  This paper presents a two-dimensional infinite dipole array system with a
mushroom-like high-impedance surface (HIS) ground plane with wide-angle
scanning capability in the E-plane. The unit cell of the proposed antenna array
consists of a dipole antenna and a four-by-four HIS ground. The simulation
results show that the proposed antenna array can achieve a wide scanning angle
of up to 65$^{\circ}$ in the E-plane with an excellent impedance match and a
small $S11$. Floquet mode analysis is utilized to analyze the active impedance
and the reflection coefficient. Good agreement is obtained between the
theoretical results and the simulations. Using numerical and theoretical
analyses, we reveal the mechanism of such excellent wide scanning properties.
For the range of small scanning angles, these excellent properties result
mainly from the special reflection phase of the HIS ground, which can cause the
mutual coupling between the elements of the real array to be compensated by the
mutual coupling effect between the real array and the mirror array. For the
range of large scanning angles, since the surface wave (SW) mode could be
resonantly excited by a high-order Floquet mode $\textrm{TM}_{-1,0}$ from the
array and since the SW mode could be converted into a leaky wave (LW) mode by
the scattering of the array, the radiation field from the LW mode is nearly in
phase with the direct radiating field from the array. Therefore, with help from
the special reflection phase of the HIS and the designed LW mode of the HIS
ground, the antenna array with an HIS ground can achieve wide-angle scanning
performance.
