Wideband Planar Four-Element Linear Antenna Array

This letter presents a planar wideband linear antenna array to cover multiple wireless standards. The array consists of four microstripline-fed open-ended quarter-wavelength slot antenna elements. By feeding the antenna properly, a fundamental radiating antenna mode can be excited over a wide frequency range. The antenna array is simulated in terms of surface current distributions and S-parameters. Simulated results are compared to the manufactured prototype antenna array. Measured results show the -10-dB impedance bandwidth is from 2.55 to 6.1 GHz, corresponding to 83% relative impedance bandwidth, while mutual coupling is less than -16.6 dB within the aforementioned impedance bandwidth. The simulated -10-dB bandwidth is from 2.0 to 6.0 GHz. Measured radiation patterns are presented at 2.4, 3.5, and 5.2 GHz with 4.6, 7.0, and 7.9 dBi maximum gain in bore-sight direction, respectively. The measured radiation patterns and grating lobe levels correlate well with the theory and are 10-15 dB below the main lobe depending on the studied frequency.