Prâna participates in different international conferences to demonstrate the Prâna development capacity.
INCEMIC 2016: Bangalore (India)
Strong microwave electric field reached by a high power wideband amplifier for automotive application
INCEMIC 2012: Bangalore (India)
High field levels generated by a 12 kW CW wideband power amplifier
EuroEM 2012: Toulouse (France)
A 12 kW wideband power amplifiers for strong field levels
Thesis: Ludovic Bacqué
This thesis deals with linearity and effciency improvements of high power microwave and RF amplifiers. When power amplifiers are working with envelop varying signals (such as 16QAM, OFDM. . . ), an output power back-off (OBO) is usually applied to reach a high linearity in order to ensure signal integrity. Unfortunately, this OBO results in a very poor efficiency of the amplifier and results in a high DC power consumption and higher working temperatures. The solution to this dilemma is to use an envelop tracking (ET) system which consists in controlling the amplifier bias point according to the input envelop power level. Such a system llows to keep a constant complex gain with high effciency over the input power range. Two techniques for implementing this dynamic bias principle have been studied and designed in this work : the first circuit is based on a high power (up to 150W) DC- DC buck converter associated to a sigma delta modulator , the second circuit is new and based on a high speed switched power supplies system. The ET techniques are detailled and validated with two power amplifiers (a UHF-VHF 100W LDMOS Push-pull amplifier and a 10 W X band GaN amplifier). Many simulations and experimental results (EVM, ACPR , PAE) are presented and discussed. An implementation of a digital predistorsion of the bias controlled amplifier have also demonstrated significant improvements of both linearity and efficiency.
Thesis: Cyril Lagarde
New power transistors technologies based on “wide bandgap” materials such as Gallium Nitride (GaN) were developed these last years. This new technology presents interesting capabilities for high power microwave amplifiers in terms of high working temperature, high power densities and high breakdown voltages. This work concerns first the development of a new tabular electrothermal non linear model including trapping effects on an AlGaN/GaN power HEMT. This model has then been used, in the second part of this thesis, to design a power amplifier based on the Doherty principle. In satellite communication systems, a good linearity and a high efficiency are drastic constraints on the power amplifier. In order to deal with these constraints, we have proposed and designed a new Doherty amplifier with a symmetrical architecture based on three GaN HEMT devices. Experimental results have shown the interesting capabilities of this new Doherty structure in terms of efficiency and linearity under output power back-off operation.