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 boresight 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.