Reconfigurable GaN Digital Tx Applying BST Bandpass Filter

A. Wentzel1, C. Schuster2, R. Jakoby2, H. Maune2, W. Heinrich1

Published in:

IEEE MTT-S Int. Microw. Symp. Dig., Boston, USA, Jun. 2-7, pp. 1484-1487 (2019).

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The paper presents the first tunable GaN-based digital transmitter chain for 0.8-1.8 GHz range, suitable for MIMO systems in software-defined radio (SDR) installations. The demonstrator includes a 4-stage digital GaN power amplifier (PA) MMIC and a continuously tunable bandpass output filter based on a barium strontium titanate (BST) thin-film varactor. The filter shows a fractional bandwidth of 7% as well as a minimum insertion loss and maximum input return loss of 0.6 dB and 13 dB, respectively. The module delivers a maximum output power of 3 W and efficiency stays above 40% over the whole tuning range, peaking at 89% for 1.2 GHz. This is to the author`s best knowledge the first reconfigurable digital Tx chain fully demonstrating the inherent advantages of the digital PA approach including broadband operation, compactness, efficiency and reconfigurability.

1 Ferdinand-Braun-Institut (FBH), Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany
2 Technical University of Darmstadt, Darmstadt, Germany

Index Terms:

software-defined radio, digital, transmitter, power amplifier, tunable filters, GaN, ferroelectric materials, BST.