Testbed for phased array communications from 275 to 325 GHz

The first modular 4-channel frontend for exploring phased array communications at a carrier frequency of 300 GHz was developed. A metamorphic HEMT process with a gate length of 35 nm was the key enabling technology for the integration of each transmit and receive channel. All channels implemented the quadrature direct conversion architecture. The measured RF bandwidth exceeded 55 GHz for the receive array respectively 45 GHz for the transmit array using a continuous wave baseband test signal. Phase shifting in the local oscillator path was the focus of this work. The concept was realized by using four synchronized direct digital synthesis channels followed by a high power frequency multiplier-by-12 MMIC. Investigating and assessing the array coherency at 300 GHz by the use of higher order modulation schemes was also proposed, highlighted on the example of a 16-QAM signal at 4 Gbaud in comparison to phase noise measurements of each channel.