Microwave and millimetre wave antipodal Vivaldi antenna with trapezoid‐shaped dielectric lens for imaging of construction materials

Abstract

High‐quality microwave and millimetre wave imaging of construction materials and structures requires ultra‐wideband (UWB) techniques to provide high‐range resolution as well as a reasonable penetration depth. A modified compact microwave and millimetre wave UWB antipodal Vivaldi antenna is designed and presented in this study. First, the conventional antipodal Vivaldi antenna is designed as a reference antenna. Then, to provide the desired frequency range (3.4–40 GHz) with increased gain at its lower frequencies, the slit edge technique is applied, thus creating a periodic slit edge antipodal Vivaldi antenna (PSEAVA). Finally, a trapezoid‐shaped dielectric lens (TDL) as an extension of the substrate is added and optimised to increase gain and directivity at higher frequencies of the frequency range, creating PSEAVA with a TDL (PSEAVA‐TDL). The results show that the PSEAVA‐TDL has the highest gain (up to 16 dB) and front‐to‐back ratio (up to 37.5 dB), and the narrowest half power beamwidth (down to 11.7°). A prototype of the proposed PSEAVA‐TDL with compact size of 40 × 90 × 0.508 mm3 is fabricated and applied for the imaging of samples made of construction materials. High‐range resolution images of the samples are obtained with this antenna by using synthetic aperture radar algorithm.

UWB antipodal vivaldi antenna for microwave imaging of construction materials and structures

“…However, its impedance bandwidth is restricted at lower operating frequencies and its gain is only 6 dB at 4 GHz. As a result, this antenna was applied for imaging of low loss construction materials such as plasterboard sheets .…”

Design of a Wideband Antipodal Vivaldi Antenna with an Asymmetric Parasitic Patch

“…It has numerous advantages in terms of weight, cost, scan angle capability, ease of fabrication, and system integration. Recently, some applications have required a Vivaldi antenna with higher directivity or gain over a wider bandwidth to achieve the desired system performance such as range resolution [1,2]. However, a conventional Vivaldi antenna has limited bandwidth because of performance degradation, including directivity or gain reduction and radiation pattern distortion at high frequencies.…”

“…Therefore, a central issue in the further development of the Vivaldi antenna is to improve the directivity at higher frequencies and the stability of the radiation pattern over the frequency range. Several techniques, such as the use of dielectric lens [1,3], directors [4,5], and negative index metamaterial [6], have been proposed to overcome these issues. These materials are located in the aperture of the tapered slot to focus energy toward the end-fire direction.…”

A directivity enhanced structure for the Vivaldi antenna using coupling patches

“…And the Vivaldi antennas with dielectric director in the end‐fire direction, which focuses the energy in the near‐field, were discussed in Refs. for higher gain especially at high frequencies. The directional dielectric rod or profiled dielectric piece with higher permittivity were viewed as a traveling wave structure for radiating most of the energy toward the aperture center.…”