Study and design of dual-band quarter-wave open-circuit stub based on Koch-fractal-shaped geometry of CSRRs

For the dual-band and miniaturization application in wireless communication, this paper presents novel arbitrary dual-band quarter-wave open-circuit stub with frequency ratio of 2.14 by combing the theory of fractal geometry and composite right/left handed transmission line(CRLH TL) for the first time. Novel open-circuit stub has been fabricated and measured in order to experimentally validate the effectiveness of the design. Measurement results show that novel open-circuit stub operating at 0.98 and 2.1GHz respectively possess return loss -27.4dB and -21.3dB, and with dimensions reduction by 47.4% compared with conventional design operating at 0.98GHz, which attributes to the unique hyperbolic-linear dispersion relation property of CRLH TL and space-filling property of fractal geometry. Good performance of the proposed structure indicates its prospective application foreground in modern wireless communication.