A Nonbalancing End-Fire Microstrip Dipole With Periodic-Offset DSPSL Substrate

A nonbalancing microstrip dipole with end-fire capability is presented. The proposed antenna consists of a simple microstrip-fed dipole with a periodic-offset double-sided parallel-strip line (DSPSL) substrate, which is used to replace the balun of a conventional end-fire antenna. The periodic-offset DSPSL substrate exhibits phase shift characteristics and excites the odd mode of the microstrip dipole. A director and a truncated ground are used to increase the directivity of the antenna. After placing the DSPSL, the bidirectional radiation pattern is converted to a unidirectional one. The measured and simulated results indicate that the antenna operates at 2.4 GHz. End-fire directional radiation patterns are obtained with this novel periodic substrate. When compared with the original design of the microstrip dipoles, the proposed microstrip dipole uses the periodic-offset DSPSL substrate to replace the balun. The front-to-back ratio is about 10 dB. The design method of the end-fire antenna is a new technique and can be easily applied in other antennas.