Microstrip Colinear Antenna Array for a Small Unmanned Aerial System Lobe Differencing Correlation Radiometer

A lobe-differencing antenna designed as a 2\times 2 rectangular L-band microstrip array used for the CU-BlackSwift Technologys (BST) lobe-differencing correlation radiometer is presented. The antenna array was integrated into the fuselage of the BST tempest small unmanned aerial system (sUAS). A prototype 2\times 1 microstrip colinear (MiCo) antenna array operating at center frequency 1.4135 GHz was characterized to validate the accuracy of HFSS simulation results of input impedance. Furthermore, a 2\times 2 MiCo antenna array with effective use of styrofoam blocks for frequency tuning and providing mechanical stability was built. The effect of separation of the upper and lower array pairs on mutual coupling and radiometer sensitivity and the tuning effect of the styrofoam blocks on resonant frequency were studied. An optimal vertical separation distance was identified that minimizes mutual coupling and provides maximum main-to-back lobe ratio. A method of antenna frequency tuning using dielectric overlay material is presented to correct the dielectric impact of the sUAS fuselage.