Beam-steering high-gain array antenna with FP Bow-tie slot antenna element for pattern stabilisation

In this work, a beam-steering array antenna for pattern stabilisation is presented. The antenna element consists of two layers with a unique structure of microstrip to coplanar waveguide (CPW) transition to cover a frequency range from 20 to 30 GHz and a stable pattern at all operating frequencies. To increase the gain of the antenna element, an elliptical broadband Fabry-Perot cavity structure is used. The element manages 3 dB gain bandwidth of almost 23-26 GHz with a 14.4 dBi peak. In addition, a modified Butler matrix consisting of two 90° and two 135° couplers without phase shift section is used to attain a stable pattern. The proposed Butler matrix performs a stationary phase with a phase error of less than ±6° over a frequency band from 21 to 29 GHz. The integration of the proposed element and feed network leads to a beam-tilting antenna capable of managing its patterns through the input ports in the operating frequency range of 20-29.5 GHz (9.5 GHz) and 20.6-29.6 GHz (9 GHz) for ports 1 and 2, respectively.