Design of wideband end‐fire composite microstrip‐monopole antenna

Abstract

This article introduces a wideband composite antenna with end-fire radiation. The structure is achieved by uniting a center-fed microstrip shorted patch and a parasitical monopole. The monopole is vertical to the substrate and work as an electric current source. Because the loaded monopole breaks the symmetry of the center-fed microstrip antenna, the original patch antenna can work as in-phase equivalent magnetic current sources radiation. Then complementary sources are generated by orthometric magnetic current source and electric current source. The typical unidirectional radiation capacity has a good endfire beam. The loaded monopole adds a resonant mode to the original microstrip antenna, which makes the composite microstrip-monopole antenna to exhibit an enhanced bandwidth of 26.9% and an average gain of 7.5 dBi. The complementary sources radiation mechanism can generate special unidirectional radiation patterns in a compact space, so this antenna type is an excellent candidate for array applications. The prototype's planar size is only 0.36λ0 × 0.39λ0 (λ0 is the free space wavelength in center frequency). The eight elements phased array with the proposed antenna show perfect simulated scanning performance.