Isolation improvement of compact LTE MIMO terminal using combination of neutralisation line and modified ground structure

Abstract

A multi-wideband MIMO antenna is presented for LTE MIMO terminals. The proposed antenna covers LTE700, GSM1800, GSM1900, UMTS, LTE2500, and Wi-Fi frequency bands. The multi-antenna elements are placed at the top two corners of printed circuit board (PCB) in the mirror image position. Each antenna element consists of a driven element and a shorted radiating element. To make the compact antenna structure, radiating element is meandered, folded, and shorted to the ground through copper wire. The size of each radiator is 15 × 25 × 4 mm3. Further, a combination of neutralisation line and modified ground structure is designed and deployed between radiating elements to reduce the mutual coupling between them. According to the measurement results of the fabricated antenna prototype, the isolation between two antenna ports is better than -12 dB over the operating frequency band. The simulated and measured results are found in close agreement. Moreover, to investigate the performance of the proposed antenna on the real application platform, mobile environment and user proximity analyses are carried out. Besides, total radiated power (TRP), channel capacity loss (CCL) and specifi c absorption rate (SAR) to peak location spacing ratio (SPLSR) are calculated and found well below the limit of Federal Communication Commission (FCC) standard.