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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:
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.
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:
Regarding the high compression level required to achieve maximum power added efficiency, RF step stress measurements are performed to identify safe operating area.
The L-band HPA module designed, manufactured and tested in the frame of this study has proven its ability to deliver high output power at L band over 50W with efficiency above 60%. These excellent performances made it a perfect candidate to high power SSPA equipment dedicated to Telecom applications. Thus, based on this L-band GH50 HPA module, EM GaN SSPA equipment brings many benefits compared to LTWTA solution and GaAs SSPA solution:
This competitive EM GaN SSPA equipment is able to address the entire renewal market of constellations of mobile communications satellites.
For Ku-band applications, the introduction of Ku-band GH25 HPA module developed in this study, has been analysed on two types of equipment: SSPA and LC-SSPA
Regarding a 20W Ku-band SSPA based on a single GaN HPA module developed in this study, the comparison between GaAs and GaN SSPA equipment versions shows important improvements and points to be addressed further:
Regarding a 160W Ku-band LC-SSPA based on 8x GaN HPA modules and low loss space combiner technique, the comparison with LC-TWTA show mitigate results for LC-SSPA in particular for electrical performance. It is then clear that a GH25 based LC-SSPA presents insufficient electric performances (low PAE and reduced frequency bandwidth) and that a technological breakthrough is required to increase this performance (Pout/PAE/NPR/Instantaneous frequency bandwidth).
The GaN HPA module based on UMS GH50 power bar is using a novel hermetic high dissipative package with Metal-Diamond material.
The measurements are excellent and are showing that output power is over 50 W in CW with more than 60% of PAE at hot temperature. RF step stress measurement performed on three HPA modules up to 10dB compression have demonstrated that high the level of compression (6,5dBc) required for high efficiency performance could be used for flight operation.
In Ku-band, for the inverted class F working mode GH25 HPA version, performance results are in line with the electrical simulations, thus, validating the NL transistor model established during the study.
Regarding the GH25 Doherty HPA version and due to specificity of the targeted linearity (NPR=15dB corresponding to 2-2,5dB OBO), the performance obtained in term of Pout/PAE/NPR (multicarrier mode) show similar results compared to the previous version. Due to the complex architecture of this Doherty HPA module (2 stages using 8x transistors in parallel for output stage), ‘’Doherty effect’’ is limited at low OBO.
L-band GaN SSPA equipment using HPA-1 module brings many benefits compared to LTWTA solution
The activities are dedicated to the development and the tests of L-band and Ku-band GaN HPA.
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.