Self-Decoupling Design for Multiple Monopole Antenna Systems by Reusing Multiple Parasitic Resonances

This paper presents a systematic design method for multiple monopole antenna systems by exploiting the existing parasitic resonances of one or several antennas to achieve decoupling between the remaining strongly coupled antennas. A three-monopole element and a seven-monopole element antenna array that are closely packed are designed as illustrative examples to elaborate on this method. The three-element array consists of two identical antennas as high band (HB) antennas working at 3.5 GHz and a single low band (LB) antenna working at 2.4 GHz. Then, a compact seven-element antenna array with a pair of middle-band (MB) antennas operating at 5G N78 band, four HB antennas working at N79 band, and one LB antenna operating at 2.4 GHz is also presented in detail. The measured results show the isolation between the antennas increases from around 10 dB to better than 15-20 dB while reflection coefficients are below -10 dB within the corresponding band is obtained. Furthermore, this method also maintains the radiation characteristics of all elements. The total efficiency of the elements is increased by an average of 13%, and envelope correlation coefficients (ECC) are lower than 0.02, showing the great potential of the proposed method to be applied to multiple antenna systems with stringent constraint on volume.