Gui Chao Huang

3D metamaterial broadband ground plane designed using genetic programming for the long slot array antenna

Previously developed MATLAB code for designing planar (2D) metamaterial broadband ground planes is extended to design volumetric (3D) metamaterial structures. A 3D ground plane designed to operate as an artificial magnetic conductor (AMC) in the 225-450 MHz frequency range is presented. Its performance when used as the ground plane of the planar long slot array (PLSA) antenna and cylindrical long slot array (CLSA) antenna is evaluated and compared to the previously used absorbing ferrite ground plane, resulting in enhanced gain performance due to in phase reflection and minimal absorption.

Advanced antenna array designs for directional networks

With the growing interest in directional wireless communications networks, there has been significant demand for advanced antenna array designs that combine high gain and broadband performance together with low cost and light weight characteristics. This paper analyzes and compares the performance of two new antenna array designs including a 4×8 right hand circularly polarized long slot antenna array and a 4×8 dual fed stacked patch antenna array, over the 4–6 GHz and 4.5–5 GHz band, respectively. The radiation characteristics were compared in terms of bandwidth, beamwidth, gain and axial ratio. Both antenna arrays have favorable axial ratio (<1.8 dB) over their bands with average measured gain of 17 dB and 18 dB. The arrays were combined with a recently developed compact Butler matrix, and measured beam directions were all in well agreement with simulation results.

Wideband EM coupler/applicator design and characterization for the clinical benchmarking tests of microwave stethoscope (MiSt)

The MiSt is a novel non-invasive vital signs sensor that can simultaneously measure and extract multiple vital signs parameters including the heart rate, respiration rate, heart waveform, and changes in lung water content from a single microwave measurement. The microwave applicator used to couple the microwave signal to the patients chest and to measure the reflection from various body tissues play an important role in the MiSt operation for detecting multiple vital signs. In this paper, the design and characterization results of four different broadband electromagnetic couplers and their inherent tradeoffs are presented and discussed. It is shown that it is possible to achieve more than 10:1 bandwidth.

Dual-polarization cylindrical long slot array (CLSA) antenna integrated with compact broadband baluns and slot impedance transformers

In this paper a realistic method for feeding the dipole mode of the dual-polarized CLSA antenna is presented. A compact lumped-element impedance transforming balun is designed, fabricated, and tested with a broadband dipole. The broadband balun is then simulated to verify its performance in the dual-polarized CLSA antenna along with the slot impedance transformers. This antenna has the capability of achieving 4 polarization modes (vertical, horizontal, LHCP, RHCP).

Development of a Wireless Monitoring System for Microwave-Based Comprehensive Vital Sign Measurement

A wireless microwave-based antenna monitoring system has been developed for measurement of comprehensive vital signs. The system employs a unique electromagnetic energy coupling sensor/antenna and is also equipped with a mobile app to display the processed values in real time, which facilitates use by mobile users. New RF components have been used, which has eliminated the need for a costly and bulky network analyzer. The developed system is more suitable for clinical use and monitoring of remote patients. Accuracy of the developed wireless system has been validated by comparing results to traditional network analyzer measurements as well as an FDA approved vital sign monitoring device where excellent agreement was observed. Specifically, an average difference of 0.7% in the measured phase and 1.4% in the magnitude of the reflection/transmission coefficients, 4.8% in measured heart rates, and 8.1% in measured respiration rates were observed.

Electromagnetics in Medical Applications: The Cardiopulmonary Stethoscope Journey

Pulmonary edema, caused by abnormal accumulation of fluid in the lungs, is a clinical manifestation of chronic illnesses such as congestive heart failure and kidney failure. Early detection of pulmonary edema is the cornerstone for management of these diseases. Although methods for detection of pulmonary edema are clinically available, they are invasive and noncontinuous. The introduction of noninvasive and continuous methods would be considered by some in the medical community as “the holy grail.” The cardiopulmonary stethoscope (CPS) system was developed to address these needs. The CPS system is a noninvasive device capable of continuous remote monitoring of heart rate, respiration rate, and changes in lung water content. Developed capabilities and features of the CPS system include wearable sensors, mobile-based platform, advanced signal processing techniques for feature extraction, realistic and dynamic 3D modeling, and clinical validation of its capabilities. Clinical validations were performed using animal and isolated lung experiments and testing on healthy populations as well as heart failure and hemodialysis patients. Results from these studies show good agreement with results from clinical standard monitoring procedures.

Antenna Arrays for Physical Layer-Based Directional Networking Technology

Due to the terrain (mountains, ridges, forest, and vast areas) challenges in the rural areas, it is difficult and costly to implement broadband and affordable coverage with currently available wireless technologies. To overcome communication networking challenges in rural areas, an advanced directional networking technology has been proposed. The approach is based on enhancing intelligence and logic capabilities in the physical layer without causing changes in the other OSI layers of the communication network. Low-cost and low-profile circularly polarized antenna arrays and beam-switching feed networks are fundamental building blocks in this approach. A broadband long-slot antenna array fed by simplified microstrip structures was designed to cover the frequency band of 4–6 GHz. For lower profile, a narrower band (4.4–5.1 GHz) high-gain stacked-patch-antenna array with annular gap was also developed. For low cost and fast beam switching, a compact broadband microstrip-based 8 × 8 Butler matrix was realized with a compact crossover. The antenna arrays and the Butler matrix were fabricated and experimentally characterized. Simulation results were verified with the measured results, as well as the beam-switching capability of the antenna arrays and the Butler matrix.

Advanced directional networking: Simulation results and prototype measurements

Advanced Directional Networking is a physical layer based technology that is composed of a network of fully-directional point-to-multipoint Advanced Nodes. This paper describes designs of advanced nodes, which are equipped with sets of antenna arrays for the tasks of scanning for user discovery, communication with users and forming node-node links. Highlights of the simulation results for advanced nodes are shown for LTE radios implementation. A hardware prototype of the advanced nodes consisting of 4×8 long slot antenna arrays, Butler Matrix based analog beamforming/scanning for mobile user discovery and dynamic digital beamforming for user tracking and maintaining directional communications, is being developed. Measurements of the prototype will be used for validation of the simulation results and provide guidelines for ultimate implementation and application in rural areas.

A L-band spherical section long slot antenna array with metamaterial ground plane for satellite communications

A new L-band long slot antenna array design is described. Besides the use of long slot array to provide dual polarization radiation pattern in the 1-2 GHz band, the antenna is integrated with a metamaterial ground plane to provide compact design and improved gains. Simulation results of S-parameters and radiation patterns will be presented and the design trade-off will be discussed in details.

Development of untral wide bandwidth (UWB) cylindrical long slot array (CLSA) antenna integrated with novel microstrip feeders

A low cost, light weight, ultra wideband width, and omni-directional cylindrical long slot array (CLSA) antenna integrated with a practical feeding structure was developed and prototyped. This antenna was designed to operate from 225 MHz to 450 MHz. The novel feeding structures were directly fabricated on the conducting strips of the CLSA and connected to typical 50 ohm coaxial cable. Performances of this antenna were evaluated by measurements. Measurement results showed that the developed antenna provided omnidirectional pattern and mostly reasonable impedance matching together when RF absorber foam was used as a backing material in the ground plane.