Ultra-Wideband Antenna Design for GPR Applications: A Review

Transcription

1 Ulta-Wideband Antenna Design fo GPR Applications: A Review Jawad Ali*,, Noosaliza Abdullah*, Muhammad Yusof Ismail*, Ezi Mohd*, Shahail Mohd Shah* *Depatment of Communication Engineeing, Faculty of Electical and Electonic Engineeing, Univesiti Tun Hussein Onn Malaysia, Joho, Malaysia Depatment of Electical Engineeing, COMSATS Institute of Infomation Technology, Lahoe, Pakistan Abstact This pape pesents a compaative eview study on ulta-wideband (UWB) antenna technology fo Gound Penetating Rada (GPR) applications. The poposed antenna designs fo UWB gound penetating ada include a bow-tie antennas, Vivaldi antennas, hon antennas, plana antennas, tapeed slot antennas, dipole antennas, and spial antennas. Futhemoe a compehensive study in tems of opeating fequency ange, gain and impedance bandwidth on each antenna is pefomed in ode to select a suitable antenna stuctue to analyze it fo GPR systems. Based on the design compaison, the antenna with a significant gain and enhanced bandwidth has been selected fo futue pespective to examine the penetation depth and esolution imaging, simultaneously suitable fo GPR detection applications. Thee diffeent types of antennas ae chosen to be moe suitable fom the final compaison which includes Vivaldi, hon and tapeed slot antennas. On futhe analysis a tapeed slot antenna is a pomising candidate as it has the ability to addess the poblems such as penetation depth and esolution imaging in GPR system due to its diectional popety, high gain and geate bandwidth opeation, both in the lowe and highe fequency ange. Keywods Ulta-wideband antennas; gound penetating ada; antennas; antenna eview I. INTRODUCTION The eseach inteest on ulta-wideband (UWB) systems has gained populaity mainly afte the yea 2002 when the US depatment of Fedeal Communications Commission (FCC) allocated a license-fee spectum fo Industial and Scientific puposes. This geate step of FCC has opened new doos of eseaches fo UWB in the field of wieless communications and micowave imaging [1], [2]. The UWB coves a fequency band anges fom 3.1 to 10.6 GHz that has foeseen the applications in the field of Wieless Local Aea Netwoks (WLAN), Wieless Body Aea Netwoks (WBAN), Wieless Inteopeability fo Micowave Access (WiMAX), Wieless Pesonal Aea Netwoks (WPAN) and Gound Penetating Rada (GPR) technology whee wide bandwidth is equied [3], [4]. GPR is one of the majo applications of UWB technology, which is widely used in militay and civilian applications such as the detection of land-mines [5]. In addition, GPR is also used in emote sensing techniques such as nondestuctive testing of concete and detection of tapped people undedebis o in opaque envionment [6]. Fo the implementation of UWB GPR systems, the pefomance of vaious antenna designs, such as bow-tie antenna [7], [8], spial antenna [7], loaded dipole antenna [9], TEM hon antenna [10], [11], tapeed slot antenna [12], [13] and Vivaldi antenna [14], [15] have been evaluated. This pape examines the technical and methodological aspects involved duing the design of ulta-wideband antennas fo gound penetating ada detection applications. The study has been pefomed based on antenna gain, diectivity, complexity of the design as well as the fequency bandwidth. Late the compaison of esults to addess the fundamentals of GPR applications, such as penetation depth and esolution has been pefomed. Finally one of the best suitable antenna design is chosen fo futhe eseach and futue diections. The oganization of this pape is as follows: Section II discusses the UWB antenna designs and methodologies suitable fo GPR application. Section III pesents the esults and analysis of the antennas discussed in the pevious section. Finally, the pape is concluded in Section IV. II. ANTENNA DESIGN FOR GPR A numbe of ulta-wideband antennas have been designed fo GPR applications. The study based on the lowe fequency band is conducted mainly to impove the penetation depth while the designing in the highe fequency band is pefomed to achieve bette esolution imaging fo GPR systems. Some of the wok focus on the entie UWB fequency ange to futhe enhance the bandwidth while othe focused on gain enhancement. Based on these peviously mentioned equiements, diffeent types of antennas such as bow-tie antennas, Vivaldi antennas hon antennas and few moe antenna designs have been studied and implemented fo GPR applications. A. Bow-tie Antenna A bow-tie UWB antenna is widely used in the design fo GPR applications, as it has the ability to educe gound susceptibility duing GPR opeations [16]. Fig. 1 shows a simple bow-tie antenna design which consists of two flaes connected to a common feed. 392 P a g e

2 Fig. 1. Bow-tie antenna design [24]. The length, l and width, w of the flaes in bow-tie stuctue can be detemined by (1) and (2) [16-19]: 1.6o l (1) w 0.5 o (2) Whee λo is the wavelength of the low fequency ange in fee space. The flae angle is totally dependent on impedance [19]. In [17], a monolithic bow-tie UWB antenna fo GPR applications is designed by using a total geometic mophing appoach with small pads to fom an aay. The antenna has been fabicated on a glass epoxy FR-4 substate with a dielectic constant value, Ԑ of 20 and it is fed by a coaxial cable fo impedance matching to the balanced cuent balun. A slot and eflecto have been intoduced into the antenna stuctue to achieve a wide beam width and unidiectional adiation patten [18]. The antenna is fed by a coplana waveguide (CPW). Futhemoe, a modified bow-tie antenna with a shielded back cavity fo omnidiectional adiation patten is also poposed fo GPR application [19]. The antenna is fabicated on a FR-4 substate with a dielectic constant, Ԑ of 4.6 and centeed at 900 MHz. The edge of the antenna is cut to make the antenna to be moe compact and study the effect of edges on eflection coefficient. As the eseach pogesses, new designs have been developed with modifications in the shapes and dimensions of the bow-tie antenna. In addition, one of the antennas has been designed by using the finite diffeence time domain appoach [20]. CPW is used as the feeding method while metal stubs is intoduced fo impedance matching. The wok in [7] intoduces the stuctue of a bow-tie antenna into its dipole antenna to impove the gain fo GPR. The ideal pefomance of a bow-tie dipole antenna can be achieved by feeding the antenna with ohm impedance. In [8], a esistive-loaded UWB bowtie antenna is poposed to impove the fowad gain fom the employment of metamateial lens. As the signal of the GPR system equied popagating though inhomogeneous media, the efficiency of the antenna must also be taken into account. Thus, in ode to enhance the efficiency, a compact shape slotted bow-tie antenna is designed [21]. The compactness in the shape of antenna is achieved by ounding the shap cones of the bow-tie stuctue and tiangula stubs with extended ams. The antenna is fed by a CPW and a thin gaphite sheet is used to educe the end-fie eflection of the UWB antenna fo GPR application. In [22], an elliptical shape of bow-tie antenna is poposed to boaden the bandwidth. A semicicula slotted-tuned halfellipse antenna in a bow-tie fomation is designed in [23]. The poposed antenna has fou semicicula slots in the bow-tie ellipse to futhe impove its penetation popeties fo vital signs detection. A low cost UWB bow-tie antenna fo GPR is pesented in [24]. A eflecto cavity design technique is used whee the model is initially tested with only a bottom eflecto followed by a side eflecto and both eflectos at the same time. Thee is also a gap between both flaes of the bow-tie whee a balun is deployed to match the impedance. Finally, the antenna is equipped with a fou-sided eflecto to study the gain paametes. B. Vivaldi Antenna Vivaldi antennas ae commonly used fo the applications such as GPR which equie a geate bandwidth usually with a atio 10:1 [16]. Theefoe, vaious designs of Vivaldi antennas have been studied and discussed. Fig. 2 shows the design of a Vivaldi antenna. A Vivaldi antenna consists of a adiating and gound planes of a simila shape placed in the opposite of each othe sepaated by a substate. The exponential cuves in the Vivaldi antenna as shown in in the figue can be descibed by (3) and (4) [15]: x 0.27y 0.14e y (3) 0.425y4.845 x 3.04e y (4) In [14], a Vivaldi antenna aay is designed fo GPR measuement application. An expeiment is conducted to obseve the penetation though a concete stuctue. Five aay elements ae used in the eceiving antenna to gathe all the infomation. In ode to achieve the compactness, small size, balanced bandwidth and a easonable gain fo GPR applications, an antipodal stuctue semi-empiical Vivaldi antenna is poposed [25]. The antenna is fed by a micostip line with PTFE boad as the substate. The antenna is designed based on two aspects: the tansition aspect and adiation aspect, to meet the UWB system equiements. Fig. 2. A Vivaldi antenna [27]. 393 P a g e

3 Anothe balanced antipodal Vivaldi antenna stuctue has been poposed in which an L-shaped slot has been intoduced at the edge of a adiating patch [26]. In the design, a stuctual incease in the adiating patch has inceased the electical length of the antenna while the L-shaped slot has enabled a adiation fom the oute edge of the antenna. A compaison is then made with a conventional Vivaldi antenna with vaious substates such as a FR-4, Roges, PTFE and TP-2. In [27], two antipodal-shaped Vivaldi antennas ae poposed. The fist antenna consists of a simple antipodal shape to achieve compactness and compaatively small in size with a wide bandwidth and good gain. U shaped slots have been intoduced into the stuctue to enhance the gain. A novel Vivaldi antenna with an exponentially tapeed slot edge (TSE) is designed in [15]. Seven pais of electomagnetic band gaps in eithe a loop o squae shapes have been intoduced in the gound plane. The pupose of these band gaps is to extend the lowe end bandwidth of the UWB antenna and impove the impedance matching ove the same band. The poposed antenna also helps in the electical length eduction in compaison with the oiginal antenna without tapeed slots. A double-slot antenna stuctue is poposed in [28] to futhe impove the gain and diectivity of the Vivaldi antenna. The antenna is also suitable fo UWB GPR applications. The slots ae excited by using a T-junction powe divide to geneate plane waves in the E-plane at the apetue of the antenna and it is compaed with a conventional Vivaldi antenna that uses an exponentially tapeed method. Anothe diectional Vivaldi antenna with eye-shaped slots is poposed in [29] to educe the side lobes and incease the efficiency to appoximately 80%. The poposed antenna also has a geate gain which makes it suitable fo GPR systems. C. Hon Antenna In a GPR system, bette depth penetation and ease of scanning the shallow tagets often equie elevated antennas because the enegy must adiates into the gound fo detection. Thus, it makes a hon antenna as one of the best candidates as it is less susceptible to the effects of gound [16]. A typical hon antenna can be seen in Fig. 3. The constuction of a hon antenna mainly consists of two pats: An apetue and waveguide tansition. The dimensions of an apetue can be appoximated by (5) and (6) [11]: 2 w (5) 8R Fig. 3. A hon antenna [30]. 2 w S (6) 8R Whee S is a dimensionless quantity, w is the distance between the hon apetues, R is the length of apetue and λ is the wavelength. A double idged hon (DRH) antenna is pesented in [30]. The antenna has a wide bandwidth and is poposed fo GPR applications. The eduction in opeating fequency will compomise the size of the antenna. Thus, in ode to achieve a small size but with lowe opeating fequency, the idges have been extended fom the apetue plane and the gap is filled with dielectic mateial. In [7], anothe DRH antenna is also designed to incease the bandwidth. An UWB quad idged hon (QRH) antenna is poposed in GPR application fo deep penetation by modifying a conventional tiangula tansvese electomagnetic (TEM) hon [11]. Fist modification is pefomed by tapeing the hon plates with a cuvatue and the second modification is the addition of double idges in between the hon apetue [30]. A substate with a high dielectic constant is used to fill the gap. The substate used is the Roges RT-3010 with Ԑ of The fabicated antenna is then compaed with the SH-68 Satimo hon antenna that is commecially available. Thee ae some eflections and inging effects in the conventional TEM hon antenna that ae not suitable in GPR application. Theefoe, an optimized design of TEM hon antenna fo UWB is poposed [10]. The antenna is designed by caving an ac in the two exponentially tapeed plates of hon and pependicula plates ae connected at the lowe end. In [31], anothe TEM hon with a flae shape is designed with a balun fo pope cuent balancing. The design consists of two flaing conductos constucted by cutting a bass sheet fo the top and bottom flae and combined togethe with a tiangula slab fom Styofoam to secue the conducto in a flae. The antenna is expeimentally tested with a concete to obseve the gain when in contact with othe mateials. In [9], an UWB hon antenna consists of a coaxial feed line and a pope waveguide with a ound and tapeed-shaped apetue. The antenna is designed by using the D-angle and W- angle methods fo the waveguide. The apetue has ounded cones to impove the pefomance. Vaious feeding techniques ae also discussed in [6] othe than poposing a new feeding technique. In ode to ealize the new technique, the waveguide of the antenna is fixed and a scew is added on the opposite side of the feede to incease the gain. D. Plana Antenna A plana antenna, as shown in Fig. 4, is a popula candidate fo UWB due to its simplicity, confomity in design, cost effectiveness and light weight popeties [32 ], [33]. A plana antenna mainly consists of a adiating patch and eithe a full o patial gound plane with a defected gound stuctue (DGS) [15] which can be vaied accoding to the 394 P a g e

4 design equiement. The length, L and width, W of the patch can be detemined fom (7) and (8) [32], [37]: Whee: c c W (7) 2 f 1 c L L (8) 2 f L h eff w eff w h h h 1 12 (10) eff 2 2 w In [34], a hexagonal factal patch antenna is poposed to achieve a wideband chaacteistic. The design is modified by iteation of hexagonal factals with slits in the gound plane to ceate a notch that affects the impedance bandwidth. Hexagonal slots ae also intoduced in the patch and slots in the gound plane alongside the slits. A modified cicula patch antenna fo UWB GPR applications is poposed in [35]. The conventional cicula disc is modified to poduce a mickey-shaped patch adiato with a CPW feed. The substate used is FR-4 with Ԑ of 4.3. A ectangula coppe eflecto is inseted below the antenna to make it diectional. Anothe cicula disc antenna is designed in [36] to impove the impedance bandwidth and efficiency of the plana antenna. A ectangula slot is intoduced at the edge of the gound. A stepped feeding and two level notched stais in the patch with a patial gound plane ove Roges Duoid RT-5880 with a dielectic constant, Ԑ of 2.2 ae included in the design of an UWB plana antenna in [37]. The antenna is tested in step-bystep basis. Fistly, the antenna is simulated and tested only with a simple ectangula patch and a patial gound followed by a stai patch and a patial gound. Finally, the stubs ae intoduced in the stais feed patch fo band notch. A multioctave fequency selective antenna with a eflecto is poposed in [38] to study the gain pefomance. (9) An UWB quasi-plana antenna in [39] is designed fo gain enhancement. The antenna consists of a CPW-fed semicicula disc monopole antenna with a shot hon. The shape of this quasi antenna makes it a potential candidate fo GPR technology. A quaduple-band plana antenna is developed in [40]. This is a simple micostip patch antenna with fou slots of diffeent geometies namely, squae, ectangle, cicle and ellipse. Similaly, anothe slotted monopole plana antenna with a key shape is designed in [41] whee the shape is achieved by etching two symmetical cuved slots in the cicula patch which in etun, inceases the efficiency of the antenna. A spanne-shaped antenna is poposed in [42] which is achieved by cutting a ectangula slot on the uppe side of mino axis in an elliptical-shaped antenna to impove the gain and bandwidth fo GPR applications. E. Tapeed Slot Antenna Gain is one impotant paamete that is equied in a GPR system as it can enhance the signal appeaance which can be affected by signal attenuation and othe losses as well [43]. In ode to impove the gain facto in an antenna design, diffeent methods ae used. One of them is the tapeed slot method. Fig. 5 shows the UWB tapeed slot antenna which consists of a coplana patch and gound that is suitable fo GPR applications. In [12], one of the tapeed slot compact antennas with a high gain fo GPR applications is poposed. This compact plana antenna is fed by a CPW with one slot line to supplement the tape slot. A esistive loading is intoduced with some discontinuities in the design to avoid any stong eflections. The antenna is designed by intoducing two main slots: one slot is epesented by a Vivaldi shape and anothe slot is a tiangula slot. A double exponentially tapeed slot antenna (DETSA) is designed in [13] in which the exponential ams of the antenna ae olled back to impove the bandwidth. Anothe modification in the design is the intoduction of a coupled-stip line (CPS) instead of a CPW fo feeding pupose. The measued losses of a CPS ae less than that of a CPW. The antenna is designed on a FR-4 dielectic mateial with Ԑ of 4.4. In [44], anothe modified slotted antenna with a backed absobe is investigated fo boadband antennas. The poposed design is modified by cutting a slot in the patch and then tapeing the slot edges so that the antenna can pefom bette in GPR applications. This model is designed on a lossy TMM-10 substate with Ԑ of 9.2. Fig. 4. A plana antenna [37]. Fig. 5. Tapeed slot antenna [12]. 395 P a g e

5 A semicicula slotted antenna is intoduced in [5] to enhance the gain facto. In the design, semicicula slots ae intoduced with tapeed tansitions fo a CPW feed. A fequency selective suface (FSS) method with a dual-laye eflecto is used which helps in the gain enhancement and impedance matching. The distance between the antenna and eflecto can be appoximated by (11) [45]: FSS 2h FSS 2n; n..., 2, 1,0,1,2,... (11) Whee: = Reflection phase FSS h = Distance between eflecto and antenna FSS = Popagation constant of fee space Anothe high gain antenna with FSS has been designed by etching two elliptical stuctues fo the slot [45]. The gain of the antenna without the FSS is vey low and has been futhe enhanced with the pesence of FSS. A sta-shaped antenna is designed with an asymmetic slot in the gound plane with an open ended CPW feed [46] fo gain enhancement fom the employment of FSS which makes it suitable fo GPR applications. F. Dipole, Cone, and Spial Antenna Dipole, canonical and spial antennas ae also the potential candidates fo GPR applications and ae discussed in this section. A dipole antenna can be constucted on eithe a plana stuctue o fom a wie [7]. Vaious dipole antennas have been designed such as wied dipole, elliptical dipole and shot dipole [47] fo UWB applications. The length, L of a dipole fom a simple wie can be calculated as follows [52]: Fig. 6. A dipole antenna [50]. A magneto-electic dipole is investigated in [52]. In the design, a geate bandwidth is achieved by intoducing two slots in the magneto-electic dipole by using a ectangula box eflecto to fix the boadside diection of main beam. Othe antenna designs fo UWB GPR applications ae constucted fom the cone and spial shapes [7]. A cone antenna, as shown in Fig. 7, is an elementay antenna in 3-D stuctue to impove the impedance bandwidth fo GPR systems. The angle of the cone is always elated to the impedance, which can be calculated fom (15) [49]: k Z 120 ln cot (15) 2 On the othe hand, spial antennas with two unifom width ams with gain ae also suitable fo GPR applications. Fig. 8 shows the spial antenna. Whee: 1 L (12) 4 c (13) f The advantage of using a wied dipole is that it ensues high micowave powe which is pefeable in GPR technology [7]. Similaly, cone and spial antennas ae also poposed fo UWB applications. To incease diectivity, a adiation stub cone o disk cone [48] has been intoduced into the antenna with a factional bandwidth of 70-80% [7]. Spial antennas ae also favoable as the antennas have a balanced feed ove the entie fequency band [49]. The ams of spial antenna can be defined by using a pola function which is given by (14) [16]: R e a (14) o Whee Ro contols the adius of the spial as it gows exponentially, while a contols the flae ate. In [50], an elliptical-shaped stuctue is intoduced into each of the dipole s am as shown in Fig. 6. The poposed design is capable to impove the gain and eflection coefficient fo UWB applications. The elliptical slots ae used fo time domain analysis. Anothe antenna consists of a 16-pot shaedam dipole aay is poposed fo ada imaging [51]. Fig. 7. Cone antenna design [7]. Fig. 8. A spial antenna [7]. 396 P a g e

6 III. RESULTS AND DISCUSSIONS Ulta-wideband antenna designs that ae suitable fo gound penetating ada applications mainly equie geate fequency bandwidth along with the paamete of high gain. Based on the above mentioned paametes, esults of antenna designs discussed in Section 2 ae pesented fo the analysis duing this section. The opeating fequency of the designed antenna, its pecentage bandwidth and the maximum value of obtained gain ove the entie UWB band ae summaized in tabula fom. This summaization helps us to develop a bette undestanding egading antenna pefomance fo GPR applications. The measued esults fo bow-tie antennas ae shown in Table 1. Fom these esults, it can be obseved that the bow-tie antenna designed by cutting edges has sufficient pecentage bandwidth, which is suitable fo an UWB GPR system. But thee ae some significant diffeences shown in the gain obtained fo these antennas. The esults of a backed cavity bow-tie antenna designed in [24] and bow-tie slotted antenna in [21] have a compaatively bette gain with the value aound 7 db. But the bow-tie antenna designed using metamateial lens has the highest gain with the value of db. In addition to this, these designed bow-tie antennas also have a sufficient flaes length which is pefeable to match the lowe fequency band. Because of this eason these antennas ae mainly capable of tageting the penetation depth popeties fo the GPR detection applications. Howeve, the discussion about the ability of these antennas to distinguish among diffeent detectable objects though imaging is difficult because of low esolution popeties, as lowe fequencies ae not suitable fo imaging chaacteistics. In a simila manne, the measued gain and bandwidth obtained fo Vivaldi antenna designs ae shown in Table 2. The pecentage bandwidth of all the poposed UWB antennas is sufficient to conside Vivaldi shape design fo GPR applications. This is due to the fact that Vivaldi antennas offe dimensionality as well as gound optimization to achieve the desied bandwidth. The exponentially tapeed slotted edge antenna designed in [15] has the least pecentage bandwidth and the value of gain fo this antenna is 8 db, due to which this design is also consideable fo GPR systems. Fom the table, it can be deduced that the gain of Vivaldi antennas have consideable values and also they coveed the complete UWB fequency band defined fom 3.1 to 10.6 GHz. The antipodal Vivaldi antenna designed in [27] pefoms bette with geate bandwidth of appoximately 15.9 GHz and the gain of 9.6 db. TABLE. I. PERFORMANCE OF BOW-TIE ANTENNAS to to to to to to to to to to TABLE. II. PERFORMANCE OF VIVALDI ANTENNAS to to to to to to to to to Anothe antipodal antenna is also poposed in [27] with U- shaped slots and a mouth opening at the ode of λ/4 also gives significant esults with a gain of 15.2 db and a geate bandwidth that coves UWB band. These esults shown in Table 2 povides a wide oppotunity fo the Vivaldi shape antenna designs that makes it one of the suitable candidate fo GPR applications with deep penetation and bette esolution imaging. Hon antenna designs, discussed in the ealie section possess high gain value mainly because of its diectional popeties. Measued esults of hon antennas in the fom of gain and pecentage bandwidth ae shown in Table 3. Fom the table, the pefomance of the antennas in tems of gain and bandwidth is analyzed and the esults showed a significant incease in gain. As such, a TEM flae hon antenna designed in [31] can be used in a GPR system fo detection as it addesses the equiements of deep wave penetation and bette esolution imaging to distinguish among the detected objects due to its high gain as well as geate bandwidth compaed to emaining hon designs. While othe designed antennas seemed to taget penetation depth as thei opeating bandwidth lies within the lowe fequency band. The hon antenna designed in [6] has the least pecentage of bandwidth even though its gain value is significantly highe due to which it can penetates up to few feet unde the gound. Nevetheless, a hon antenna design is still one of the best suitable candidates fo GPR applications because of its highly diectional popeties, suitable gain, pope impedance bandwidth and less susceptibility to gound effect the pefomance of antenna. TABLE. III. PERFORMANCE OF HORN ANTENNAS to to to to to to to P a g e

7 The esults obtained fom plana antenna designs ae shown in Table 4. Fom the given table, pinted cicula patch antennas with the slotted gound ae designed in [36], [38]. These antenna have sufficient gain value which is appoximately 7.5 db and also have geate bandwidth. This significant incease in the bandwidth of plana antennas can be attibuted to the exta electomagnetic coupling between the gound and the adiating patch [36]. The pefomance of a cicula patch antenna designed in [36], makes plana antenna a suitable candidate fo GPR applications. The pefomance of the othe designed plana antennas is also consideable only fo deep penetation as the bandwidth opeates in lowe fequencies. Tables 5 and 6 shows the esults obtained fom a tapeed slotted antennas, dipole, spial and cone antennas. Fom the esults shown in Table 5, it can be obseved that the tapeed slot antenna (TSA) designed in [12], double exponentially tapeed slot antenna (DETSA) designed in [13] and eye-shaped slotted antenna designed in [45] have compaatively high gain with geate pecentage of bandwidth. The good pefomance of tapeed slot antennas is mainly due to the coplana popeties of adiato and gound, and tapeing chaacteistics, which is helpful in ode to impove the pefomance of the antennas. Theefoe, these tapeed slot antennas have the ability to addess the poblem of deep penetation popeties and high esolution imaging in GPR applications. Fom the esults obtained in Table 6, it can be obseved that the magneto-electic dipole antenna designed in [52] has significantly high gain value ove the entie opeating bandwidth. This magneto-electic antenna also cove the complete UWB band which makes this antenna design as one of the suitable antenna that can be designed fo GPR detection applications. TABLE. IV. PERFORMANCE OF PLANAR ANTENNAS to to to to to to to to to to TABLE. V. PERFORMANCE OF TAPERED SLOT ANTENNAS 5 3 to to to to to to TABLE. VI. PERFORMANCE OF DIPOLE, CONE AND SPIRAL ANTENNAS to to to to to Fom the esults obtained fo diffeent types of antennas, designed specifically fo GPR applications fo detection pupose, it can be obseved that the Vivaldi, hon and tapeed slot antenna designs have significantly bette pefomance. Howeve, based on futhe compaison between these designed antennas, a tapeed slot antenna is the best suitable candidate fo UWB gound penetating ada system and it has the potential to be futhe developed due to significant gain and geate bandwidth. IV. CONCLUSION A compaative eview based study into a potential ultawideband antenna fo GPR applications has been pefomed in this pape. The detailed summay of a bow-tie antenna, Vivaldi antenna, hon antenna, plana antenna and tapeed slot antenna along with diffeent design methodologies have been pesented. The demonstation of esults and the discussion about it, mainly focused on the gain as well as the bandwidth because these two paametes shows a geatest inteest to design UWB antennas fo GPR systems. Based on the measued esults, thee diffeent types of antennas have been selected which includes Vivaldi, hon and tapeed slot antennas. But on futhe compaison it is concluded fom the study that a tapeed slot antenna can be consideed fo futue eseach. These antennas have the potential to addess the issues of deep penetation unde the suface of gound and bette esolution imaging fo GPR systems mainly because of its diectional popeties, high gain and geate opeational bandwidth, both in the lowe as well as highe fequency ange. REFERENCES [1] M. M. Islam, M. Samsuzzaman, and M. R. I. Fauque, Five bandnotched ultawide band (UWB) antenna loaded with c-shaped slots, Micowave and Optical Technology Lettes, vol. 57, pp , [2] P. Saka, R. Ghatak, M. Pal, and D. R. Podda, Compact UWB Bandpass filte with dual notch bands using open Cicuited stubs, IEEE Micowave and Wieless Component Lettes, vol. 22, pp , [3] S. Shi, W.-W. Choi, W. Che, K.-W. Tam, and Q. Xue, Ulta-Wideband Diffeential Bandpass filte with naow notched band and impoved common-mode suppession by DGS, IEEE Micowave and Wieless Component Lettes, vol. 22, pp , [4] J. Zhang, S. W. Cheung, L. Liu, and T. I. Yuk, Simple notches design fo ulta-wideband monopole antennas with coplana-waveguidecoupled-fed, Micowave and Optical Technology Lettes, vol. 55, pp , [5] Y. Ranga, K. P. Esselle, L. Matekovits and S. G. Hay, Inceasing the gain of a semicicula slot UWB antenna using an FSS eflecto, IEEE- APS Topical Confeence on Antenna and Popagation in Wieless Communication (APWC), Cape Town, pp , P a g e

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