Semiconductor scaling has continued for almost half a century, as Moore's law predicted. It has been the source of low-cost, efficient, and high-speed electronics for numerous applications. This trend, however, is about to slow down or even stop in the next few years due to several limitations. This is particularly consequential for high-speed and high-power electronics as they become extremely challenging to implement due to the technology limitations. For example, millimeter wave (mm-wave) and terahertz (THz) systems are known to have unique and significant applications in health, security and industry. Detection of concealed weapons, cancer diagnosis, high-resolution radar, medical imaging, 3D imaging, and semiconductor wafer/device inspection, along with bio/molecular spectroscopy for drug detection, food quality control, and breath analyses for disease diagnosis are among many examples of these applications. In particular remote sensing, active/passive imaging and short-range communication are continually evolving at a rapid pace toward mm-wave and THz frequencies in order to achieve superior resolution and higher data rate. Today, however, THz systems are realized using expensive and bulky devices such as gas lasers and discrete bulky components. If compact and on-chip THz systems are realized the numerous related applications will rapidly flourish, resulting in new opportunities in high-tech marketplace and research and teaching institutions. Today's solid-state technologies including silicon and compound semiconductors can barley cover the lower part of the THz band with useful amount of radiated power. Moreover, phased arrays are essential in some of these applications to boost and localize the radiated power. Phase shifters are critical in a conventional phased array system but they are extremely lossy at high frequencies. The complications of integrating these phase shifters and a stable signal in phased array systems have prevented designers to implement THz high power transmitters on chip. To overcome these problems the PI introduces fundamentally new approaches to design harmonic voltage-controlled oscillators (VCO), radiator array and phased array systems at THz and mm-wave frequencies. The PI's research plan is to use these approaches to make solid-state electronics the default platform for high-performance on-chip THz systems, which are hard to envision today.
First the PI introduces novel array structures based on the unique properties of traveling and standing waves that enable efficient and high power signal generation and radiation. The important properties of these structures are as follows: 1- they greatly simplify the structure of the array and result in high radiated power and high DC to RF efficiency, 2- no additional global or local routing is needed other than the ones that belong to the oscillator structure, thereby making this architecture inherently scalable to larger array sizes for both the radiator and the phased array, 3- when used in the phased array they completely eliminate the need of phase shifters anywhere in the structure, and 4- only one high frequency divider is needed to sense the fundamental frequency and lock the whole array in a frequency synthesizer, resulting in a low power operation. Next, the PI uses the "Optimum Signal Condition" methodology and introduces a new technique to shape the transistor signals and boost the harmonic power in oscillators. Combining the scalable array structures with the signal shaping technique the PI proposes VCOs, radiator arrays and phased arrays that have significantly higher performances than the state of the art. The PI believes the proposed radiator and phased array would be the cornerstone of future phased array systems for radar, sensor and communication applications at THz and mm-wave frequencies.
