Defected Ground Structure (DGS) Based MIMO Antenna Array With Decent Isolation Characteristics for Satellite Communications in Unified S‐Band (USB)

This research focuses on developing an efficient, high‐isolation Multi‐Input Multi‐Output (MIMO) antenna array for Mobile Satellite Services (MSS). A portion of the S‐band (2–4 GHz) ranging from 2 to 2.2 GHz, known as Unified S‐Band (USB), is utilized for MSS, particularly for Space‐to‐Earth communications. The ultimate objective of the proposed MIMO is to cover the USB spectrum and resonate at 2.2 GHz. As the first step of the design process, a meandered line (ML) monopole patch with good radiation characteristics in the desired frequency band is designed. Then, the mirror image of the proposed ML radiator is added to the design to form a two‐element ML‐MIMO array. A well‐designed MIMO is highly beneficial for boosting the reliabilities, channel capacities, and frequency reuse in next‐generation communication. But at the same time, it inherently increases the coupling effect between closely placed radiators, which may degrade the performance of the overall design. To overcome the coupling effect, a defected ground structure (DGS) is proposed in the partial ground plane of the ML‐MIMO. The proposed DGS intends to reduce the coupling effects by perturbing the surface current distributions in the partial ground plane. Meanwhile, the DGS also enhances the compactness of the entire structure by boosting the gain and reducing the total weight. MIMO parameter metrics such as axial ratio below 3 dB, envelope correlation coefficient less than 0.0005, and a diversity gain close to 10 are also aimed by simultaneously reducing the mutual coupling below −30 dB and return loss below −25 dB for standard MIMO applications. The ML‐MIMO is then fabricated on a FR4 substrate with a dimension of 40 mm by 48 mm, and measured. The simulated outcomes are found to be in close approximation with the measurement outcomes. A detailed comparison and trade‐off analysis of the proposed design with respect to other contemporary research is also presented for further validation.