Quasi-optical active antennas

• Main Author: Moussessian, Alina
• Format: Others
• Language: en
• Published: 1997
• Online Access: https://thesis.library.caltech.edu/6074/1/Moussessian_a_1997.pdf; Moussessian, Alina (1997) Quasi-optical active antennas. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/0nah-v928. https://resolver.caltech.edu/CaltechTHESIS:09292010-105455980 <https://resolver.caltech.edu/CaltechTHESIS:09292010-105455980>

Quasi-optical power combiners such as quasi-optical grids provide an efficient means of combining the output power of many solid-state devices in free space. Unlike traditional power combiners no transmission lines are used, therefore, high output powers with less loss can be achieved at higher frequencies. This thesis investigates four different active antenna grids. The first investigation is into X-band High Electron Mobility Transistor (HEMT) grid amplifiers. Modelling and stability issues of these grids are discussed, and gain and power measurements are presented. A grid amplifier with a maximum efficiency of 22.5% at 10 GHz and a peak gain of 11 dB is presented. The second grid is a varactor grid used as a positive feedback network for a grid amplifier to construct a tunable grid oscillator. Reflection measurements for the varactor grid show a tuning range of 1.2 GHz. The third grid is a self-complementary grid amplifier. The goal is to design a new amplifier with a unit cell structure that can be directly modelled using CAD tools. The properties of self-complementary structures are studied and used in the design of this new amplifier grid. The fourth grid is a 12 x 12 terahertz Schottky grid frequency doubler with a measured output power of 24 mW at 1 THz for 3.1- µs 500-GHz input pulses with a peak power of 47 W. A passive millimeter-wave travelling-wave antenna built on a dielectric substrate is also presented. Calculations indicate that the antenna has a gain of 15 dB with 3-dB beamwidths of 10° in the H-plane and 64° in the E-plane. Pattern measurements at 90 GHz support the theory. The antenna is expected to have an impedance in the range of 505Ω to 80Ω.