Biomedical Engineering - Theses
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ItemLow power transmitter for implanted bio-devices( 2018)With today’s aging population and the rising number of people suffering from chronic diseases, demand for implantable medical devices is expected to grow. Many of these devices need wireless data communication between the implant and an external device to reduce the risk of infection and improve patient comfort. However, wireless communication circuitry can be the most power-hungry component of an implantable device. Most recently proposed low-power transmitters are only optimized for high data rates and they do not scale well to work in low data rate applications. In many biomedical sensing applications, changes in the monitored physiological parameters occur slowly and so low data rates are needed for transmission. In addition, factors such as limited access to power, constrained physical size, low efficiency of small size antennas, and biocompatibility illustrate the importance of innovative low-power design approaches to advance wireless transmitters in bio-implants. One of the biomedical sensing applications is Intra-cranial pressure (ICP) monitoring, which is used to measure brain pressure due to trauma or injury. This is a critical measure in the hospitals and is the information it provides is critical for the patient wellbeing. Currently, all available ICP devices have a physical connection, such as wire or catheter, to the external device. This makes these systems inappropriate for long-term monitoring because of the risk of infection. Therefore, there is a need for a wireless implantable ICP monitoring device and, thus, a need for a low-power wireless transmitter for this application. In this thesis, an ultra-low-power 2.4 GHz narrowband transmitter chip for implantable medical devices is designed, built, and tested. Some of the design specifications are based on application to an ICP monitoring device. To be able to use the scarce energy generated by energy scavengers, various circuit design and power reduction techniques are taken into consideration to reduce both active and standby powers of the system. A mm-size, energy efficient, silver-diamond antenna is designed and fabricated to increase the efficiency of the transmitter. Fabricated in UMC 180 nm CMOS technology, the transmitter supports both OOK and FSK modulation and achieves a total power consumption of 68 uW and energy per bit performance of 6.8 pJ/bit at 10 Mbps and 1.2 V.