# A Miniaturized RHCP Slot Antenna for Wideband Applications Including Sub-6 GHz 5G
## 6 Measured Results  
The front and back views of the prototype of the presented wide-slot antenna are illustrated in Figures 15a,b, respectively. It should be noted that the measured reflection coefficient is achieved with the help of the Amitec VNA40 network analyzer. The measurement setup of the radiation pattern, axial ratio, and gain is exhibited in Figure 16a inside an anechoic chamber, while Figure 16b shows the CNC milling machine (LPKF ProtoMat S42) used for fabricating the proposed antenna. The antenna was fabricated using an FR4 substrate manufactured by pwcircuits.co.uk Canal Street, South Wigston, Leicester LE18 4 PN, UK (h = 1.6 mm, \(\varepsilon_{r}\) = 4.3) with 0.035 mm copper thickness. To fabricate the antenna layout, the design was first exported from the simulation software (CST) [52] in the Gerber file format, which is the industry-standard format for PCB manufacturing. This file was imported by the LPKF CircuitPro CAM software, which converted for the CNC milling machine (LPKF ProtoMat S42) manufactured by LPKF (Tianjin) Co., Ltd. Tianjin, China (100%) as shown in Figure 16b. This allowed the machine to accurately remove the unwanted copper areas and realize the antenna structure on the FR4 substrate. Figure 14: Simulated 3D normalized power pattern of the proposed antenna at f = 2.2 GHz. Figure 15: The prototype of the proposed wide-slot antenna: (**a**) front view and (**b**) back view. The simulated and measured results of the \(S_{11}\) and Ars are demonstrated in Figures 17a,b, respectively. The BW is calculated based on (\(f_{1}\), \(f_{2}\) for simulated results) and (\(f_{1}^{\prime}\), \(f_{2}^{\prime}\) for measured results), which are marked in the figure. These frequencies represent the lower and upper cutoff frequencies, respectively, where the BW criterion is satisfied (\(\mid\)\(S_{11}\)\(\mid\)\(<\)\(-\)10 dB and AR \(<\) 3 dB). The simulated \(-\)10 dB impedance BW is equal to 2.8 GHz (85%) along the range (1.90-4.7 GHz), while the measured \(-\)10 dB impedance BW is 2.65 GHz (78%) (from 2.08 to 4.73 GHz). On the other hand, the simulated 3 dB ARBW is 2.52 GHz (80%) extending along the range (1.90-4.42 GHz), whereas the measured 3 dB ARBW is equal to 2.31 GHz (71.6%) over the frequency range (2.07-4.38 GHz). The difference between the simulated and measured results can be attributed to several factors. These factors include fabrication tolerances and imperfections in the SMA connector soldering. The measurement setup limitations includereflections from nearby equipment inside the anechoic chamber or cable losses. Additionally, parasitic effects of the SMA connector can lead to an impedance mismatch, causing a slight shift in the resonance frequency. Moreover, substrate moisture absorption, especially in FR4 materials, may increase the effective dielectric constant, resulting in a lower resonant frequency and reduced bandwidth. Figure 16: (**a**) The measurement setup of the radiation pattern, AR, and gain, and the (**b**) LPKF CNC machine. Figure 17: Simulated and measured results of the proposed antenna: (**a**) reflection coefficient and (**b**) AR. Figure 18 depicts the simulated and measured results of the realized gain as a function of the frequency. This figure shows gain values larger than 2 dBi along the antenna BW. At 4.73 GHz, a peak gain can be observed, which is equal to 4.68 dBi. The realized gain values shown in Figure 18 are based on both simulation and experimental measurements. The measurements were conducted in an anechoic chamber using the gain comparison method in which a standard horn antenna was used as a reference (see Figure 16a). To ensure the accuracy and reliability of the measured gain, the measurement setup was carefully calibrated prior to testing, and a standard horn antenna with known gain was used. The measured gain values were compared with the simulated results and a reasonable agreement was observed, confirming the validity of the presented data.