Research on Mutual Coupling of Array Antenna

Phased Array Feed is a receiver technology that places the array antenna at the focal plane field of radio telescope to achieve higher gain and more flexible beam regulation. As same as the array antenna, it is composed of multiple antenna elements in a certain way, so electromagnetic coupling between the array elements during operation is inevitable. In this paper, the helical antenna is selected as the array antenna unit, and the working frequency is 1.25 GHz. The independent antenna is simulated and optimized, and the -10 dB impedance bandwidth is only 70 MHz. Relying on the antenna unit for the model of rectangular arrangement 5×5 helical antenna array, the array element spacing of 1, 0.5, 0.25 and 0.125 times of wavelength are selected respectively (1.25 GHz@0.24 m), in order to verify the influence of mutual coupling effect under different array element spacing on the bandwidth of the whole array. Finally, by matching the input impedance of each array element, the simulation shows that under 0.25 times the wavelength spacing, the -10 dB impedance bandwidth of the central element of the array is expanded to 550 MHz, and the bandwidth of the array antenna basically represents the working bandwidth used as the phased array feed. The above work not only deepens the understanding of the bandwidth characteristics of the array antenna, but also makes it possible for the phased array feed applied to the radio telescope system to achieve a wider working bandwidth.