Vacuum microelectronic devices for THz communication systems

Terahertz (THz) frequencies especially in the 94GHz and 220GHz frequency bands are very much demanding for ultra broadband communication, remote sensing, security, medical imaging, and many other new applications. There is an urgent need of compact devices for efficient high power generation and amplification at THz frequencies. Present solid-state devices cannot be used at 100GHz and above for power more than 10mW. Vacuum electronic devices (VEDs) like travelling-wave tubes have many advantages over solid-state devices at high frequencies. Electron transport in vacuum conveys as advantages to VEDs such features as wide band performance, high efficiency, high thermal robustness and radiation hardness. But VEDs are difficult to fabricate with the conventional tube technologies because of small dimensions of parts of the RF circuit at THz frequencies. MEMS technologies are used for fabrication of RF structure and field-emitter array (FEA) cathode. Such devices are named vacuum microelectronic devices (VMDs) needing fusion of vacuum tube technology with semiconductor technology. Significant efforts are being carried out to develop compact VMDs for meeting our future communication systems and other applications.