Small internal antennas for indoor UMTS base station with WLAN access point

In this paper the use of small internal mobile terminal type of antennas in a typically-sized indoor mobile communication base station is studied. The covered radio systems are 2 GHz UMTS and 2.45 GHz WLAN with diversity path for both thereby leading to four antenna elements placed at the corners of the printed wiring board (PWB). Separate solutions based on a planar loop and a PWB IFA -type of antenna elements are presented with optimal antenna arrangements and orientations. Simulated impedance bandwidths, isolations, radiation properties and estimated envelope correlations are shown. Based on the results, sufficient performances are achievable with both antenna types leading to at least 15 dB isolations and correlations less than 0.1 between the antenna elements. The proposed approach thereby offers a lightweight and a low-cost solution for the application, although the resulting radiation patterns are more irregular compared with a typical sleeve-dipole solution.