Ultra-low power, low-noise and small size transceiver for wearable and implantable biomedical devices and neural prosthesis

© 2018 Dr Bahram GhafariThere is high demand for research into the innovation and development of miniaturized electronics devices for biomedical applications such as implantable medical devices (IMD), neural prostheses (NP), embedded neural systems, body area network (BAN) systems and wireless biosensors systems (WBS) for the monitoring, treatment and diagnostics of diseases such as retinal degenerative diseases (bionic eye), hearing loss (bionic ear), and epilepsy (neurobionics). These electronic systems must be wireless as wires penetrating through human skin increase the risk of infections as they act as conduits for viruses and bacteria and they also limit the flexibility of movement for patients. It is critical to have the smallest size possible for implanted devices to minimize required space, and to have high quality implant grades and off-chip components. Therefore, an integrated design for transceivers in single chips without any cheap components is preferable. Another advantage of minimum size and integrated transceiver design in a single chip is that it minimizes power consumption and heating. Ultra-low power transceivers are essential because implanted batteries are undesirable due to their limited lifespan and the risk of infection they pose. Also, a limited amount of power can be transferred through the wireless power link system, and in the bionic eye, most of the transferred power will be consumed for stimulation in the electrodes array. Frequency is another important factor and limitation of transceiver designs in biomedical applications. The Medical Implant Communication Service (MICS) frequency band (402-405 MHz) is a relatively low frequency and has a small channel bandwidth. Therefore, achieving an ultra-low power design of less than one milliwatt remains challenging. There is a high amount of data transmitted and received in some implantable biomedical devices like retinal prostheses (bionic eyes) so high-speed transceiver systems are required for these applications. This work endeavours to explore the development of techniques for designing single chip ultra-low power, low noise, high speed and small sized transceivers for implantable biomedical devices for the bionic eye as an example. Ring oscillators were examined because they do not require external inductors or capacitors, and are area-efficient compared to LC oscillators. Because the VCO is the most critical part of the transceiver design in terms of power consumption and phase noise, a linear model of CMOS ring oscillator was used to derive a phase noise model. A phase noise versus power consumption of a five-stage ring oscillator was formulated, and a new model for optimizing phase noise versus power consumption for different frequencies and based on different transistor aspect ratio is presented. This thesis is predominantly devoted to the design and implementation of a MICS band transceiver with super low power consumption. A new ultra-low power, low-phase-noise and small sized ring VCO for use in PLL is introduced in this research. This VCO operates in the Medical Implant Communication Service (MICS) frequency band. This ring oscillator VCO does not need external inductors and capacitors like other LC oscillators and requires a small die area. A new control loop for low power, low noise, and quick settlement PLL is also outlined. Furthermore, a new architecture and modulation technique for the ultra-low power, low noise and high-speed transceiver for biomedical applications is presented. The proposed architecture and modulation technique can increase data transmission and receive speed as well as reduce the power consumption of the transceiver and the die size area, and minimize the complexity of the receiver and transmitter architectures