Utilizing a High-Speed Marx Supply Modulator in an Amplitude-Modulated Mixerless Transmitter for 64 QAM

IEEE Transactions on Microwave Theory and Techniques, vol. 69, pp. 1063–1071

Abstract

This article reports on the theory and application of a high-speed Marx generator (HSMG) circuit to realize supply modulation (SM). In order to achieve high-modulation bandwidth, the supply modulator complexity is kept low, enabling multilevel SM with four discrete voltage levels. A prototype is designed and fabricated on a four-layer FR4 board. The efficiency of the proposed modulator is measured with passive loads, achieving 89% at the 5-MHz switching frequency. Applied to a power amplifier (PA), the modulator demonstrates an error vector magnitude (EVM) of 2.64% at 10-MHz switching frequency with a four-ASK signal. Finally, the HSMG is utilized in an innovative mixerless transmitter architecture. Its capabilities are validated at the center frequency of 3.5 GHz for different modulation bandwidths from 2 up to 70 MHz and different constellation schemes-16 QAM, 32 QAM, and 64 QAM. EVM of 5.88% at 10-MHz bandwidth with 64 QAM is obtained without digital predistortion (DPD).

Authors 3

1. Peco Gjurovski Aachen Chair of High Frequency Electronics

   RWTH Aachen University

   Affiliation as printed

   Chair of High Frequency Electronics (HFE), RWTH Aachen University, Aachen, Germany

2. Lukas Hüssen Aachen Chair of High Frequency Electronics

   RWTH Aachen University

   Affiliation as printed

   Chair of High Frequency Electronics (HFE), RWTH Aachen University, Aachen, Germany

3. Renato Negra Aachen Chair of High Frequency Electronics

   RWTH Aachen University

   Affiliation as printed

   Chair of High Frequency Electronics (HFE), RWTH Aachen University, Aachen, Germany