A compact umbrella shaped UWB antenna for ground‐coupling GPR applications

Abstract

A compact (35 3 30 3 0.8 mm 3 ) umbrella shaped ultra wideband antenna that gives wide impedance bandwidth of more than 123% with low dispersion, 3-5 dBi gain and average efficiency of 84% is proposed. The antenna is tested in close proximity of soil. Satisfactory results ensure its ability to work as GPR antenna. K E Y W O R D Sground coupling, ground penetrating radar, ultra wide-band antenna, umbrella shape | I NT RODU CTI ONGround penetrating radar is widely used to scan the sub surface of interest by transmitting and receiving electromagnetic waves using UWB antenna. 1 Different types of UWB antenna like horn and Vivaldi, 2-6 valentine, 7 bow-tie, 8,9 rugby ball, 10 frequency independent, 11 and slot antenna 12,13 were proposed earlier for GPR applications. Horn, Vivaldi and Valentine antenna can provide satisfactory GPR performances but heavy weight and bulky structures limited their uses in GPR. Frequency independent like spiral antenna can provide wide bandwidth but it also introduce significant ringing effect. Bowtie, rugby ball antenna can be very compact in size and able to give good GPR performance but it require capacitive and inductive loading to broaden impedance bandwidth and minimize ringing effect, respectively. The loading increases antenna efficiency loss significantly. Also low gain profile is another drawback of such antenna. Slot type GPR antenna also has larger dimensions. Recently Ming Li et al. proposed a high gain, low dispersive slot 146 | KUNDU AND JANA antenna having dimension of 106 3 68 mm 2 and limited impedance bandwidth of 1.4-3.5 GHz. 13 Wide bandwidth is required to get better plan resolution of GPR. Plan or lateral resolution indicates the scanning ability to differentiate between any two buried objects of same depth. The relation between antenna bandwidth (B) and plan resolution length (Dr) is given by the expression, B ! V/4Dr where V indicates speed of electromagnetic wave in subsurface material.In this article, a compact, coplanar waveguide fed, umbrella shaped monopole antenna is proposed. The antenna gives a wide impedance bandwidth from 3.1 to 13.1 GHz covering the unlicensed 3.1-10.6 GHz UWB band as allotted by FCC in 2002. 14 Fundamental antenna parameters like VSWR, pattern, efficiency, gain, transfer function (S 21 ) and group delay were simulated and measured. Good agreement is observed in the results. The antenna is also tested in ground coupling mode to ensure its ability as GPR antenna. | A NTEN NA DE S I GNGeometry of the proposed antenna is shown in Figure 1. Figure 1A shows the construction of radiating patch by taking the intersection of two ellipses of radius (1.7R, R) and (1.5R, 2R), respectively. The maximum patch length is 2R and width is 3R. The maximum patch dimension (D), that is, maximum patch width is taken as k L /4 where k L 5 c/f L . Here, c indicates speed of light and f L represents lower cutoff frequency that is 3.1 GHz. Figure 1B,C represents the design flow. Design A and B indicate microstrip fed and coplanar fed antenna structure...

Experimental study of a printed ultra‐wideband modified circular monopole antenna

“…The allocation of huge unlicensed spectrum of 7.5 GHz (3.1‐10.6 GHz) by Federal Communication Commission (FCC) in 2002 grew more research interest in this domain . Design of transmitting and receiving antennae for UWB radio demands to match some special requirements such as very wide impedance band, flat gain, high radiation efficiency, light weight, and compact size . The antenna also needs to be nondispersive in nature .…”

Design of a miniaturized planar half elliptical ultra‐wideband dipole using a concaved arm

“…In particular, miniaturized ultra‐wideband (UWB) antennas are highly desired in space‐limited applications such as body‐centric wireless communications, wireless universal serial bus, and biomedical implants . Several miniaturization approaches have been proposed to realize small UWB antennas . For instance, a compact hexagonal fractal planar UWB antenna was presented in Reference .…”

“…The antenna has an electrical size of 0.36 λ × 0.26 λ with operating band ranging from 3.1 to 16.3 GHz. A small coplanar waveguide‐fed UWB antenna with an umbrella shape was recently reported in Reference . The structure comprises an umbrella‐shaped radiator and an altered ground plane.…”

Gain enhancement of a printed leaf shaped UWB antenna using dual FSS layers and experimental study for ground coupling GPR applications

“…GPR devices can be used in air‐coupling mode and ground coupling mode . Wide antenna bandwidth is crucial to achieve as it can increase the GPR lateral resolution .…”