Ultra-broadband antenna with robustness to body detuning for 4G eyewear devices

An ultra-broadband antenna design for 4G cellular coverage in eyewear devices is presented in this paper. The antenna has been designed considering a realistic eyewear PCB and its dielectric frame. In order to overcome any negative effects from the antenna's surroundings (frequency detuning due to the head and the hand of the user), the antenna was designed to cover continuously the 700-2700 MHz band with a reflection coefficient below -6 dB instead of a dual-band behavior usually required for 4G operation: 700-960 MHz and 1700-2700 MHz. The antenna was of capacitive coupling element type with its appropriate matching network to cover the mentioned frequency interval. To emulate a realistic device, an ABS plastic dielectric frame was manufactured using 3D-printing technology. The antenna was simulated and tested in three different use-cases as: "default case with user's head", "with head and hand" and "free space" cases. State-of-the art performance is demonstrated. The specific absorption rate (SAR) behavior was also investigated through simulations and measurements to check the compliance with regulations.