22-pJ/bit Energy-Efficient 2.4-GHz Implantable OOK Transmitter for Wireless Biotelemetry Systems: In Vitro Experiments Using Rat Skin-Mimic
ABSTRACT A wireless biotelemetry system operates in vivo, which requires low power consumption for long-lasting operation, high output power for long transferable distance, and high throughput for incorporating many recording electrodes and transmitting raw brain signals. An implantable 2.4-GHz on-off keying (OOK) transmitter with high throughput and high energy efficiency for wireless biotelemetry systems has been designed in a 0.18-μm CMOS process. To balance power consumption and output power, a complementary voltage-controlled oscillator for the proposed transmitter is employed. Power consumption of the transmitter is reduced by switching the oscillator on and off to generate an OOK modulated signal. The transient delay for the transmitter is derived and applied to implement a high throughput transmitter. Rat skin-mimic emulating the implant environment such as electrical properties of the skin is used to measure the proposed transmitter in vitro. To transmit 136 Mb/s of OOK data, the transmitter consumes 3 mW of dc power and generates an output power of -14 dBm. The transmitter achieves energy efficiency of 22 pJ/bit with an associated bit error rate of 1.7 × 10- 3 without using an error correction scheme.
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ABSTRACT: Characterization of implantable planar inverted-F antennas, designed for intracranial pressure (ICP) monitoring at 2.45 GHz, is presented. A setup, incorporating a scalp phantom emulating the implant environment and an absorbing chamber, was implemented for characterizing the antennas, in terms of their reflection coefficient ( S <sub>11</sub>), resonance frequency ( fr ), and transmission coefficient through the phantom ( S <sub>21</sub>) , and is reported for the first time. As a result of our observations that even a very slight change of the biocompatible (silicone) thickness can drastically change the characteristics of such antennas, several antenna prototypes with various silicone thicknesses were tested for a better understanding of the change in their performance with thickness. The main contributions of this paper rest in the evaluation of the antenna characteristics with respect to time, temperature, and far-field radiation, in an emulated biological environment. In this regard, the impact of the coating thickness on fr , drift of fr , S <sub>11</sub>, and S <sub>21</sub> over time, and the effective radiated power (ERP) from the transmission ( S <sub>21</sub>) measurements were evaluated through careful measurements. A decrease in S <sub>11</sub> of 1.2-2.3 dB and an increase in S <sub>21</sub> of 2.2-2.4 dB, over a period of two days, were observed at 2.45 GHz. A decrease of 8-18 MHz for fr was also observed over the same period of time. This drift was due to the absorption of saline by the silicone, leading to a change in its effective dielectric property. An fr increase of approximately 14.5 MHz was also observed by raising the temperature from 20 <sup>deg</sup>C to 37 <sup>deg</sup>C, mainly because of the negative temperature coefficient of the phantom permittivity. Transmission measurements performed using both S <sub>21</sub> and the received power measurement (for- - an ICP device mimic) yielded a maximum ERP of approximately 2 mW per 1 W of power delivered to the antennas at 2.45 GHz.IEEE Transactions on Microwave Theory and Techniques 11/2008; · 2.23 Impact Factor
Conference Proceeding: In-vivo EEG recording using a wireless implantable neural transceiver[show abstract] [hide abstract]
ABSTRACT: We have recorded continuous in-vivo EEG and single-unit electrical activity from un-tethered rodents using an inductively powered and implantable wireless neural recording device. The device uses an integrated circuit to amplify modulate and transmit neural signals. The IC transmits neural signals (15 μV to 15 mV) at 3.2 GHz to a receiver located outside the environment of a behaving test animal with an input output correlation better than 90%. The design of the IC and the inductive powering are described.Neural Engineering, 2003. Conference Proceedings. First International IEEE EMBS Conference on; 04/2003
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ABSTRACT: The design and test is described of a small size dual band implantable antenna operating in Medical Implant Communications Service (MICS) (402 MHz-405 MHz) and Industrial, Scientific and Medical (ISM) (2.4 GHz-2.48 GHz) bands to be used in animal studies for medical research. The antenna is intended for wireless medical monitoring of the physiological parameters such as glucose, pressure, temperature, etc. First, the electrical properties (epsiv r and sigma) of skin samples from donor rats are measured at Mississippi State University's (MSU) College of Veterinary Medicine. A dual band antenna is then designed using an in-house finite element boundary integral solver in conjunction with particle swarm optimization algorithm. Finally, the antenna is tested using both skin-mimicking materials and real skin samples. The development details of the skin-mimicking materials are also given. Results regarding the S<sub>11</sub> and gain of the designed antenna are given and discussed in detail.IEEE Transactions on Antennas and Propagation 10/2009; · 2.33 Impact Factor