The Rise of Ka-Band Solid State Power Amplifiers (SSPAs) in Teleport Technology

For years, Ka-Band solid state power amplifiers (SSPAs) were rarely used for high data rate transmission. Unable to offer the kind of reliability or cost-effectiveness that broadcasters needed, professionals passed over them in favour of Travelling Wave Tube Amplifiers (TWTAs) for most applications. 

In 2024, the poles have reversed. Modern Ka-Band SSPA capabilities are almost unrecognisable compared to their counterparts of previous decades. Sector titans like SpaceX (Starlink), Amazon (Project Kuiper) and Telesat (Project Light Speed) have all made Ka-Band a central pillar of their global internet coverage and satellite communication operations, and more of this capability is down to SSPA technology. 

What’s changed? Put simply – weather mitigation and technology. Traditionally the Achilles heel of Ka-Band transmission, sensitivity to rain and other atmospheric conditions were a vulnerability of the frequency. With a number of technological developments now at hand, this weakness has largely disappeared.  

Resistance to rain fade was the saving grace of  the C and Ku-Band frequency. Now with new modulation schemes and improvements in the whole RF chain, the strengths of Ka-Band systems come shining through. 

Ka-Band Solid State Power Amplifiers (SSPA) outperform TWTA technology in almost all areas, including: 

1. Reliability 
2. Energy efficiency 
3. Size and weight 
4. Linearity and spectral purity 
5. Thermal management 
6. Instant On/Off 
7. Lifetime cost 

Despite its technical dominance, SSPA technology continues to wait in the wings for many who choose to stick with their legacy systems. Old habits understandably die hard in satcom, where any risk to signal consistency is critical and upfront costs for new infrastructure are sometime hard to justify. 

In an industry where maximising data transmission rates and efficiency at the lowest cost is the name of the game, slow action on Ka-Band BUC’s might turn out to be the riskiest choice. 

Why the rain problem has faded for Ka-Band  

Ka-band frequencies (28.5 to 31 GHZ) are significantly affected by rain and other atmospheric conditions – commonly termed “rain fade”.  This can cause signal attenuation and degradation during heavy rainfall, which means decreased signal strength, reduced data rates, or even a temporary loss of signal. 

C and Ku-Band using TWTAs are traditionally favoured in high rain regions throughout the globe due to their higher output power, allowing them to overcome some signal attenuation – though at the cost of efficiency and bulkiness compared to SSPAs. 

Recent years have seen a proliferation of mitigation techniques to shield Ka-Band setups from the rain fade threat, providing transmission resilience in all but the most extreme weather. They include: 

Adaptive Coding and Modulation (ACM) 

This technique dynamically adjusts the modulation scheme and coding rate based on current weather conditions to maintain a reliable connection. 

Power Control 

Increasing the transmission power during heavy rain can help compensate for signal loss. 

Diversity Techniques 

Using multiple antennas or sites (spatial diversity) can provide alternative signal paths, reducing the likelihood of complete signal loss. 

Weather Prediction Models 

Implementing prediction models helps in anticipating and mitigating the impact of rain fade. 

Backup Links 

Establishing backup links in different frequency bands (e.g., Ku-band or C-band) can help provide  resilience. 

Different mitigation techniques might be relevant for you depending on your infrastructure, environmental conditions, and performance requirements. Careful consideration of the rain fade risk profile, and the appropriate choices for mitigation, are critical for operators during the design and implementation phase of Ka-Band ground systems. 

Ka-Band SSPA vs. TWTA: A technical comparison 

With the rain fade issue largely nullified and SSPAs narrowing the gap in terms of raw output power, the scales are tipping when it comes to optimal infrastructure configurations. Let’s look at the key areas in which solid state power is going toe-to-toe with the incumbent travelling wave tube amplifier. 

Reliability 

SSPAs have no internal moving parts,  significantly enhancing their reliability and longevity. You’ll typically find them to have much longer operational lifespans and require less maintenance than TWTAs and their electron tubes. 

The performance of the tubes can degrade over time, leading to higher maintenance needs and shorter lifespans for your equipment. 

Energy efficiency 

Generally, SSPAs are more energy-efficient than TWTAs. They convert more input power into RF output power, resulting in lower power consumption and operational costs. TWTAs are less efficient, demand more power, and lose  a significant portion of their input power as heat. 

This has important implications for your bottom line, as TWTAs become a more expensive operational cost  over time. 

It’s more costly for the planet, too. Higher energy usage  means a higher carbon footprint and greater costs. SSPAs might emerge as an increasingly important step towards sustainable operations. 

Size and weight 

SSPAs are typically smaller and lighter, making them easier to integrate into various systems. They are ideal for applications where space and weight are critical considerations, such as in teleports and mobile communication units. 

TWTAs are generally bulkier and heavier, which can be a drawback in space-constrained applications. Overall, you can expect your SSPA system to occupy less space than a tube-based amplifier.  

Linearity and spectral purity 

At high frequencies like Ka-band, even minor non-linearities can significantly distort your signal. This can lead to increased errors, data corruption, and reduced signal integrity. 

SSPAs offer better linearity and spectral purity, which is crucial for good quality signal transmission, particularly in high-frequency bands like Ka-Band. 

While TWTAs can provide high power outputs, they may suffer from non-linearity issues that can degrade signal quality. 

By choosing SSPAs, you will minimise the occurrence of signal distortions and other unwanted frequency components. 

Thermal management 

Due to their higher efficiency, SSPAs generate less heat, simplifying thermal management requirements. This can lead to more compact and less complex cooling solutions, likely resulting in lower maintenance headaches and reduced operating costs. You’ll be able to configure your SSPAs in dense or specific ways, allowing for a greater range of solutions to meet the requirements of any project. 

TWTAs produce more heat, necessitating more robust and often more cumbersome systems for cooling, with knock-on impacts for your energy costs, carbon emissions and the size of your equipment. 

Instant On/Off 

SSPAs can be turned on and off instantly without warm-up or cool-down periods, providing greater operational flexibility. You’ll be able to shut your amplifiers down when not in use, or turn off some units if full capacity isn’t required, saving energy and money. 

TWTAs typically require a warm-up period before they can operate at full capacity and a cool-down period after use, so are often operated for larger periods of time and when they aren’t fully required. 

Lifetime cost 

Although the initial cost of high powered SSPAs could be more expensive, their lower maintenance requirements and longer lifespan can lead to lower total cost of ownership over time. 

In modern satellite communication applications, efficiency, reliability, and performance are paramount – and shine a light on SSPAs as the ideal choice for forward-looking operations. 

In modern satellite communication applications, efficiency, reliability, and performance are paramount – and shine a light on SSPAs as the ideal choice for forward-looking operations. 

Closing thoughts 

With the weather related risks clearing away for Ka-Band systems, it’s fast becoming the high-capacity transmission frequency of choice. 

Reduced weather risks mean that within the Ka-band options, cost-benefit calculations have shifted in favour of SSPAs. They’re quickly pulling ahead in a number of key performance areas, offering operators a range of impressive output, reliability and sustainability gains. 

At Milexia, we understand the constant need to balance between reliability and cost effectiveness when developing satcom infrastructure. It’s clear that the new generation of Ka-Band SSPAs offer unprecedented flexibility, along with a tranche of new efficiencies, for operators with an eye on the future. 

As a leading value-added distributor of satcom equipment, connected to globally leading suppliers, Milexia is perfectly placed to advise on the best hardware and designs for high-performance satcom operations.  

Whether you’re looking to construct new Ka-Band infrastructure, move up from a legacy system, or simply boost performance, SSPAs are certain to play a role.