Isolation Enhancement in Microstrip Antenna Arrays 
Slotted Meander-Line Resonator (SMLR) is implemented by creating defect in the microstrip structure. This resonator is designed to block the surface current at the resonant frequency of the two patch antennas coupled along H-plane operating at 3.6 GHz. The proposed configuration provides an improvement in isolation by 10 dB (measured value) with a reduced edge-to-edge spacing of 7 mm (λ0/9). This resonator has been designed, simulated, and validated experimentally. KeywordsAntenna array, isolation enhancement, meander lines, mutual coupling reduction, resonators.
Mutual Coupling Reduction Between Microstrip Patch Antennas Using Slotted-Complementary Split-Ring Resonators
A novel structure based on complementary split-ring resonators (SRRs) is introduced to reduce the mutual coupling between two coplanar microstrip antennas that radiate in the same frequency band. The new unit cell consists of two complementary SRR inclusions connected by an additional slot. This modification improves the rejection response in terms of bandwidth and suppression. The filtering characteristics of the band-gap structure are investigated using dispersion analysis. Using the new structure, it was possible to achieve a 10-dB reduction in the mutual coupling between two patch antennas with a separation of only 1/4 free-space wavelength between them. Since the proposed structures are broadband, they can be used to minimize coupling and co-channel interference in multiband antennas.
Electromagnetic bandgap phased array antenna controlled by piezoelectric transducer
The optimal performance of a phased array antenna controlled by a piezoelectric transducer, having an electromagnetic bandgap (EBG) structure in the ground plane of the feed microstrip lines, is illustrated. The EBG presence increases by about 10/spl deg/ the beam scanning angle achieved by the multiline phase shifter.