Wideband Fish-Bone Antenna Utilizing Odd-Mode Spoof Surface Plasmon Polaritons for Endfire Radiation

Abstract

A wideband fish-bone-shaped end-fire antenna utilizing odd-mode Spoof Surface Plasmon Polaritons (SSPPs) is proposed in this communication. Consisting of a microstrip-to-slotline converter and a differential-mode exciter, the feeding structure of this antenna can excite odd-mode signal on the SSPPs structure. The fish-bone-shaped SSPPs radiator can realize end-fire radiation, which is equivalent to a row of small current sources. A tapering end is introduced to the SSPPs radiator, realizing broader upper bandwidth. A prototype of this antenna is fabricated. Measured results exhibit that a wide impedance bandwidth of 70.3% (2.4.5.0 GHz) for |S11|<-10 dB is obtained. Stable end-fire radiation patterns and low cross polarization below -20 dB are also realized in desired frequency band. The gain varies from 4.4 to 8.6 dBi within the whole operating band while a radiating efficiency of 90% can be observed. This antenna has a compact size of 1.36λc ×0.86λc ×0.012λc (λc is the free space wavelength at 3.7GHz)