Investigations on miniaturized endfire vertically polarized quasi-fractal log-periodic zigzag antenna

This paper presents the investigations on a miniaturized vertically polarized traveling wave antenna for operation in the high frequency band (3-6 MHz), with a specific requirement of keeping its height near 1/8th of a wavelength. The antenna is desired to have a good endfire gain and front to back ratio, and small radiation levels in the vertical direction at broadside angle. A log-periodic Zigzag antenna (LPZA) has acceptable performance in both gain and polarization. Its height however is large, at about one wavelength (1 lambda(L)). The concept of fractal antenna is employed in this antenna to achieve the necessary height reduction to lambda(L)/8, while keeping its radiation characteristics nearly constant. Both single and dual arm quasifractal log-periodic zigzag antenna (QFLPZA) configurations are investigated, with a maximum antenna height of only 1/8th of a wavelength, showing the desired radiation characteristics, and a wide impedance bandwidth of 67%. This type of antenna may. find applications in surveillance radar.