (SOSA)-aligned products because they create flexibility, testability, and extendibility.

This digital gateway into RF can be created with a common software interface similar to a digital card, creating a clear communications path. The result is compatible functionality, including circuitry and voltage. With the gateway, RF engineers have a clear vision of the digital aspects, such as calibration controls and temperature compensation. Digital and RF designs are then right sized for the specific project.

A digital gateway facilitates a new level of software control delivering a greater level of RF flexibility, interoperability, and mission agility. RF controls and software can be integrated seamlessly and efficiently. Many issues and problems associated with the more traditional approach are eliminated, creating a time savings.

The development of this digital gateway that serves as a common interface creates a plug-n-play RF solution. There are three main benefits realized with the new design approach include on-time delivery, repeatable RF performance and faster modifications. RF designs are notorious for being delayed. Plug-n-play RF solutions solve this dilemma so that timelines are much more frequently met. The creation of the digital gateway results in RF solutions that are functionality similar, so every system is more efficiently developed. The DoD initiative for shorter timelines and development cycles is met. Military/aerospace systems can be modified much faster using this approach because all that is necessary is software enhancements. Traditional RF systems also had a hardware upgrade requirement, which resulted in longer turnaround times. What had traditionally taken months or a year can now be done in days or weeks. Adaptability such as this is critical in the 21st century battlefield.

A New Generation of Modules

Efficient integration of RF and digital technologies are cornerstones to a new generation of digitally enabled RF/microwave solutions that support producibility, maintainability, and built-in test (BIT) and align with SOSA. They can help engineers design solutions to meet stringent size, weight, power, and cost (SWaP-C) constraints from the DoD, as well.

Two other foundational pieces to support the military’s stated goals that cannot be overlooked are filtering and packaging. Advanced filtering is an enabling technology for an open-ready, hierarchical, secure digital control architecture. It allows for the design of RF systems-in-package (RF SiPs) that meet SOSA and SWaP-C requirements. One example of such a solution is the RF SiP shown in figure 2. It combines the RF, power, and digital circuitry of a traditional IMA for one-third the cost and occupies less than one-quarter of the space. 3D packaging technology can provide significantly higher densities with full RF isolation to meet SWaP-C requirements. 3D glass acts as a superior insulator compared to traditional semiconductor technology and is more economical. It also leads to faster development cycles.

Modern military/aerospace systems are being designed in smaller packages on open architectures and with greater complexity. A digital gateway into the RF domain creates plug-n-play RF solutions that meet the design requirements, while also addressing the cost reductions and development cycles sought by the DoD.

This article was written by Ian Dunn, Chief Technology Officer, Spectrum Control. For more information, visit here .

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