The array consists of a 3 x 3 series fed configuration of rectangular patches. By adjusting the excitation of these ports, the direction of the main beam (squint) as well as the sense of linear polarization – diagonal, vertical or horizontal - can be controlled.Figure 1: Typical total gain pattern comparison of radiation pattern performance at the center frequency for different excitation methods. (a) all ports excited in phase; (b) vertical ports excited with progressive phasing; (c) horizontal ports excited with progressive phasing.
When all 6 ports are excited simultaneously and in phase, a symmetrical broadside lobe in the zenith direction with low sidelobe levels and diagonal linear polarization - as shown in figure 1(a) - is achieved....
By exciting the three vertical ports only, a vertical linear polarized radiation pattern can be achieved and the direction of the main beam steered left and right (in the Φ = 0° plane) as shown in figure 1(b). If a horizontal linear polarized radiation pattern which may be steered up and down (in the Φ = 90° plane) is required, only the three horizontal ports should be excited as shown in figure 1(c).
The operating bandwidth of this antenna configuration is approximately 1%, as illustrated by the reflection coefficient of the three vertical ports.Typical reflection coefficient versus frequency for the vertical ports
The agile polarization and steering capabilities of this antenna makes it well suited to dual polarized narrow-band airborne synthetic aperture radar (SAR) applications.