Project Background

1. Non-Invasive Blood Glucose Monitor Team Members : Yongjie Cao (EE), Jared Bold (EE), John Louma (EE), Andrew Rosen (EE), Daniel Sinciewicz (EE) Sponser : Dr. JayantiVenkataraman (Sponsor) Team Guide : Professor George Slack (Team Guide) • Project Background • Currently, the most common technique for sampling blood glucose levels by breaking skin and taking a blood sample. Our non-invasive method uses an antenna to correlate the change in the antenna’s resonant frequency to the change in blood glucose levels. The accuracy of our device’s measurement is done through a resonant frequency shift comparison with a network analyzer. • Key Objectives • Design, build, and validate two antennas: a narrowband one for transmission and a wideband for reception. • Design a compact PCB to operate from 800 to 2000 MHz in steps of 15 KHz • Complete a measurement sweep of the antenna parameters, S11 and S21, every 30 seconds • Validate results with a comparison to a network analyzer. • Design a calibration system to correct for natural errors that arise from the transmission lines and surface mount RF chips • Creating an Antenna • It is desirable that the first antenna used to transmit power is narrow band, meaning that it transmits power over a small frequency band. This allows us to detect very minute changes in resonant frequency. • The most challenging aspect of the antenna design was to have the antennas operate at sub 2 GHz frequencies. The antennas needed to be electrically large, but physically small enough to fit on the forearm of the body. • The transmission antenna originated from a basic patch antenna that resonated at 1.1 GHz. To shrink the physical dimensions, but maintain it’s electrical properties, symmetric cutouts related to the wavelength of operation were made. The theory of the patch dictates the current travels around the outside of the patch. The cutouts make the antenna electrically larger to maintain the resonate frequency of 1.1 GHz. • The receiving antenna, which receives power going through the arm, was designed to be wide band. Our wide band design implies that when the transmission antenna’s properties change, due to a blood glucose shift, our receive antenna will still receive a signal through the arm. • Through IEEE, an antenna with the desirable properties required for our project was found. It is physically small enough to fit on someone's forearm and it is resonant under 2 GHz. • Program • Place description of code flow and PICTURE of CODE FLOW here. Place description of algorithm for max resolution around resonant frequency here. Place PICTURE of GUI here. • Vector Measurement System • Place description of AD8302 here. Place description of why our PLL was chosen here. I don’t think we need to have a separate section for this, so I combined them into one. • Calibration System • The calibration system eradicates the phase error that occurs in the transmission lines. • The phase error arises when the comparison from the reflected signal (blue arrow) is made to the reference signal (yellow arrow). The reflected signal takes a significantly longer path than the reference signal, which results in an extra phase difference between the two signals. To eradicate this error, an open will be placed at the end of the SMA connector to create a complete reflection with a 180° phase shift. Theoretically, these signals should be completely out of phase and cancel when compared in the AD8302. Their phase difference will be the phase error and will be applied by subtracting off the extra phase in future measurements. • When the reflected signal is compared to the reference signal takes a significantly longer path to the AD8302. Therefore, there will be some phase change associated with it that we don’t want to take into account. To calibrate out the phase change we place an open (from NA cal kit) on the sma connector to get complete reflection. We know that the phase should be the same when it gets to the AD8302, so during the post data collection we correct for this with Matlab (our interface program). • Johns Remaining Writing • The measurements of resonant frequency were made using a circuit that P13071 constructed. This circuitry is currently designed to interface with a computer. The RF signal is generated on the circuitry. The measurements of power reflected and transmitted are made on this circuit and sent to the computer. A program on the PC then finds the resonant frequency and tracks the change. A more powerful processor with addition onboard storage and an LCD could make this project completely portable. • Results • Place results here