Theory, design, and measurement of novel uniform circular antenna arrays for direction of arrival estimation

The theory, design, fabrication, and measurement of new uniform circular arrays (UCAs) for direction of arrival (DOA) estimation is presented in this report. In particular, the effect of directional antenna elements in UCAs for DOA estimation is studied in detail. While the vast majority of previous work assumes isotropic antenna elements or omnidirectional dipoles, this work demonstrates that improved DOA estimation accuracy and increased bandwidth is achievable with appropriatelydesigned directional antennas. Simulation results in this report show improved DOA estimation accuracy and robustness using microstrip patch antennas as opposed to conventional dipoles. Additionally, it is shown that the bandwidth of a UCA for DOA estimation is limited only by the broadband characteristics of the directional antenna elements and not the electrical size of the array as is the case with omnidirectional antennas. Three novel UCAs were fabricated and tested: (1) a dipole UCA with integrated microstrip tapered baluns; (2) a narrow-spacing microstrip patch UCA; and (3) a wide-spacing microstrip patch UCA. Practical design aspects of all three arrays is detailed in this report and measurement results from an anechoic chamber are presented. This work shows that there are opportunities to improve direction finding performance through optimization of antenna array elements which could potentially improve Canadian Armed Forces direction finding and situational awareness capabilities. Significance for defence and security Direction finding (DF), also known as direction of arrival (DOA) estimation or angle of arrival (AOA) estimation, is a critical capability for the Canadian Armed Forces (CAF). The ability to accurately determine a line of bearing (LOB) toward an adversary’s radio frequency (RF) emitter can provide vital situational awareness. In order to estimate the direction to an RF transmitter, an antenna array is generally used, which often consists of multiple identical individual antennas arranged in a uniform pattern. It is perhaps surprising that, although DF capabilities have existed for over a century, there is very little literature available on the optimization of antenna elements to improve the overall DF performance of an array. At Defence Research & Development Canada (DRDC) – Ottawa Research Centre there has been an effort to optimize DF estimation accuracy through the use of non-traditional antenna elements. This report details new theory, simulations, and measurements that show the potential for improved DF accuracy through the use of directive antennas in uniform circular arrays (UCAs), as opposed to omnidirectional elements such as dipoles or monopoles. Improved DF performance would result in enhanced situational awareness on the battlefield for the CAF. DRDC-RDDC-2015-R010 i