Development of Low Profile Hybrid Printed UWB Monopole Antenna for Handheld GPR Applications

Handheld ground penetrating Radar needs to have a directional low profile light weight UWB antennas preferably in the frequency range of 500 MHz-3 GHz. A hybrid printed monopole antenna back by a reflector is designed and developed for requisite frequency band. The impedance matching and directional property is mentioned throughout the frequency band. Keywords-UWB; GPR;Bow-tie I. INTRODUCTION Ground-penetrating radar (GPR) offers a good solution for detection and imaging of buried plastic mines, IEDs and UXOs. Ground penetrating radars (GPRs) are realized in either in time domain or in frequency domain (1). In time domain approach either baseband radiation or modulated time domain waveforms are used. Stepped frequency is one of the commonly used frequency domain approach. The resistively loaded dipoles, bow-tie, vee and monopoles commonly used antennas (1-3) for both time domains and frequency domain approaches. The requirement of low frequency for better penetration and large bandwidth for finer resolution and size constraints for hand held GPR makes it very difficult to choose the most appropriate antenna type. The required frequency band of 500MHz-3GHz and size constraints for hand held requirement leads to design of printed bow-tie antenna category .The antenna profile is obtained using combination of bow-tie and elliptical profile (4). The issues with this design are that its differential feed requirement and non-directional radiation pattern. The differential feed can be converted to single ended feed using UWB balanced to unbalanced (BALUN) line, which may add up to the size of the antenna. The single ended version of this antenna was designed using printed monopole and microstrip line impedance adaptor to match to 50Ω waveform generators. The directional property was improved by backing the printed hybrid monopole with a curved reflector In Section II of this paper design details of antenna element is presented. The analysis and measured results are discussed in Section III. Conclusion is presented in Section IV.