In the paper the results of numerical and experimental studies of ultra-wideband dipole radiator and optimized CPW-to-CPS transformer (balun) are presented. Such dipole is used in GPR scanning system based on the Agilent E5071B VNA, and is located in direct proximity to object surface. Different theoretical models were developed to optimize and analyze the 50 to 100 Ohms balun with passband 1-7 GHz. The special attention was paid to matching antennas open with properties of the media under test. All numerical results were performed using CST Microwave Studio software.