Low-Profile Frequency-Reconfigurable LTE-CRLH Antenna for Smartphones

This paper presents a monopole antenna loaded with one frequency-reconfigurable composite right/left-handed (CRLH) unit cell. This antenna is designed by means of two varactor diodes and with changing capacitance operating at LTE700 (698-798 MHz), LTE850 (824-894 MHz), LTE900 (880-960 MHz), LTE1700 (1710-2155 MHz), LTE1800 (1710-1880 MHz), LTE1900 (1850-1990 MHz), LTE2100 (1920-2170 MHz), LTE2300 (2305-2360 MHz), LTE2500 (2496-2690 MHz), LTE2600 (2500-2690 MHz), and GPS (1176 MHz, 1227 MHz) frequencies that cover most of the LTE bands for smartphone handsets, which is a combination of two distributed and compact modes, in which the varactor diodes, as compact elements, play a significant role in reducing the antenna dimensions. By changing the capacitance, the entire frequency band of 700 MHz and 900 MHz was achieved. The CRLH structure, in turn, reduces the dimensions of the antenna and generates resonant frequencies less than the resonance frequency of the monopole. At these frequencies, the radiation patterns are quasi-omnidirectional.