Study On Wearable Antenna Based On The Substrate Integrated Waveguide Structure

Substrate Integrated Waveguide（SIW）is a new type of planar waveguide structure,which has the advantages of low transmission loss,high Q value and easy planar integration.Applying this structure to the design of wearable antennas has become one of the research hotspots in recent years.This article mainly designs five wearable antennas for on-body and off-body modes based on the substrate integrated waveguide resonant cavity structure.The specific work contents are as follows:（1）A wideband wearable SIW antenna for off-body mode is designed.A square slot is drilled in the center of the circular SIW resonant cavity,which divides the antenna into two parts:the SIW resonant cavity and the square patch.The TM₀₁ mode of the square patch and the quasi TM₀₁₀ mode of the SIW resonant cavity are excited by the bias feeding.By adjusting the position of the feeding point and the size of the square slot,the resonant frequency points of the two modes are combined to achieve a relative bandwidth of 14.42%.（2）Two wearable SIW antennas have been designed for on-and off-body modes.The first antenna achieves omnidirectional pattern by exciting the TE₁₁₀ mode of the SIW resonant cavity,and unidirectional pattern by exciting the TM₁₁ mode of the circular patch.The second antenna is a double-layer flexible antenna.By introducing a rectangular patch into the rectangular SIW antenna and adding four short pins at the corners of the patch,the TM₀₀ and TM₀₁ modes of the rectangular patch and the quasi TE₃₀₀ mode of the SIW resonator are excited to achieve an omnidirectional and two unidirectional patterns,respectively.By adding a layer of 3×3 square metasurface,the resonance frequency points of TM₀₀ and TM₀₁ modes are reduced,which reduces the antenna volume.（3）Two circularly polarized wearable SIW antennas have been designed for off-body mode.The first antenna is a single-layer structure,which excites the degenerated TE₁₂₀ and TE₂₁₀ modes of the antenna by adding short pins at the four corners and center of the rectangular SIW resonant cavity.Eight rectangular slots and one ring slot are loaded,improving the axial ratio and broadening the antenna bandwidth.The second antenna is a single-layer flexible antenna.By adding an inclined rectangular slot on the circular patch at the center of the circular SIW resonant cavity,the TM₁₁ mode is interfered to achieve circular polarization.By combining the TM₀₁₀ mode of the SIW resonant cavity and the TM₁₁ mode of the patch,a wideband characteristic is achieved,covering the entire 5 GHz WLAN frequency band.