We describe the opportunities and challenges in developing 100-300 GHz wireless communications and imaging systems. The short wavelengths permit massive spatial multiplexing in both backhaul and endpoint links, permitting aggregate transmission capacities exceeding 100 Gb/s. 100-300 GHz radar imaging systems can provide many image pixels and sharp angular resolution from small apertures, supporting foul-weather driving and aviation. Challenges include the mm-wave integrated circuit (IC) designs, the physical design of the front-end modules, and the complexity of the back-end digital beamformer required for spatial multiplexing. We will describe transistor development, IC design, and system design, and show IC and systems examples, including 140 GHz MIMO hubs, and 205 GHz backhaul links.

A millimeter (mm) wave amplifier that combines both high-power output and a wide bandwidth would enable dramatic improvements in areas where high-power radio signals with significant information content are required. However, to date, the only available devices are either high-power vacuum electronic devices with limited bandwidths, or larger bandwidth semiconductor amplifiers with low-power output. Here, we show a new design of a vacuum electronic traveling-wave tube amplifier that has a measured output power of 107 W with a 3-dB bandwidth of 6 GHz centered on 200 GHz. The power-bandwidth product of this amplifier is 642 W-GHz. These results provide a demonstration of a high-power mm-wave source with significant bandwidth. This device is readily scalable to other frequencybands, particularly those in themm-and sub-mmwave frequency bands from 100 GHz to 1 THz.

Short-Abstract—Recent advances in InP semiconductor device design and high-yield processing have led to the demonstration of transistors with power gain cut-off frequencies (fmax) greater than 1 THz. More importantly, the devices are supported by low-loss interconnects, accurate models and robust design kits. Employing a systematic design methodology that includes significant EM and thermal modeling, we have demonstrated circuit components for transceivers up to 670 GHz and power amplifiers with >100mW of output power operating at 230 GHz. Insertion of these high frequency chips requires additional breakthroughs in packaging, and thermal management. Other applications of the technology would allow the high gain-bandwidth to be traded for high dynamic range and efficiency at mmWave frequencies.

We report on progress in developing a travelling wave tube amplifier with significant gain and power at 220 GHz. This paper provides an overview of the program, describing fabrication and test of slow-wave structures with bandwidths exceeding 50 GHz centered at 220 GHz, the production of a sheet electron beam, development of a solid state preamplifier delivering 50 mW to the tube with > 17 dB of gain and beam-wave simulation of the entire circuit leading to expected output powers of over 50 W. Two further papers from the group are also submitted to IVEC: from UC Davis describing the interaction structure fabrication and hot test, and from CPI describing the sheet electron beam, TWT design and beam - wave simulations. The tube is currently under test and results will be reported in this paper.