In Fig. 4, we show with the simulated scattering parameters (S-parameters) at broadside, that the reflection resonance frequencies of the MS are above 15.8 GHz, which is much higher than the intended operational frequencies of the antenna array (below 5.0 GHz). The return loss for both the TE and TM polarizations is greater than 20 dB across the frequency band of interest and, hence, the insertion loss is virtually zero. Due to the unequal lengths of the two arms of the TC-UAJC element, they exhibit slightly different reflection resonance frequencies when illuminated by the TM and TE incident waves. Each resonance frequency is directly proportional to the unwound length, L, of the TC-UAJC element51.The first reflection resonance occurs at 15.8 GHz for the TM excitation when the electric field is along the longer arm; the second one occurs at 19.5 GHz for the TE excitation when it is along the shorter arm.Figure 4Magnitudes of the S-parameters for normal incidence. (a) TE and TM excitations of the MS. (b) An expanded view showing the first TM reflection resonance at 15.8 GHz and the first TE reflection resonance at 19.5 GHz. A TE transmission resonance can also be seen at 19.7 GHz.