SIW technology is essentially a hybrid of microstrip and dielectric-filled waveguide (DFW) technologies. Starting with a PCB substrate, top and bottom metal layers provide two of the waveguide walls. Then, two parallel rows of vias are added, forming the side walls of the waveguide. Figure 1 shows a microwave filter constructed using SIW technology. The SIW technology for passive circuit design has been implemented for its low cost, compact topology and high performance. There has been increasing interest in implementing SIW technology in active circuits and complete systems, including active integrated antennas.
Antennas designed with SIW technology have excellent performance because they suppress the propagation of surface waves, increase the bandwidth, and decrease both end-fire radiation and cross-polarization radiation. 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. SIW technology can also be utilized for microwave cavity-backed antennas like the one shown in Figure 2. Circuits like these can be found in compact receiver front-end modules and self-oscillating mixer arrays.
In order to design these antennas, full-wave EM solvers can be used to analyze the performance of the antenna before fabrication, and try several “what-if” scenarios to optimize the antenna geometry. The most popular EM solver technologies for this type of analysis are Method of Moments (MoM), Finite Element Method (FEM) and Finite Difference Time Domain (FDTD).