Four-transmitter time-switching symmetric TX antenna array for stable power reception under 1D rotation and 3D location variation

When a bee is flying in the air, its abdomen is at a fixed angle relative to the ground. If a dipole is attached to a bee horizontally, its polarization is always on the horizontal direction regardless of its fly direction. Vertical polarization radiation is therefore not required for the transmitting array. A four-transmitter array that radiates only at horizontal polarization is proposed at this paper. Under the same total input power to the transmitting array, the proposed four-transmitter array can increase received power by 50% as compared with the previously proposed 6T array under 1D rotation and 3D location variation. The 4T array, therefore, has better service area and volume performance than the 6T array. The 4T array also eliminates the need to install antennas at +z and -z directions, this can reduce the wiring complexity. Measurement results at 915 MHz also confirm the calculation results using the Friis equation.