Xuyang Li

A Compact Double-Layer On-Body Matched Bowtie Antenna for Medical Diagnosis

A compact double-layer Bowtie antenna optimized for medical diagnosis is presented in this paper. This on-body antenna is matched to the human body to allow more energy to be radiated into the human body to obtain stronger reflections for image processing. By using a Bowtie antenna with double layers as well as a folded structure and meandered microstrip lines at the bottom of the antenna, a small size of 30 × 30 mm2 with a size reduction of 40% is achieved, compared to the reference antenna of 50 × 50 mm2 within the same operational frequency range. After the optimization of the antenna parameters, the antenna is characterized from 0.5 to 2 GHz, where the low frequencies enable a high penetration into human body and the large frequency range contributes to a high bandwidth and hence a fine range resolution. The simulated and measured results are shown with respect to the impedance matching, near-field pattern, gain and SAR distributions. With features such as a very small size, very low operational frequency, high front-to-back ratio, this design shows a high potential for use in medical diagnosis of stroke, breast cancer and water accumulation detection in the human body.

Sensor data fusion in UWB-supported inertial navigation systems for indoor navigation

Indoor navigation using inertial sensors with additional radio-signal support is considered in this paper. The experimental results of data fusion between a navigation system, based on inertial measurement unit (IMU) and impulse-based UWB localization system, are presented. The IMU is additionally supported by a pedestrian step length estimations, barometer and electronic compass. The Ultra-Wideband part consists of receiver, carried by the person, and access points distributed in the scenario. The focus of the paper is put on hardware implementation and choice of the optimal data fusion technique. The presented results indicate the clear benefit of tightly coupled navigation filter, where the time differences of arrival of UWB signals are directly processed, without prior calculation of the localization solution.

An UWB correlation receiver for performance assessment of synchronization algorithms

This contribution deals with the topic of Ultra-Wideband correlation receivers and methods for their synchronization. In the first part of the paper the generic UWB transmitter and self-synchronizing correlation receiver are proposed and the measurements of the single building blocks are discussed. Further advanced synchronization scheme, allowing more efficient data transmission is proposed and finally the RF front end of the UWB transceiver is verified by the measurement in the real channel.

Design and near-field characterization of a planar on-body UWB slot-antenna for stroke detection

A planar UWB slot-antenna with a size of 35×35mm2 is proposed for stroke detection. The antenna is optimized for operation directly on human skin in the frequency range from 1 to 9 GHz. A sector-like slot is applied to the design to enhance the bandwidth regarding the current distribution. The near-field performance of the antenna is characterized and verified by the measurements. Benefiting from a symmetrical structure and differential feeding technique the antenna owns a very stable radiation behavior in the whole frequency range and a very high front-to-back ratio which would improve the stroke detection capability of the brain imaging system with robust performance.

Polarization diversity in Ultra-Wideband imaging systems

This paper presents an Ultra-Wideband (UWB) indoor imaging system with dual-orthogonal polarized antennas. Both the measurement setup and the algorithm implemented for data processing are introduced. In the presented approach, a 4×1 vertically oriented antenna array is used in order to perform 2D scan. For 3D imaging, single antennas are applied. Emphasis is given to the polarization diversity, through which additional properties of objects such as form, surface structure and orientation are investigated. In this way, some objects are detected, which may remain invisible for single-polarized systems. In addition, the presented approach extends UWB-Radar/Imaging with very high resolution to a high-end system with robust target detection, while providing extensive information about the environment. Such a system can be of great interest in applications such as indoor search-and-rescue operations, motion tracking and indoor navigation.

Physics-based propagation characterisations of UWB signals for the urine detection in human bladder

In this paper, an IR-UWB radar for the detection of water accumulation in human bladder is presented. The goal is to monitor the level of urine in patients who suffer from urinary incontinence. This is achieved by detecting the reflected UWB signals from the boundaries of human tissues such as muscle and bladder. However, the detection ability of the UWB radar system is strongly impaired due to the high attenuation and frequency dispersion of the UWB signal in human tissues. Based on the dielectric properties of the various human tissues, the physics-based propagation characterisations of electromagnetic waves are investigated with respect to their reflection, attenuation and transmission. A model of human bladder with different tissue layers including frequency dependent dielectric properties is proposed. Furthermore, a system concept of UWB radar for the detection of water accumulation in human bladder is introduced. The UWB pulse attenuation and distortion in different human tissues are investigated and evaluated with respect to the system performance. The results show the potential of detection of urine in the human bladder, which may lead to development of new non-invasive sensors locating water accumulations in human body.

Fidelity criterion for UWB medical diagnostic

In this paper an Ultra Wideband (UWB) system based method is introduced, which permits to analyze and to extract information from the back reflected time domain signals originated by a UWB Radar signal impinging on the human body. The criterion is based on the fidelity parameter. In the paper the developed method is firstly mathematically introduced and then measurement results are presented.

Novel design method for frequency agile beam scanning antenna arrays

In order to aid in the design of frequency agile antennas used for beam scanning purposes a design method based on dispersion-like frequency diagrams is proposed in this paper. This method results from a reinterpretation of the workings of both slotted waveguide antennas and leaky wave antennas. In this way it is shown that antennas based on periodic structures can be described in a general manner by expressing the phase difference between antenna elements in terms of a frequency dependent and a frequency independent component which may have a different periodicity as that of typical beam scanning antennas. In consequence, based on this methodology it is possible to predict the behavior of beam scanning antenna arrays based on any type of radiating elements, by independently adjusting the periodicity of the radiating elements and the phase delay between them.

Performance analysis of various UWB radar approaches for medical diagnostics

In this paper, the challenge of the UWB radar for medical applications is presented in terms of high signal attenuation and multiple reflections in human tissues. Different UWB radar approaches are reviewed in this research. The IR-UWB approaches, the PN approach and the frequency measurement with the Vector Network Analyzer are introduced and discussed. Furthermore, the demonstrators of all of the three approaches are provided. The system performance of these three approaches are verified by measurements in anechoic chamber. The usage of three radar approaches for medical diagnostics are given. The measurement results show that the frequency measurement with the Vector Network Analyzer performs better than the other two approaches in terms of system dynamic range and stability.

Synthetic aperture-based UWB imaging system for detection of urine accumulation in human bladder

This paper presents a synthetic aperture-based UWB radar imaging system. The goal is to detect the urine accumulation in the human bladder. To verify this radar concept a bladder model with various human tissues including realistic dielectric properties is simulated. Two scan configurations with different antenna positions are used to investigate the influence of the synthetic aperture length and position number in the microwave images. To generate the imaging results, Delay and Sum algorithm together with coherent weighting is applied. The achieved imaging results demonstrate the possibility of detecting the position and volume of urine in the human bladder and therefore the potential application of this radar imaging system in the clinics for diagnosis purposes.