4096-QAM Microwave Transmitter Providing Efficiency Exceeding 50% and EVM Below 1%

Abstract

While users of spectrum pay large sums of money for spectrum access, they do not sell spectrum to their customers but rather they market data rates. Developing radio technologies that maximize data rate within a finite spectrum slice is a very important goal to such spectrum access businesses. This requires radios to provide high values of spectrum efficiency (bits per second per Hertz-bandwidth (bps/Hz)). This paper is the first to introduce a conventional Nyquist filtered 4096-QAM signal implemented with a switching-circuit based transmitter. Even by having no circuit linearity in the RF path and using polar modulation, the reported signal quality measurements confirm less than 0.9% error-vector magnitude for this 12 bps/Hz constellation. Signal ACLR is -54dB, peak output power is 2.5 watts, and the transmitter efficiency exceeds 50% when modulated and including all linearization power. The limits of using EVM as a signal quality metric are presented and discussed.