A Simple Broadband Antenna for MIMO Applications in Cognitive Radio

In this paper, a simple type of printed dipole is proposed for Multi-Input Multi-Output (MIMO) applications in cognitive radio. The antenna is composed of a transmission line and a dipole. Some examinations of key factors and optimized parameters of the antenna are presented. The measured results illustrate that the proposed antenna offers a bandwidth of over 50% for VSWR less than 2, extending from 2.4 GHz to 4.02 GHz. The antenna peak gain in E-plane and radiation patterns at different frequencies are also explored. In addition, based on the proposed antenna, we introduce two simple broadband arrays for MIMO applications in cognitive radio. One has two ports and the other has four ports. Measurement results indicate that the arrays also work in a broad bandwidth. Furthermore, mutual couplings between ports in each array are kept under -10 dB at the low frequencies and under -20 dB at the high frequencies of bandwidth of the arrays.