## 3 Results and Analysis
### Measurement Results  
To validate the polarization characteristics of the square patch metasurface energy-harvesting experimentally, four 10 \(\times\) 10 arrays were fabricated, with via positions from the center of the patch (\(\varphi_{p}\)) at angles of \(0^{\circ}\), \(30^{\circ}\), \(45^{\circ}\), and \(60^{\circ}\), as shown in Figure 9a,b. The 10 \(\times\) 10 array configuration was selected to provide an adequate electromagnetic response for experimental validation, minimizing edge effects and enhancing the measurement accuracy of the metasurface's polarization characteristics. Figure 8: The relationship between dip angle of voltage and geometry angle position of resistor from center of the patch. A blue dashed line represents a linear relation between dip angle of voltage and geometry angle position of resistor from center of the patch. The metasurface was fabricated using an FR-4 substrate with a thickness of 1 mm, and other parameters were set to be the same as those listed in Table 1. The total size of each 10 \(\times\) 10 array is 15 cm \(\times\) 15 cm. The front of the unit cell and the back-side of the ground plane were coated with a green resist to prevent oxidation and avoid short circuits during component soldering. A dedicated soldering pad pattern was provided on each unit cell on the ground plane for mounting a lumped resistor or a connector, as shown in Figure 9b. The metasurface was illuminated by a horn antenna connected to a vector network analyzer (VNA) positioned at a distance of 110 cm (R = 110 cm), providing incident power uniformly across all unit cells. The distance R was determined based on the horn antenna's aperture to ensure far-field conditions. All measurements were conducted inside an anechoic chamber to eliminate reflections and external electromagnetic interference. In the experimental setup shown in Figure 9c, a Rohde & Schwarz ZVB VNA and an A-INFO LB-10125-SF broadband horn antenna were used to measure the transmission coefficient (S21) of the designed metasurface. The VNA was calibrated using the UOSM (Unknown Through-Open-Short-Match) method with a Rohde & Schwarz ZN-Z51 calibration kit, including the connected cables, prior to conducting the measurements. The S21 parameter, representing the harvested signal through the lumped resistor, was then compared with the simulation results. The central unit cell was chosen for measurement due to its minimal edge effects and closest to the conditions of an infinite array. The measurement connection was established using a U.FL connector, which was soldered onto the metasurface and modeled in the simulation as a lumped resistor oriented in a specific direction. To emulate the electromagnetic coupling environment observed in the simulations, all other output ports from the unit cells in the array were terminated with 50 \(\Omega\) loads by soldering lumped resistors onto the designated pads (see Figure 9b). To vary the polarization angle during the experiment the metasurface was rotated while the transmitting horn remained stationary. The center of the metasurface was precisely aligned with the center of the horn's aperture. To make a fair comparison between simulation and measurement, the measured S21 parameter from the VNA is interpreted as an indicator of the voltage across the 50 ohm resistor. In the experiment, the metasurface was illuminated by a plane wave, and the central unit cell was connected to port 2 of the VNA through a matched coaxial connector. The S21 value thus reflects the amount of power that is harvested and delivered through the lumped resistor. Figure 9: Fabricated 10 \(\times\) 10 array of the metasurface unit cells: (**a**) the top and (**b**) the bottom. (**c**) The measurement setup used in the experiment. Although S21 is measured as a transmission coefficient, it can be considered proportional to the voltage across the resistor under the assumption of proper impedance matching.