S2 Corporation
Photonic Spatial Spectral Holographic Signal Processing Technology

Today, a variety of system designers working in communication, infrastructure, instrumentation, aerospace, and defense applications are facing complex challenges of the ever-increasing bandwidth demands in a complex and highly congested radio frequency (RF) spectrum. Against this backdrop, Dr. Kris Merkel, President and CEO of S2 Corporation, and the fellow founders of the company have spent the lion’s share of the last fifteen years engaged in the R&D of a unique photonic signal processor and receiver. Realizing that the concept shouldn’t be confined to the physics departments of universities’ laboratories, the company was determined to develop a broad-use RF spectrum analyzer and signal processor for critical, wide instantaneous bandwidth applications, based on the key idea of using a crystal doped with a rare-earth element as the core component.

In doing so, S2 has pushed boundaries of innovation to develop wideband sensing and expanded RF signal processing and monitoring capabilities in dynamic environments. “Our vision was to get the technology out of the lab, with mature components, as well as attain progress through different stages of development to reach a consistent level of efficiency and functionality,” begins Kris. Since its inception, the company has provided revolutionary RF and signal processing solutions using its proprietary photonic spatial-spectral (S2) holographic technology. The system concept is an Extreme Bandwidth Analyzer and Correlator (EBAC), which enables a variety of applications in electronic warfare and signals intelligence, analog signal processing, mining, and continuous RF monitoring, along with offering other groundbreaking capabilities. This enables S2’s Spectrum Analyzer to stand out from today’s conventional electronics and photonics market competition, with its wideband stare and adaptive functionality. Recalling S2’s efforts for developing the EBAC system, Kris says, “As a company, we took on this long-term challenge of changing the paradigm of radio spectrum awareness and signal processing.”

The Radio Spectrum in a Flash

S2 Spectrum Analyzer’s unique processing capability makes it well-suited for RF signal detection and general signal processing. The system offers a 100 percent probability of intercept (POI) in awareness with high fidelity for RF spectrum monitoring. Its base EBAC is currently configured to process radio frequencies between “0.03 to 110 GHz and beyond, instantaneously in large bandwidth swaths as limited by the antennas and RF front ends.

As a standard capability, the S2 wideband radio frequency Spectrum Analyzer detects RF frequencies fed from extreme-bandwidth RF antennas, then converts them into a modulated laser beam that is an optical carrier for the signals and processes them through the absorption of the light by the crystallized material. A massive amount of information is processed in minimal time. For some applications, this is simply pre-filtering of the analog input signals from RF antennas to detect energy and remove noise. This can eliminate the need to digitize the entire radiospectrum for signal detection and thus improve the efficiency of subsequent required digital signal processing operations. Other applications based on correlation or pattern matching may not use a conventional digitizer at all.

A baseline sector where S2’s Spectral Analyzer displays its outstanding performance is in test and measurement, where the system provides continuous pictures of the RF spectrum (such as that shown in the backdrop) and helps the users generate signal data with high sensitivity. There are typically 1000’s of full-spectrum measurements generated per second, which, when compared to a conventional spectrum analyzer, either the super-heterodyne swept carrier design or a stepped digital capture window across frequency, only achieves < 1 percent of the instantaneous bandwidth coverage and with similar sensitivity.

Elaborating more on the practicality of S2’s EBAC, Kris states, “The system can be set up essentially anywhere, and thus does not require large hardware to be located near the antenna. The user can connect fiber optic cables from the antennas to the system and create a fiber-optic network of RF coverage.” Owing to this capability, users can install antennas in hard-to-reach places, whether on top of a tower, at the edge of a secured area, or within the walls of a building. Another unique aspect of the S2 Spectrum Analyzer is that it can be customized for users’ specific bandwidth requirements and applications such as data mining, geo-tracking, waveform generation, and more.

Designed and developed by its team of in-house engineers, the EBAC system’s critical components consist of photonic components built around a small, “sugar-cube” sized cooled crystal. With the need for a cooling system for the crystal, S2 developed its own additions for the rugged and smooth operation of commercial, low-temperature coolers. As for the crystal, the doping atoms encompass atomic-scale memory and inherent large-scale parallel processing, with the extremely wideband optical absorption lines. These lines are formed due to multiple stacks of absorption resonances, each with an ultra-narrow high-resolution spectral response. Thus, the atoms in the crystalline structures remember when and how they were illuminated by the laser beam doing massive frequency analysis functions continuously. “The crystal-based hardware is in essence an optical computer. This is not going to replace your laptop, but it works as a multi-configurable processor that performs massive Fourier transforms very efficiently,” explains Kris.

Shaping a New Paradigm in Radio Frequency and Data Signal Processing

S2 was established in the quiet mountain town of Bozeman, Montana, world-renowned for offering adventure and nature enthusiasts to develop, advance, deploy, and commercialize its revolutionary spatial-spectral holography technology. Over the years, the company has collaborated extensively with Montana State University and has 20 patents issued or pending for its revolutionary EBAC technology. Currently, it is actively working with several organizations, including large companies, the Montana Photonics Alliance, and National Spectrum Consortium, to name a few.

Since its first successful field test over ten years ago, S2’s EBACtechnology has progressed remarkably. Its latest versions use smaller and more rugged components that are significantly more power-efficient than conventional systems. Considering how S2’s technology can detect even the weakest RF signals and efficiently provide a view of the full spectrum in real-time, its ability to supervise the electromagnetic spectrum appears clear. The sheer speed and scale at which the company’s solution processes signals enable users to execute defense operations with high accuracy, efficiency, and reliability in real-time. The US Department of Defense has awarded S2 Corp contracts to advance and expand its spectrum analyzer’s electronic warfare applications. Last year, the company started a new project with the Defense Advanced Research Projects Agency (DARPA) to prototype and demonstrate a broadband, electro-magnetic spectrum receiver system.

Today, the company has proven itself as a pioneer and is shaping a new paradigm in RF and data signal processing with its innovations for years to come. Speaking about the philosophy of S2, Kris replies, “We are risk-takers and innovators, who are very passionate to see this innovation benefit its users.” As part of its latest endeavors, S2 is now executing a low-rate production strategy. In parallel, the company is working on developing multiple platforms that will enable fixed-ground and hybrid capabilities. “Our vision is to dominate the RF spectrum analysis sector across many applications by reshaping the concepts of awareness and adaptation in real-time,” concludes Kris.