Broadband Direction-Finding Antenna Using Suspended Microstrip-Line Hybrid Coupler for Handheld Devices

A compact, wideband, vertically polarized two-element sum/difference antenna with a suspended microstrip-line hybrid coupler is proposed, designed, fabricated, and measured. The antenna array has two independent ports that provide the sum and difference pattern. Therefore, it gives opportunity to detect the direction of an unwanted signal by comparing the signal levels. The simulated and measured results show that the antenna bandwidth where S₁₁ below -10 dB for both sum and difference ports is between 2.4 and 4 GHz. The isolation between the sum and difference ports is measured better than 14.5 dB. These features result in a wideband and compact sum/difference antenna-coupler mechanism, which is suitable for handheld terminal applications of unwanted signal detection.