@article{jia_lee_kong_zeng_connolly_mahmoudi_ghovanloo_2020, title={A Software-Defined Radio Receiver for Wireless Recording From Freely Behaving Animals (vol 13, pg 979, 2019)}, volume={14}, ISSN={["1940-9990"]}, DOI={10.1109/TBCAS.2020.2991644}, abstractNote={Presents corrections to author affiliation information in the above named paper.}, number={3}, journal={IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS}, author={Jia, Yaoyao and Lee, Byunghun and Kong, Fanpeng and Zeng, Zhaoping and Connolly, Mark and Mahmoudi, Babak and Ghovanloo, Maysam}, year={2020}, month={Jun}, pages={631–631} }
 @article{jia_guler_lai_gong_weber_li_ghovanloo_2020, title={A Trimodal Wireless Implantable Neural Interface System-on-Chip}, volume={14}, ISSN={["1940-9990"]}, DOI={10.1109/TBCAS.2020.3037452}, abstractNote={A wireless and battery-less trimodal neural interface system-on-chip (SoC), capable of 16-ch neural recording, 8-ch electrical stimulation, and 16-ch optical stimulation, all integrated on a 5 ×  3 mm2 chip fabricated in 0.35-μm standard CMOS process. The trimodal SoC is designed to be inductively powered and communicated. The downlink data telemetry utilizes on–off keying pulse-position modulation (OOK-PPM) of the power carrier to deliver configuration and control commands at 50 kbps. The analog front-end (AFE) provides adjustable mid-band gain of 55–70 dB, low/high cut-off frequencies of 1–100 Hz/10 kHz, and input-referred noise of 3.46 μVrms within 1 Hz-50 kHz band. AFE outputs of every two-channel are digitized by a 50 kS/s 10-bit SAR-ADC, and multiplexed together to form a 6.78 Mbps data stream to be sent out by OOK modulating a 434 MHz RF carrier through a power amplifier (PA) and 6 cm monopole antenna, which form the uplink data telemetry. Optical stimulation has a switched-capacitor based stimulation (SCS) architecture, which can sequentially charge four storage capacitor banks up to 4 V and discharge them in selected μLEDs at instantaneous current levels of up to 24.8 mA on demand. Electrical stimulation is supported by four independently driven stimulating sites at 5-bit controllable current levels in ±(25–775) μA range, while active/passive charge balancing circuits ensure safety. In vivo testing was conducted on four anesthetized rats to verify the functionality of the trimodal SoC.}, number={6}, journal={IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS}, author={Jia, Yaoyao and Guler, Ulkuhan and Lai, Yen-Pang and Gong, Yan and Weber, Arthur and Li, Wen and Ghovanloo, Maysam}, year={2020}, month={Dec}, pages={1207–1217} }
 @article{jia_gong_weber_li_ghovanloo_2020, title={A mm-Sized Free-Floating Wireless Implantable Opto-Electro Stimulation Device}, volume={11}, ISSN={["2072-666X"]}, DOI={10.3390/mi11060621}, abstractNote={Towards a distributed neural interface, consisting of multiple miniaturized implants, for interfacing with large-scale neuronal ensembles over large brain areas, this paper presents a mm-sized free-floating wirelessly-powered implantable opto-electro stimulation (FF-WIOS2) device equipped with 16-ch optical and 4-ch electrical stimulation for reconfigurable neuromodulation. The FF-WIOS2 is wirelessly powered and controlled through a 3-coil inductive link at 60 MHz. The FF-WIOS2 receives stimulation parameters via on-off keying (OOK) while sending its rectified voltage information to an external headstage for closed-loop power control (CLPC) via load-shift-keying (LSK). The FF-WIOS2 system-on-chip (SoC), fabricated in a 0.35-µm standard CMOS process, employs switched-capacitor-based stimulation (SCS) architecture to provide large instantaneous current needed for surpassing the optical stimulation threshold. The SCS charger charges an off-chip capacitor up to 5 V at 37% efficiency. At the onset of stimulation, the capacitor delivers charge with peak current in 1.7–12 mA range to a micro-LED (µLED) array for optical stimulation or 100–700 μA range to a micro-electrode array (MEA) for biphasic electrical stimulation. Active and passive charge balancing circuits are activated in electrical stimulation mode to ensure stimulation safety. In vivo experiments conducted on three anesthetized rats verified the efficacy of the two stimulation mechanisms. The proposed FF-WIOS2 is potentially a reconfigurable tool for performing untethered neuromodulation.}, number={6}, journal={MICROMACHINES}, author={Jia, Yaoyao and Gong, Yan and Weber, Arthur and Li, Wen and Ghovanloo, Maysam}, year={2020}, month={Jun} }
 @article{mirbozorgi_jia_zhang_ghovanloo_2020, title={Toward a High-Throughput Wireless Smart Arena for Behavioral Experiments on Small Animals}, volume={67}, ISSN={["1558-2531"]}, DOI={10.1109/TBME.2019.2961297}, abstractNote={This work presents a high-throughput and scalable wirelessly-powered smart arena for behavioral experiments made of multiple EnerCage Homecage (HC) systems, operating in parallel in a way that they can fit in standard racks that are commonly used in animal facilities. The proposed system, which is referred to as the multi-EnerCage-HC (mEHC), increases the volume of data that can be collected from more animal subjects, while lowering the cost and duration of experiments as well as stress-induced bias by minimizing the involvement of human operators. Thus improving the quality, reproducibility, and statistical power of experiment outcomes, while saving precious lab space. The system is equipped with an auto-tuning mechanism to compensate for the resonance frequency shifts caused by the dynamic nature of the mutual inductance between adjacent homecages. A functional prototype of the mEHC system has been implemented with 7 units and analyzed for theoretical design considerations that would minimize the effects of interference and resonance frequency bifurcation. Experiment results demonstrate robust wireless power and data transmissions capabilities of this system within the noisy lab environment.}, number={8}, journal={IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING}, author={Mirbozorgi, S. Abdollah and Jia, Yaoyao and Zhang, Pengcheng and Ghovanloo, Maysam}, year={2020}, pages={2359–2369} }
 @article{jia_lee_kong_zeng_connolly_mahmoudi_ghovanloo_2019, title={A Software-Defined Radio Receiver for Wireless Recording From Freely Behaving Animals}, volume={13}, ISSN={["1940-9990"]}, DOI={10.1109/TBCAS.2019.2949233}, abstractNote={To eliminate tethering effects on the small animals’ behavior during electrophysiology experiments, such as neural interfacing, a robust and wideband wireless data link is needed for communicating with the implanted sensing elements without blind spots. We present a software-defined radio (SDR) based scalable data acquisition system, which can be programmed to provide coverage over standard-sized or customized experimental arenas. The incoming RF signal with the highest power among SDRs is selected in real-time to prevent data loss in the presence of spatial and angular misalignments between the transmitter (Tx) and receiver (Rx) antennas. A 32-channel wireless neural recording system-on-a-chip (SoC), known as WINeRS-8, is embedded in a headstage and transmits digitalized raw neural signals, which are sampled at 25 kHz/ch, at 9 Mbps via on-off keying (OOK) of a 434 MHz RF carrier. Measurement results show that the dual-SDR Rx system reduces the packet loss down to 0.12%, on average, by eliminating the blind spots caused by the moving Tx directionality. The system operation is verified in vivo on a freely behaving rat and compared with a commercial hardwired system.}, number={6}, journal={IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS}, author={Jia, Yaoyao and Lee, Byunghun and Kong, Fanpeng and Zeng, Zhaoping and Connolly, Mark and Mahmoudi, Babak and Ghovanloo, Maysam}, year={2019}, month={Dec}, pages={1645–1654} }
 @article{cheng_wang_ghovanloo_2017, title={Analytical modeling and optimization of small solenoid coils for millimeter-sized biomedical implants}, volume={65}, number={3}, journal={IEEE Transactions on Microwave Theory and Techniques}, author={Cheng, Y. H. and Wang, G. F. and Ghovanloo, M.}, year={2017}, pages={1024–1035} }
 @inproceedings{bawa_huang_ghovanloo_2010, title={An efficient 13.56 MHz active back-telemetry rectifier in standard CMOS technology}, DOI={10.1109/iscas.2010.5537296}, abstractNote={In this paper, we present the design of a high-frequency (HF) rectifier implemented in a 0.5-μm 3M/2P 5V standard CMOS process for wireless power transmission across short-range inductive links. The rectifier has been optimized for 13.56 MHz ISM band, and achieves power conversion efficiency (PCE) of ~83% and voltage conversion ratio > 92% in post-layout simulations. We have successfully incorporated a dual-mode back-telemetry capability in this rectifier with little area or efficiency overhead, which tolerates wide load-fluctuations at the secondary side. With these improvements, this active back-telemetry rectifier (ABTR) is geared towards increasing the overall system efficiency, data transfer rate, and reading range in applications such as implantable microelectronic devices (IMD) and radio frequency identification (RFID).}, booktitle={2010 ieee international symposium on circuits and systems}, author={Bawa, G. and Huang, A. Q. and Ghovanloo, M.}, year={2010}, pages={1201–1204} }
 @article{yin_ghovanloo_2009, title={Using Pulse Width Modulation for Wireless Transmission of Neural Signals in Multichannel Neural Recording Systems}, volume={17}, ISSN={["1558-0210"]}, DOI={10.1109/TNSRE.2009.2023302}, abstractNote={We have used a well-known technique in wireless communication, pulse width modulation (PWM) of time division multiplexed (TDM) signals, within the architecture of a novel wireless integrated neural recording (WINeR) system. We have evaluated the performance of the PWM-based architecture and indicated its accuracy and potential sources of error through detailed theoretical analysis, simulations, and measurements on a setup consisting of a 15-channel WINeR prototype as the transmitter and two types of receivers; an Agilent 89600 vector signal analyzer and a custom wideband receiver, with 36 and 75 MHz of maximum bandwidth, respectively. Furthermore, we present simulation results from a realistic MATLAB-Simulink model of the entire WINeR system to observe the system behavior in response to changes in various parameters. We have concluded that the 15-ch WINeR prototype, which is fabricated in a 0.5-mum standard CMOS process and consumes 4.5 mW from plusmn1.5 V supplies, can acquire and wirelessly transmit up to 320 k-samples/s to a 75-MHz receiver with 8.4 bits of resolution, which is equivalent to a wireless data rate of ~ 2.56 Mb/s.}, number={4}, journal={IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING}, author={Yin, Ming and Ghovanloo, Maysam}, year={2009}, month={Aug}, pages={354–363} }
 @article{huo_wang_ghovanloo_2008, title={A Magneto-Inductive Sensor Based Wireless Tongue-Computer Interface}, volume={16}, ISSN={["1558-0210"]}, DOI={10.1109/TNSRE.2008.2003375}, abstractNote={We have developed a noninvasive, unobtrusive magnetic wireless tongue-computer interface, called ldquoTongue Drive,rdquo to provide people with severe disabilities with flexible and effective computer access and environment control. A small permanent magnet secured on the tongue by implantation, piercing, or tissue adhesives, is utilized as a tracer to track the tongue movements. The magnetic field variations inside and around the mouth due to the tongue movements are detected by a pair of three-axial linear magneto-inductive sensor modules mounted bilaterally on a headset near the user's cheeks. After being wirelessly transmitted to a portable computer, the sensor output signals are processed by a differential field cancellation algorithm to eliminate the external magnetic field interference, and translated into user control commands, which could then be used to access a desktop computer, maneuver a powered wheelchair, or control other devices in the user's environment. The system has been successfully tested on six able-bodied subjects for computer access by defining six individual commands to resemble mouse functions. Results show that the Tongue Drive system response time for 87% correctly completed commands is 0.8 s, which yields to an information transfer rate of ~ 130 b/min.}, number={5}, journal={IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING}, author={Huo, Xueliang and Wang, Jia and Ghovanloo, Maysam}, year={2008}, month={Oct}, pages={497–504} }
 @article{huo_wang_ghovanloo_2008, title={Introduction and preliminary evaluation of the Tongue Drive System: Wireless tongue-operated assistive technology for people with little or no upper-limb function}, volume={45}, ISSN={["1938-1352"]}, DOI={10.1682/JRRD.2007.06.0096}, abstractNote={We have developed a wireless, noncontact, unobtrusive, tongue-operated assistive technology called the Tongue Drive System (TDS). The TDS provides people with minimal or no movement ability in their upper limbs with an efficacious tool for computer access and environmental control. A small permanent magnet secured on the tongue by implantation, piercing, or tissue adhesives is used as a tracer, the movement of which is detected by an array of magnetic field sensors mounted on a headset outside the mouth or on an orthodontic brace inside. The sensor output signals are wirelessly transmitted to an ultraportable computer carried on the user's clothing or wheelchair and are processed to extract the user's commands. The user can then use these commands to access a desktop computer, control a power wheelchair, or interact with his or her environment. To conduct human experiments, we developed on a face shield a prototype TDS with six direct commands and tested it on six nondisabled male subjects. Laboratory-based experimental results show that the TDS response time for >90% correctly completed commands is about 1 s, yielding an information transfer rate of approximately 120 bits/min.}, number={6}, journal={JOURNAL OF REHABILITATION RESEARCH AND DEVELOPMENT}, author={Huo, Xueliang and Wang, Jia and Ghovanloo, Maysam}, year={2008}, pages={921–930} }
 @article{ghovanloo_najafi_2005, title={A compact large voltage-compliance high output-impedance programmable current source for implantable microstimulators}, volume={52}, ISSN={["1558-2531"]}, DOI={10.1109/TBME.2004.839797}, abstractNote={A new CMOS current source is described for biomedical implantable microstimulator applications, which utilizes MOS transistors in deep triode region as linearized voltage controlled resistors (VCR). The VCR current source achieves large voltage compliance, up to 97% of the supply voltage, while maintaining high output impedance in the 100 M/spl Omega/ range to keep the stimulus current constant within 1% of the desired value irrespective of the site and tissue impedances. This approach improves stimulation efficiency, extends power supply lifetime, and saves chip area especially when the stimulation current level is high in the milliampere range. A prototype 4-channel microstimulator chip is fabricated in the AMI 1.5-/spl mu/m, 2-metal, 2-poly, n-well standard CMOS process. With a 5-V supply, each stimulating site driver provides at least 4.25-V compliance and >10 M/spl Omega/ output impedance, while sinking up to 210 /spl mu/A, and occupies 0.05 mm/sup 2/ in chip area. A modular 32-site wireless neural stimulation microsystem, utilizing the VCR current source, is under development.}, number={1}, journal={IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING}, author={Ghovanloo, M and Najafi, K}, year={2005}, month={Jan}, pages={97–105} }
 @article{ghovanloo_najafi_2004, title={A modular 32-site wireless neural stimulation microsystem}, volume={39}, ISSN={["1558-173X"]}, DOI={10.1109/JSSC.2004.837026}, abstractNote={This paper presents Interestim-2B, a modular 32-site wireless microstimulating ASIC for neural prosthesis applications, to alleviate disorders such as blindness, deafness, and severe epilepsy. Implanted just below the skull along with a high-density intracortical microelectrode array, the chip enables leadless operation of the resulting microsystem, accepting power and data through an inductive link from the outside world and inserting information into the nervous system in the form of stimulating currents. Each module contains eight current drivers, generating stimulus currents up to /spl plusmn/270 /spl mu/A with 5-b resolution, /spl sim/100M/spl Omega/ output impedance, and a dynamic range (headroom voltage) that extends within 150 mV of the 5 V supply rail, and 250 mV of the ground level. As many as 64 modules can be used in parallel, to drive multiprobe arrays of up to 2048 sites, with only a pair of connections to a common inductive-capacitive (LC) tank circuit, while receiving power (8.25 mW/module) and data (2.5 Mb/s) from a 5/10-MHz frequency shift keyed carrier. Every 4.6 mm /spl times/ 4.6 mm chip fabricated in a 1.5-/spl mu/m, 2M/2P standard CMOS process through MOSIS, houses two modules and generates up to 65 800 stimulus pulses/s.}, number={12}, journal={IEEE JOURNAL OF SOLID-STATE CIRCUITS}, author={Ghovanloo, M and Najafi, K}, year={2004}, month={Dec}, pages={2457–2466} }
 @article{ghovanloo_najafi_2004, title={Fully integrated wideband high-current rectifiers for inductively powered devices}, volume={39}, ISSN={["1558-173X"]}, DOI={10.1109/JSSC.2004.835822}, abstractNote={This paper describes the design and implementation of fully integrated rectifiers in BiCMOS and standard CMOS technologies for rectifying an externally generated RF carrier signal in inductively powered wireless devices, such as biomedical implants, radio-frequency identification (RFID) tags, and smartcards to generate an on-chip dc supply. Various full-wave rectifier topologies and low-power circuit design techniques are employed to decrease substrate leakage current and parasitic components, reduce the possibility of latch-up, and improve power transmission efficiency and high-frequency performance of the rectifier block. These circuits are used in wireless neural stimulating microsystems, fabricated in two processes: the University of Michigan's 3-/spl mu/m 1M/2P N-epi BiCMOS, and the AMI 1.5-/spl mu/m 2M/2P N-well standard CMOS. The rectifier areas are 0.12-0.48 mm/sup 2/ in the above processes and they are capable of delivering >25mW from a receiver coil to the implant circuitry. The performance of these integrated rectifiers has been tested and compared, using carrier signals in 0.1-10-MHz range.}, number={11}, journal={IEEE JOURNAL OF SOLID-STATE CIRCUITS}, author={Ghovanloo, M and Najafi, K}, year={2004}, month={Nov}, pages={1976–1984} }