Parametric study on capacitive and inductive couplers for exciting characteristic modes on CPE

Options for the realization of geometrically small but well isolated 4-port antenna systems for Customer Premises Equipment (CPE) in TV White Spaces from 470MHz to 790MHz are investigated. In order to arrive at a design with minimum protrusion of antenna elements from the enclosure of the device, capacitive and inductive couplers for excitation of the first characteristic modes on the enclosure of the device are considered. Isolation is addressed by exploiting the mutually exclusive symmetry properties of the characteristic modes which are employed. Attainable modal bandwidths of the resulting 4 radiation modes are reported as functions of the geometrical parameters of capacitive and inductive couplers and useful combinations thereof.