Novel Antenna Designs for Compact Ground Penetrating Radar Systems and in-Traffic Air-Coupled Applications

Abstract

Ground penetrating radar (GPR) antennas are key elements for the operation of aircoupled, compact, low-cost systems that can be operated at road speeds in order to map subsurface defects such as corroded rebar, trapped moisture, voids, and pavement layers. This paper presents requirements and tradeoffs for such antennas as well as a brief methodology for the design process in order to frame the context and boundary conditions of the antenna problem. Furthermore, the paper discusses a number of planar antennas that have been designed in printed circuit board (PCB) technology using low-cost, glass-reinforced epoxy laminate sheets such as FR4.Ultra-wide-band operation of the antennas along with other key parameters such as gain and beamwidth are very important in the design of a useful antenna for air-coupled operation. The interconnected relationship between antenna parameters limits the designs and constrains the upper bounds of the performance that be achieved. Regulatory specifications such as FCC compliance create additional burden on the specifications and requirements.A rounded bowtie antenna, a slotted bowtie antenna and two types of Vivaldi antenna are designed, simulated, fabricated, and measured. All are intended to operate within the 1.5 -3.5 GHz frequency band and benefit from compact size while providing high gain to allow for the detection of pavement layers and rebar in bridge decks to a depth of up to 2 feet. In-field measurements of the antennas together with the GPR system are presented for static testing scenarios such as buried rebar in sand box. Symposium on the Application of Geophysics to Engineering and Environmental Problems 2013Downloaded from library.seg.org by Yale University: Geology Library on 05/16/15. For personal use only. FCC ConstraintApart from considerations of antenna performance, the FCC (Federal Communications Commission) imposes regulations on UWB systems that also have to be taken into account. Since the FCC 02-48 specification exerts strict limits on maximum average emission above 960 MHz, especially at frequency range of 960-1610 MHz. This specification restricts the power level to as low as -65.3 dBm as illustrated in Figure 1. The frequency band above 2 GHz was considered to be the key frequency of operation (Federal Communications Commission, 2002). Furthermore, in order to maintain good penetrating ability of the radar, the lower frequency band less than 900 MHz was also considered as a secondary option. Symposium on the Application of Geophysics to Engineering and Environmental Problems 2013 Downloaded from library.seg.org by Yale University: Geology Library on 05/16/15. For personal use only. Symposium on the Application of Geophysics to Engineering and Environmental Problems 2013 Downloaded from library.seg.org by Yale University: Geology Library on 05/16/15. For personal use only.

Development of a design optimization algorithm for a bowtie antenna

“…Due to using triangular elements instead of the usual straight ones, the bandwidth of the bowtie antenna is increased. The bowtie antenna can also receive signals from varying sources due to its ability to receive signals from a 60-degree angle [10], [11]. The antenna is also lighter and becomes wind resistant due to the triangular elements.…”

“…Figures 9,10,and 11 shows the 2D and 3D radiation patterns, RF plot of S-parameters and impeadance of the slotted bowtie antenna respectively. The next part of the simulation will focus on the double flare bowtie antenna.…”