Compact Circularly Polarized Array for Direction Finding: Use of Conventional Steering Vector versus Embedded Radiation Patterns

In this contribution, we explore a novel approach in the framework of direction finding for Bluetooth Low Energy application. Embedded Radiation Patterns are used to compute the required pseudo-spectrum, by experiencing an improvement with respect to Conventional Steering Vector approach. Specific tests on direction of arrival computation have been performed on a novel monolithic circularly polarized 3 x 3 microstrip antenna-array locator, fed by a grounded coplanar waveguide (GCPW). The array single element exhibits a 3.1% 6-dB axial ratio bandwidth, larger than other monolithic antennas proposed in the literature. The GCPW configuration ensures low crosstalk in the feeding network of a 3x3 array, with inter-element distance d = 0.4 lambda. We show that, thanks to the use of Embedded Radiation Patterns, that compensate mutual coupling and non-idealities, the inter-element distance can be reduced without affecting overall antenna performances in direction finding application.