Mutual coupling is not an independent phenomenon. It describes the effects of incomplete boundary condition specification in the original problem. It operates at short-range and is not always apparent. In a very large array, the effect of the coupling for most elements is identical and its effect is incorporated into the element pattern leaving the array factor unchanged. The treatment of mutual coupling in this section is qualitative as analytic tech-niques have not been very effective. It is difficult to measure in physical arrays. Its practical consequences have diminished as improved electromagnetic models and solvers deal with its effects directly with suitable boundary conditions. Mutual coupling may introduce significant errors and uncertainties in the analysis. Of most concern, it may create unexpected nulls in the antenna pattern (scan blindness), but it also affects the element pattern and the array pattern. It is important to evaluate mutual coupling by various means including simulation and subscale tests. Frequently it is necessary to build test articles before accepting the design. The array size is a consideration: small arrays may be modeled in their entirety with numerical methods; large arrays may be partitioned or analyzed as infinite in extent.

Chapter Contents:

• 5.1 Definition
• 5.2 Problem
• 5.3 Parametric analysis
• 5.4 Patch element example
• 5.5 Waveguide element example
• 5.6 Dipole example
• References

Inspec keywords: scanning antennas; electromagnetic coupling; antenna radiation patterns; design engineering; radiowave propagation; numerical analysis; antenna arrays

Other keywords: array pattern; scan blindness; boundary condition specification; electromagnetic model; mutual coupling effects; error analysis; antenna array design; element pattern

Subjects: Other numerical methods; Antenna arrays; Radiowave propagation