TWT

The « Export Restriction Free Travelling Wave tubes Materials » (ERFTM) project is an HORIZON 2020 SPACE Research and Innovation Action, within the frame of “Technologies for European non-dependence and competitiveness” (COMPET-01-2015), starting on April 1rst 2016, with a three years duration.

The ERFTM project aims to develop new European manufacturing processes for preparing material components of power amplifiers based on Travelling Wave Tubes (TWT) for space and ground applications, using raw materials not governed by Export Restriction comprising an helix made with flat ribbon maintained by ceramic support rods.

The studies will advance work from Technology Readiness Level (TRL) 3 (corresponding to experimental proof of concept) to TRL 6 (technology demonstrated in industrially relevant environment), in compliance with the non-dependence action “U7 – Power Amplification TWT materials” as described in the Joint Task Force (European Commission, European Space Agency, European Defence Agency) document upon the Critical Space Technologies for European Strategic Non-Dependence Actions for 2015-2017.

The main applications of these power amplifiers are Space Satellites and ground applications such as Telecommunications.

The ERFTM project will specify, develop, test and qualify the helix wire materials and the dielectric materials for helix support rods. Both will be subject to a complete qualification process for space TWT and terrestrial communication TWT.
The ERFTM consortium is purely European and includes 2 Thales entities, worldwide leaders in space TWT development and production, 3 industrial technology providers for the raw materials and key involved components and 1 research laboratory for materials characterization.

 

Focus on three scientific publications:

Since the invention of the travelling wave tube principle by Kompfner (1) in 1943 the TWT technology has changed dramatically, altering almost each device component except their basic principles as the synchronous electron beam / RF wave interaction, or thermionic cathode emission itself. The past almost six decades of helix TWT development resulted in an increase in the overall DC to RF conversion efficiency from about 1% (including solenoid power) to today’s 73%, with the future potential to approach 75% or even 80% for commercial satellite communication applications. These achievements were driven by the never ending demand of commercial geo-stationary satellites systems to save DC power for the possibility to install more channels with higher RF power. This capability of Helix TWT’s in combination with their large bandwidth, high reliability and long life made the helix TWT an ideal microwave power amplifier on board of all types of inherently power limited satellites.

The paper shows a new antenna concept or idea for satellites using high efficiency high power traveling wave tube (TWT) amplifiers, dedicated especially for geostationary satellite systems. A new TWT, named TL 2500, a high efficiency S-band TWT feasible for 500W continuous wave output power will be used inside this idea. Usually today a single deployable antenna is used for  eostationary S-Band systems and 32-96 TWTs feasible each for 250W are power combined to reach an output power between 7 kW up to around 20 kW[1]. Due to the fact that the output power of today SSPA (solid state power amplifier) are far below 250W a power combining would be very complex and would end in high implementation losses. Therefore, often group antenna concepts are the preferred solution for SSPAs. For redundancy reasons and due to the need for high overall output power today all amplifiers run at same output power and usually the antenna beams with the lowest elevation angle will suffer with the lowest EIRP (equivalent isotropically radiated power) on earth. With the new TL 2500 TWT two output power versions with 500W and 400W will be available with nearly same efficiency. Together with the today available 200W – 275W TWT [2] a high output power range can be generated for a new group antenna idea with TWTs.

The ongoing development in satellite application requires more and more high power Travelling Wave Tubes (TWT) to relieve the requirements for end user terminals and to improve the quality and channel capacity of the satellite down link. Also more types of TWTs are demanded by the customers to obtain a higher flexibility in satellite design with respect to output power, weight and thermal requirements. THALES ELECTRON DEVICES (TED) therefore has filled up its portfolio of different TWTs for L-Band and S-Band. This paper will present some technical details and illustrate the performance of state-of- the-art tubes.