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What are the guidelines for selecting substrate dimensions for microstrip patch antennas?

The substrate in patch antennas affects bandwidth, efficiency, and radiation characteristics. I want to understand how to choose substrate thickness, length, and width relative to frequency, dielectric constant, and intended application, and how these dimensions influence matching, surface waves, and overall performance.

 

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By Jeff Answered 1 year ago

From my experience designing microstrip patch antennas, I have seen that substrate thickness and lateral dimensions must be carefully chosen to balance bandwidth, efficiency, and physical size. I would recommend selecting thicker substrates for broader bandwidth but being aware that excessive thickness can excite unwanted surface waves, reducing efficiency. The length and width of the substrate should exceed the patch dimensions by at least 5–10% to avoid edge diffraction effects and maintain impedance stability. I have seen designers also consider the dielectric constant: lower εr substrates increase bandwidth but require larger patch sizes, while higher εr allows compact designs at the cost of reduced efficiency. In practice, iterative simulations help optimize substrate dimensions for the target frequency, impedance matching, and radiation performance.  

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