# A Rectangular Notch-Band UWB Antenna with Controllable Notched Bandwidth and Centre Frequency
## 3 Antenna Measurements  
The modeled antenna was fabricated on Taconic TLY 5A (1.52 mm) for experimental verification, as shown in Figure 13. The impedance and radiation characteristics of the designed antenna were measured by an Agilent vector network. Figure 14 shows the simulated and measured impedance characteristics. The measured and simulated results are well-matched. The antenna showed good impedance matching characteristics throughout the entire UWB spectrum (3.1-12.5 GHz) with the exception of the WLAN band (5.1-5.9 GHz), which was rejected to avoid interference. There is a difference between simulated and measurement \(|\)S\({}_{11}\)\(|\) results, especially at high frequencies. This discrepancy is most likely due to cable losses and fabrication tolerances. Figure 12: Demonstration of controllable notch band of the proposed antenna: (**a**) bandwidth and (**b**) frequency. The measured and simulated peak gains of the antenna are plotted as a function of frequency, as shown in Figure 15. In the measurement of peak gain, a well-calibrated standard horn antenna was used as the source antenna while the fabricated prototype was measured as the receiving antenna. Transmit and receiver amplifiers were used to provide stable power reception. The antenna under test was rotated to measure the peak gain at different orientations. A stable peak gain curve was obtained in the frequency range of interest with a maximum value of 4.5 dBi, but it sharply decreased to about -6 dBi at the notch band. This demonstrates the effectiveness of the antenna's rectangular notching characteristics. Figure 16 shows the simulated and measured radiation patterns in \(H\)-plane (xz-plane) and \(E\)-plane (yz-plane) at 3, 7, and 10 GHz. The radiation pattern at \(H\)-plane is nearly symmetrical and omnidirectional for 3, 7, and 10 GHz, however, in \(E\)-plane the radiation patterns are bidirectional with dumbbell shape. The radiation pattern at \(E\)-plane in 10 GHz shows little deterioration because of the increased radiating area at higher frequencies. Figure 14: \(\lvert\)S\({}_{11}\rvert\) characteristics of the proposed antenna. Figure 13: Photo of fabricated UWB antenna with rectangular notched band: (**a**) front side (**b**) back side. Figure 15: The measured and simulated gain of the proposed antenna. Finally, the antenna is compared with the previously reported rectangular notched band antennas [19; 20; 21; 22; 23; 24] in terms of overall size, controllability of the notch-band bandwidth and frequency, and design complexity (Table 1). Almost all the antennas are large and have complex geometries. The antenna presented in [19; 21] are very large and lack controllable frequency and bandwidth. Although the antennas reported in [20; 22] offer the advantages of controllable bandwidth and frequency, the former is very large, and the latter have the disadvantage of design complexity, which is due to the presence of many stubs and slots; moreover, they require two-port excitations in its operation. The antenna designs proposed in [23; 24] offer controllable bandwidth without frequency shifting of the notch band, which is due to their complex geometry. In summary, the proposed antenna outperformed the existing rectangular notch UWB antennas based on its simple design and small size, as well as the controllable bandwidth and frequency of the notch band.