In this paper, we propose a new configuration of an ARMSA fed by a 90[degrees] branch-line hybrid coupler.
The configuration of the ARMSA fed by a 90[degrees] branch-line hybrid with the parasitic element is illustrated in Figure 1.
As we all know, when ARMSA operates at T[M.sub.11] mode, it is difficult to achieve good impedance matching because of the very large input-impedance.
Some literatures had reported the uses for the inner space of the ARMSA. In  the meandered impedance transformer lines are a good choice to adopt, but the impedance bandwidth of which is too narrow.
As we all know, the impedance of the ARMSA with T[M.sub.11] mode is large, and the ratio of a to b affects the impedance obviously.
So from Figure 3 and Figure 4 we can conclude that the ARMSA presents a feature of double resonant modes.
According to the design procedure for the stacked ARMSA, the required side length of the ground plane and the thickness of substrate are also considered.