Design of Broadband Compact Grid Array Antennas Using Gradient Slow-Wave Structures

Compact grid array antennas (GAAs) with the gradient slow-wave structures are designed in this letter. The electrical lengths of slow-wave transmission lines (SW-TLs) with gradient structures are investigated based on the equivalent microwave network. By utilizing SW-TLs with exponential gradient structure on the long sides of GAAs, the proposed antenna achieves an area-reduction factor of 24.4%, with a measured 10 dB impedance bandwidth from 27.50 to 33.86 GHz and a maximum gain of 15.71 dBi.