Recent advancement in Ka-Band satellite payloads and equipment drive the power level requirements to several hundred Watts per transponder.
Travelling Wave Tube Amplifiers (TWTAs) in the 170 to 200 Watt range currently under qualification will soon become available, while the target of future developments is in the 300 Watt class operation. In the Output Multiplexer (OMUX) arena, channel filters for 250 to 500 Watt power handling are also under development.
Current classical Y junctions isolators cannot handle more than 150CW W, therefore a novel isolator able to handle high power levels 350 Watt RF power is necessary. This isolator should have an innovative design in order to support the increased power level requested for future payload equipments.
The ultimate objective of this project is the design, manufacturing and test of a Ka-Band 350 Watt CW isolator Engineering Model (EM) capable to operate in worst case condition (full reflected power).
Today the major design driver for isolators is the peak power handling (Multipactor) and the thermal management in particular for the circulator in full-reflection. For power levels higher than 150-200 Watt, the temperatures reached by standard designs easily approach the material allowable capability.
Availability of components with reproducible and stable performance.
This design, unlike standard designs e.g. classical Y-junction and resonance isolator, is based on an innovative technology in order to reduce the power density travelling in the centre of the junction. The proposed isolators cover the band 17.3-20.2 GHz. The typical electrical performances are less than 0.15dB for insertion loss and higher than 23dB for isolation and for input and output return losses in the operating temperature range (from -20°C to +85°C).
This work was carried out with technical phases as follows:
Phase 1: Technology Review and Breadboards development
A Technology review of existing circulators and terminations is done. Full-wave simulations (electromagnetic, thermal, mechanical, etc.) are used to demonstrate compliance with the RF specifications.
Breadboards are manufactured, tuned and measured. A high power test is also performed to prove the capacity of the design to handle such high power levels (350CW-W).
Phase 2: 350 Watt Ka-Band Isolator Design, Manufacturing and Test
Engineering Models are manufactured, assembled and verified. In order to ensure that the EMs meet the specifications, following tests are performed: TVAC-burn-in, mechanical vibrations (sinus, random & sine survey), SRS shock, thermal cycles, power handling in nominal mode (forward mode) and fault case (output port short-circuited), Multipactor test and EMC.
All these tests show positive margins.
The development phase of the project has now ended: The isolator is fully tested with expected performances.
The key project objective (to develop a high power Ka band Isolator capable to handle 350W) was achieved.