## 4 Comparison between Simulation and Measurement  
Further investigation into the simulated characteristics of the proposed antenna design is provided and verified through measurement. The proposed planar, wideband, bow-tie antenna is fabricated by etching copper onto a flexible 50 \(\upmu\)m thick PET film, which has a permittivity of 3.3 and a loss tangent of 0.005. The prototype, shown in Figure 9, is then measured in an anechoic chamber using a 180\({}^{\circ}\), -3 dB hybrid coupler (Krytar 4005070) operating from 0.5 to 7 GHz as a balun [19]. Two input ports of the hybrid coupler are 180\({}^{\circ}\) out of phase with each other. These ports are connected to SMA cables, which are soldered together on the sides. The open end of each cable is soldered to each arm of the prototype, as shown by the silver dots of the soldering material on the center of the fabricated antenna in Figure 9. The hybrid coupler also has two output ports--the summing port and the differential port. The summing port is terminated by a 50 \(\Omega\) load and the differential port is connected to an Agilent E5071C network analyzer to record the measurement data. The measurement of the wideband, planar, bow-tie antenna in an anechoic chamber is shown in Figure 10.  
Figure 10: The measurement of the proposed wideband, planar, bow-tie antenna in an anechoic chamber. Figure 9: The prototype of the proposed wideband, planar, bow-tie antenna. The measured \(S_{11}\) is shown in Figure 11, overlapped with the simulated one. From the measurement, the \(-10\) dB bandwidth is 80.3% (1.23-2.88 GHz), and matches well with the simulation results (highlighted by the grey area) of 80.2% (1.26-2.97 GHz). Since the PET supporting structure is extremely thin, it has a negligible effect on the antenna performance, as demonstrated by the similarity between the simulation (where the PET film is not included) and the measurement (where the PET film is used to support the antenna) results. The simulated and measured forward realized gains are also shown in Figure 11. The simulation results confirm that the backward realized gain is identical to the forward realized gain, and, therefore, the backward realized gain is omitted in Figure 11. Both the simulation and measurement results show that a steady realized gain is maintained throughout the \(-10\) dB bandwidth, with simulated values of 1.6-3.8 dBi and measured values of 1.5-3.8 dBi. The measurement results agree well with those of the simulation. The measured radiation patterns at the lowest frequency (1.26 GHz), at one-third of the \(-10\) dB bandwidth (1.84 GHz), at two-thirds of the \(-10\) dB bandwidth (2.41 GHz), and at the highest frequency (2.97 GHz) are compared with the simulated ones in Figure 12. The simulated XY-plane radiation patterns are also shown in Figure 12 for a comprehensive view. The proposed antenna design is linearly polarized. For each frequency, the radiation patterns in both the XZ plane (parallel to the plane the antenna lies in) and YZ plane (perpendicular to the plane of the antenna) are shown. Overall, the simulation and measurement results match fairly well. Bi-directionality is demonstrated at each of the frequencies investigated. As previously mentioned, the opposing currents on bow-tie-86 and bow-tie-130 shown in Figure 8d result in a minor distortion of the radiation pattern at the highest frequency (2.97 GHz) of the \(-10\) dB bandwidth in the XZ plane (Figure 12d), and a gradual loss of omnidirectionality in the XY plane as the frequency increases.