PAGE CONTENTS
Objectives
The main objective is to evaluate last improvements of the European commercial 0.5μm (GH50) and 0.25μm (GH25) GaN HEMT technologies from United Monolithic Semiconductors Foundry. These two GaN technologies studied in the frame of the GREAT² ESA contract have reached a satisfactory level of maturity that makes them the good candidates for space applications from L-band to Ku-band.
Main proposed activity is to design, manufacture and test:
- 1 hybrid HPA module (two iterations) at L-band and based on the UMS GH50 technology
- 1 MMIC HPA module at Ku-band and based on the UMS GH25 technology
To ensure maximum power added efficiency (PAE), the HPA module relies on the design of an optimal inverted class F working mode. The optimization of the output combiner has to be managed in order to match as close as possible the optimum output load including 2nd harmonic with minimum of losses..
The introduction of the GaN technology in SSPA equipment and the objective to use GaN SSPA equipment with more stringent thermal specification are inducing an increase of component temperature and high heat flux density to be managed at the interface between the units and the spacecraft panel.
To demonstrate that high level of compression could be used for flight operation, RF step stress measurements on HPA modules are performed in order to identify the safe operating area.
Challenges
To answer to the requirements imposed by the technical aspects described above, the development of HPA modules are based on the following techniques and solutions:
- For an optimal RF performance prediction (Pout/PAE/Linearity) of L-band and Ku-band HPA modules, active devices (transistors and power-bars) have been characterized and modelled through harmonics load-pull measurements campaign.
- To ensure maximum power added efficiency (PAE), the HPA relies on the design of an optimal inverted class F working mode. The optimization of the output combiner has to be managed in order to match as close as possible the optimum output load including 2nd harmonic with minimum of losses. For Ku-band applications, HPA modules based on Doherty architecture have also been evaluated.
- In order to manage the important heat flux under GaN devices, new material with high thermal conductivity has to be privileged for the baseplate of the micro-package.
Regarding the high compression level required to achieve maximum power added efficiency, RF step stress measurements are performed to identify safe operating area.
System Architecture
L-band GaN SSPA equipment using HPA-1 module brings many benefits compared to LTWTA solution
- Mass reduction of 66% compared to a L-band LTWTA solution
- Footprint reduction of 65% compared to a L-band LTWTA
Solution
- Simplified implementation during payload integration
- Cost reduction compared to LTWTA solution
Plan
The activities are dedicated to the development and the tests of L-band and Ku-band GaN HPA.
Phase 1:
- Study of SSPA equipment for space-borne Telecom applications
- Baseline design of L-band GH50 HPA module
- Run-1 Manufacture of GH50 transistors and power-bars
- Run-1 Non-linear modelling and performance validation
- Run-1 Detailed design of L-band GH50 HPA module
- Run-1 Manufacture and test of L-band GH50 HPA module
Phase 2:
- Run-2 Manufacture of GH50 transistors and power-bars
- Run-2 Non-linear modelling and performance validation
- Run-2 Detailed design of L-band GH50 HPA module
- Run-2 Manufacture and test of L-band GH50 HPA module
- Baseline design of Ku-band GH25 HPA module
- GH25 Non-linear modelling and performance validation
- Detailed design of Ku-band GH25 HPA module including Doherty versions
- Manufacture of GH25 MMIC
- Manufacture and test of Ku-band GH25 HPA modules
Current Status
All key reviews have been held successfully. The L-band GaN HPA was fully tested with the expected performance. Benefits of the introduction of the L-band GaN HPA module into SSPA equipment dedicated to Telecom applications are demonstrated.
Regarding Ku-band HPA module with GH25 technology, different architectures (Class AB and Doherty) were tested. Through two kind of measurements during RF step campaign, the reliability on the Ku HPA has been validated.
The contract is now closed.
