A Log-Periodic Monopole Array with Uniform Spacing

This paper presents a log-periodic monopole array antenna with end-fire radiation and vertical polarization. It consists of 13 monopole elements and a meandering microstrip line on the bottom as the feeding line. The adjacent monopoles are of uniform spacing instead of conventional logarithmic spacing. A prototype is fabricated and tested. Measured results show that an impedance bandwidth from 2 to 6 GHz (3:1) for VSWR <;2 and a realized gain better than 7.6 dBi over the same operating frequency band are obtained.