Ultra-Wideband Antenna Design for GPR Applications: A Review <s> E. Tapered Slot Antenna <s> Ground-penetrating radar (GPR) is a rapidly developing field that has seen tremendous progress over the past 15 years. The development of GPR spans aspects of geophysical science, technology, and a wide range of scientific and engineering applications. It is the breadth of applications that has made GPR such a valuable tool in the geophysical consulting and geotechnical engineering industries, has lead to its rapid development, and inspired new areas of research in academia. The topic of GPR has gone from not even being mentioned in geophysical texts ten years ago to being the focus of hundreds of research papers and special issues of journals dedicated to the topic. The explosion of primary literature devoted to GPR technology, theory and applications, has lead to a strong demand for an up-to-date synthesis and overview of this rapidly developing field. Because there are specifics in the utilization of GPR for different applications, a review of the current state of development of the applications along with the fundamental theory is required. This book will provide sufficient detail to allow both practitioners and newcomers to the area of GPR to use it as a handbook and primary research reference. *Review of GPR theory and applications by leaders in the field *Up-to-date information and references *Effective handbook and primary research reference for both experienced practitioners and newcomers <s> BIB001 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> E. Tapered Slot Antenna <s> A novel compact double exponentially tapered slot antenna (DETSA) for GPR applications is presented. To extend the antenna's impedance bandwidth, the antenna arms are rolled back and lengthened, and lumped resistors are used near the ends of the rolled arms. An improved coplanar waveguide (CPW) to coupled stripline (CPS) transition for feeding is also investigated. The measured transmission loss of two back-to-back CPW-to-CPS transitions is less than 2.6 dB in the frequency band of 200 MHz-6 GHz, which agrees well with the simulated result. The measured S11 of the antenna in frequency domain is less than -10 dB in the band of 220 MHz-6 GHz, and it is also verified that the resistors mainly have influence on the antenna's S11 below 1 GHz. The measured reflected pulses show that there are only two reflecting points, and the reflection is weak. The simulated and measured antenna gains at boresight show little variations with loading resistors of different values, and this means that the resistive loadings do not affect the gain characteristics of the antenna. The antenna's transmission re- sponse in time domain is also tested, and its application in GPR detection of a buried target is validated by experiments. <s> BIB002 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> E. Tapered Slot Antenna <s> In this paper we demonstrate the gain enhancement of a semicircular slot antenna using a multilayer frequency-selective surface (FSS). A theoretical analysis of the FSS with a UWB semicircular slot antenna is presented. The multilayer FSS provides an appropriate reflection phase to act as a reflector and is able to enhance the gain of the slot antenna. Simulations show a linear phase response from 3.5 GHz to 12 GHz that is sufficient for ultra wideband operation. A significant improvement of 3 to 4 dB gain over the whole frequency range is demonstrated. The composite antenna has a theoretical gain of 8 dBi and a very small maximum gain variation of ±1.5 dB over the 3.5 to 10 GHz frequency range. Its compact configuration provides flexibility for mounting the reflector close to the slot antenna and makes it more suitable for modern UWB devices. <s> BIB003 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> E. Tapered Slot Antenna <s> A compact quad-ridged horn antenna (QRH) for the deep ground penetrating radar water detection applications is designed operate in frequency range of 50MHz to 500MHz. Within this contribution the design and simulation of such an antenna is considered for water level detection in Egyptian dessert aquifers. Among the varying horn design parameters, the linear and exponentially tapered walls are studied as well as variations of the curvature of the dielectric waveguide between the two ridges enhancing the matching conditions hence, reducing size and increasing the antenna operational bandwidth. The design goal is to achieve broad bandwidth antenna with maintaining compact dimensions. Two modifications have been introduced on the conventional triangular TEM horn antenna. First multifunction tapering of the horn plates with curvature ending, second inserting perturbing two different ridges between the aperture planes and filling the space between the ridges with high dielectric constant material, in order to lower the operating frequency without increasing the size of the original setup. Replacing the two ridges with four ones, each pair is perpendicular to the other, reduces more the antenna size and improves more its matching. The antenna dimensions are 145 × 102 × 124 cm ::: 3 ::: that resembles improvement in size as compared with similar commercial GPR horn antennas as Satimo Horn model SH 68 with dimensions 2983×1615×2505 cm ::: 3 ::: . <s> BIB004 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> E. Tapered Slot Antenna <s> A CPW-feed prototype slot antenna for ultra-wideband applications is proposed. The slot is made by etching on the ground plane, the union of two elliptical structures placed at right angles. The fractal shape antenna is excited by two stepped CPW feed. To enhance the gain, a compact ultra-wideband frequency selective surface (FSS) structure is designed and implemented. The measured impedance bandwidth of antenna with and without FSS is nearly same and equal to 9.0 GHz from 3.6 to 12.6 GHz. The measured peak gain varies from 3 to 5 dB without FSS and from 5 to 12.5 dB with FSS. Measured results are found in good agreement with the simulated results. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1498–1502, 2014 <s> BIB005 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> E. Tapered Slot Antenna <s> A High gain antenna for UWB application is presented in this paper. The UWB characteristic of the antenna is achieved by asymmetric slot in the ground plane. A compact multilayer FSS is designed to achieve the UWB performance. A significant improvement in the peak gain value of antenna is obtained in low profile design, while maintaining the excellent impedance bandwidth of ultra wide band antenna. The average peak gain of antenna is increased from 4 dBi to 7 dBi as a result of FSS superstrate as a reflector. The average peak gain variation in the operating frequency range of antenna (2.5 GHz–14 GHz) is only 1–2 dB, which is a significant improvement over the gain variation of 3 to 4 dB for antenna alone system without using FSS. The most attractive feature of the design is that, it maintains compactness in the geometry along with all other features. This compact, optimized FSS reflector provide flexibility to the design to mount on any antenna situated closer to conducting bodies, example metal sheet, screen and cases. <s> BIB006 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> E. Tapered Slot Antenna <s> Planar antenna designs have many advantages such as low-profile, light-weight, and ease of fabrication and integration. Low-cost is often desired but this depends on the chosen substrate. The substrate can also dominate the ruggedness of the antenna, such as the use of ceramics which can be brittle. Here, a planar slot antenna implemented on ceramic substrate with coplanar waveguide feed is considered. With absorber loading the design provides 50 Ω input impedance over the frequency range 0.3–3 GHz so it is considered ultra-wideband. This paper summarizes a numerical investigation using both frequency and time-domain solvers. The results serve to guide the future analysis of broadband antennas with lossy dielectric loading for ground penetrating radars. The evaluation of radar performance requires further simulation and model validation based on antenna measurements. <s> BIB007
Gain is one important parameter that is required in a GPR system as it can enhance the signal appearance which can be affected by signal attenuation and other losses as well BIB001 . In order to improve the gain factor in an antenna design, different methods are used. One of them is the tapered slot method. Fig. 5 shows the UWB tapered slot antenna which consists of a coplanar patch and ground that is suitable for GPR applications. In  , one of the tapered slot compact antennas with a high gain for GPR applications is proposed. This compact planar antenna is fed by a CPW with one slot line to supplement the taper slot. A resistive loading is introduced with some discontinuities in the design to avoid any strong reflections. The antenna is designed by introducing two main slots: one slot is represented by a Vivaldi shape and another slot is a triangular slot. A double exponentially tapered slot antenna (DETSA) is designed in BIB002 in which the exponential arms of the antenna are rolled back to improve the bandwidth. Another modification in the design is the introduction of a coupled-strip line (CPS) instead of a CPW for feeding purpose. The measured losses of a CPS are less than that of a CPW. The antenna is designed on a FR-4 dielectric material with Ԑr of 4.4. In BIB007 , another modified slotted antenna with a backed absorber is investigated for broadband antennas. The proposed design is modified by cutting a slot in the patch and then tapering the slot edges so that the antenna can perform better in GPR applications. This model is designed on a lossy TMM-10 substrate with Ԑr of 9.2. Fig. 5 . Tapered slot antenna  . www.ijacsa.thesai.org A semicircular slotted antenna is introduced in BIB003 to enhance the gain factor. In the design, semicircular slots are introduced with tapered transitions for a CPW feed. A frequency selective surface (FSS) method with a dual-layer reflector is used which helps in the gain enhancement and impedance matching. The distance between the antenna and reflector can be approximated by BIB004 Another high gain antenna with FSS has been designed by etching two elliptical structures for the slot BIB005 . The gain of the antenna without the FSS is very low and has been further enhanced with the presence of FSS. A star-shaped antenna is designed with an asymmetric slot in the ground plane with an open ended CPW feed BIB006 for gain enhancement from the employment of FSS which makes it suitable for GPR applications.