Taeyoung Yang

Cellular-Phone and Hearing-Aid Interaction: An Antenna Solution

With the introduction of digital cellular phones, hearing-aid users have experienced a severe buzzing noise caused by the interaction between digital cellular phones and hearing aids. The cellular-phone industry, the hearing-aid industry, and consumers have been seeking a solution for the interference issue. Efforts reported in the literature have focused on measurements, modeling, and evaluation of interference and RF emission, but not on methods to solve the problem. In this paper, we focus on the causes of the interference and an understanding of the problem. We also present a method to reduce near-field electromagnetic energy around a cellular phone, mitigating the interference between cellular phones and hearing aids. The theoretical investigation of both the radiation mechanisms and fundamental limits on antennas suggested that a low-g antenna, such as an ultra-wideband antenna, could reduce the near-field intensity. Simulations and measurements were performed at 900 and 1880 MHz, using both low- and high-Q test antennas mounted on a mock cellular phone. The results showed that the peak electric and magnetic near-field strengths of the low-g test antenna were lower than those of a high-Q test antenna by at least 5 dBV/m and 4 dBA/m, respectively. The improvement in the near-field performance for the low-g antenna was without any sacrifice in far-field performance. Furthermore, in the presence of a human head, the simulation results showed that the radiation efficiency of the low-Q test antenna was better than that of the high-Q test antenna.

Compact antennas for UWB applications

This paper reports on an investigation of spherical, disc, and half-disc antennas in the frequency and time domains with the objective of developing small planar versions of the antennas. These antennas have an omni-directional impulse response in azimuth and a pulse duration of 0.5 - 0.65 nanoseconds. In addition, the measured data show a reasonable peak received signal in a pulse communication link using two identical antennas.A report on an investigation of spherical, disc, and half-disc antennas in the frequency and time domains with the objective of developing small planar versions of the antennas. These antennas have an omni-directional impulse response in azimuth and pulse duration of 0.5-0.65 nanoseconds. In addition, the measured data show a reasonable peak received signal in a pulse communication link using two identical antennas.

Practical Issues for Spectrum Management With Cognitive Radios

The policy of permanently assigning a frequency band to a single application has led to extremely low utilization of the available spectrum. Cognitive radio, with its ability to be both intelligent and frequency agile, is thought to be one of the prime contenders to provide the necessary capabilities needed for dynamic spectrum access systems. With this in mind, this paper discusses the practical issues inherent to the deployment of spectrum management systems utilizing cognitive radios.

Wearable ultra-wideband half-disk antennas

We investigate the feasibility of ultra-wideband half-disk structures as wearable antennas for indoor and outdoor applications of ultra-wideband bodyworn devices (3.1-10.6 GHz). First, we characterize camouflage cloth in terms of relative permittivity and loss tangent. Then, based on the estimated substrate information, we design wearable half-disk antennas and compare the performance of solid copper and woven versions in the frequency and time domains.

On the Co-Existence of TD-LTE and Radar Over 3.5 GHz Band: An Experimental Study

This letter presents a pioneering study based on a series of experiments on the operation of commercial Time-Division Long-Term Evolution (TD-LTE) systems in the presence of pulsed interfering signals in the 3550-3650 MHz band. TD-LTE operations were carried out in channels overlapping and adjacent to the high power SPN-43 radar with various frequency offsets between the two systems to evaluate the susceptibility of LTE to a high power interfering signal. Our results demonstrate that LTE communication using low antenna heights was not adversely affected by the pulsed interfering signal operating on adjacent frequencies irrespective of the distance of interfering transmitter. Performance was degraded only for very close distances (1-2 km) of overlapping frequencies of interfering transmitter.

Small, planar, ultra-wideband antennas with top-loading

A new top-loaded ultra-wideband antenna covering the 2.4-10.6 GHz impedance bandwidth (VSWR<2.5) and the 2.05-11.6 GHz UWB bandwidth with nearly constant radiated power was introduced. The proposed antenna is a good candidate for backward compatibility of IEEE 802.11g in the 2.4 GHz ISM band, as well as providing an indoor/outdoor ultra-wideband frequency range of 3.1-10.6 GHz. In addition, it can be used for both multi-band OFDM and impulse UWB applications.

Folded-notch dual band ultra-wideband antenna

In this paper, we introduce the folded-notch half-disk antenna to support dual band operation covering 2.4-2.5 and 3.1-10.6 GHz without increasing the antenna size greater than needed for the 3.1 to 10.6 GHz band. Results of a parametric study demonstrate that the frequency notch can be controlled. In addition, antenna characterization results are provided in both the frequency and time domains

Demonstration Paper: Wirelessly Sensing Medication Administration: Cyber-Physical Event Detection and Notification Utilizing Multi-Element Chipless RFID

Medication administration is one pathway by which Adverse Drug Events (ADE) can occur. While Electronic Medical Administration Record (eMAR) systems help reduce the number of ADEs, current eMAR implementations suffer from workarounds that defeat safety and verification mechanisms meant to limit the number of potential ADEs that occur during medication administration. In this paper, we introduce Multi-Element ChipLess (MECL) RFID tags which enable real-time event notifications through event signatures. Event signatures correspond to the physical configuration of different RFID elements in a chipless RFID tag. Augmenting physical objects, such as a pill container, with MECL-RFID can allow caregivers to detect the moment a particular pill container is opened or closed. We present the fundamentals behind real-time event detection using MECL-RFID and propose a cyber-physical intervention system that can be used to reduce ADEs through realtime event monitoring and notifications sent to clinicians administering medication. We also present a prototype MECL-RFID to demonstrate potential future improvements to eMAR systems that minimize ADEs.

Addressing a Neighboring-Channel Interference From High-Powered Radar

This paper investigates the scenario in which a weak desired signal reaches a poorly selective receiver along with a high-powered pulsed radar occupying a neighboring channel. Traditionally, an automatic gain control (AGC) is used to fit the high-powered radar into the dynamic range of the receiver. However, this approach desensitizes the receiver because it also sacrifices the signal-to-noise ratio (SNR) of the desired signal. We propose the use of an auxiliary receive path to address this problem of strong neighboring channel signals. In this method, receiver gain is not lowered to avoid clipping. Instead, the strong signal is allowed to clip and distort the desired signal. This paper shows that only a subset of the symbols contained in the desired signal will be distorted; hence, redundancy within the desired signal (due to forward error correction) can be exploited to “fill the gaps” created by the distortion. The auxiliary path samples the envelope of the strong neighboring-channel signal and informs the decoder about which symbols are distorted (or “bad”) and which symbols are not distorted (or “good”). This additional information is shown to improve the estimation performance of the decoder in the presence of high-powered neighboring-channel radar. Using simulation and hardware-based experiments, it is shown that auxiliary-path-based receivers can obtain a significantly better throughput performance than AGC-based receivers.

Dual probe use for the remote measurement of an antenna under test

This paper explores an alternative to the previous remote impedance measurement of antennas to improve the dynamic range of the needed data for the measurements. Previous work evaluated the refection coefficient of a source antenna as a function of the termination on the antenna under test (AUT). The loads used in the measurement are the classic open-short-load, with measured data used for the actual termination impedances. The impedance of the AUT is determined by a standard calibration approach. For current vector network analyzers, the dynamic range of the analog-to-digital converter limits the impedance estimate, particularly if the distance between the source and AUT is increased to reduce interaction affecting the impedance of the AUT. The new approach separates the transmit and receive functions to allow the use of a LNA to improve the receive signal strength and offer the opportunity to overcome some of the limitations of the reflection approach.