Ultra-Wideband Antenna Design for GPR Applications: A Review <s> B. Vivaldi Antenna <s> Chapter 1 Ultra-Wideband Antenna Arrays Chapter 2 Smart Antennas Chapter 3 Vivaldi Antenna Arrays Chapter 4 Artificial Magnetic Conductors/High Impedance Surfaces Chapter 5 Metamaterial Antennas Chapter 6 Biological Antenna Design Methods Chapter 7 Reconfigurable Antennas Chapter 8 Antennas in Medicine: Ingestible Capsule Antennas Chapter 9 Leaky-Wave Antennas Chapter 10 Plasma Antennas Chapter 11 Numerical Methods in Antenna Modeling <s> BIB001 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> B. Vivaldi Antenna <s> Vivaldi antenna is a traditional ultra-wideband(UWB) antenna, and this paper focuses on designing its structural parameters properly to balance the bandwidth, gain, cross-polarization and other key parameters. By studying the effects of various parameters on the antenna performance, a compact Vivaldi antenna for ultra-wideband system is designed and realized. The antenna has a small size, high gain and small cross-polarization characteristics compared with the antannas in the relevant references, and it can meet the requirements of UWB system. <s> BIB002 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> B. Vivaldi Antenna <s> A novel microstrip ultra-wideband (UWB) differential filter with narrow notched band based on the transversal signal- interference concept is presented. In order to enhance the interference immunity from undesired signals efficiently, the notched band is implemented by coupling with quarter wavelength shorted-line at input and output ports. By taking advantage of the bandgap characteristic of defected ground structure (DGS), a slot-line DGS is used for improving the common-mode rejection. In this work, at the center frequency of the notched band which is 2.45 GHz, about 7.3% bandwidth (2.35-2.53 GHz) is realized by full-wave simulator. Agreement between experiment and simulation is observed. <s> BIB003 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> B. Vivaldi Antenna <s> In this article, the design of a ultra-wideband (UWB) monopole antenna with coplanar-waveguide (CPW)-coupled-fed is presented. The antenna is composed of a trapezium patch with a CPW-fed printed on one side of the substrate and an elliptical radiator on the other side. By simply cutting slits on the radiation patch, a single, dual, and triple band notched characteristics can be achieved. Parametric studies on the antenna and slits are carried out by computer simulation. Results show that the notch frequencies can be set by using dimensions of the slits. The antennas are designed and optimized using computer simulation. For verification, the antennas with single and dual band-notched characteristics are fabricated and measured. The simulated and measured results on the return loss, radiation pattern, peak gain, and efficiency of the antenna are presented. Due to the small ground-plane size of the antenna, the feeding cable used in the measurement equipment significantly affects the measured results and leads to large discrepancies between the simulated and measured results at low frequencies. To study this, the simulation model of the feeding cable is also used in simulation and results show that the discrepancies are substantially reduced. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1017–1027, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27530 <s> BIB004 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> B. Vivaldi Antenna <s> Novel planar Vivaldi antenna with better performance compared to conventional TEM horn antenna is introduced. An exponential tapered slot edge (TSE) structure is employed. Electromagnetic band gap structure as seven pair of loop or square shaped defected ground structure is added to the ground antenna plane. The proposed shape has the advantage of extending the low-end bandwidth limit due to improving the antenna matching especially at low frequency and reduced the electrical length of the antenna by 45% compared to the original antenna size. <s> BIB005 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> B. Vivaldi Antenna <s> The conventional Vivaldi antenna is known for its ultrawideband characteristic, but low directivity. In order to improve the directivity, a double-slot structure is proposed to design a new Vivaldi antenna. The two slots are excited in uniform amplitude and phase by using a T-junction power divider. The double-slot structure can generate plane-like waves in the E-plane of the antenna. As a result, directivity of the double-slot Vivaldi antenna is significantly improved by comparison to a conventional Vivaldi antenna of the same size. The measured results show that impedance bandwidth of the double-slot Vivaldi antenna is from 2.5 to 15 GHz. Gain and directivity of the proposed antenna is considerably improved at the frequencies above 6 GHz. Furthermore, the main beam splitting at high frequencies of the conventional Vivaldi antenna on thick dielectric substrates is eliminated by the double-slot structure. <s> BIB006 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> B. Vivaldi Antenna <s> Abstract We present a ground penetrating radar (GPR) system, which uses an antenna array for in situ measurements of the thickness and dielectric permittivity of an asphalt pavement layer. We calibrated the antenna array by considering the antenna phase center and the antenna offset. The results of the laboratory measurements demonstrate that the proposed calibration method can greatly improve the accuracy of the velocity and thickness estimations when compared with the conventional method. A field measurement conducted on a highway pavement shows that the error of the thickness estimation of the asphalt layer is less than 6 mm (10%). <s> BIB007 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> B. Vivaldi Antenna <s> In this paper, a printed Vivaldi antenna with two pairs of eye-shaped slots is proposed for UWB applications. By using two pairs of eye-shaped slots, the side lobe levels of the radiation pattern are reduced, and the antenna gain is improved at low frequencies. To illustrate the efiectiveness of the proposed design, a prototype of the proposed antenna is fabricated and measured. Experimental results show that the proposed antenna presents a measured impedance bandwidth, deflned by jS11j < i10dB, from 3 to 12.8GHz with a compact size (36mm£36mm). Good unidirectional radiation characteristics with a front-to-back ratio better than 10dB are also achieved. The measured gain is better than 3.7dBi in the operating frequency band. In addition, the measured group delay of the proposed antenna is around 1.2ns with a variation less than §0:5ns. <s> BIB008 </s> Ultra-Wideband Antenna Design for GPR Applications: A Review <s> B. Vivaldi Antenna <s> A compact antipodal Vivaldi antenna (AVA) with the dimension of $42 \times 36 \times 1.6~\hbox{mm}{^3}$ is proposed in this letter. Structural modifications in the radiating fins have increased the electrical length thereby reducing the lower operating frequency from 5.2 GHz to 3.7 GHz. Proposed antenna maintains $-20~\hbox{dB}$ copolarization to cross-polarization ratio throughout the operating bandwidth. The prototype is fabricated and the measurement results are presented to validate the performance of the proposed AVA. <s> BIB009
Vivaldi antennas are commonly used for the applications such as GPR which require a greater bandwidth usually with a ratio 10:1 BIB001 . Therefore, various designs of Vivaldi antennas have been studied and discussed. Fig. 2 shows the design of a Vivaldi antenna. A Vivaldi antenna consists of a radiating and ground planes of a similar shape placed in the opposite of each other separated by a substrate. The exponential curves in the Vivaldi antenna as shown in in the figure can be described by BIB003 and (4) BIB004 In BIB007 , a Vivaldi antenna array is designed for GPR measurement application. An experiment is conducted to observe the penetration through a concrete structure. Five array elements are used in the receiving antenna to gather all the information. In order to achieve the compactness, small size, balanced bandwidth and a reasonable gain for GPR applications, an antipodal structure semi-empirical Vivaldi antenna is proposed BIB002 . The antenna is fed by a microstrip line with PTFE board as the substrate. The antenna is designed based on two aspects: the transition aspect and radiation aspect, to meet the UWB system requirements. Fig. 2 . A Vivaldi antenna  . www.ijacsa.thesai.org Another balanced antipodal Vivaldi antenna structure has been proposed in which an L-shaped slot has been introduced at the edge of a radiating patch BIB009 . In the design, a structural increase in the radiating patch has increased the electrical length of the antenna while the L-shaped slot has enabled a radiation from the outer edge of the antenna. A comparison is then made with a conventional Vivaldi antenna with various substrates such as a FR-4, Rogers, PTFE and TP-2. In  , two antipodal-shaped Vivaldi antennas are proposed. The first antenna consists of a simple antipodal shape to achieve compactness and comparatively small in size with a wider bandwidth and good gain. U shaped slots have been introduced into the structure to enhance the gain. A novel Vivaldi antenna with an exponentially tapered slot edge (TSE) is designed in BIB005 . Seven pairs of electromagnetic band gaps in either a loop or square shapes have been introduced in the ground plane. The purpose of these band gaps is to extend the lower end bandwidth of the UWB antenna and improve the impedance matching over the same band. The proposed antenna also helps in the electrical length reduction in comparison with the original antenna without tapered slots. A double-slot antenna structure is proposed in BIB006 to further improve the gain and directivity of the Vivaldi antenna. The antenna is also suitable for UWB GPR applications. The slots are excited by using a T-junction power divider to generate plane waves in the E-plane at the aperture of the antenna and it is compared with a conventional Vivaldi antenna that uses an exponentially tapered method. Another directional Vivaldi antenna with eye-shaped slots is proposed in BIB008 to reduce the side lobes and increase the efficiency to approximately 80%. The proposed antenna also has a greater gain which makes it suitable for GPR systems.