Impact of Mutual Coupling on Operating Frequency of Compact Microstrip Arrays

Mutual coupling has an impact on antenna array characteristics like capacity, direction finding, correlation, and operating frequencies. In this paper, the operating frequencies of a single microstrip antenna and a compact microstrip array are compared. The investigation of the array design proves that mutual coupling has an impact on the operating frequency since it is decreased far below the corresponding operating frequency of a single microstrip antenna with the same physical characteristics. In this study, the single microstrip antenna works at an operating frequency of 3.235 GHz, while an array of 4 smaller strips operates at only 1.75021 GHz for the same physical characteristics. The array design is modified to have small metallic circles centered at the corners of the array elements. The modified array allows for lowering the operating frequency to be 1.7385 GHz when the metallic circles have a radius of 0.18 mm. The design is also tested for higher numbers of smaller strips (five and seven strips) to show that the operating frequency is getting lower with higher number of strips