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Part 2: Taking Compact High-Power RF to the Next Level

In Part 1 of this article, From Customer Request to Product Line, we discussed how a US Department of Defense customer requirement for a portable high-power RF wideband radiator launched an entire product line of cutting-edge systems and simulators. In Part 2, we will discuss more specifically how this technology adapted and matured to meet the testing needs of additional customers within the DoD and DoE.

High-Power Wideband RF: A Versatile Tool for Both Effects Testing & Defense

As we discussed in our 2021 blog post, Increased EMP Threats and Testing Standards, wideband RF is but one of several types of directed energy used by the DoD for assessing vulnerabilities and providing defensive countermeasures against things such as improvised explosive devices (IEDs), enemy electronics, and drone attacks. While ultra-wideband (UWB) and narrowband high-power microwave (HPM) each have their beneficial use cases, wideband RF systems have several unique strengths that make them ideal for a number of applications we will discuss later in this article. To begin, here is a brief listing of wideband RF’s inherent strengths:

  • Unique ability to generate extremely high electric field strengths (>100kV/m) in a compact/portable footprint.
  • Reduced system complexity (e.g. no vacuum hardware) aiding in reduced SWAP, increased reliability, and minimal maintenance.
  • Wideband frequency content can provide frequency-specific coupling into electronic systems by designing the center-frequency to match the target, while also providing enough energy across the spectrum to utilize backdoor coupling onto poorly defined targets.
  • While HPM systems can be limited in their repetition rate and duty-cycle by diode materials and the speed of vacuum systems, wideband systems can be designed to operate continuously in the tens of Hz, and in bursts up into the kHz.

Perhaps the number one weakness of wideband systems is their lack of directivity and range. However, their portability helps overcome this limitation by providing a lightweight system capable of fitting onto a deployable platform such as an unmanned aerial vehicle (UAV). (See: APELC’s RFXC-400) Moreover, by using a backing reflector, enough directivity can be achieved to protect the host while delivering a wide enough beam to illuminate a large swarm of drones. Something high-power lasers and some narrowband systems are incapable of. An illustration of this concept is presented in the figure below, which was taken from our blog High-Power Wideband for Counter UAS/UAV:

Figure 1 Illustration showing potential illumination of a drone swarm using a wideband radiator

Utilizing the Agility and Spectrum of Wideband Systems

Following the development of our RFSC-400 suitcase system, APELC now had in their intellectual arsenal a technology that could be scaled in both intensity and frequency. With the creation of MIL-STD-464C, the DoD Electromagnetic and Environmental Effects (a.k.a. E3 or E3) community suddenly had the need for a suite of sources capable of covering a wide portion of the RF spectrum from 30 MHz up to 300 MHz. Previous wideband and HPM systems had covered the upper requirement from Table A.5 of the MIL-STD, but no solution existed for the first three bands, as shown in the table below:

Table 1 Table A.5 from MIL-STD-464C

Initially, APELC saw this need and utilized our quick-disconnect connector to create a wideband test stand that could cover this range and beyond by quickly and easily swapping out antennas/resonators on a common, cable-attached compact Marx generator, as shown on our RFTS-DP-X wideband test stand in the figure below:

Figure 2 APELC’s RFTS-DP-X Wideband Test Stand

While the RFTS did it’s job in demonstrating a versatile test resource for the T&E and E3 communities, it wasn’t quite meeting the exact spectral and field requirements for all of our customers. As a result, APELC was awarded a contract to increase and mature this capability even further.

Meeting a New Standard with Higher Field-Strengths and Specifically-Designed Spectrum

The latest DoD requirement met by APELC called for a system that not only met the exact spectral requirements of the customer, but also needed to illuminate a very large test object (i.e. a vehicle) from a distance that allowed for even illumination in the far-field while also providing higher pulse repetition frequencies (PRF). By increasing the size of the Marx generator and designing it for rapid removal of the heat produced during high-PRF operation, APELC was able to create a new system that yielded the same frequency agility as the original RFTS with the additional capabilities of >400 Hz PRF, field strengths >500kV/m at 1m, and an extremely wide beam-width. The result a suite of wideband test-stands shown in the figure below:

Figure 3 APELC’s latest addition to the Wideband RF testing family

Careful engineering of the dipole antenna, resonator, antenna feed, and reflector provided the power and spectrum meeting the customer’s strict requirements. A plot of the required spectral content for two of the Table A.5 bands (the lowest band was covered using a system not shown in this article) and measured spectrum from the APELC wideband system is shown in the figure below:

Figure 4 FFT of the APELC Wideband System with 464C limit at 1m shown

A Swiss-Army Knife for the T&E Community

In case you couldn’t tell, APELC is very proud of these wideband systems. They represent a lot of hard work, ingenuity, and thorough engineering. Beyond that, we see their usefulness in a wide range of use-cases, and hope to convince you of the same. We don’t believe in creating a one-off system that gathers dust in a DoD storage building. We want these products out there helping to save lives and protect our nation! Based upon our own research and input from the T&E community, here is a comprehensive, though not complete, list of use-cases for these high-power wideband RF systems:

  • Counter UAS/UAV/drone defense for large swarms
  • Portable/deployable directed energy systems
  • Electronic effects and vulnerability testing
  • Vehicle stopping
  • Critical infrastructure testing against intentional electromagnetic interference (IEMI)
  • Research into high-power RF biological effects to ensure the protection of personnel

We hope you enjoyed this brief history of one of APELC’s many technological accomplishments. If you found it interesting and would like to learn more, you can learn more by:

We look forward to chatting with you soon!

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