Approach for miniaturisation of planar antenna based on CRLH structure

Abstract

The need to miniaturise antenna size comes from that most mobile platforms having limited space for all the antennas required in the constantly growing wireless systems. Metamaterial-based transmission line, commonly referred to, composite right/left-handed (CRLH) transmission line has a unique feature of supporting an infinite-wavelength wave at a finite and non-zero frequency. As a result, zero- and negative-order resonance can be achieved. This Letter investigates the application of this concept for miniaturisation of planar antenna based on CRLH structure implemented with the microstrip line technology by using zero and high negative value of the phase constant ( β ). The concept is realised by applying microstrip-bends approach in the design of the CRLH unit cell in which high reactance can be provided by the constitutive parameters of the unit cell. Analytical results have validated the design concept and the modified CRLH unit cell based microstrip-fed monopole antenna, showing a high level of miniaturisation up to 85% from the conventional half-wavelength antenna. These results were obtained by CST Microwave Studio and verified by experimental data.