Riemann-Pump based RF-Power DACs in GaN Technology for 5G Base Stations

This paper introduces two realizations of a Riemann-Pump based digital transmitter geared towards software defined radio in 5G systems. In contrast to traditional digital-to-analog converter (DAC) concepts, the Riemann Pump exhibits a higher signal-to-noise ratio (SNR). Since the used 0.25 μm gallium nitride (GaN) technology has a transit frequency of 30 GHz, an oversampling ratio (OSR) of five for the targeted frequency range from DC to 6 GHz is enabled. As the Riemann Pump serves as a digital driver, a co-integration with a suitable wideband power amplifier is possible to reach high power levels. A hybrid assembly is compared to the fully integrated Riemann Pump circuit in GaN technology. The world’s first measurement data of a two bit resolution Riemann Pump in GaN technology are discussed. Radio frequency (RF) power in the watt level range is measured for frequencies between 0.5 GHz - 12 GHz into a capacitive load representing the input capacitance of a power amplifier.