Design of a Wideband Single-Layer Slot MIMO Antenna and Its Decoupling Method: Using the Odd- and Even-Mode Analysis Approach

This article proposes a novel wideband single-layer coplanar waveguide (CPW)-fed antenna element and multiple-input, multiple-output (MIMO) antenna based on a multimode resonator. Equivalent circuits of the multimode resonator are analyzed by adopting the odd- and even-mode analysis approach. To prove the effectiveness of the equivalent circuit, scattering (S)-parameters of the equivalent circuit are simulated in Advanced Design System (ADS). Additionally, transmission coefficients are studied under the weakly coupling condition. The first and second resonant points are introduced by even and odd modes, respectively, whereas the third resonance is caused by the embedded stepped impedance resonator (ESIR). The CPW-fed antenna element is designed based on the proposed resonator. CPW fed not only excites the multimode resonator but also generates an extra resonance between the odd mode and ESIR resonant frequencies. Furthermore, the odd-mode resonance creates the lower cutoff frequency, and the resonance caused by ESIR forms the higher cutoff frequency. Hence, a filteringlike operating frequency band is achieved without introducing an extra filtering circuit. The filtering characteristic is favorable for the system to realize high sensitivity and reduce outof-band interferences simultaneously.