Very‐low‐profile dual‐wideband loop antenna for LTE tablet computer

A very‐low‐profile (8 mm in height), small‐size (8 × 3 × 40 mm3), and dual‐wideband loop antenna suitable for applications in the LTE tablet device such as a tablet computer is presented. Dual‐wideband operation of the proposed loop antenna is achieved using a wideband feed structure formed by a coupling feed, a high‐pass matching circuit, and a tuning inductor. The coupling feed leads to successful excitation of a quarter‐wavelength loop mode in the desired lower band. The high‐pass matching circuit causes an additional resonance occurred near the excited quarter‐wavelength loop mode to widen the low‐band bandwidth to cover the 698–960 MHz band. The tuning inductor can adjust the frequency ratio of the first two higher‐order loop modes to form a wide higher band to cover the 1710–2690 MHz band. Dual‐wideband operation of the proposed loop antenna for the LTE operation is hence obtained. Details of the proposed loop antenna are addressed. Working principle of the antenna, especially the function of the wideband feed structure thereof, is described. Experimental results of the fabricated prototype are also presented.