October 20, 2021

What are FLEXWELL elliptical waveguides?

In this week’s blog, we look at another of our most popular flagship products – the FLEXWELL® elliptical waveguides. Since RFS pioneered the FLEXWELL solution in 1961, it has constantly evolved to meet the needs of our customers, and so we caught up with Gerd Bohnet, Product Manager Waveguides and Accessories at RFS to find out what makes this such a key solution for our customers.

Gerd Bohnet, Product Manager Waveguides and Accessories

Let’s start with the obvious question, what are FLEXWELL® elliptical waveguides?

The purpose of the elliptical waveguides is quite straightforward; waveguides are used for the transmission of RF energy, and combine the advantages of different cable types, optimizing the electrical and mechanical performance at higher frequencies. 

Part of the microwave family, the solution itself is an elliptical shaped metallic tube which is corrugated for flexibility. This allows the benefit of flexibility that comes with out range of corrugated coaxial cables but overcomes the fact that this solution has unacceptable attenuation at higher frequencies. The key to this product is the elliptical shape as it allows a defined polarization of the signal which in turn allows the best possible performance for our customers. To date, we have tens of thousands of kilometers of the waveguides deployed all over the world.  

How has the product evolved since its initial launch in 1961?

As you mention, this is one of our longest standing products with a 60-year-old history. It was designed by RFS as an improved alternative to rectangular and circular rigid waveguides which were the most common solution at the time for microwave applications. Despite being close to pension age, the solution is still a key part of the RFS microwave portfolio and has adapted over time to reflect the needs of the changing wireless world. 

The original solution was a big step up from existing alternative options, with the corrugated copper tube taking the length of continuous cable possible from a few meters, to several hundred meters for microwave applications. The waveguides have evolved over time, tracking the move from analog microwave systems with their high requirements for electrical performance, to digital systems which have enabled a much larger range of frequencies to be supported. What originally began as a product supporting between 3 and 6 GHz only, has now expanded to serve all frequencies up to 39.5 GHz. We also have a range of premium solutions up to 18GHz. They are now helping to address the huge demand for 5G data capacity which requires the maximum optimization of every component including waveguides and their accessories.

The latest development of our elliptical waveguides is the radiating waveguide which is used in tunnels. In-tunnel solutions are a huge part of our overall portfolio and so this development allowing frequency ranges up to 6 GHz and increasing the capacity of our tunnel systems enables us to further support our in-tunnel customers.  

What are some of the applications that FLEXWELL is being used for?

The main application our customers are using elliptical waveguides for is in long haul microwave links from 3.6 to 13 GHz. However, we’ve seen a greater range of applications develop in the last six decades. We have waveguides installed in a variety of businesses, particularly where they encounter challenges with accessing antennas after installation. Take the example of a microwave antenna installed on the top of a windmill. Usually, the outdoor unit would be installed directly next to the antenna, but in this case, to ensure access for maintenance it makes much more sense to install the outdoor unit separately and connect using elliptical waveguides. We see the same situation on electrical towers and the FLEXWELL solution prevents a choice between a practical deployment that enables easy, undisruptive maintenance access and a compromise on connectivity. 

Beyond microwave applications, our elliptical waveguides are used in earth stations for satellite application to connect the parabolic antennas with the transmitters. We see more and more potential for radar applications, particularly ASR (Airport Surveillance Radar) and CSP (Coastal Surveillance Radar) which are using elliptical waveguides to enable high power signals with very low attenuation which is important for the range of these radars. In short, there are various directions where the FLEXWELL solution can add value and we’re continuing to develop the technology to fully support these.

What role do you anticipate these solutions will play in the role out of 5G?

The example of antennas mounted on structures that work well from a location perspective but come with access challenges, will be increasingly common in 5G. As the number of sites increases and there is more creativity needed on how to expand infrastructure without spiralling costs, using existing structures is key to a low TCO, even if outdoor unit access then becomes awkward. Based on this, more and more sites will require outdoor units located away from the antenna to ensure access, and elliptical waveguides make this site set up feasible and cost effective.  

We also see a real opportunity with in-tunnel applications. Our radiating elliptical waveguide RE60 allows the use of WiFi at 6 GHz in tunnels which has not been previously possible due to high attenuation. The use of 6 GHz opens the door to high-capacity real time applications like autonomously controlled transport systems or video streaming in underground trains, so we are hugely excited to see what the future holds for FLEXWELL as a longstanding, but constantly moving technology.

If you would like to hear more about the FLEXWELL Elliptical Waveguides, get in touch with Gerd Bohnet, Product Manager Waveguides and Accessories at RFS.