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Wide Band High Power Amplifier for Digitally Modulated Signals (QAM and COFDM)

Area of Applications:
Broadband Transmission of Digitally Modulated Signals .

Engineering Expertise Involved:

One of our main goals in this work was to achieve high linearity and stability of designed 200 W (53dBm) HPA employing GaN transistors capable of transmitting digitally modulated signals such as QAM-256 (Quadrature Amplitude Modulation) in frequency range 800MHz to 3GHz

The main technological advancement achieved during this work was experimental verification that the new technological approach employing GaN power transistors allowed to design a 200 W (53dBm) HPA module capable of transmitting digitally modulated signals. Overall system modularity and packaging were optimized to achieve minimum space and size of the system modules while considering power loss reduction.

A special method of providing safe sequence and amplitude of applied voltages to gate and drain of transistors was conceptualized and experimentally implemented.

The HPA was experimentally optimized for maximum power 53dBm and efficiency while maintaining high linearity (-34dBc) at 3dB power back off which is essential for COFDM signals.

Portable Linear S-Band 250W DVB-S2X Transmitter

Area of Applications:
Portable Linear S-Band 250W DVB-S2X Transmitter.

Engineering Expertise Involved:

The goal of this project is to design and implement a low cost, power efficient (>40%) and linear (third order IMD < -40dBc) 250W S-band pallet to be used as a building module for light weight portable outdoor transmitters.

The main technological objective to be achieved is creation of a new method of designing 250W S-band pallet for High Power Amplifier (HPA) based on a Doherty amplifier for broadcasting 256APSK modulated signals to support satellite uplink communications and return channels according to the new DVB-S2X standard. The most challenging task to achieve in this experimental work is to finding an optimum trade-off between biasing circuits’ optimization, the load-pulling behavior between the “main” and “peaking” amplifiers, transistors’ temperature, and other parameters.

To meet all the specified requirements, the solid state design approach is employed based on low cost LDMOS transistors operating as a Doherty amplifier with high efficiency >40% targeting to reduce power consumption and weight of the portable transmitter.