Meaning
Electromagnetic interactions between adjacent antenna elements alter their individual radiation characteristics and input impedances. This phenomenon of mutual coupling occurs when the energy radiated by one antenna is intercepted by a neighboring element. The effect changes the currents on the antenna surfaces and degrades system performance.
Antenna Proximity
Placing antenna elements close together in compact wireless devices increases the strength of their mutual interaction. This proximity leads to energy transfer directly between the ports rather than into the surrounding environment. In modern multi-input multi-output terminals, constrained physical dimensions make this coupling a critical engineering challenge.
Impedance Distortion
Alterations in the input impedance of coupled antennas cause impedance mismatches at the transceiver interfaces. These mismatches result in reflected power, which reduces the overall radiation efficiency of the terminal. Designers use decoupling networks or physical isolation structures to restore the correct impedance matching.
Radiation Pattern
Antenna array performance depends on predictable radiation patterns and independent signal pathways. Coupling distorts the individual beam shapes, shifting their directions and increasing sidelobe levels. This distortion reduces the spatial resolution of the beamforming system, impairing its ability to isolate user signals.
In multi-user scenarios, the resulting correlation between channels prevents the spatial multiplexing algorithms from functioning effectively, which ultimately lowers the aggregate data rate of the system and diminishes its coverage area.
