A Review of Passive and Active Ultra-Wideband Baluns for Use in Ground Penetrating Radar

Abstract

Microwave ultra-wideband technology has been widely adopted in instrumentation and measurement systems, including ground-penetrating radar (GPR) sensors. Baluns are essential components in these systems to feed balanced antennas from unbalanced feed cables. Baluns are typically introduced to avoid issues with return signals, asymmetrical radiation patterns and radiation from cables. In GPR systems, these issues can cause poor sensitivity due to a reduction in radiated power, blind spots due to changes in the radiation pattern and additional clutter from common mode radiation. The different balun technologies currently available exhibit a wide variation in performance characteristics such as insertion loss, reflection coefficient and phase balance, as well as physical properties such as size and manufacturability. In this study, the performance of two magnetic transformer baluns, two tapered microstrip baluns and an active balun based on high-speed amplifiers were investigated, all up to frequencies of 6 GHz. A radio frequency current probe was used to measure the common mode currents on the feed cables that occur with poor performing baluns. It was found that commercially available magnetic transformer baluns have the best phase linearity, while also having the highest insertion losses. The active balun design has the best reflection coefficient at low frequencies, while, at high frequencies, its performance is similar to the other baluns tested. It was found that the active balun had the lowest common mode current on the feed cables.

Robotic-biological systems for detection and identification of explosive ordnance: concept, general structure, and models

“…An example of means using the electromagnetic method is metal detectors (electromagnetic induction devices), which are now one of the primary means used in mine countermeasures. The advantages of the method are the ability to detect metal objects smaller than 1 cm at a depth of 50 cm [21]; all-weather; and low-cost.…”

Directional and High-Gain Ultra-Wideband Bow-Tie Antenna for Ground-Penetrating Radar Applications

“…The resistors increase the loss of the antenna, but given that the return loss of the bow-tie antenna will deteriorate after loading the metal reflector, which may cause the S11 curve In order to connect with a general 50 Ω microwave system, the characteristic impedance of the antenna is usually designed to be close to 50 Ω. When the field angle θ of the traditional bow-tie antenna is small, the impedance is usually large, and an additional impedance converter needs to be designed [32], which complicates the structure of the antenna. Increasing the field angle θ is beneficial to reduce impedance, but the triangular arms increase the size of the antenna.…”

Editorial for the Special Issue “Review of Application Areas of GPR”

“…The currently available balun technologies for GPR instrumentation design and the associated architectural implementations are critically reviewed and assessed in the contribution by van Verre et al [9]. By taking into account the UWB nature of GPR methodology, as well as the experienced inefficiencies in traditional design solutions, this paper provides a robust ground for evaluating the optimal choice for GPR system design.…”