A high gain filtenna with radiation nulls using a novel split-merge feed line on a slot-loaded rectangular patch for X-band RADAR application

Abstract

This study presents a single-layer microstrip filtenna designed to achieve a high gain performance. The design incorporates a slot-loaded rectangular patch along with a defected ground structure (DGS). The design of antenna-1 begins with a rectangular patch that includes four vias, a rectangular ring slot and two triangular slots in the ground structure. For improved bandwidth and enhanced filtering performance, antenna-2 employs a unique split-merge feeding approach, incorporating a rectangular slot into the antenna-1 structure. For the proposed filtenna, two rectangular parasitic patches are placed on either side of the split-merge feedline, with a diamond-shaped slot inserted in the middle of the patch in the antenna-2 for improved upper stopband rejection and less reflection coefficient. The proposed antenna ensures accurate frequency selectivity and effective radiation performance by utilizing the TM₁₀ and TM₁₁ resonant modes. The antenna is developed, fabricated, and tested experimentally on Rogers 4003C material. The proposed filtenna’s measured results show that its radiation nulls in the lower and upper rejection bands are $-25.19$ dB and $-35.01$ dB, respectively, a reflection coefficient less than $-14$ dB and a peak gain of 11 dB. Its overall dimensions measure $60\times 46\times 0.8$ mm³.