Medical Implant Communication Service Band Research Articles

A Wireless ECoG Recording System to Detect Brain Responses to Tactile Stimulation

Many neural recording systems with wired connections to electrodes have suffered from the disadvantage that the wired connections restrict the movement of the subject. To overcome this restriction, wireless neural interfaces have been developed. However, due to the adoption of low transmission rates and protocols in the medical implant communication service band, it has been challenging to develop a high-resolution wireless recording interface that can utilize the functionality of multichannel electrodes at maximum. In this study, we developed a high-throughput wireless recording system assembled using only off-the-shelf components, resulting in a lightweight of 2.1 g. The developed wireless system can transmit 32 channels of neural signals with up to 30 kHz sampling rate per channel and 16-bit analog-to-digital conversion (ADC) resolution seamlessly. The system was connected to a flexible 32-channel electrocorticogram (ECoG) electrode array, and successfully recorded somatosensory evoked potentials (SEPs) from the in vivo brain in response to tactile stimulation, demonstrating a high signal-to-noise ratio (SNR), and high spatial and temporal resolutions in wireless neural signal recording.

An Ultra-Miniaturized High Efficiency Implanted Spiral Antenna for Leadless Cardiac Pacemakers.

This paper presents an ultra-miniaturized implant antenna with a volume of 22.22mm3 in the Medical Implant Communication Service (MICS) frequency band 402-405MHz to be integrated with a leadless cardiac pacemaker. The proposed antenna has a planar spiral geometry with a defective ground plane exhibiting a radiation efficiency of 3.3% in the lossy medium with more than 20dB of improved forward transmission, while the coupling can be further enhanced by adjusting the thickness of the antenna insulation and the antenna size according to the application area. The implanted antenna demonstrates a measured bandwidth of 28MHz, covering beyond the MICS band needs. The proposed circuit model of the antenna describes the different behaviors of the implanted antenna over a wide bandwidth. The antenna interaction within human tissues and the improved behavior of the electrically small antenna are explained in terms of radiation resistance, inductance, and capacitance that are obtained from the circuit model. The results are demonstrated using electromagnetic computations and are validated by the measurement using liquid phantom and animal experiments.

A Lamb wave magnetoelectric antenna design for implantable devices

A 400 MHz magnetoelectric (ME) Lamb wave antenna design to function in the medical implant communication service band is proposed. The antenna employs a heterostructure of piezoelectric and magnetostrictive membranes to acoustically excite standing shear bulk wave and radiate as a magnetic dipole. Multiphysics finite element analysis simulations are performed for transmission and reception modes. In these simulations, three aspects are investigated: piezoelectricity, micromagnetic precession, and magnetic dipole radiation. An experimental demonstration of the antenna is also conducted and shows mechanical resonance with a Q-factor of 500 and ME coupling. These results indicate that the design can be operated in zero-order antisymmetric (A0) mode as a tunable oscillator or sensor. This ME approach provides a solution to the miniaturization problem of traditional current-based implantable antennas.

MICS-Band Helical Dipole Antenna for Biomedical Implants

This letter presents the design, analysis, and measurement of a miniaturized ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{7}\!\times\!\text{7.5}$</tex-math></inline-formula> mm) electrically small helical dipole antenna with the introduction of a flexible magnetic sheet of high permittivity and permeability for biomedical implants. The proposed helical dipole, operating at 402–405 MHz Medical Implant Communication Services (MICS) band, supports wider bandwidths (10 dB bandwidth: simulated 33 MHz; measured 49.5 MHz) compared to the state-of-the-art designs. In addition, as a hybrid between a magnetic loop antenna and an electric dipole antenna and operating in the normal mode with small radian (ka < 0.36), enhanced radiation efficiency has been achieved as a result of the magnetic sheet. Measured in-body to on-body transmission verifies the antenna performance.

Modeling of a Compact Dual Band and Flexible Elliptical-Shape Implantable Antenna in Multi-Layer Tissue Model

A flexible antenna of compact size with a dual band elliptical-shape implantable is designed for biomedical purposes. The suggested antenna has an elliptical shape to be more comfortable for being implanted in human tissue. The implantable antenna is printed on RO3010 substrate with 2 mm as a thickness and 10.2 as a dielectric constant. It consists of an active planar C-shaped element and a parasitic planar inverted C-shaped element. The proposed antenna is designed with a major axis radius of 12 mm and a minor axis radius of 8 mm. It operates in dual bands: The Industrial Scientific and Medical band (ISM) [2.4 GHz–3.5 GHz] and Medical Implant Communications Service band (MICS) [394 MHz–407.61 MHz]. A short-circuited pin is used to minimize the antenna’s overall size and for further size reduction a capacitive load is used between the radiator and the ground plane. For biocompatibility, a thin-thickness layer of Alumina is used as a superstrate. The suggested antenna is tested in a multi-layer tissue model and the Specific Absorption Rate (SAR) value is computed. The proposed antenna was fabricated, and the reflection coefficient is measured and compared with simulated results.

Miniaturized antenna verified with diffuse optical measurements for native and boiled adipose tissue differentiation

Medical industries are continuously working towards the development of wearable theragnostic devices which enable monitoring various ailments in the body and then transmitting them to the base-station. The antenna design is of prime importance where the suitable design guarantees proper communication between the antenna and the base-station. In this paper, a co-planar wave-guide antenna is proposed for the use in the medical implant communication service (MICS) band for data transmission. The proposed antenna is studied for ex-vivo applications where the antenna is simulated for bovine intramuscular fat (adipose tissue). The preliminary results showed that the antenna radiates in MICS band. Two types of samples are tested; namely, native fat and boiled fat. The boiled fat is used in order to represent the infected fat tissue. Hence, the antenna was implanted into the fat samples and the results revealed noticeable variations in the radiation characteristics between native and boiled fat. Different parameters of the proposed antenna including the reflection coefficient (S11), radiation patterns, gain, efficiency, and front-to-back ratio are investigated. The simulations showed that S11 parameter was − 12.4 dB in MICS band for the normal fat. On the other hand, the measured S11 values were − 12.3 dB for the native samples and − 9.9 dB for the boiled fat samples. To assert the variation in the biological characteristics of the boiled fat as compared to those of the native fat, diffuse optical measurements of the examined samples were investigated. Such variation in the light scattering and absorbance by the tissue is responsible for varying the S11 parameter for each case. The results have shown that the proposed design is a good candidate for detecting the change in biological tissue.

Multilayer Archimedean spiral antenna design for dual-band intra-arm implantable biotelemetric smart health care monitoring system covering MICS and ISM bands

Abstract In this paper, a novel multilayer microstrip implant antenna (MIA) design based on the Archimedean spiral (AS) radiator element is presented for dual-band biotelemetric health care monitoring system. The proposed AS-MIA design has a layered structure consists of the spiral antenna elements and superstrate, namely layer #1 , layer #2 and layer #3 , respectively. While achieving the dual-band multi-layer implantable antenna design, firstly, each of the radiating elements in the respective layers is designed to cover separately in the desired bands, that is, layer#1 and layer#2 operate in the ISM (Industrial, Scientific, and Medical 2.4–2.48 GHz) and MICS (Medical Implant Communication Services 402–405 MHz) bands, respectively. Subsequently the ultimate multilayered AS-MIA design is formed by combining the individually designed layers. The compact implantable antenna has a dimension of r = 5 mm radius and h = 3.81 mm height, owning the electrically size of 0.067 λ 0 and h = 0.051 λ 0, respectively, where λ 0 is free space wavelength at 402 MHz in MICS band. Since the AS-MIA is intended to be used in an intra-arm smart health system, the simulated radiation performances of the antenna in a created numerical arm phantom are presented in the article. Also note that numerical analysis of the implant antenna was carried out using CST MW studio simulator based on finite integral method. The prototype of the implantable antenna was fabricated using Rogers 3210 substrate with electrical permittivity of ε r = 10.2. In-vitro return loss measurements were realized in skin mimicking gels, suggested in the literature. It was observed that in vitro measurement and simulation results were quite compatible with each other, except for some discrepancies due to the manufacturing and material tolerances during the preparation of the prototype antenna and skin mimicking gels. The proposed AS-MIA offers a dual-band operation with 15 and 16% S 11 bandwidth at each band of 402 MHz and 2.4 GHz respectively where |S 11| ≤ 10 dB criterion along with 50-Ω system is considered. Also the proposed design can be a good candidate to be used in dual-band medical implant communication systems with its miniature size and reasonable radiation characteristics.

Compact triple‐broadband implantable antenna for multi‐functions in telemedicine

A compact implantable antenna is designed to operate in the Medical Implant Communication Services (MICS; 402–405 MHz) band, 915-MHz Industrial, Scientific, and Medical (ISM; 902–928 MHz) band, and 2.4-GHz ISM (2.4–2.48 GHz) band; via the triple bands, the multi functions, such as biomedical data transferring, wireless energy supply, and control signal sending, can be implemented. By embedding symmetric slots in the radiation patch and introducing a shorting pin, multiple resonances are generated with −10-dB simulated bandwidths of 76 MHz (369–445 MHz) at the MICS band, 45 MHz (891–936 MHz) at the 915-MHz ISM band, and 1025 MHz (1930–2955 MHz) at the 2.45-GHz ISM band. In addition, compact dimensions of 11.6 × 11.6 × 1.27 mm (170.89 mm3) are obtained with the simulated peak gains of −41.3 dBi, −23.5 dBi, and −28.7 dBi in the triple bands. To improve impedance matching of the proposed antenna in the upper band, two symmetric U-shaped slots are etched in the ground. The fabricated antenna was tested in fresh pork, and the measured results agree well with those simulated in the phantom. Advantages of compact size and broad triple bands make the proposed antenna great potential for telemedicine applications.

Optimal sub‐harmonic injection‐locked MICS band transmitter for wireless CW‐fNIRS systems

AbstractPortable and wireless functional near‐infrared spectroscopy is a growing field of research for real‐time monitoring of brain functions. The most critical challenges in this field are the use of low‐power and calibrated circuits. A novel transmitter architecture is proposed to overcome these barriers. This transmitter is low power, capable of being calibrated against process variation, and has a better phase noise and spurious‐free dynamic range (SFDR) at the antenna. Besides that, the transmitter can be calibrated, which is not seen in similar research. In this transmitter, injection locking and frequency calibration lead to having an optimal and low‐power circuit. The circuit is capable of transmitting data with BFSK and OOK modulations in the frequency band of the medical implant communication service (MICS). The transmitter is designed and simulated in a typical CMOS 0.18‐μm technology with a 1‐V power supply. The transmitter's power consumption is around 146 and 123 μW, equal to 5.92 nJ/bit and 246–630 pJ/bit for BFSK and OOK modulations, respectively. The signal's phase noise at the antenna is almost −109 dBc/Hz at 1‐MHz frequency offset.

A Compact Triple-Band Antenna With a Broadside Radiation Characteristic for Head-Implantable Wireless Communications

This letter presents a compact triple-band antenna composed of a spiral radiator with an open-ended slot at the ground for human head-implantable wireless communications. It operates simultaneously at a Medical Implant Communications Service (MICS) band (402-405 MHz), a Wireless Medical Telemetry Service (WMTS) band (1427-1432 MHz), and an Industrial, Scientific, and Medical (ISM) band (2400-2480 MHz). The proposed antenna has a thin profile of 0.5 mm with a volume of 197 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Semisolid phantoms are used for the design and experimental validation, and detailed parameter studies are carried out to determine the working principles of the antenna. Based on simulations and measurements, it was found that the proposed antenna covers all the desired frequency bands with comparably high boresight gains given its compact dimensions.

A CMOS implementation of controller based all digital phase locked loop (ADPLL)

PurposeBiomedical radio frequency (RF) transceivers require miniaturized forms with long battery life and low power consumption. The medical implant communication service (MICS) band in the frequency range of 402–405 MHz is widely used for medical RF transceivers because the MICS band signals have reasonable propagation characteristics and are suited to achieve good results. The implementation of the RF front-end for medical devices has many challenges as these dictate low power consumption. In particular, phase-locked loop is one of the most critical blocks of the RF front-end. The purpose of this paper is to the design of controller-based all-digital phase-locked loop (ADPLL) in a 45 nm CMOS process.Design/methodology/approachInitially, an open-loop architecture phase frequency detector (PFD) is designed. Then based on the concept of differential buffer, a differential ring oscillator (RO) is built using capacitive boosting technique. After that, the frequency controller block is built by proper mathematical modeling that does the job of loop filter, which behaves like a phase interpolator. Frequency controller block has tuning register block, tuning word register. The tuning block is built using the Metal Oxide Semiconductor (MOS) caps. Finally, the integration of all the blocks is done and the ADPLL architecture that locks at 402 MHz is achieved.FindingsThe designed PFD is dead zone free that operates at 1 GHz. The differential RO oscillates at 495 MHz. The proposed ADPLL operates at 402 MHz with measured phase noise of −98.36 at 1-MHz offset. This ADPLL exhibits rms jitter of 4.626 ps with a total power consumption of 216.5 µW.Research limitations/implicationsA time to digital converter (TDC)-less controller-based low power ADPLL covering the MICS frequency band for biomedical applications has been designed in 45 nm/0.68 V CMOS technology. The ADPLL proposed in this draft uses differential oscillator with capacitively boosted technique which reduced the operating voltage to as low as 0.68 V. This ADPLL has a bandwidth of 20 kHz and works at reference frequency of 20 MHz consumed power of 216.5 µW, while generating an output frequency of 402 MHz. The tuning range is from 375 to 428 MHz. With the phase noise of −98.36 dbc/Hz at 1 MHz, a frequency controller block replaces the usage of TDC.Social implicationsThe designed ADPLL will definitely pave way to greater research arena in the field of biomedical field. This ADPLL is a unique combination that combines electronics and biomedical field. The designed ADPLL is itself a broader application to biomedical field that will have a positive impact on the society.Originality/valueThe implementation of open-loop PFD and RO using the capacitive boosting technique is a unique combination. This is comprehended well with frequency controller block that eliminates the usage of TDC and behaves as phase interpolator. The entire design of ADPLL which suits the application of MICS band of frequency has been designed carefully to work at low power.

Novel Microstrip Patch Antenna for implantable medical telemetry devices

ABSTRACT In recent years, close collaboration has been forged between telecommunications and medicine, which has enabled the birth of medical telemetry and therefore implanting medical devices on the human and animal body. The latter is based on implantable antennas design in the MICS (Medical Implant Communication Service) band (402-405) MHz. The frequency band is explored to design mobile and comfortable communication systems to support human life. The objective of this paper is to design and optimization of implantable printed antennas in human body for medical telemetry. The proposed antenna operates in the MICS band between 402 and 405 MHz. The antenna is simulated using HFSS software. The proposed antenna resonates at 404 MHz with a return loss of -32.58 dB, bandwidth of 26 MHz and gain of 6.5 dB.

In‐silico and in‐vitro testing of an implantable superstrate loaded biocompatible antenna for MICS band applications

AbstractA superstrate loaded body implantable microstrip patch antenna working on Medical Implant Communications Service (MICS) (402‐405 MHz) band for biotelemetry applications is proposed. A 0.64‐mm thick high‐dielectric material Rogers RO Duroid 3010 is used both as substrate and superstrate of dielectric constant 10.2. Shorting pin is used to make compact antenna with footprint of 13.3 × 14.6 mm2. Appreciable bandwidth of 40% is covered by antenna with return loss of −30.95. In‐silico testing inside skin, brain and three layered tissue models is done to test functionality of antenna in homogeneous as well as inhomogeneous tissue environment. For validation of results the fabricated antenna is successfully tested inside in‐vitro solution of homogeneous skin mimicking liquid.

A Dual-Circular-Polarized Endoscopic Antenna With Wideband Characteristics and Wireless Biotelemetric Link Characterization

In this article, the first-ever dual-circular-polarized wideband conformal endoscopic antenna is designed at the medical implant communication service band (402 MHz) and industrial, scientific, and medical bands (915 MHz and 2.4 GHz). The proposed antenna with a small footprint of 8 mm3 (32 mm $\times 10$ mm $\times0.025$ mm) is printed on flexible polyamide and wrapped onto the inner wall of the capsule to spare the space for the capsule integrated components. For evaluation of the antenna’s performance within a full-package endoscopic device, a homogeneous muscle box and realistic Duke human phantoms were used. For measurement, the fabricated antenna is enclosed inside a 3-D-printed capsule along with the endoscopic system, and the enclosed system is waterproofed. The S-parameters and radiation patterns are measured in a saline-filled American Society for Testing and Materials (ASTM) model and a minced-pork phantom. The measured impedance bandwidths and gains at 402 MHz, 915 MHz, and 2.4 GHz are 236.2%, 104%, and 55.4% and −29.71, −28.7, and −20.8 dBi, respectively. The measured axial-ratio bandwidths are 45.9% and 21.3% at 915 MHz and 2.4 GHz, respectively. Furthermore, the link budget is numerically analyzed and measured via real-time telemetry using software-defined radios. The proposed antenna complies well with the human safety standards and satisfies the range and high data-rate requirements.

Comparative Analysis of the Effect of Loaded Quality Factor, Technology Node and Operating Frequency on Various Class E Power Amplifier Topologies

This paper aims to explore and compare the dependence of power amplifier performance parameters on the loaded quality factor of the resonant circuit, the technology node used and the operating frequency for different variants of the class E power amplifier. In spite of the fact that the circuit parameter variations of the basic class E amplifier are present in the literature, there is a lack of comparative analysis with respect to other class E power amplifiers based on diverse tuned load networks. Moreover, the effects of these three parameters are rarely discussed. The comparative analysis helps the designers to narrow down the selection of a power amplifier to be used for a particular application. This study is focused on the use of class E power amplifiers in biomedical implants at the Medical Implant Communication Service band and Industrial Scientific and Medical band. It is observed that the power added efficiency and the power gain have an inverse dependence on the loaded quality factor, frequency and the technology node while the output power depends directly on these parameters.

Investigation on Insulated, Brain-Implanted Antenna for Highly Reliable Biotelemetry Communication in MICS and ISM Bands.

We derived a closed-form expression of the maximum power transfer efficiency (MPTE) between a transmitting antenna inside the brain and a receiving antenna outside the head using spherical wave expansion. The derived expression was validated using a FEKO simulation. The properties of the insulator and radiation mode were analyzed in each available medical implant communications service (MICS) and industrial, scientific and medical (ISM) band as a means of increasing the reliability of wireless biotelemetry implementation. Some interesting preceding results in the literature were revisited with the figure-of-merit MPTE. It was also newly found that the effect on MPTE by the physical size and material properties of the insulator in both transverse magnetic (TM) and transverse electric (TE) mode decreases for 2.4 GHz and 5.8 GHz and the loss of the insulator does not have a severe impact on MPTE once the dielectric constant is greater than a certain value. This work can be used as an implanted-antenna design guide for building reliable biotelemetry communication.

Design of a Dual-Band Circular Implantable Antenna for Biomedical Applications

This letter presents the design of a dual-band circular implantable antenna for biomedical applications. The proposed antenna operates at the Medical Implant Communication Services band (402–405 MHz) and Industrial, Scientific, and Medical band (2400–2483.5 MHz). The antenna occupies an area of π × 102 × 2.54 mm3 (797.96 mm3). The dual-band is realized in a circular patch by deploying via holes, open-ended slots in the ground plane, and a superstrate. The prototype antenna is fabricated and measured using tissue-equivalent liquid model and pork meat to verify the suitability design. The proposed antenna has a peak gain of –33.1 and –14.55 dBi at 400 MHz and 2.45 GHz, respectively. The specific absorption rate is 241.5 W/kg for 1 g of tissue with a maximum input power of 6.625 mW. Furthermore, the proposed antenna's salient features are compared with the state-of-the-art implantable antennas.

Compact implantable antenna design for MICS and ISM band biotelemetry applications

AbstractA dual‐band implantable complementary split‐ring (CSR) antenna is proposed for Medical Implant Communication Services (MICS) and Industrial Scientific and Medical (ISM) bands biotelemetry applications. The proposed antenna is printed on a grounded RO3010 substrate and the total size of the compact design is only 14 × 14 × 1.27 mm3. The metallic top layer of the antenna is composed of three homocentric rectangular CSR elements and slots inserted between the rings. While the slots are used for fine frequency tuning, a shorting pin appropriately placed between the top copper radiator and the ground plane is utilized for miniaturization purpose. In order to improve impedance matching and enhance bandwidths of the antenna, we employ a hook‐shaped slot in the ground plane. The proposed implantable CSR antenna (ICSRA) is fed by a coaxial probe. The proposed ICSRA was fabricated and measured in two different gels mimicking the real human skin tissue at the MICS and ISM bands. Also, a prototype of ICSRA was measured in a real skin sample obtained from a donor rat for in vivo verification. The ICSRA provides 23.5% bandwidth at 460 MHz and 12% bandwidth at 2.34 GHz and it exhibits acceptable radiation pattern characteristics at the respective bands. The specific absorption rate values of the antenna satisfy the limits set by standard safety guidelines.

Analysis and Optimization of Voltage-Driven Double-Balanced Passive Mixer for MICS Band Receiver

This paper presents analysis of a 25% duty-cycle fully-differential double-balanced passive mixer dedicated to medical implantable devices. The proposed passive mixer is part of a medical implant communication service (MICS) receiver front-end operating at 402–405[Formula: see text]MHz. By performing time-domain analysis, two LTI models have been developed to study the fully-differential double-balanced passive mixer: A simplified model and a complete model taking into account harmonic components. Both models account for the AC coupling capacitors at the mixer input and account for baseband voltage variation over one LO period. In this study it has been shown the ability of mixer input impedance matching by varying baseband resistor at the mixer output. The frequency of match can be controlled by varying the AC coupling capacitors and baseband capacitors. The performance of the proposed models was compared with that of the mixer and the results were very close. In particular, the results of simulations of the input impedance as a function of the baseband resistance and as a function of the IF frequency show the validity of the proposed models. The main parameters of the passive mixer such as input impedance, gain and noise figure (NF) were optimized taking into account the constraints of our application. The proposed mixer is designed to operate at LO frequency of 403.2[Formula: see text]MHz. Transistors size is optimized to meet the receiver specifications. The mixer realizes a conversion gain of 0[Formula: see text]dB and an NF of 4.8[Formula: see text]dB. Linearity simulations show 25.2[Formula: see text]dBm for IIP3 and 9.66[Formula: see text]dBm for [Formula: see text]dB. The mixer consumes 1.44[Formula: see text]pW without LO circuit.

Compact dual‐band implantable planar inverted‐F antenna with bandwidth enhancement

AbstractIn this paper, a miniaturized planar inverted‐F antenna (PIFA) with a volume of 49.5 mm3 is proposed for biomedical implantable devices, operating in Medical Implant Communications Service (MICS, 402‐405 MHz) band and Industrial, Scientific, and Medical (ISM, 2.40‐2.48 GHz) band. It has a wide operating bandwidth in MICS band. The initial PIFA is designed with dual‐band performance, where the lower band is formed by quarter‐guided‐wavelength resonance and the higher band is formed by two‐guided‐wavelength resonance. Furthermore, by etching open‐slots between short and feed on the ground, a new resonance is introduced and moved towards the fundamental one, expanding the bandwidth in MICS band. Also, the introduction of slots lowers the initial resonant frequency in higher band, meeting the frequency demands of ISM band. Finally, the proposed antenna is measured in pork as well as skin‐mimicking gels, showing a bandwidth of 50.7% and 38% in MICS band, and 13.9% and 6.9% in ISM band.