Wireless Medical Telemetry Research Articles

Electromagnetic Compatibility Issues in 400-MHz-Band Wireless Medical Telemetry Systems and Their Management Using Simplified Methods for Safe Operation.

Wireless medical telemetry systems (WMTSs) are typical radio communication-based medical devices that monitor various biological parameters, such as electrocardiograms and respiration rates. In Japan, the assigned frequency band for WMTSs is 400 MHz. However, the issues accounting for poor reception in WMTS constitute major concerns. In this study, we analyzed the effects of electromagnetic interferences (EMIs) caused by other radio communication systems, the intermodulation (IM) effect, and noises generated from electrical devices on WMTS and discussed their management. The 400-MHz frequency band is also shared by other radio communication systems. We showed the instantaneous and impulsive voltages generated from the location-detection system for wandering patients and their potential to exhibit EMI effects on WMTS. Further, we presented the IM effect significantly reduces reception in WMTS. Additionally, the electromagnetic noises generated from electrical devices, such as light-emitting diode lamps and security cameras, can exceed the 400 MHz frequency band as these devices employ the switched-mode power supply and/or central processing unit and radiate wideband emissions. Moreover, we proposed and evaluated simple and facile methods using a simplified spectrum analysis function installed in the WMTS receiver and software-defined radio for evaluating the electromagnetic environment.

Conformal wideband ingestible capsule MIMO antenna system for multi-channel communication in biotelemetry

This article presents the design of a compact conformal multiple-input-multiple-output (MIMO) capsule antenna aimed at enabling robust communication and high data rates over a broad frequency range spanning from 0.3 to 2.5 GHz. This range encompasses essential frequency bands such as medical implant communications services (MICS) (401–406 MHz), wireless medical telemetry services (WMTS) (1.4 GHz), and industrial, scientific, and medical (ISM) (0.433 GHz, 0.915 GHz, and 2.45 GHz) for wireless capsule biotelemetry. The size of the capsule is reduced to 17 mm × 7 mm (typically 26 mm × 11 mm) to ensure the safe passage of the capsule without being trapped inside the intestine. The proposed antenna (integrated with dummy electronics to build a fully encased capsule endoscope design) is placed inside homogeneous and heterogeneous phantoms in the simulation. The antenna prototype is fabricated, and performance metrics are measured by implanting it inside pork meat and phantom solution. The proposed MIMO antenna offers a wide impedance bandwidth of ∼2200 MHz, and the measured isolation between the antenna elements is > 20 dB. The proposed antenna is also tested for robustness (interaction between the electronic components and the endoscope’s antenna) and human safety using system considerations and realistic voxel models.

Designing a Compact Dual-Band, Dual-Polarized Antenna for Biotelemetry Communications Using the Characteristic Mode Method.

A compact dual-band, dual-polarized, implantable antenna was designed using the characteristic mode method for operation in the wireless medical telemetry service (WMTS) band (1.4 GHz) and the industrial, scientific, and medical (ISM) band (2.45 GHz). By utilizing slotting techniques and materials with high dielectric constants, the antenna volume was minimized to 47.4 mm3, and circular polarization was gained in the WMTS band by using the characteristic mode method. A three-layer physical model of human tissues was constructed in a simulation, and a biogel and minced pork were used in the measurements. The measured peak gains are -20.85 dBi (1.4 GHz) and -22.15 dBi (2.45 GHz). The measured effective axis ratio bandwidth in the WMTS band is 170 MHz (1.33-1.50 GHz, 12.0%), and the impedance bandwidth in the ISM band is 390 MHz (2.21-2.60 GHz, 16.2%). At 1.4 GHz and 2.45 GHz, the largest 1 g average SAR values are 376 W/Kg and 318 W/Kg, which comply with IEEE C95.1-1999. Moreover, when the communication chain affinity exceeds 20 dB for 1.4 GHz and 2.4 GHz, the transceiver range reaches 8.2 m and 9.7 m. This antenna can be used for implantable wireless telemetry systems.

A Triple-Band Broadband Miniature Antenna Design for Implantable Continuous Glucose Monitoring

This paper presents a miniaturized triband implantable planar antenna that covers the industrial, scientific, and medical (ISM) band and the Wireless Medical Telemetry Service (WMTS) band which can be used in a continuous blood glucose monitoring device. The antenna consists of a slotted radiating patch and a ground plane with a cross slot to miniaturize its size. The overall antenna size is only 51.35 mm3 (7.6 × 7.6 × 0.889 mm3) due to the reduced size by the slotting technique. Compared to other implantable antennas with similar performance, the proposed antenna is smaller in size, simple in construction, and easy to be fabricated. By cutting a cross slot in GND, impedance matching is improved, especially at the two higher frequency bands. We have fabricated the prototype and carried out measurements. The results show its gains are −32.2 dBi, −18.8 dBi, and −19.1 dBi at 0.9 GHz, 1.4 GHz, and 2.45 GHz, respectively. Its radiation patterns have good symmetry in the two lower operating frequency bands. In addition, the maximum SAR values comply with the IEEE standard safety guidelines (IEEE C95.1-2019).

A dual wide-band ingestible antenna design for wireless capsule endoscopy

In this paper, we present a dual wide-band ingestible antenna design for wireless capsule endoscopy (WCE) biotelemetry applications. The design process employs Characteristic Mode Analysis (CMA) and driven modal analysis. The effectiveness of the prototype antenna is afterward assessed through measurements using a tissue-equivalent phantom liquid model. We investigate the effects of antenna implantation depth and capsule shell thickness on its performance, providing insights into practical considerations. The proposed dual-band antenna demonstrates good performance in both the 1.4 GHz Wireless Medical Telemetry Services (WMTS) and 2.45 GHz Industrial, Scientific, and Medical (ISM) bands, exhibiting measured impedance bandwidths of 36% and 22%, respectively. The measured peak realized gains are −22.9 dBi and −25.3 dBi for the WMTS and ISM bands, respectively, with a compact footprint of 78.5 mm2. To ensure health and safety and optimal performance, we evaluate the antenna's specific absorption rate (SAR) and link margin (LM). Additionally, we assess the performance of the proposed antenna in comparison with the state-of-the-art design for capsule antennas in WCE applications.

A Miniaturized Tri-Band Implantable Antenna for ISM/WMTS/Lower UWB/Wi-Fi Frequencies.

This study aims to design a compact antenna structure suitable for implantable devices, with a broad frequency range covering various bands such as the Industrial Scientific and Medical band (868-868.6 MHz, 902-928 MHz, 5.725-5.875 GHz), the Wireless Medical Telemetry Service (WMTS) band, a subset of the unlicensed 3.5-4.5 GHz ultra-wideband (UWB) that is free of interference, and various Wi-Fi spectra (3.6 GHz, 4.9 GHz, 5 GHz, 5.9 GHz, 6 GHz). The antenna supports both low and high frequencies for efficient data transfer and is compatible with various communication technologies. The antenna features an asynchronous-meandered radiator, a parasitic patch, and an open-ended square ring-shaped ground plane. The antenna is deployed deep inside the muscle layer of a rectangular phantom below the skin and fat layer at a depth of 7 mm for numerical simulation. Furthermore, the antenna is deployed in a cylindrical phantom and bent to check the suitability for different organs. A prototype of the antenna is created, and its reflection coefficient and radiation patterns are measured in fresh pork tissue. The proposed antenna is considered a suitable candidate for implantable technology compared to other designs reported in the literature. It can be observed that the proposed antenna in this study has the smallest volume (75 mm3) and widest bandwidth (181.8% for 0.86 GHz, 9.58% for 1.43 GHz, and 285.7% for the UWB subset and Wi-Fi). It also has the highest gain (-26 dBi for ISM, -14 dBi for WMTS, and -14.2 dBi for UWB subset and Wi-Fi) compared to other antennas in the literature. In addition, the SAR values for the proposed antenna are well below the safety limits prescribed by IEEE Std C95.1-1999, with SAR values of 0.409 W/Kg for 0.8 GHz, 0.534 W/Kg for 1.43 GHz, 0.529 W/Kg for 3.5 GHz, and 0.665 W/Kg for 5.5 GHz when the applied input power is 10 mW. Overall, the proposed antenna in this study demonstrates superior performance compared to existing tri-band implantable antennas in terms of size, bandwidth, gain, and SAR values.

Miniaturized meander‐line dual‐band implantable antenna for biotelemetry applications

AbstractA dual‐band bio‐implantable compact antenna with a meander‐line structure is presented. The proposed meander‐line antenna resonates at the industrial, scientific, and medical (2.4 GHz) and wireless medical telemetry (1.4 GHz) bands. The meander‐line structure is selected as a radiating patch given its versatile and effective design. With a dimension of only , the designed antenna is compact. Considering a skin phantom, the proposed antenna was designed, optimized, and simulated. The Rogers RT/duroid 6010 substrate material with high dielectric constant was used to fabricate the meander‐line dual‐band implantable antenna, which was validated experimentally. The superstrate was made of the same material. Experiments were conducted on skin‐mimicking gel. The designed meander‐line antenna has a high peak gain of −21 dBi at 2.4 GHz, and its maximum specific absorption rate is compliant with IEEE safety standards.

Highly selective, fractal-configured UWB-FSS for sub-6 GHz 5G, GSM, WLAN, and C band electromagnetic stealth application

AbstractA miniaturized and flexible frequency-selective surface (FSS) has been presented in this article with a unit cell size of 0.049 λc × 0.049 λc where λc is the free space wavelength at the lower cut-off frequency. In order to achieve an ultra-wide (−3 dB) second order pass band of 151.3% with enhanced selectivity factor of 0.887, a cascaded triple layered hybrid resonating structure has been proposed with symmetrical Minkowski island-shaped fractal geometry pair and spiral-shaped middle layer in optimized air gap coupling. Furthermore, 149.8% ultra-wide pass band also ascertains the conformal feature of the proposed structure. In addition to this, the proposed FSS provides the stable angular response for both TE and TM polarization. An equivalent circuit model has been synthesized for accurate frequency response. Finally, a sample prototype has been fabricated to verify the experimental validation. Excellent angular stability under large oblique incident and significant conformal characteristics ensure the compatibility of the proposed structure for electromagnetic stealth in 0.9–1.8 GHz GSM band, 2.10–2.14 GHz wireless medical telemetry band, 2.4–2.5 and 4.9–5.8 GHz WLAN band, 3.4–3.7 and 4.4–4.9 GHz sub-6 GHz 5 G band, and 3.7–4.2 GHz C band.

Novel estimation technique for the carrier-to-noise ratio of wireless medical telemetry using software-defined radio with machine-learning

In this study, we developed a novel machine-learning model to estimate the carrier-to-noise ratio (CNR) of wireless medical telemetry (WMT) using time-domain waveform data measured by a low-cost software-defined radio. With automatic estimation of CNR, the management of the electromagnetic environment of WMT can be made easier. Therefore, we proposed a machine-learning method for estimating CNR. According to the performance evaluation results by 5-segment cross-validation on 704 types of measured data, CNR was estimated with 99.5% R-square and 0.844 dB mean absolute error using a gradient boosting regression tree. The gradient boosting decision tree classifiers predicted if the CNR exceeded 30 dB with 99.5% accuracy. The proposed method is effective for investigating electromagnetic environments in clinical settings.

Design of a hexagonal slot rectenna for RF energy harvesting in Wi‐Fi / WLAN applications

This work proposes a single port hexagonal slotted rectenna operating at 2.45 GHz Wi-Fi bands, using a hexagonally slotted shape of microstrip radiator surface followed by a voltage rectifier circuit using Schottky diode. A symmetrically extended ground plane and rectangular slots help in obtaining the desired resonance characteristics with improved antenna bandwidth. Three different antenna designs have been compared and analyzed. Best gain and wide most bandwidth is seen in the newly designed rectangular and hexagonal slotted design having symmetrically extended ground plane. A RF capacitor and inductor based matching network has been designed to maximize the wireless power transmission at 2.45 GHz. This also helps to enhance the rectifier efficiency for various values of load resistance and input power. Furthermore, for maintaining the small size and ensuring least amount of energy loss, the rectifier's ground has been directly connected to the antenna's ground plane. The proposed design has been simulated in HFSS and ADS software, prototyped, and measured. It has been seen in the results that, the proposed radio frequency (RF) power receiving antenna is performing very well at 2.45 GHz with a wide bandwidth ranging from 1.25 to 2.63 GHz. The proposed rectenna is having a maximum efficiency of 62.4% at 2.45 GHz with an input power of 0 dBm. Furthermore, with variations in the load resistance across a wide range of values from 4 to 12 kΩ $$ \mathrm{k}\Omega $$ under a wide range of low input power, the rectenna maintains an efficient power conversion, which is found to be an important parameter when the ambient RF signal input to the antenna is weak. As a result, the rectenna may be adaptable to a variety of low-power electronic circuits by harvesting RF energy at 2.45 GHz Wi-Fi Band. Furthermore, the proposed antenna can also be used for wireless medical telemetry, satellite phone and Wi-Fi applications used for the frequency band 1.45 GHz as well.

Compact Wideband Implanted Antenna for Medical Device Radiocommunications Service, Long Term Evolution, Global System for Mobile Communications, and Wireless Medical Telemetry Service Band Biosensing Applications

Compact Wideband Implanted Antenna for Medical Device Radiocommunications Service, Long Term Evolution, Global System for Mobile Communications, and Wireless Medical Telemetry Service Band Biosensing Applications

A Miniaturized Implantable Antenna for Wireless Power Transfer and Communication in Biomedical Applications

A miniaturized, triple-band, implantable antenna for biomedical applications is presented in this paper. The proposed antenna with dimensions of 8.1 mm × 8.1 mm × 0.64 mm, combined with a shorting pin and a ground slot, operates at bands between 401–406 MHz for the medical implant communications service (MICS); 1,395–1,400 MHz and 1,427–1,432 MHz for the wireless medical telemetry service (WMTS); and 2,400–2,500 MHz for industrial, scientific, and medical (ISM) applications. The antenna is deployed simultaneously for data transmission and wireless power transfer (WPT) at the two frequencies of communications and the ISM band, respectively. The antenna achieves peak gain values of -35.7 dBi, -25.1 dBi, and -19.5 dBi with the impedance bandwidths of 10.1%, 15.5%, and 9.58% at 402 MHz, 1.4 GHz, and 2.45 GHz, respectively. The experiments in the muscle tissue were implemented to demonstrate the reliability of the proposed antenna. To ensure safety standards in the human body environment, the specific absorption rate (SAR) value is simulated and evaluated thoroughly.

An Ultra-Miniaturized Antenna With Ultra-Wide Bandwidth for Future Cardiac Leadless Pacemaker

The detuning owing to the complex in-body operating scenarios, environmental factors, and circuitry of the implantable medical devices (IMDs) are the primary concerns in integrating implantable antennas with their corresponding systems. The wide bandwidth achievement for avoiding the detuning challenges is constrained by device specifications and antenna miniaturization. This study presents an ultra-miniaturized antenna of only 10.66 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> volume with an ultra-wide bandwidth of 3040 MHz (0.79–3.83 GHz) for a leadless pacemaker (LP). The proposed antenna encompasses the five important bands: ISM (868–868.6 MHz, 902–928 MHz, and 2.4–2.48 GHz), Wireless Medical Telemetry Service (WMTS) (1395–1400 MHz), and the midfield (1.45–1.6 GHz) bands. To consider a practical operating scenario, the antenna was integrated with a battery and controlling electronics of an LP. In a homogeneous heart phantom (HHP), the proposed antenna showed a higher gain of −28.7, −20.02, and −16.7 dBi at 915 MHz, 1.4 GHz, and 2.45 GHz, respectively. The specific absorption rate (SAR) evaluation in the heart of a realistic model guaranteed patient safety by satisfying the IEEE C95.1-2005 and C95.1-1999 guidelines. The antenna is experimentally validated through measurements in minced pork. The strength of the received signal in the measurements confirms a stable biotelemetric link of the proposed ultra-wideband (UWB) antenna with an external monitoring system. The results obtained through simulations and in vitro testing emphasized that the proposed ultra-miniaturized and UWB antenna could operate more efficiently in the heart, thus establishing itself as a suitable candidate for the LPs.

A Novel Wideband and Multi-band Implantable Antenna Design for Biomedical Telemetry

In this work, a novel multi-tracks wideband and multi-band miniaturized antenna design for implanted medical devices biomedical telemetry is proposed. This antenna entirely covers seven frequency bands which are the bands (401−406) MHz of the Medical Device Radiocommunications Service (MedRadio), the three bands (433.1−434.8), (868.0−868.6), and (902.8−928.0) MHz of the Industrial, Scientific, and Medical (ISM), and the three bands (608−614) MHz, and (1.395−1.400) and (1.427−1.432) GHz of the Wireless Medical Telemetry Service (WMTS). The antenna possesses a compact full size of (19.5 × 12.9 × 0.456) mm3. The antenna miniaturization and impedance bandwidth enhancement are achieved using two techniques: the patch slotting and insertion of open-end slots in the ground plane, respectively. Prototype of proposed antenna with multi-tracks has been fabricated and tested in free space. The comparison between the simulated and measured reflection coefficient has been done and found in good agreement with each other. Furthermore, simulations of the proposed antenna implanted in the underneath the scalp in a realistic human model shows a wideband operation from 0.19 to 0.94 GHz, and from 1.38 to 1.54 GHz corresponding to return loss (S11 ≤ −10 dB). Link budget calculation is performed to specify the range of telemetry considering both Specific Absorption Rate (SAR) restrictions and effective isotropic radiated power (EIRP) limitations. The designed implantable antenna with full ground plane presents an appropriate reflection coefficient for muscle implantation. Furthermore, the designed implanted muscle antenna may be also suitable for skin implantation.

Design and implementation of compact dual-band conformal antenna for leadless cardiac pacemaker system

The leadless cardiac pacemaker is a pioneering device for heart patients. Its rising success requires the design of compact implantable antennas. In this paper, we describe a circularly polarized Hilbert curve inspired loop antenna. The proposed antenna works in the WMTS (Wireless Medical Telemetry Services) 1.4 GHz and ISM (Industrial, Scientific, and Medical) 2.45 GHz bands. High dielectric constant material Rogers RT/Duroid 6010 LM ({epsilon }_{r}=10) and fractal geometry helps to design the antenna with a small footprint of 9.1 mm3 (6 mm × 6 mm × 0.254 mm). The designed antenna has a conformal shape that fits inside a leadless pacemaker’s capsule is surrounded by IC models and battery, which are tightly packed in the device enclosure. Subsequently, the integrated prototype is simulated deep inside at the center of the multi-layer canonical heart model. To verify experimentally, we have put dummy electronics (IC and battery) inside the 3D printed pacemaker’s capsule and surfaced the fabricated conformal antenna around the inner curved body of the TCP (Transcatheter Pacing) capsule. Furthermore, we have tested the TCP capsule by inserting it in a ballistic gel phantom and minced pork. The measured impedance bandwidths at 1.4 GHz and 2.45 GHz are 250 MHz and 430 MHz, whereas measured gains are − 33.2 dBi, and − 28.5 dBi, respectively.

A compact implantable MIMO antenna with high isolation and wide bandwidth

ABSTRACT A compact wideband three-unit implantable multiple-in-multiple-out (MIMO) antenna for biomedical applications is proposed in this paper. By loading a “Y” slots on the radiation patch, and a metallized via between the radiation patch and the ground plane, they are jointly designed to reduce the Q value of the antenna unit and improve its bandwidth. At same time, three “wolf-teeth club “ slots with filtering characteristics are introduced into the ground plane to isolate the coupling of ground surface current at feed ports of antenna units, so as to improve the isolation between feed ports. The 10 dB bandwidth of the MIMO antenna unit is 1.21 GHz-1.66 GHz, covering the commonly used Wireless Medical Telemetry Services (WMTS) band (1.427–1.432 GHz). And the isolation between units is more than 29 dB in the whole 450 MHz bandwidth, among which the isolation in WMTS band are more than 31 dB. Compared with other implantable MIMO antennas, this design not only integrates more MIMO antenna units in a small area but also each MIMO unit has broadband characteristics.

医用テレメータ受信機で発生する相互変調に関する研究

Passive intermodulation may generate when two signals are input in the receiver and is an issue that threatens wireless communications. It has been recommended that medical facilities operating wireless medical telemetry services should be conduct zone management for avoiding the effect of passive intermodulation. In this study, the occurrence frequency of passive intermodulation in a wireless medical telemetry service was investigated using simulated environment. Passive intermodulation occurred when two input signal levels were high and frequency deviation of two signals were narrow. The amplitude of passive intermodulation depends on the input signal level in which near its frequency. Passive intermodulation effected the reception of wireless medical telemetry services and degraded carrier to noise ratio as 2 to 4 dB worse rather than Gaussian noise. The signal level of wireless medical telemetry service coming from another floor has no potential to cause passive intermodulation by conducting zone management as properly. However, the output power of wireless communication devices that using same frequency of wireless medical telemetry services such as telecontrol devices is generally greater (10 mW). When the introduction of these devices, it would be desirable for clinical settings to conduct prepare zone management to avoiding passive intermodulation.

Estimation of Electromagnetic Environment of Wireless Medical Telemetry Services Using Machine Learning

In this study, we developed the novel machine learning model to estimate electromagnetic environment of wireless medical telemetry services (WMTS) using In-phase / Quadrature phase data (I/Q data) of normal and interfered its signals. If the occurrence of electromagnetic interference (EMI) sources and carrier to noise ratio (CNR) can be estimated automatically, the management of electromagnetic environment of WMTS can be easier. We, therefore, proposed the machine learning method for estimating an occurrence of EMI and calculating CNR. As the results of the performance evaluation by Stratified K-Fold cross-validation on 74 types of recorded I/Q data, an occurrence of EMI was predicted with 97.6% accuracy by AdaBoost classifier. Whether the CNR was more than 30 dB was predicted with 95.6% accuracy by decision tree classifier. In addition, this method classified 4 CNR levels such as < 20 dB, 20 to 30 dB, 30 to 40 dB, and 40 dB ≦ with 90.5% accuracy by random forest classifier. Moreover, CNR was estimated with 99.5% R-square and 0.661 dB mean absolute error by K-Fold cross-validation using gradient boosting regression tree. Our method is effective for investigating electromagnetic environments in clinical settings.

A Compact Wideband Flexible Antenna for Wireless Medical Telemetry Services

A Compact Wideband Flexible Antenna for Wireless Medical Telemetry Services

A Symmetrical Closed-Loop Conformal Antenna With Wideband for Capsule Endoscope

A symmetrical closed-loop conformal antenna is designed for capsule endoscope at wireless medical telemetry service (608–614 MHz) band and industrial, scientific, and medical (902–918 MHz and 2.4–2.4835 GHz) band. The antenna is compartmentalized into two loops with an inverted-Ω loop and a hollow-T loop by the differential feeding. The antenna has a wideband (| <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | < −10 dB) covering 0.47–1.14 GHz and 1.38–3 GHz. The omnidirectional radiation pattern of the antenna is verified by measurement, and the peak gains are (−15.5, −16.8, and −23.1) dBi for the (611, 915, and 2400) MHz designs, respectively. The antenna possesses excellent environmental tolerance <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vivo</i> environment test. Moreover, the specific absorption rate value of the antenna can satisfy the IEEE regulations under the limit of 2.42 mW net-input power.