Design of compact multiple‐input and multiple‐output antenna based on slow‐wave corrugated strips

Abstract

A method of designing two-element compact multiple-input and multiple-output (MIMO) antennas with good isolation based on slow-wave corrugated strips (CSs) is presented in this paper. Using the slow-wave characteristic, a pair of CSs is applied as arms of each dipole antenna element to realise the compact design. A metal plane is placed between the two dielectric boards serving as the reflector so that the antenna can achieve good forward radiation. There are two coupling paths between the closely placed antennas: the coupling between the adjacent antenna arms and the coupling with the reflector. By adjusting the phase constants of the two coupling paths, good isolation is achieved in the operating frequency band without any additional de-coupling structures. A sample of a two-element MIMO antenna is fabricated at the centre frequency of 5.1 GHz with a bandwidth of 330 MHz. Measured results show good performance to support the design method. As each arm is about 1/8λ0 (λ0 is wavelength in free space), the edge-to-edge distance is 0.04λ0, and the isolation in the operating frequency is 15 dB.