AbstractsEngineering

High Efficiency Transmitter Architecture for Nano-satellites:

by V. Karunanithi




Institution: Delft University of Technology
Department:
Year: 2014
Keywords: nano-satellites; downlinks; high efficiency transmitters; LINC PA architecture
Record ID: 1254134
Full text PDF: http://resolver.tudelft.nl/uuid:bab00c1d-7467-45a7-a8de-422174bb84a8


Abstract

The fast growing interest in nano-satellite development and the use of nano-satellite for complex missions has led to an increase in the downlink data-rate. The availability of free bands (amateur frequency bands: VHF and UHF) is getting limited and more challenging to do the frequency coordination. This can be attributed to the surge in number of nano-satellite being launched. There has been 430% increase in the number of satellites launched in 2013 compared to 2012. This trend has led the nano-satellite developers to start looking into higher frequency bands and S-band has been a popular choice. But, going by the trend, frequency coordination in the S-band can also get challenging. Thus, there is a need to develop a nano-satellite transmitter that uses spectrally efficient modulation scheme, at the same time it has to be power efficient and be compatible with some of the existing communication standards. This work deals with developing the requirements on a nano-satellite transmitter based on mission case study, look at the need for efficiency and linearity enhancement technique for the transmitter, select the most appropriate architecture for nano-satellite application and show a proof of concept using a prototype. Using system engineering approach the efficiency and linearity enhancement technique that was chosen was LINC architecture. ADS simulations were performed to understand different configurations of LINC and finally, measurements were performed on the chosen configuration to characterize its efficiency and linearity. 16-QAM, 16-APSK, 32-QAM, 32-APSK and 64-QAM modulation schemes were implemented and tested. The best EVM was obtained for 16-APSK with 20 degrees compensation stub in the Chireix combiner which was 0.27% and the best efficiency was obtained for 16-APSK modulation scheme which was implemented without any compensation stubs. Based on the lessons learnt during simulations and measurements, recommendations are provided to improve the LINC configuration and improve the reliability of the measurement setup.