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The theory and design of a new family of ultra-wideband (UWB) metamaterial (MTM) microstrip array antennas based on fractal and Fibonacci geometric patterns are investigated. First, the UWB microstrip array antenna is presented with two radiating MTM elements. Then, using fractal and Fibonacci geometric patterns, the array antenna is expanded. Improvements in the antenna parameters is achieved by repeating the second and third iterations of the fractal and Fibonacci patterns. As the order of iteration of the fractal and Fibonacci geometric patterns increases, the impedance bandwidth of the MTM microstrip array antenna increases, and its radar cross-section (RCS) decreases. The impedance bandwidth of the array antenna with two MTM elements is 3.37–9.2 GHz, while the bandwidth of the third-iteration Fibonacci and fractal MTM array antennas are 3.5–10.1 GHz and 3.55–10.34 GHz, respectively. Furthermore, the proposed array antennas exhibit lower RCS due to metal area reduction, with respect to the array antenna with two MTM elements.

In this study; theory, design and modeling of a new topology of ultra-wideband (UWB) metamaterial (MTM) loaded microstrip array antenna using Fibonacci & fractal geometric patterns are analyzed. This antenna is made basically from many monopole elements which are loaded by complementary metamaterial transmission line (CMTL) unit cells. The distributed CMTL element, contains a Koch-shaped expanded complementary single split ring resonator (CSRR) pair. At first step, the UWB microstrip array antenna designed with two CMTL-loaded monopole element. So, using an iterative method based on the Fibonacci and fractal geometry patterns, the array antenna is expanded. As the order of iteration increases, the impedance bandwidth of the proposed array antennas improve more, and the radar cross section (RCS) decreases. the impedance bandwidth of the proposed third-order Fibonacci and fractal CMTL-loaded array antennas are 250 MHz and 539 MHz more than the two-element CMTL-loaded array antenna, respectively. Finally, this paper presents an improved method to extract the parameters of an equivalent circuit model of the proposed MTM-loaded array antenna. Verification of the equivalent model have been validated utilizing ADS software. The obtained model, in addition to numerically efficient in comparison with the full wave analysis utilizing the moment method, gives a good physical insight to the mutual coupling mechanism of the array antenna.