K. G. Jangid, P. K. Jain, B. R. Sharma, V. K. Saxena, V. S. Kulhar, and D. Bhatnagar, “Ring Slotted Circularly Polarized U-Shaped Printed Monopole Antenna for Various Wireless Applications”, AEM, vol. 6, no. 1, pp. 70–76, Mar. 2017.