A Study of Low-Profile, Broadside Radiation, Efficient, Electrically Small Antennas Based on Complementary Split Ring Resonators

The designs and performance characteristics of several electrically small antennas based on complementary split ring resonators (CSRRs) are reported. A coaxial-fed monopole is first integrated with a CSRR that is cut from a grounded finite copper disc. The presence of the electrically small CSRR element facilitates a nearly complete impedance match to the source, a nearly broadside radiation pattern, and a high radiation efficiency. The addition of a circular top-hat to the monopole then achieves an ultra-low profile (0.005 lambda(o)) design and an improved broadside pattern, while maintaining all other desirable features. Finally, to enrich their potential usefulness, two additional enhancements of these designs were accomplished. One is a further miniaturization (ka < 0.5) that is achieved by introducing a more complex CSRR element, while maintaining a high, 82%, radiation efficiency. The second is a further enhancement of the directivity and front-to-back ratio through the introduction of a slot-modified parasitic disc, while maintaining the original impedance matching, low-profile and electrically small properties. These designs were consummated and their performance characteristics evaluated with the frequency domain ANSYS-ANSOFT High Frequency Structure Simulator (HFSS) and were confirmed independently using the time domain CST Microwave Studio (MWS) simulator. A prototype of the basic system was fabricated and tested; the agreement between the simulated and measured results validates the design principles.