High-Efficiency Periodic Sparse Microstrip Array Based on Mutual Coupling

In this paper, a novel idea to reduce the number of active elements in a large periodic array is presented and demonstrated firstly by an E-plane microstrip array. High aperture efficiency can be achieved by making use of mutual coupling between array elements, and then the total production cost of the array is greatly decreased by reducing the number of active array elements and associated components. A simple way to control the mutual coupling of the microstrip array is given as an example in this paper. Simulations and measurements show that when the active element spacing is as large as 1.6λ₀ ( λ₀ is the free-space wavelength at the operating frequency), a - 18.3 dB side lobe level (SLL) and an approximately equal aperture efficiency can be achieved. No obvious performance degradations are found compared to a conventional array with half the element spacing (0.8λ₀) and an identical total size. Then, simulations and measurements of an H-plane sparse array are given based on the same idea, followed by the simulated results of a planar two-dimensional (2-D) one.