<p> Recently, there has been a strong trend in medicine to use implanted electronic devices
for diagnostic and/or therapeutic purposes. These devices usually involve a one- or twoway
communication link, allowing communication with the implant. One revolutionary
implanted system that was recently launched into the healthcare market is the wireless
imaging capsule for monitoring the gastrointestinal tract. Among the application-specific
design challenges of such a wireless system are the severe constraints on low power and
on small physical size. Besides, the allowed power levels of signals due to in-body
radiating devices are restricted to very low values due to human safety concerns. To meet
the requirements of such a wireless system, highly efficient, small-size, low-power
transmitting radio frequency (RF) blocks are needed. </p> <p> This thesis focuses on the design, implementation and measurements of the last
two blocks in the transmitter, namely the antenna and the power amplifier (PA). Three PA
circuits have been designed and measured, all of class AB topology. The first two PAs
operate at 2.4 GHz, while the third is designed for 405-MHz operation. All designs are
fully integrated and realized in a standard mixed-signal 0.18 ~m complementary metaloxide-
semiconductor (CMOS) process. Measurement results show that at a supply
voltage of 1.4 V, the circuits have a maximum drain efficiency of 32% and 40.7% for the
2.4-GHz and the 405-MHz designs, respectively, while providing an output power of 7.2
and 8 dBm to the load. These results greatly outperform similar designs in the literature,
proving that class AB PAs, if properly designed, are well-suited for low-power
biotelemetry application. </p> <p> A simple layout design approach was developed to minimize the parasitic effects
of on-silicon interconnections that cause significant degradation in the performance of RF
integrated circuits (RF ICs ). This approach was used to design the layouts of the three PA
circuits presented in this work, and the approach was tested on a low-noise amplifier
(LNA) operating at 5 GHz, since at such a high frequency the parasitics become more
pronounced. Measurements on the LNA circuit show good agreement with simulations. </p> <p> Thus, next to allowing for optimized circuit performance, this approach can shorten the
design time of RF ICs by providing very good predictions of performance characteristics. </p> <p> The last part of this thesis deals with the analysis and design of efficient in-body
antennas. A study of the use of loop antennas in medical implants was conducted.
Simulations and measurements have been used to characterize the radiation performance
of loop antennas in terms of their radiation resistance, transmitting bandwidth and
biocompatibility. At 405 MHz, the antenna has proven to be efficient in the dissipative
biological tissues, to have a wide transmitting bandwidth, and a specific absorption rate
(SAR) distribution that is well below the safety limits. To further verify its suitability for
in-body operation, a miniature loop antenna was fabricated and measured at 405 MHz
and 2.4 GHz. For measurement purposes, two body simulating chemical solutions were
prepared in-house to provide the necessary radiation environment. Measurements show
that small loop antennas are well matched in the medium and are thus good in-body
radiators. </p> / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/21905 |
| Date | 04 1900 |
| Creators | Abdelsayed, Samar |
| Contributors | Deen, M. Jamal, Nikolova, Natalia, Electrical and Computer Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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