Determining Antenna Separation Requirements for Co-Located Transmitters
Minimum antenna separation depends on transmitter power, receiver blocking thresholds, intermodulation mixing products, and regulatory simultaneous exposure ratios.
Surface Wave Suppression
Meaning
Electromagnetic energy can propagate along the boundary between a dielectric substrate and air, leading to unwanted coupling and radiation patterns in antenna arrays. The technique of surface wave suppression refers to the reduction of these parasitic surface currents. Achieving this suppression improves the radiation efficiency and radiation pattern of the integrated antennas.
Wave Propagation
High-dielectric constant substrates used in compact patch antennas are highly prone to supporting surface waves that travel along the board. Implementing surface wave suppression prevents these waves from reaching the edges of the substrate where they would cause unwanted side lobes in the radiation pattern. This control is achieved by using electromagnetic bandgap structures or etching arrays of slots in the ground plane.
Enclosure Integration
When mounting a wireless module inside a metallic enclosure, surface waves can couple to the housing and create unpredictable antenna patterns. Designing effective surface wave suppression on the printed circuit board ensures that the antenna’s performance remains stable after installation. This separation prevents the housing from acting as an unwanted radiator.
Design Validation
Engineers measure the radiation pattern in a test chamber to verify that side lobes are minimized. Successful suppression yields clean patterns and high gain. This test confirms design success.