Three 10W C-band Power Amplifier Alternatives for use in TTC-Transmitters

摘要

This thesis describes the first stage in designing and realizing three 10W C-band poweramplifier alternatives based on the GaN-technology for use in Kongsberg Norspace futureTT&C-transmitters. The operational frequency range spanned from 3.4GHz to 4.25GHz.It was decided to build one single-stage amplifier based on the 10W CGH40010F transistorfrom Cree and two dual-stage amplifiers with a balanced second stage based on the 6WCGH40006P transistor, from the same manufacturer. AWilkinson power divider was usedto feed each branch in the second stage.In the design procedure, source and load pull simulations were performed in order toretrieve the optimal impedances for each transistor and as a basis for the design of thematching networks. By utilizing a looping method in the design process of the matchingnetworks, it was possible to obtain results that, to some extent, fulfilled the requirements.Simulations and design were carried out in ADS by Keysight (former Agilent).The simulated results showed that all three designs were capable of delivering 10Woutput power throughout the frequency band. The single-stage amplifier obtained a simulatedpower added efficiency (PAE) above 45% at 40dBm output power, while the twodual-stage designs achieved a PAE between 41-44% and 34-36%, respectively.S-parameter simulations reviled that the single-stage design accomplished a small signalgain of 11.3dB-11.7dB, while the input reflection coefficients varied between -3dBand -5dB. To achieve the requirement of having the input reflection coefficients less than-10dB, the dual-stage designs utilized an attenuator with 1.5dB loss at the input match,both designs obtained a small signal gain above 20dB.Like the simulated results, the large signal measurements showed that the amplifierswere capable of delivering 10W output power, except the single-stage design at4.0375GHz (which were one of the test frequencies). The measured power added efficiencyfor the single-stage amplifier varied between 27%-44%, while the two dual-stageamplifiers obtained a PAE between 39-43% and 35-42%, respectively. This implied thatnon of the designs managed to fulfill the requirement of having a total power consumptionless than 25W over the specified frequency range.A simulated large signal stability analysis were performed on each design and the resultsrevealed that one of the dual-stage designs had a potential instability around 790MHz,and practical spectrum measurements confirmed frequency components at 750MHz, 1.51GHzand 2.25GHz. However, the spurious frequency components had no measurable impact onthe performance.A small section presenting the future prospects in terms of utilizing the GaN-technologyin Space and suggestions for future work, have also been included.The thesis concluded that several iterations must be done before an integration withthe transmitter can be made.