Cavity-backed Bow-tie Antenna Research Articles

Radiation Enhancement of an Ultrawideband Unidirectional Folded Bowtie Antenna for GPR Applications

An arc-shaped distributed multilayer capacitive loading structure combined with resistive loading is presented in this paper to enhance the radiation performance of folded bowtie antenna (FBA). The radiation efficiency of the loaded bowtie antenna (BA) is improved, and the low-frequency bandwidth is broadened by the bent loop circuits. Additionally, a novel technique of cavity groove is proposed to design the reflector. The optimized cavity tightly coupling with the radiation part overcomes the shortcomings of conventional cavity-backed BAs. The improved ultra-wideband (UWB) FBA with low profile is then designed and fabricated. The basic geometry of the proposed antenna is combined by a novel acorn-shaped bent bowtie patch and a hollowed stepped back cavity. The simulated -10 dB impedance bandwidth of the proposed antenna is over 100 MHz-1100 MHz while the measured operating bandwidth is 250 MHz-850 MHz. This BA of folded type obtains a high realized gain of 4 dBi at 850 MHz and a narrow pattern over the whole band. Time-domain measurements and field tests for practical ground-penetrating radar (GPR) applications have been carried out and the results demonstrate the advanced performance.

Cavity‐backed bow‐tie antenna with dielectric loading for ground‐penetrating radar application

Bow-tie antennas are widely used in practical ground-penetrating radars. In spite of simple structure and wideband characteristics, boresight gain of the antenna is small and the radiation pattern is omnidirectional. In this study, a cavity-backed bow-tie antenna with dielectric loading is presented. The bow-tie antenna is resistively loaded to reduce ringing effects. The resistively loaded antenna is placed within a rectangle cavity, which acts as a reflector, for unidirectional radiation and high gain. A dielectric is loaded on the antenna aperture to enlarge the operational bandwidth and stabilise the radiation patterns. Parameter studies of the dielectric substrate are performed to optimise the antenna performance. The final design is fabricated and measured. It has been shown that the antenna exhibits wide impedance bandwidth of 120% for VSWR≤2. The boresight gain is more than 5 dBi. The radiation patterns are stable and unidirectional over the whole band, and the late-time ringing is small.

Design of Cavity-Backed Bow-Tie Antenna with Matching Layer for Human Body Application.

This paper presents the broadband antenna for the microwave radiometric sensing of internal body temperature. For broadband operation, the bow-tie antenna was designed and backed with a cylindrical cavity, which decreased environmental electromagnetic interference and also improved the directivity of the antenna. The broadband impedance-transforming balun in microstrip form was also designed to feed the bow-tie antenna, and was located inside the cavity. An impedance-matching dielectric layer (IMDL) was introduced on top of the bow-tie antenna, for impedance match with the human body with high permittivity. The fabricated antenna was measured in free space with the IMDL removed, showing an input reflection coefficient lower than −10 dB from 2.64 to > 3.60 GHz with antenna gain over 6.0 dBi and radiation efficiency over 74.7% from 2.7 to 3.5 GHz. The IMDL was re-installed on the cavity-backed bow-tie antenna to measure the antenna performance for the human head with relative permittivity of about 40. The measured reflection coefficient was as low as −28.9 dB at 2.95 GHz and lower than −10 dB from 2.65 to > 3.5 GHz. It was also shown that the designed antenna recovered a good impedance match by adjusting the permittivity and thickness of the IMDL for the different parts of the human body with different permittivities.

A low profile, wideband cavity‐backed bowtie antenna

AbstractIn this article, a cavity‐backed bowtie antenna (CBBA) is proposed and investigated.Compared with the conventional CBBA, parasitic stubs are added to the open‐end of the Bowtie. The parasitic stubs provide capacitive loading and allows the design to exhibit a low profile over a relatively wide bandwidth. Parametric studies are performed to optimize the antenna performance. For verification, a prototype was fabricated and measured. Experimental results show the VSWR of less than 2.0:1 from 1.97 to 8.5 GHz. However, the radiation pattern degrades beyond 7.5 GHz. This limits the operating bandwidth to about 117%. The height of the prototype is 15 mm which is only 0.1 λmax (λmax is the wavelength at the lowest operating frequency) © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1422–1426, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27573

Wideband Cavity-Backed Bowtie Antenna With Pattern Improvement

A wide-band unidirectional cavity-backed bowtie antenna with stable radiation patterns is proposed in this paper. It is differentially fed by a parallel strip line via a transition from a microstrip line. The corners of the conventional triangular bowtie dipole are rounded to achieve a larger impedance bandwidth. A circular ring, acting as a special reflector, is placed within the cavity, between the ground plane and the bowtie dipole, for stabilizing the broadside radiation patterns over the whole operating band. Numerical simulations and parametric studies are performed to verify the effectiveness of the ring reflector for radiation pattern improvement when it is electrically close to the bowtie dipole. The final design is fabricated and measured. Measured results indicate that the proposed antenna features an impedance bandwidth of 91.4% for SWR les 2, a 7.3-9.5 dBi broadside gain, a total size of 1.56 times 0.325lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength at the center frequency) and stable radiation patterns over the whole band.