Metamaterial Microwave Absorber (MMA) for Electromagnetic Interference (EMI) Shielding in X-Band

The present paper is aimed at investigating application of planar metamaterial (MM) structures for effective EMI shielding and stealth capability in X-Band. Various MM structures using FR-4 substrate and copper conductors were conceived and designed followed by simulations carried out using CST MWS Suite software. As a first step, the designs were aimed at achieving extremely high absorption for normal incidence, polarisation independence and maintaining high absorption in wide-angle performance while keeping the requirement of light weight, flexibility and environmental ruggedness in mind for deployability on platforms to achieve effective stealth capability against radars and for other EMI shielding applications. Circularly symmetric, single layer Metamaterial Microwave Absorber (MMA) design over thin FR-4 substrate in spokes and wheel structural arrangement provided these desired features. The thin FR4 substrate of 0.6 mm provides the light weight and flexibility while absorbing the EM waves. Rotational symmetry of the spoke and cut-wheel design gives it polarisation independence and 4 ring planar array concept with rings scaled to different sizes in the same plane in the unit cell provided the increase in bandwidth. Reduction in received signal level of the echo is depicted by the S-parameter at the input port. Getting values of this S-parameter less than -60 dB at resonant frequency for MMAs is highly encouraging and is not reported much in literature. Enhancement of nearly 3-8 times in operating bandwidth was achieved by changing size of rings in each quadrant in the co-planar array having four resonant rings in each unit cell.