Parasitic element dependent scattering parameter evaluation of GaN MESFET

Abstract

that its resonant frequency is far beyond the operating bandwidth of the antenna, thus minimizing the back radiation. The two orthogonal polarizations (Figures 1 and 2) including microstriplines are made in two different layers. This feeding technique is preferable, as it improves decoupling between the ports. The parameters of the antenna were optimized with the use of the electromagnetic software package Ansoft Ensemble. The two corporate feed networks were optimized with the use of LINMIC as well as Ansoft Ensemble. EXPERIMENTAL RESULTS AND DISCUSSIONIn order to characterize the planar array antenna for input impedance and mutual coupling as a function of frequency, the return loss and coupling coefficient were measured at both feeding ports. The bandwidth was around 20% at both ports for horizontal and vertical polarizations over the frequency range; the coupling coefficient varied from below Ϫ20 to Ϫ23 dB. The measured S parameters are shown in Figure 3.The measured array radiation patterns are shown in Figures 4 and 5 in both the elevation and azimuth planes at a horizontal port. The radiation pattern for the port exhibits almost similar characteristics. The patterns at the band edges as well as at the center frequency are given in the same figures. Measurements were carried out for both co-and cross polarization. The radiation patterns show at both ports a first side-lobe level between Ϫ14 and Ϫ18 dB for both planes. The cross-polarization performance over the band was found to be within Ϫ19 and Ϫ22 dB. The beamwidths at the azimuth and elevation planes are, respectively, 11°a nd 36°at the center frequency. The measured gain is approximately 17 dBi. As compared to the performance of the single radiating element, which exhibits 26% bandwidth, the array bandwidth is reduced to 20%. This is attributed to the mutual coupling between the antenna elements and the coupling due to microstrip lines in the feed network disturb the power weightings (and therefore the side-lobe levels). All these factors also contribute to an increase in the cross-polarization level. Figure 6 shows a photo of the fabricated array. CONCLUSIONBroadband performance of a 3 ϫ 6-element array antenna has been achieved with the use of a stacked SSFIP antenna with stacked feed lines for dual polarization. The measured results show desired bandwidth performance as well as very low back radiation on the order of Ϫ30 dB, thus ensuring better gain. The isolation between the ports is better than Ϫ23 dB, and cross-polarization suppression is between Ϫ19 and Ϫ22 dB. ACKNOWLEDGMENTThe authors thank Director SAC for necessary support and encouragement.

Design of interconnected 1D nanomaterials with selective localization in biodegradable binary thermoplastic nanocomposite films for effective electromagnetic interference shielding effectiveness

“…The total shielding effectiveness and its components could also be expressed as scattering parameters or S‐parameters (Equations 11, 12, and 13) which are essential parameters to describe the shielding efficiency of polymer nanocomposites in a VNA. In the case of a two‐port VNA, the S‐parameters are: Input reflection coefficient (), reverse transmission coefficient (), output reflection coefficient (), and forward transmission coefficient () 2,38 …”

Synthesis of ionic liquid modified 1‐D nanomaterial and its strategical distribution into the biodegradable binary polymer matrix to get reduced electrical percolation threshold and electromagnetic interference shielding effectiveness

“…The multiple reflection co‐efficient is negligible if the < −10 dB 35–38 . The mathematical relationships between different components of Total EMI shielding efficiency have been depicted in Data S1 (section 5).…”