A Novel Compact Single-Layer Single-Patch Dual-Band Filtenna

This communication proposes a compact single-layer singlepatch (SLSP) dual-band filtenna within a half wavelength. A stub load (SL) dual-band structure and an oblique slot line (OSL) structure are introduced in the patch for additional filtering. The SL structure is designed for the coexistence of the TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode and an equivalent TE01 mode within a patch. Both modes resonate at their respective half-wavelength fundamental modes, avoiding a large electrical size. The resonant frequencies of these modes can be independently adjusted. Furthermore, the OSL structure is designed in the patch which splits the original TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode into two modes with approximately spatially complementary field distributions. Simulations and experiments demonstrate that the OSL provides a controllable out-of-band radiation null (RN) point. The working mechanism of the SL and OSL is analyzed, providing the principle of controlling the RN. By selecting an appropriate location for the OSL, the higher-order TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> mode can be suppressed, further deepening the out-of-band rejection between the two operating bands. To enhance the suppression performance in the higher frequency band, an additional RN is introduced through a U-shaped slot. The final SLSP filtenna operates at 4.55–4.85 GHz and 6.83–7.16 GHz, with 7.65 and 7.38 dBi maximum measured gains. It exhibits a compact structure, stable dual-band radiation performance, and good out-of-band suppression. All structures are designed on the top of a single-layer PCB.