Practical use of realizable circuit structures such as stepped impedance resonators (SIRs) and various forms of transmission lines (TLs) can lead to highly selective, yet also quite small, single- and dual-band antennas. Analysis of antenna designs based on SIRs and composite right/left-handed (CRLH) transmission lines can show how to cover several frequency bands while also miniaturizing the antenna designs, for both quarter-wavelength and half-wavelength antenna configurations.
To demonstrate the approach, quarter- and half-wavelength antennas were designed with a common band centered at 4.5 GHz and an impedance bandwidth (|S11| < −10 dB) of 500 MHz, and with the half-wavelength antenna also handling a second frequency band centered at 1.8 GHz. For a fair comparison of the two configurations, the size of both antennas is the same (26 × 21.3 mm2).