“Design Study of Normal Mode Helical Antenna With Dual-Frequency and Circular Polarization Used in Mobile”. Journal of Engineering and Sustainable Development 17, no. 3 (August 1, 2013): 79–93. Accessed July 3, 2024. https://jeasd.uomustansiriyah.edu.iq/index.php/jeasd/article/view/999.