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This paper presents a magnetic sensor based autotracking method for a phased array based wireless power transfer system to be implemented in neuromodulation applications. This method is proposed to track the position of the receiver(placed on a freely moving animal) and transmit the microwave signal with a focused beam to the target receiver. The coordinate locations of the target are obtained from the magnetic sensor and converted into phase information for the phased array. The system is constructed by a 2.4 GHz near-field 4×4 phased array transmitter antenna with 4-bit phase shifters. The phased array TX antenna steers the beam from -5° to -155° in the θ plane. The magnetic sensor can detect the location of the receiver and the in this steering range. The process of tracking the the target and focusing the beam has been evaluated by simulation. 

The next evolutionary step in biological signal monitoring will be enabled by wireless communication. Low power and cost-efficient wireless transceivers are currently being employed for implantable medical devices (IMDs), in addition to military and civilian applications such as monitoring, surveillance, and home automation. The major goal of this paper is to do a thorough and realistic link budget analysis for an implantable wireless transceiver operating in the 3–5 GHz ultrawideband frequency with a link distance of 2 m (which includes 10 mm of brain tissue layer and 1.99 m of air medium), data rate of 100 Mbps with On-Off keying (OOK) modulation, and a minimum receiver sensitivity of −58.01 dBm. The proposed power budget analysis is particularly well suited for distributed brain implant applications as it models the path loss including the tissue layer without compromising the spectrum regulation imposed by the Federal Communications Commission (FCC) for UWB communication. 

Presented in this paper is the design of a level-crossing ADC for biomedical potentials. This architecture takes advantage of the time sparse nature of neural signal recording applications by only sampling when the signal is moving. A 10-bit architecture with a novel threshold control scheme was chosen to help capture both the higher amplitude local field potentials and lower amplitude action potentials found in these systems. The ADC operates on a power of 13.5μW from a 1.8 V supply and achieves a root-mean-square error (RMSE) of 0.65 mV. The design is implemented and simulated in a 180 nm CMOS process using the Cadence Virtuoso Custom IC design tool. 

To avoid interruption of experiment and risk of infection, wireless power transfer (WPT) techniques have been used to eliminate the bulky wires and batteries attached to the animals in rodent electrophysiological applications for long-term in-vivo electrophysiological recordings. Headstage-based neuromodulation device has become one of the most popular methods for neural stimulation in recent times. In this work, a wireless power transfer system is designed which provides a constant power to a headstage based optogenetic stimulator. The proposed research is composed of two parts: i) a unidirectional 28 cm × 21 cm phased array transmitter antenna, and ii) an electrically small bi-directional 2.4 cm × 2.4 cm receiver antenna. A phased array transmitter antenna is designed to provide a uniform power transmission over the 27 cm × 23 cm × 16 cm rat behavioral cage area. The proposed WPT scheme utilizes a near-field power transmission scheme at 2.4 GHz frequency. Simulation results show that the transmitter antenna achieves a -24 dB and receiver antenna achieves a −27 dB return loss (S 11 ) at the resonating frequency. The proposed WPT system shows a maximum of 24.5% power transfer efficiency (PTE) when the receiver is in the center position and is 10 cm distance apart from the transmitter, which is much higher compared to the other state-of-the-art works. The transmitter antenna steers beam from −21° to 27° in ϕ axis and −108° to 74° in θ axis which covers the maximum 6.27 cm 2 area of the cage. The preliminary simulation results of the proposed WPT module show a better prospect for future optogenetics based applications. 

For the diagnosis and treatment of various chronic neurological diseases such as Epilepsy, Seizure and, chronic pain, a long-term electrophysiological recording and stimulation are required for the patients. This type of study can be done through implantable neuromodulation devices. One of the key challenges in designing such implantable medical devices is the size restriction. Even the antennas transmitting the recorded signals must be small, miniaturized, and light-weight in order for the small animals used in the clinical studies to carry it easily. In this paper, two 15mm×15mm antennas are designed which have ultra-wide bandwidths making them suitable for the high data rate electrophysiological recording applications. The proposed antennas are bidirectional and small in size making them suitable to be added to the headstage based electrophysiological recording devices. Both antennas have a similar radiating patches with each ground patch modified by creating two different slots. A comparison of the proposed antenna is presented in the paper where both antennas operate within 4.7 GHz to 8.3 GHz and having average gain above 4.35 dBi. Though the proposed antennas are 40% smaller in size, they have 6% higher gain compared to the state of the arts. 

This paper presents a power-efficient complementary metal-oxide-semiconductor (CMOS) neural signal-recording read-out circuit for multichannel neuromodulation implants. The system includes a neural amplifier and a successive approximation register analog-to-digital converter (SAR-ADC) for recording and digitizing neural signal data to transmit to a remote receiver. The synthetic neural signal is generated using a LabVIEW myDAQ device and processed through a LabVIEW GUI. The read-out circuit is designed and fabricated in the standard 0.5 μμm CMOS process. The proposed amplifier uses a fully differential two-stage topology with a reconfigurable capacitive-resistive feedback network. The amplifier achieves 49.26 dB and 60.53 dB gain within the frequency bandwidth of 0.57–301 Hz and 0.27–12.9 kHz to record the local field potentials (LFPs) and the action potentials (APs), respectively. The amplifier maintains a noise–power tradeoff by reducing the noise efficiency factor (NEF) to 2.53. The capacitors are manually laid out using the common-centroid placement technique, which increases the linearity of the ADC. The SAR-ADC achieves a signal-to-noise ratio (SNR) of 45.8 dB, with a resolution of 8 bits. The ADC exhibits an effective number of bits of 7.32 at a low sampling rate of 10 ksamples/s. The total power consumption of the chip is 26.02 μμW, which makes it highly suitable for a multi-channel neural signal recording system. 

One of the design challenges of the implantable medical devices (IMD) is the power requirement that needs to be minimum to avoid frequent battery-replacement and surgeries. This paper presents a duty-cycled IR-UWB transmitter designed using standard 180 nm CMOS process that achieves an energy efficiency (energy-per-pulse) of 11.5 pJ/pulse at 100 Mbps data rate. Working in the frequency range of 4 - 6 GHz, the transmitter achieves a peak power spectral density (PSD) of -42.1 dBm/MHz with 950 MHz bandwidth which makes it highly suitable for high data rate biotelemetry applications. The bandwidth of the proposed transmitter system can also be varied from 500 MHz-950 MHz using control voltage of the impulse generator (IG). The wide frequency range and bandwidth range of the proposed transmitter also makes it highly suitable for distributed brain implant applications covering both lower and upper UWB frequency bands. 

Multi-channel data acquisition of bio-signals is a promising technology that is being used in many fields these days. Compressed sensing (CS) is an innovative approach of signal processing that facilitates sub-Nyquist processing of bio-signals, such as an electrocardiogram (ECG) and electroencephalogram (EEG). This strategy can be used to lower the data rate to realize ultra-low-power performance, As the count of recording channels increase, data volume is increased resulting in impermissible transmitting power. This paper presents the implementation of a CMOS-based front-end design with the CS in the standard 180 nm CMOS process. A novel pseudo-random sequence generator is proposed, which consists of two different types of D flip-flops that are used for obtaining a completely random sequence. The power consumed by the bio-signal amplifier block is 2.35 μW. The SAR-ADC block that is designed to digitize the amplified signal consumes 277 μW of power and the power consumption value of the pseudo-random bit sequence generator (PRBS) is 344.2μW. The sampling rate of PRBS block is 611.76 Kbps. We have considered collecting neural data from the 32 channels, and achieved an 8.5X compression rate. The low power consumption per channel confirms the importance of the proposed approach for multiple channel high-density neural interfaces. 

For the treatment of chronic neuropathic diseases, long-term behavior study of the patient is very important. The behavior study is performed using neural stimulation and simultaneously recording the response from the neural cells. Headstage-based neuromodulation device has become one of the popular methods for neural stimulation in recent times. In this work, a wirelessly powered system is presented that provides constant power to a headstage based optogenetic stimulator, which includes a receiver (RX) coil, a rectifier, and an mm-sized light-emitting-diode (LED). A multi-layered transmitter (TX) coil is designed to provide uniform power transmission over the 20.7 cm × 14 cm mouse behavioral cage area. A maximum of ~49% efficiency is achieved using the proposed system at 3 cm distance through the air media at 13.56 MHz operating frequency. The proposed system uses less number of headstage resonators on the 3-D printed light-weight headstage which is able to achieve higher efficiency compared to the other state-of-the-art.