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Wideband Multiport Measurements for MIMO and Beamforming Hardware
The introduction of MIMO in 5G mm-wave systems and beamforming in general for telecommunication and radar for terrestrial as well as space applications, has increased the demands on multiport wideband (WB) measurements in calibrated reference-planes. Complex parallel multi-cell amplifier hardware needs to be tested and modelled under emulated real-life conditions with multi-port excitation. Thermal and electrical coupling between elements in the array-type systems can then be identified and modelled under real conditions prior to expensive packaging and module assembly. Such measurements require coherent excitation of wideband signals verified for all calibrated ports. Here we present such a system developed for on-wafer 16-port WB measurements up to 67GHz with a possible instantaneous bandwidth exceeding 5GHz. The system is based on 4 modified PNA-X vector network analysers (VNAs) with extended bandwidth WB intermediate frequency (IF) outputs for direct external IF capture of the full IF bandwidth signals. System control including, WB signal generation, signal conditioning, synchronization and calibration of the multiport WB measurements are conducted externally using algorithms that are in continuous development at FBH. The system also allows the WB characterization and optimization of single amplifiers (PAs) based on active WB load-pull or multiport PA topologies like outphasing, Doherty, and supply modulated PAs etc. In addition, the measurement hardware allows comparison and research of alternative WB capturing methods including stitching since the narrowband features of the VNAs are still intact in the modified units.