A matrix-based design of broadband low-profile isolation and matching circuit for compact Wi-Fi/WLAN MIMO antenna arrays

Abstract

Abstract A novel microstrip network is proposed for simultaneously controlling and improving the isolation and impedance matching in a highly-coupled printed monopole antenna array. This easy-to-fabricate network with a reduced number of key parameters including only an inductive microstrip line between two feeds, some functional simple links and two shorted stubs is designed in a small area. A matrix-based study on the total system along with an equivalent analysis method on the subsystem is presented to simplify the total study, noticeably. Network-based closed-form equations for real and imaginary parts of the self and mutual admittance of the antennas are extracted to establish the conditions and determine the parameters. A good agreement between the simulation and measurement of the prototypes is also provided. The results propose a broad bandwidth about 200\xa0MHz at 2.45\xa0GHz with an improved matching over 15\xa0dB from 2.39 to 2.5\xa0GHz. In this band, the isolation is improved over 32\xa0dB with a maximum of about 70\xa0dB. Using this network, not only good space diversity and high polarization purity are achieved, but also the correlation coefficient is reduced, notably. According to these suitable specifications, this efficient circuit can be a promising design for new compact MIMO-based Wi-Fi/Bluetooth/WLAN systems.