Enabling Phase Coherency In Compact RF Systems

The architecture of radio frequency (RF) systems and software-defined radios (SDR) has seen a seismic shift from single antenna systems to multi-antenna architectures. The move from single input single output (SISO) to multiple input multiple output (MIMO), single input multiple output (SIMO), and multiple input single output (MISO) architectures has opened up a wealth of opportunities for richer signal and spectrum analysis. This progression, however, introduces new requirements, with phase coherency topping the list.

Multiple antennas and RF channels allow the user to extract significantly more information from the signals and spectrum that the radio operates on, but it also creates new requirements that the radio must meet. A key requirement for multi-channel SDR and RF systems is phase coherency — the concept of having multiple RF receive or transmit channels able to simultaneously operate on the same frequency and phase.

Phase Coherency: A Requirement for Modern RF Systems

Understanding and leveraging signal propagation in real-world scenarios is no small feat, especially when it comes to applications like direction finding, time difference of arrival (TDoA), phased array radar, and beamforming. These applications all share one common requirement: phase coherency.

In a nutshell, phase coherency is all about having multiple RF receive or transmit channels that can:

• Operate simultaneously on the same frequency
• Maintain consistent phase

Without this, you're missing out on understanding information about the propagation of the desired signal that could be critical for your operations.

At Epiq Solutions, we recognize these needs and strive to build solutions that not only meet but exceed these requirements. Our focus on phase coherency has been instrumental in enhancing the capabilities of our SDRs. But don't just take our word for it! In our detailed white paper, you'll find an in-depth exploration of the concepts, challenges, and innovative solutions we've come up with.

See how Epiq Solutions addressed phase coherency challenges in our detailed white paper.

If you're keen on understanding the ins and outs of phase coherency and how it impacts your work, this white paper is a must-read!

Achieving Phase Coherency

The frequency aspect of phase coherency is an easier problem to solve. As long as a common reference clock is distributed to all local oscillators in the radio, the resulting RF conversion stages should, by design, operate on the same frequency. However, the phase aspect of phase coherency is a challenge for an RF or SDR designer. Even small variations in RF cable or PCB trace length matching, clocking configurations, or system temperature can cause phase errors or drift across the RF channels. This requires a cross-disciplinary team to tackle these challenges, ensuring that the RF front end, RF transceiver, FPGA, and clock network are all operating in a coherent manner.

To overcome these hurdles, we need an interdisciplinary approach, ensuring that the RF front end, RF transceiver, FPGA, and clock network all work together. Here at Epiq Solutions, we have embraced this challenge and developed solutions that effectively manage phase coherency, thus facilitating rapid application development and deployment for multi-channel SDR and RF systems.

How Epiq Approaches Phase Coherency

To achieve precise phase coherency, we employ a combination of advanced techniques including phase-locked loop (PLL) synchronization for the local oscillators, careful PCB design to ensure equal trace lengths, and temperature stability. Phase coherency is a released feature on the Sidekiq™ M.2, MiniPCIe, Stretch, X2, and X4. And with the latest release of libsidekiq, this capability is also being introduced to the Sidekiq™ NV100. Adding this capability to the NV100 is critical, as this SDR offers a unique combination of high performance RF with very low SWaP, making it ideal for small form factor vehicles, like UAS payloads. Those payloads are often very limited in power consumption but still require high-performance RF applications, like beamforming and direction finding. Integrating phase coherency into the NV100 itself reduces the system complexity and helps Epiq’s customers more easily realize a complete solution.

Phase coherency is not just a critical requirement—it's a key enabler for the next generation of RF and SDR systems. With Epiq Solutions at the helm, we're opening the door to innovations that will redefine the future of RF technology.

Learn more about the NV100 and other Epic's phase-coherent SDRs