Wideband decoupling technique for two-element antenna array by using pixel neutralization line

This letter proposes a high isolation two-element multiple input multiple output (MIMO) antenna by using a wideband pixel neutralization line (NL). The design procedures are simplified as follows: (1) Obtaining the Y-parameters of the original two-element antenna with a grid of microstrip stubs, and discrete ports are inserted among microstrip stubs; (2) obtaining the binary codes of the optimum route. Importing Y-parameters into MATLAB, and using a genetic algorithm to obtain the optimum connection route by design formulas upon scattering matrix which guarantees high isolation; (3) translating the binary codes into the actual connection metallic lines; (4) adding the designed pixel NL and appropriate matching branches into EM simulator to optimize the antenna; (5) obtaining a high isolation two-element antenna. The original two-element antenna has poor isolation with the main path coupling, and the pixel NL provides an auxiliary coupling path between two elements. By adjusting pixel NL, the magnitude strengths of two coupling signals realize the same, while the phases are exactly opposite. Therefore, the wideband high isolation between antenna elements is realized. To verify the practicability of the proposed pixel decoupling neutral line, a reference and proposed two-element MIMO antennas are fabricated and measured. In the experiment, the isolation of the proposed two-element antenna with an edge-to-edge distance of 0.0943 lambda(0) (lambda(0) is the wavelength in free space at the center frequency) is enhanced by about 17 dB in the working frequency band from 0.975 to 1.025 GHz. Besides, an L-typed feeding network is added to guarantee a good matching condition. The proposed two-element antenna has a size of 0.617 lambda(0) x 0.667 lambda(0), and the dimension of each radiation patch is 0.3267 lambda(0) x 0.0725 lambda(0). The proposed GA algorithm-based decoupling technique has a significant superiority over traditional ones. Efficient, simple, and one-time EM simulation are its major advantages, which can liberate the RF engineer from the heavy debugging work.