A Single Inverted-F Antenna With Intrinsic Elliptical Polarization for Smartwatches

In this letter, a single inverted-F antenna (IFA) with intrinsic elliptical polarization in GPS L1 band is proposed for smartwatches, featuring a skyward-tilted and right-handed elliptically polarized (RHEP) beam under on-wrist conditions. First, it is demonstrated that a non-planar inverted-L antenna (ILA) can be equivalent to a V-shaped dipole (V-dipole). Elliptically polarized (EP) radiation can be achieved by adjusting the height of the V-dipole. In particular, the phase difference introduced by the height equals the angle of the V-dipole. Furthermore, under on-wrist conditions, a skyward-tilted RHEP beam is achieved by adjusting the bending direction and placement of the radiator. The measured results of the antenna prototype exhibit close agreement with simulations. The carrier-to-noise density ratio (C/N0) tests show that the proposed antenna achieves an average increase of 5.3 detectable satellites (C/N0 > 40 dB-Hz) and an average C/N0 improvement of 3.4 dB under identical ground dimensions and IFA clearance conditions.