SIW Cavity-Backed Antenna
Abstract:FEM simulation is used to analyze a SIW cavity-backed patch antenna.In high frequency applications, microstrip devices may not be efficient, and because wavelengths at high frequencies are small, microstrip device manufacturing requires very tight tolerances. At high frequencies, waveguide devices are preferred, however the manufacturing process is more expensive. Therefore a new concept has emerged: substrate integrated waveguide (SIW). SIW is based on a transition between microstrip and dielectric-filled waveguide (DFW). A dielectric filled waveguide is implemented as a substrate integrated waveguide using vias for the side walls of the waveguide.
The SIW technology enables cavity-backed antennas. These kinds of antennas have better performance because they suppress the propagation of surface waves, increase the bandwidth, decrease end-fire radiation, decrease cross-polarization radiation and increase the applicable frequency range. The cavity-backed antenna structure also overcomes potential problems such as heat dissipation and unwanted surface wave modes. These low cost implementations are useful in radar and communication applications.
In this example (see References) full-wave FEM-based analysis is used to simulate the antenna, whose frequency responses have been evaluated for different values of certain geometrical parameters.
Figure 1: Configuration and dimensions for SIW cavity backed antenna
Figure 2: Antenna model in EMPro
Design Challenges & Results
A key design parameter that impacts the resonant frequency of the antenna is the length of the stubs. As shown below, multiple FEM simulations are run with stub lengths from 1.9mm to 2.1mm, and the resonant frequency varies from 9.7GHz to 10.1GHz.
Figure 3: Stub length varied from 1.9mm to 2.1mm
Figure 4: Resonant Frequency varies from 9.7 GHz to 10.1 GHz as the stub length changes
Figure 5: Measured results based on a stub length of 2.08mm (see reference below)
Figure 6: 3D antenna gain @ 10 GHz
(1) Renzo Díaz Portilla, “X-Band Substrate Integrated Waveguide Cavity-backed Patch Antenna Self-Oscillating Mixer,” Thesis Work, Departament de Teoria del Senyal i Comunicacions, October 2010.