Mutual Coupling Reduction in Patch Antenna Arrays Using Corrugated Structure

Microstrip antennas are widely used in a broad range of military and commercial applications due to its low cost, low profile, easy fabrication and light weight. But this kind of antenna also has some drawbacks. For example, the diffraction of surface waves at the edge of finite grounded substrate decreases the antenna efficiency and degrades the antenna pattern [1]. In the phased array antenna, serious surface wave would produce strong mutual coupling between elements, which may cause scan blindness and reduces the scan range [2]. So far, some effective technologies have been intensively investigated for suppressing the surface wave propagation, such as electromagnetic band gap material [3], defected ground structure [4], choke grooves [5] and metal fences [2]. Our latest work has proposed a new method to reduce mutual coupling between elements, which is to introduce surface corrugation in the waveguide-end slots array for modulating the propagation of surface wave instead of suppression [6]. This kind of surface corrugation was firstly reported in the optical region [7] and then scaled into microwave region [8-9], which both can realize extraordinary transmission and a highly directive beam. Based on the above two unique properties, this surface corrugated structure has been applied in the antenna field for improving radiation performance [10-12]. The surface wave in this corrugated structure is excited, modulated and reradiated. Obviously, its work mechanism is different from that of the choke grooves which is well known to have the main ability to suppress surface wave propagation due to its surface impedance characteristics. The groove depth of the choke grooves is often required to be a quarter of the resonance wavelength (λ/4) for forming high surface impedance, while in our corrugated structure, the groove depth is not limited to λ/4, and the groove cavity resonance and coupling between grooves and array element can determine the distribution of surface electromagnetic (EM) resonance mode [13]. In this paper, this kind of corrugated structure is loaded on the ground plane of patch antenna array for reducing mutual coupling between elements. Simulation results show that employment of the grooves can effectively reduce the mutual coupling to less than -40dB. Moreover, when the elements space is reduced to about 0.5λ, the corrugated structure can be still utilized in the patch array to perform its effective performance in the mutual coupling reduction.