Comparison between CRLH zeroth-order antenna and series-fed microstrip patch array antenna

A metal-insulator-metal (MIM) composite right/left-handed (CRLH) series-mode zeroth-order resonant antenna (ZORA) optimized for the 24 GHz ISM band is presented and compared to a series-fed patch array (SFPA) antenna. The CRLH ZORA exhibits superior performances for relatively short lengths (< 3lambda₀) whereas the SFPA may performs better, depending on the specific design, when the length is very long (> 5lambda₀), so that the resonant antennas operate as leaky-wave antennas with a leakage factor proportional to the density of the radiators along the structure. To our knowledge it the first time that the leaky-wave operation of an electrically very large ldquoresonatorrdquo has been explicitly identified. The ZORA is particularly recommended for average electrical sizes in the order of 2lambda₀, where it should be systematically superior to a SFPA.