On the gain of a reconfigurable-aperture antenna

A full-wave analysis based on the method of moments (MoM) is carried out for a reconfigurable-aperture antenna consisting of a two-dimensional (2-D) array of filamentary microstrip-dipoles interconnected by lossy microelectromechanical-system (MEMS) switches. Activation of specific MEMS switches allows the dipoles to be maintained near the halfwave-resonant length as the frequency is reduced in octave increments between 16 and 2 GHz. This keeps the real part of the dipole self-impedance much higher and the imaginary part much lower than in a dipole having a fixed length of lambda /2 at 16 GHz. Hence, the array-antenna gain and aperture efficiency remain much higher with frequency than in an array of fixed dipoles. Broad side aperture efficiencies of -3.9, -6.0, -9.5, and -10.6 dB are predicted for 16 x 16, 8 x 8, 4 x 4, and 2 x 2 recap dipole arrays at frequencies of 16, 8, 4, and 2 GHz, respectively, for MEMS switches having 0.5 dB insertion loss. In contrast, fixed-element lambda /2-separated arrays operating at the same frequencies have predicted efficiencies of -3.9, -24.2, -45.0, and -63.0 dB, respectively.