A Dual Band Decoupling Technique for MIMO Antenna Systems Using Composite Capacitor Circuits

This paper presents a dual-band antenna decoupling technique with independent control using composite capacitors. Due to the inherent frequency-selective characteristic of the decoupling structure, the decoupling in one band has almost no effect on that in the other band, so the decoupling in the two bands can be independently controlled simply by providing two different desired capacitances, which is achieved using the proposed composite capacitors. An equivalent circuit is presented to reveal the mechanism of the decoupling and frequency-selective characteristics. Two demonstrative examples using proposed composite capacitor circuits are extensively studied by simulation and measurement. The results show that with the proposed decoupling scheme, not only the isolation but also the performance of the total efficiencies and the envelope correlation coefficients are all improved. Benefiting from the composite capacitors, the total footprint of the dual-band decoupling structure is only 5 × 3 mm2, which is extremely compact compared with the existing methods.