This paper presents the effect of internal reflections on the beam pattern and input impedance of integrated lens antennas. A silicon lens was designed and manufactured, and measurements were conducted at a frequency of 100 (impedance) and 500 GHz (beam pattern). A frequency-dependence characterization of the beam pattern clearly showed the existence and impact of internal reflections. The measurements confirmed that most of the frequency variations of the beam pattern could be attributed to internal reflections, as predicted by the model. An on-wafer measurement strategy for determining the antenna impedance at millimeter-wave frequencies is presented. The validity of the model was also proven by an excellent match of the input impedance measurements and predictions. Not only the level, but also the oscillation on the impedance curve was predicted accurately. Initial space qualification was performed in the form of thermal cycling.
Index Terms-Integrated lens antennas, internal reflections and input impedance.
Fully digital transmitters (DTXs) have the potential of replacing analog-intensive transmitter (TX) line-ups in future massive multiple-input and multiple-output (mMIMO) systems since they hold the promise of higher system integration level and energy efficiency. DTX operation so far has been limited to low RF output powers. This article introduces a concept that enables high-power DTX operation. A DTX demonstrator targeting both high output power and high efficiency is realized as a proof of concept. It is based on a custom V T -shifted laterally-diffused MOS (LDMOS) technology, which is utilized to implement a segmented high-power output stage operated in class-BE. A lowvoltage high-speed 40-nm CMOS controller drives the individual output stage segments at gigahertz rates. Measurements show the promising results for the proposed high-power DTX concept and provide valuable lessons for future DTX implementations.
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