Global Positioning System is increasingly getting melt in our everyday life. In order to keep the GPS devices low-profile and portable, designers often resort to printed antennas. GPS applications use a very narrow bandwidth around 1.575 GHz, since they cannot afford any interference. For this purpose, we present in this example an HFWorks simulation for a patch microstrip antenna operating at 1.575 GHz with a very narrow band. The dimension of the patch is almost 2*2 cm which is convenient to integration in a portable device.
Figure 1 - GPS antenna 3D structure
The Perfect Electric Conductor surfaces (Zero thickness) of the antenna are built thanks to the Split line feature of Solidworks.
All dimensions are in mm. As we can see, the size of the antenna is very small which makes it a good candidate for the nature of the intended applications (GPS for mobile devices).
The feed of the antenna is located beneath the board of the four split surfaces. We select its bottom surface for the port assignment. The dielectric of the board is TMM 13 and the feed coax is assigned the material Duroid 5880. We model an air box above the board to provide us with the radiation surfaces which should be located not less than one wavelength away from the antenna's surfaces.
The mesh of this example must be accurate enough on the signal paths which means the coax feed and the PEC surfaces. HFWorks performs by default accurate meshing for small parts thanks to the average global size found in the mesh settings.
The meshing being realized, we run an antenna simulation in the frequency range from 1.5 GHz to 1.65 GHz to precisely visualize the behavior of the antenna around the intended frequency 1.575 GHz of the GPS application. In this figure, we see that the return loss increases rapidly from 0.3 dB to above 20 dB at the desired frequency.
Figure 3 - Reflection coefficient at port 1
In the next figure, we have the radiation of the total electric field in linear and dB situated in the Phi=0 plane.
Figure 4 - Total radiated E field (in Linear and dB units) in Phi=0 plane
We can refine the angles' steps during the creation of the study to get smooth plots whether in 2D or 3D. In this figure, we have plotted the 3D radiation of the electric field in linear format.
To conclude, we recall that the performance of any design always originates from its 3D model's accuracy: the result of the simulation always follows what the system has as an entry in the SolidWorks 3D model. This antenna has been optimized to respond to the specifications of the intended application and to its portability character. The antenna shows acceptable performances by operatiing at the right frequency range and with good levels of return loss.