Ultra-wideband Bow-tie Antenna Research Articles

Temperature-Induced Contrast Enhancement for Radar-Based Breast Tumor Detection at K-Band Using Tissue Mimicking Phantoms

Conventional approaches for microwave breast tumor detection are limited by the imaging resolution due to the low operating frequency. The objective of this work is to provide a proof of concept for radar-based detection of breast tumors in K-band using the temperature-dependent permittivity of the tissue for contrast enhancement. The innovation of this work is given by i) investigating higher microwave frequencies for breast cancer diagnostics and improved resolution; ii) exploiting variations in tissue temperature as a non-invasive approach for contrast-induced radar imaging eliminating the need for contrast agents such as nanoparticles; iii) using a well-defined setup with the breast compressed similar to mammography; iv) eliminating the need for coupling liquid through the usage of ultra-wideband bow-tie antennas operating from 16.55 to 40 GHz for a reflection coefficient lower than −10 dB; v) validating the experimental findings through numerical modelling. The experimental setup in this work consists of a single-pixel transmission setup with the antennas placed in a 3D printed container. Two different tissue mimicking phantoms have been studied that both model the temperature-dependent permittivity of biological tissue. The first phantom represents homogeneous fatty tissue properties and the second phantom simulates fatty tissue with a tumor inclusion. A uniform phantom warming is realized through a water bath combined with a continuous monitoring of the phantoms temperature. We show that a homogeneous phantom without tumor can be distinguished from a heterogeneous phantom with tumor in the temperature range of 28 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> C to 38 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> C.

An Ultra-Wideband Integrated Filtering Antenna with Improved Band-Edge Selectivity Using Multimode Resonator

In this paper, a novel design of ultra-wideband (UWB) filtering antenna integrated with the multimode resonator (MMR) bandpass filter is proposed, aiming to enhance band-edge selectivity. At the beginning, a MMR bandpass filter is modified and studied. Based on the classic MMR filter, the proposed filter folds the microstrip transmission line to reduce its size while retaining the original filtering performance. Moreover, an open stub and short stub are added to the proposed filter to obtain a transmission of zero. Then, the folded filter with stubs and a UWB bow-tie antenna are integrated together to form a filtering antenna. The open stub and short stub in the MMR structure enhance the antenna’s upper and lower band-edge selectivity, respectively. Series of parameters are studied to analyze their influences on the frequency selection range and band-edge characteristics. Compared with the original UWB dipole antenna, such an integrated approach brings many benefits. Firstly, the UWB filter not only broadens the bandwidth of the device, but also improves band-edge selectivity, which can eliminate the unwanted passband near the operating frequencies. Secondly, the integrated system reduces the size and cost of the devices, which is very important in the miniaturization of wireless systems. In this research, the reflection coefficient (S11) of integrated filtering antenna is lower than −10 dB between 2.92 and 11.51 GHz, and it has a fractional bandwidth of 119%. The measured shape factor is 1.027 (very close to 1), which proves that this design has a better band-edge selectivity. Simultaneously, good radiation characteristics are also attained, with a maximum realized gain of 6 dBi. Theoretical simulation results are similar to the experimental results. The measurement results of the manufactured device effectively validate that its performances have reached the simulation design requirements.

Directional and High-Gain Ultra-Wideband Bow-Tie Antenna for Ground-Penetrating Radar Applications

Bow-tie antennas are utilized extensively in ground-penetrating radar (GPR) systems. In order to achieve sufficient penetration depth and resolution, the bow-tie antennas for GPR applications require low operating frequency, high gain, and excellent broadband. A novel ultra-wideband (UWB) bow-tie antenna with gain enhancement for GPR applications is proposed in this paper. First, a UWB bow-tie antenna with resistive loading is designed. The metal reflector and metamaterial loading make the bow-tie antenna directional, and loading the same metamaterial on the front side of the antenna further improves directional gain. After testing, the lowest frequency of the fabricated antenna is 317 MHz, the relative bandwidth is 98.6%, the peak gain in the frequency range is 9.3 dBi, and the size is only 0.38 λ at the lowest frequency. The proposed compact antenna takes both gain and bandwidth into consideration. Finally, in order to further verify the effectiveness of the proposed antenna in the GPR system, a stepped frequency continuous wave ground-penetrating radar (SFCW-GPR) system was built. The experimental results show that the designed antenna is suitable for the GPR system of deep penetration and high-resolution detection, which is beneficial to the imaging of underground structures.

UWB Bowtie Antenna for Medical Microwave Imaging Applications

This work presents a design and experimental validation of a compact ultrawideband (UWB) bowtie antenna and balanced-to-unbalanced (balun) circuit for medical microwave imaging (MWI) applications working in the frequency band of 1–6 GHz. The UWB balun is perpendicularly attached to the planar bowtie arms, whose dimensions were miniaturized by rounding the bowtie edges. The antenna reflection coefficient was lower than −12 dB for tissues with a higher water content. The antenna possesses a high radiation efficiency (over 80%) and very low backward radiation. The predicted and measured specific absorption rate (SAR) distributions together with the electric field <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert E\vert $ </tex-math></inline-formula> distribution proved a symmetrical radiation pattern. The potential of the presented antenna element was demonstrated by successful reconstruction of the images from the measured data by MWI methods. For this purpose, an MWI system equipped with eight antennas was implemented. The radar approach was used to determine the region of interest (ROI) where the area for microwave tomography reconstruction was identified. The dielectric properties within the ROI were reconstructed by using the Born approximation method at 1 GHz. This confirmed that the antenna can be used as the basis for more accurate multifrequency MWI systems and can be implemented in UWB MWI hybrid systems.

Design, Fabrication and Testing of an Ultra-Wide Band Bowtie Antenna for Wireless Radar (UHF, L and S Band) Communication

A low-cost and light-weight ultra-wideband bowtie antenna for radar applications was simulated, fabricated and tested. A concise and easy to follow step-by-step description of the performed bowtie antenna simulation in Ansys HFSS software is presented. Optimized antenna parameters were utilized to fabricate the antenna. Fabrication was achieved by utilizing an FR4 PCB. The prototype was tested using a spectrum analyzer. The fabricated bowtie antenna results were used to validate the simulation results. The results obtained from the simulation platform were in close agreement to those of the prototype antenna. Results on effect of substrate thickness and frequency on S11 are also presented. The prototype produced improved overall S11 as compared to the simulation. The results indicate that the fabricated antenna satisfies bandwidth requirements for the UHF, L and S bands.

Exploiting Sensitivity Enhancement in Micro-wave Planar Sensors Using Intermodulation Products With Phase Noise Analysis

In this paper, a new technique to enhance the sensitivity of microwave resonators is introduced. Double split ring resonators are implemented as the core of a loss-compensated resonator. It is illustrated that regenerative oscillators when mixed together can produce higher order intermodulation products (IMP) at the output. The variations in sensing tone are multiplied and exhibit considerably higher sensitivities at 3rd, 5th, and 7th IMP components compared to the main resonant frequency. The sensor is also integrated into wireless platform with ultra-wideband bowtie antennas. Common fluids such as Toluene, n-Heptane, IPA, Ethanol, Methanol, Acetone, and Water are tested in fluidic channel and demonstrated that the sensitivity for intermodulation products are significantly increased proportional to the order of IMP. The proposed sensor is also examined with glucose concentration sensing for the range of 0– 600 mg/dL and significant variation for 7th IMP sensor is observed as opposed to saturation of conventional sensor. Also, asphaltene concentrations down to 6 ppm are recognizable when precipitated from toluene solution using the proposed sensor. Moreover, a rigorous analytical study is presented for phase noise of the IMP originated from reference signals.

Ultra-Wideband Bow-tie Antenna for Ground Penetrating Radar Applications

The Ground-penetrating radar (GPR) system is used for the detection of buried objects inside the earth and the classification of the subsurface structures. Ultra-wide band antenna is one of the major component of the GPR system; which is used to transmit and receive short pulse of electromagnetic nature. The performance of the GPR system in detecting buried object is mainly affected by the reflections of the GPR antenna. The reflections from the antennas itself is a basis of late-time ringing and distortion of antenna. These factors create problem in the identification of the objects. Several UWB antennas are used in the GPR system. This paper presents theoretical study for the design of ultra-wideband Bow-tie antenna as a GPR antenna. Bow-tie antenna is designed for a frequency range of 4-18 GHz. Transient and spectral behavior of the antenna is simulated. The time behavior of the antenna shows a reflected signal from the bow-tie antenna of the duration of 2.0 ns. The antenna provides a VSWR less than 2.0 and a return loss of less than -15 dB in the operating frequency range. Bow-tie antenna is then modeled and simulated in the GPR environments which includes the buried object (i.e. scatterer) and beam floor. The design, modeling and simulations are performed by using CST Microwave Studio.

Positioning system on impulse ultrawideband fields

Background: The systems of positioning on the base of radiowaves are widely used both in a global scale and for the exact position-finding of objects indoors. Global systems of positioning usually need valuable high-quality time synchronization, assume substantial errors at improper weather, at falling of radio waves on the earth surface at small angles, shading of transceivers by large obstacles, and at presence of radio electronic interferences of different nature. Objectives Investigation of the new system of positioning on the ultrawideband impulse electromagnetic fields and their analysis by an artificial neural network is proposed. Materials and methods: The phenomenon of the pulse form change on angle of radiation by antenna is used for the determination of the position of ultrawideband receiver. At first, the two-dimensional case of the problem is considered. Exciting two antennas separated at known distance by means of different impulse signals it is possible to define the place of location of receiver if we know the angles of arrival of impulses from each antenna. The ultrawideband bow-tie antennas excited by the Gaussian impulses of different durations are used as irradiators. The forms of the received impulses are calculated by method of Finite Differences in Time Domain (FDTD). The classification of the time forms of the received electromagnetic waves from different antennas at different angles of radiation is carried out by a deep neural network. Results: It is shown that for the classification the artificial neural network pays special attention to the intervals of time where the received impulse changes quickly. The four-layer network faultlessly distinguishes the obtained signals from different antennas. The numerical calculation of the electromagnetic problem and artificial neural network training show the possibility of determination of angles of radiation by the network with the accuracy of one degree excepting some cases. Using the basis between antennas of 50 meters the precision of receiver position determination is not worse than 62 cm in the square domain of 50 meter size eliminating some angles where the accuracy falls to 2 meters. Conclusion: Property of antennas to change the form of radiated ultrawideband impulses for different angles can be used for the construction of the new system of positioning that does not need the time synchronization with transmitters. The proposed system can be effectively employed indoors. The distinctive feature of the impulse electromagnetic wave positioning system is its immunity to the existent narrowband electromagnetic waves.

Breast cancer detection using K-nearest neighbors data mining method obtained from the bow-tie antenna dataset

Breast cancer, has been a significant cancer type for women on the society. Early diagnosis and timely medical treatment are important key factors spreading to the other tissues and permitting long-time survival of patients. Since the existing methods have several serious shortfalls, microwave imaging method for the diagnosis of early stage tumors has been interested by different scientific research groups in terms of moderating endogenous the electrical property difference between healthy tissue and malignancies. In this article, both an ultra-wideband bow-tie antenna with enhanced bandwidth and a 3D breast model which has different electrical properties which are permittivity and conductivity is created in simulation tool to solve electromagnetic field values. Return loss, VSWR, and radiation pattern characteristics, which are significant antenna parameters, are simulated and obtained whether the antenna possess an efficient characteristic or not. Electric field values over the breast tissue in which there is a tumor or not tumor are evaluated. In this article, above-mentioned values of frequency bandwidth, dielectric constant of antenna's substrate, electric field, and tumor information were consisted in their dataset. This dataset obtained from the Bow-Tie Antenna was used to detect the breast cancer with one of the data mining method, which is K-Nearest Neighbor Algorithm.

Novel ultra‐wideband bow‐tie antenna with high front‐to‐back ratio and directivity

AbstractWe present a novel directional ultra‐wideband antenna based on the bow‐tie geometry. The proposed design, unlike the conventional bow‐tie radiator, has an inherently different radiation mechanism, which relies on magnetic currents excited in properly designed slots. This in turn allows to maintain good antenna performance even when a planar reflector is placed below the antenna that gives rise to high front‐to‐back ratio and directivity over a band extending from 4.8 to 6.1 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1016–1020, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25108