Return loss reduction of the metamaterial CRLH antenna using short-ended reactive stubs

The paper describes a method of reducing the return loss (RL) of a CoPlanar Waveguide (CPW) Composite Right/Left-Handed (CRLH) zeroth order resonance (ZOR) antenna by matching the radiating structure to the characteristic impedance Z₀ of a mm-wave circuit. The frequency of the studied antenna was f = 40 GHz. The initial RL value was S₁₁ = -16.21dB. The matching method use reactive stubs of length l placed on the antenna feeding line at a suitable point d. After that, the return loss at the feeding line input drastically improved to S₁₁ = -43.50 dB, demonstrating effectiveness of the matching process.