Wideband Microwave Imaging Systems for the Diagnosis of Fluid Accumulation in the Human Torso

According to the World Health Organization (WHO), cardiovascular diseases (CVDs) are the leading causes of death worldwide, with one third of deaths attributed to CVDs in 2012. Pulmonary oedema and pleural effusion are the most apparent symptoms of many diseases categorized under CVDs such as heart failure and lung cancer, at which fluid (mainly with high water content) is accumulated in or around the lungs. Therefore, constant monitoring of fluid levels inside the lungs is one of the most efficient ways of early detection of CVDs. Chest X-Rays and computational tomography (CT)-scans are the most widely used devices for fluid detection; however, they suffer from lack of sensitivity and ionizing radiation, respectively, that makes them unsuitable for long term monitoring purposes. Currently, magnetic resonance imaging (MRI) is the most reliable device that can be utilized for fluid accumulation detection. However, considering the fact that more than 75% of the CVDs occur in countries with low or middle income, it is not widely available. Moreover, due to their bulky structures, the abovementioned devices lack the capability of being used in mobile emergency units such as ambulances or clinics at rural areas. To that end, this thesis is dedicated to design and fabrication of a low cost, portable and non-invasive device that can be used as an initial decision making tool for medical staff to pursue further investigations to define the exact cause of the oedema. First chapter of the thesis is allocated to introduction of the cardiovascular diseases and their effects on the dielectric properties of the tissues inside the lungs. A complete literature review on various alternative methods for replacing the conventional devices is performed. The obtained results by these systems and their advantages as well as their limitations are discussed. Microwave imaging technique is then presented in chapter two as a robust method which can both provide information about the presence and location of the accumulated fluid. This is specifically of great importance for cases where biopsy is required to remove or take sample of the accumulated fluid for saving the life of the patient. Chapter two is also allocated to the introduction of microwave-based medical diagnostic and monitoring systems for different applications such as breast cancer detection and brain imaging. A prospect of the possible realizable systems is investigated and existing scanning approaches are discussed. The main contributions of the thesis that are the design of several complete platforms, design of novel and unidirectional microwave sensors (antennas), promotion of novel scanning and detection methods are clarified in these chapters. In chapter three, firstly the optimum operating frequency for torso imaging is defined. By applying a circuit model that models different layers of torso as circuit elements, it is shown that a wide operating bandwidth at lower ultra-high frequency (UHF) band provides a reasonable compensation between the resolution of the obtained images and signal penetration inside the body. It is explained that due to the limited allowed microwave power for safety considerations unidirectional antennas are required. Then, it is explained that due to the large wavelengths at lower UHF band the sizes of the prospective antennas are expected to be large. To that end, novel miniaturization techniques are proposed to reduce the sizes of the conventional antennas in chapters three and four. These antennas are categorized under three dimensional (3-D) and planar structure. A folding technique is introduced and used in the proposed 3-D structures and it is shown that by using this technique both size and directivity/back radiation suppression is improved. 3-D slot-antenna and cubic monopole-fed antennas are also proposed that wide operating bandwidth is achieved using slot impedance transformer, and multiple resonance-merging techniques, respectively. Regarding the planar structures that are presented in chapter four, it is shown that by combining the loop-dipole modes, both wide-operating bandwidth and directivity enhancement is achievable. Capacitive-loading of a loop antenna is the other proposed technique in which a loop antenna is partially and/or non-uniformly loaded with capacitors in the forms of simple slots and mu-negative (MNG) metamaterial-unitcells that help miniaturizing the size of the antenna by lowering its first resonance frequency. In chapters five and six, several platforms using single and multiple antennas with linear and circular configurations are presented and the utilized imaging technique for data processing is explained. The platforms are presented in a systematic progressive manner in which each system is covering the limitations of its previous prototype. Two final clinical platforms in the shape of clinical bed and doughnut-shaped chamber are proposed and the obtained test results on artificial phantom, animal lungs and human tests are presented. Based on the obtained results on healthy human beings it is shown that the scattered-field from torso of people with different body sizes vary in a reasonably limited range that is a welcoming result for building a global-database to define a threshold for healthy range. Chapter seven concludes the discussions made throughout the thesis and explains future works that can be carried out to further improve the reported systems

Microwave System for the Early Stage Detection of Congestive Heart Failure

Fluid accumulation inside the lungs, known as cardiac pulmonary edema, is one of the main early symptoms of congestive heart failure (CHF). That accumulation causes significant changes in the electrical properties of the lung tissues, which in turn can be detected using microwave techniques. To that end, the design and implementation of an automated ultrahigh-frequency microwave-based system for CHF detection and monitoring is presented. The hardware of the system consists of a wideband folded antenna attached to a fully automated vertical scanning platform, compact microwave transceiver, and laptop. The system includes software in the form of operational control, signal processing, and visualizing algorithms. To detect CHF, the system is designed to vertically scan the rear side of the human torso in a monostatic radar approach. The collected data from the scanning is then visualized in the time domain using the inverse Fourier transform. These images show the intensity of the reflected signals from different parts of the torso. Using a differential based detection technique, a threshold is defined to differentiate between healthy and unhealthy cases. This paper includes details of developing the automated platform, designing the antenna with the required properties imposed by the system, developing a signal processing algorithm, and introducing differential detection technique besides investigating miscellaneous probable CHF cases

Compact dual band CPW-fed monopole antenna with L-strips for WLAN/WiMax applications

A novel dual band CPW-fed antenna with symmetrical L-strips is presented for WLAN and WiMax applications. The proposed antenna is composed of a square ring feedline with a pair of L-strips added to it for building the radiator structure. By employing these strips, antenna can yield two different resonances to cover the desired bands while maintaining small size and simple structure. Based on this concept, a prototype of antenna is fabricated and tested. The experimental results show that the antenna has the impedance bandwidths of 930 MHz (2.48-3.54 GHz) and 290 MHz (5.12-5.41 GHz), which can cover both WLAN in the 5.2 GHz band and WiMax in the 2.5/3.5 GHz bands

Miniaturized leaf-shaped monopole antenna with filtering properties

A miniaturized monopole antenna design with filtering properties is presented.The proposed antenna has a leaf-shaped radiating patch, which enhances antenna with larger current path leading to wider impedance matching bandwidth in lower frequencies. By creating two ellipse-shaped slots with the same radiuses on the radiating patch and locating a parasitic circle on the opposite side, a band-stop property is obtained. Its band-stop characteristic is controlled by changing the slots' length and circle's radius. The designed antenna has a small size of 20 × 20 × 1 mm while showing the band rejection performance in the frequency range of 4.2-7.2 GHz

A novel compact antenna enhanced with variable notches

A novel, compact, variable-notch omnidirectional antenna is presented.The antenna has a compact size of 22.5 mm (0.3Δ) × 22.5 mm (0.3Δ) × 1 mm and made on cheap FR4 with relative permittivity of 4.4 and dielectric loss tangent of 0.02. It has a stable omnidirectional pattern all over its operating frequencies and a satisfactory gain. Antenna geometry consists of a T-shape cut in the patch plane and an inverse T-shape parasitic element

Broadband CPW-fed slot antenna with circular polarization for on-body applications at ISM band

A broadband coplanar waveguide (CPW) fed antenna which has circular polarization is presented. The antenna is designed to operate at the frequency band (2.45 GHz) that is widely used for industrial, scientific and medical (ISM) applications. The proposed antenna has a uniplanar structure. A square slot is created in the ground which is located at the top layer of a printed circuit board. The CPW feeder is connected to a horseshoe shaped radiator inside the square slot. The circular polarization of the antenna is achieved through inserting T- and L-shaped strips inside the slot. The proposed antenna has a 3 dB axial ratio bandwidth from 2.1 GHz to 2.67 GHz, i.e. 20% fractional bandwidth, and impedance matching bandwidth from 1.5 GHz to 3.15 GHz, which is equivalent to 67.5% fractional bandwidth. The whole structure of the proposed antenna has a compact size of 40 mm x 40 mm

A new triple band circularly polarized square slot antenna design with crooked T and F-shape strips for wireless applications

A new design for circularly polarized square slot antenna (CPSSA) is presented. The circular polarization operation in the proposed single-layer antenna is created through two equal sized crooked T-shape and an F-shape strips located on the patch. Compared to most of the previously reported CPSSA structures, the impedance bandwidth and the axial ratio bandwidth of the antenna are increased and also the size of the antenna becomes smaller. The presented CPSSA design has the compact dimensions of 40 × 40 × 0.8 mm, total impedance matching bandwidth of 8.04GHz and exhibiting a 28.03% (4.6-6.1 GHz) 3dB axial ratio bandwidth. A prototype of the antenna is fabricated and tested, and a great agreement with simulated results is obtained

Double channel triple band MIMO antenna with high isolation performance and pattern diversity for wireless applications

A miniaturized monopole antenna with filtering properties is presented.An S-shape double channel compact multi-input multi-output antenna with high isolation performance for DSC-1800, PCS-1900, WiMax 3.5 GHz, and WLAN applications is presented in this letter. A total impedance matching bandwidth of larger than 40% for three operating bands is attained through measurements. S-shape structure has been introduced to reduce the overall width of the diversity configuration to 50 mm. The isolation between the two ports is greater than 24 dB and the envelope correlation is less than 0.0058 over all three bands

A novel bear-head-shaped compact UWB monopole antenna enhanced with variable notch-bands

A novel bear-head-shaped compact UWB antenna, with a variable notch-band is proposed. It has a compact size of 22.5 × 22.5 × 1 mm . It has variable stop bands that are obtained through changing U-slot place on the patch, and it presents the selectable stop band frequency ranges

Broadband CPW-fed circularly polarized square slot antenna with inverted-L strips for wireless applications

This article proposes an impressive design of a circular polarized square slot antenna (CPSSA). The proposed single layer antenna composed of a square ground plane embedded with three unequal sized inverted-L strips around corners, which are capable of generating a resonant mode for exciting two orthogonal E vectors. Compared to the previous similar CPSSA designs, the axial-ratio bandwidth of the antenna is increased, more than two times. The designed CPSS antenna with its compact 40 × 40 × 0.8 mm size operates over the frequency band between 2.63 and 6.38 GHz for VSW