On the Effects of Decoupling and Matching Networks in Phase Array Radiation Patterns for Radar Applications

Phased array systems employ a set of properly cho- sen radiating elements, geometrically configured and strategically excited in order to render a specific radiation pattern, best suited for a given application. When the total antenna size emerges as an application constraint, both size of the radiating elements as well as the distance between them need to be optimized. If the spacing between neighboring elements reduces to less than half of the free-space wavelength, electromagnetic coupling becomes stronger. The consequences are the following: the radiation pat- terns are distorted, the antenna ports become mismatched, and the effective degrees of freedom (DoF) are reduced. To overcome the degrading effects that strong electromagnetic coupling may bring to phased array radars, transmission lines are designed with the purpose of decoupling and matching the excitation ports. Within this context, this paper investigates the effects of an eigenmode based decoupling technique in phase array radiation patterns for Radar applications.