| Summary: | Wireless power transfer (WPT) using far-field microwave radiation beam can be used to power unmanned aerial vehicles (UAVs) thus eliminating the need to land on the ground to charge. In a distributed WPT system, impulse radio ultrawideband (IR-UWB) signals can provide continuous power at the receiver end with a high rectification efficiency. Such far-field based distributed WPT systems require high gain ultrawideband (UWB) antenna arrays with a unidirectional radiation patterns and beam steering capability. This paper proposes a <inline-formula> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> phased array antenna with an ultrawideband (UWB) operating frequency range of <inline-formula> <tex-math notation="LaTeX">$7.5-8.5 GHz$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$20.9 dBi$ </tex-math></inline-formula> gain. The novelty of this work lies in the design of a single unit antenna to achieve UWB operation while maintaining high gain and unidirectional radiation pattern. Another contribution of this work is the determination of the array element spacing based on the theoretical modeling and simulation and measurement based validation to achieve the highest gain, minimum coupling coefficient, and lower side lobe level (SLL). In order to achieve beam steering, each <inline-formula> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> subarray is considered as a single quadrant thus dividing the <inline-formula> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> phased array antenna into four quadrants where all 16 single elements are individually fed. The far-field radiation beam is steered by controlling the phase difference between each quadrant. The proposed phased array antenna achieves a scanning range <inline-formula> <tex-math notation="LaTeX">$ > 51^{\circ }$ </tex-math></inline-formula> with 28° half power beam width (HPBW), gain ranging from <inline-formula> <tex-math notation="LaTeX">$15.4 dBi$ </tex-math></inline-formula> to <inline-formula> <tex-math notation="LaTeX">$20.9 dBi$ </tex-math></inline-formula>, and a maximum scanning loss of <inline-formula> <tex-math notation="LaTeX">$2.8 dB$ </tex-math></inline-formula> over the UWB operating frequency range.
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