## 3 Proposed Ku-Band Sharp Bent Right-Hand/Left-Hand Transmission Line-Based LWA
### Validation and Implementation of Proposed Ku-Band LWA  
Figure 5 shows the geometry of the proposed Ku-band leaky wave antenna. The length of the antenna was 71.4 mm with the period \"d\" of each unit element equal to 10.6 mm. The proposed antenna has been fabricated using the standard fabrication technology. The dielectric constant of the substrate was 2.2, and it had a 0.5-mm thickness. The fabricated prototype of the proposed dual band leaky wave antenna is shown in Figure 6. For simulating the design, the transient solver in CST Studio Suite has been used.  
Figure 7 depicts the simulated and measured results of the S-parameter (S\({}_{11}\) and S\({}_{22}\)) for the proposed antenna design. It can be clearly seen from Figure 7 that the antenna has achieved a broadband impedance matching in the frequency region of the Ku-band. The maximum return loss was around 40 dB. S\({}_{21}\) varied from \(-\)5 dB--10 dB across the whole frequency band. This shows a very good leakage property of the proposed leaky wave antenna. A dual resonance has been obtained in the Ku-band as desired and estimated.  
Figure 5: Geometry of the proposed Ku-band leaky wave antenna (length = 71.4 mm, d = period of each unit element, \(\theta_{\text{C}}\) = bending angle.)  
Figure 6: Prototype of the proposed Ku-band leaky wave antenna.  
Figure 7: S-parameters of the proposed Ku-band leaky wave antenna (reflection S11 and transmission S21 parameters: simulated and measured).  
Figure 8 shows the measured co-polar and cross-polar radiation patterns of the proposed Ku-band CRLH leaky wave antenna. Figure 8a is the pattern at 13.0 GHz, Figure 8b the pattern at 14.0 GHz, Figure 8c the pattern at 16.0 GHz, and Figure 8d the pattern at 16.5 GHz. It can be observed from the results that the antenna has achieved forward scanning at frequencies of 16.0 GHz and 16.5 GHz and backward scanning at frequencies of 13.0 GHz-14.0 GHz. This type of left-hand right-hand scanning was obtained as a result of the fast wave mode defined by the air line in the dispersion diagram. The gain obtained was very good throughout the frequency bands of operation varying from 11 dBi-14 dBi. At a frequency of 13.0 GHz, the main beam direction was about \(-30\) degrees and at 17 GHz, the main beam scanned to +45 degrees. This phenomenon has already been discussed in the sections above and was a result of the CRLH-type behavior of higher modes. The results of this investigation have proven beyond any doubt that forward and backward scanning has been observed in the two frequency bands of operation. The minimum cross-polar levels obtained were around \(-18\) dB in the operating frequency band.  
Figure 9a depicts the efficiency and Figure 9b depicts the 3-dB beamwidth graph of the proposed leaky wave antenna as a function of frequency. The efficiency has improved from 80-95 percent as the frequency increased from 14.0 GHz-17.0 GHz. Due to the increase in the leakage radiation, the gain increased from lower frequencies to higher frequencies. At higher frequencies, the efficiency reached 90-95 percent, satisfying the criteria for leaky wave generation. Figure 9b shows the variation of the 3-dB beamwidth with the frequency. The beamwidth was slightly higher due to the fact that the attenuation constant may be large at a few frequency points especially at the extreme ends of the frequency band.  
Figure 8: Measured radiation patterns (co-polar and cross-polar) with scanning: (**a**) 13 GHz, (**b**) 14 GHz, (**c**) 16 GHz, (**d**) 16.5 GHz.  
Figure 10 shows the E-field distribution, and Figure 11 shows the 3D radiation patterns at different frequencies for the proposed leaky wave antenna. The 3D pattern has clearly shown the scanning feature and beam directions at different frequencies in the left-hand and right-hand quadrants.  
Figure 10: Field distribution of the proposed Ku-band leaky wave antenna.  
Figure 9: (**a**) Efficiency of the proposed Ku-band leaky wave antenna and (**b**) 3-dB beamwidth variation with frequency.