A design of a microwave noninvasive continuous blood glucose monitoring sensor and its interference test results are presented. The novelty of the proposed sensor is that it comprises two spatially separated split-ring resonators, where one interacts with the change in glucose level of a sample under test while the other ring is used as a reference. The reference ring has a slightly different resonant frequency and is desensitized to the sample owing to its location, thus allowing changes in temperature to be calibrated out. From an oral glucose tolerance test with two additional commercially available sensors (blood strip and continuous glucose monitor) in parallel, we obtained encouraging performance for our sensor comparable with those of the commercial sensors. The effects of endogenous interferents common to all subjects, i.e., common sugars, vitamins (ascorbic acid), and metabolites (uric acid) have also been investigated by using a large Franz cell assembly. From the interference test, it is shown that the change in sensor response is dominated by changes in glucose level for concentrations relevant to blood, and the effects of interferents are negligible in comparison.

Abstract-We will demonstrate an alternative topology to greatly increase the operating bandwidth of an analog RF feedback power amplifier. A limited operating bandwidth due to the group delay mismatch of a feedback loop discouraged the use of an RF feedback technique in spite of its powerful linearization performance and great tolerance capability. By introducing a negative group delay circuit (NGDC) in the feedback loop, group delay match condition could be satisfied. With the fabricated 2-stage distributed element negative group delay circuit with a 30 MHz of bandwidth and a −9 ns of group delay for a wideband code division multiple access (WCDMA) downlink band, the proposed feedback amplifier with the proposed topology experimentally achieved an adjacent channel leakage ratio of −53.2 dBc with a cancellation bandwidth of over 50 MHz.Corresponding author: Y. Jeong (ycjeong@jbnu.ac.kr). 254Choi et al.

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In this paper, a microwave non-invasive blood glucose monitoring system operating at around 1.4 GHz is designed and its performance in terms of accuracy and repeatability is evaluated by a clinical trial involving 24 human subjects, with and without diabetes. Direct comparison with the most accurate benchtop glucose analyzer shows the exceptional accuracy and repeatability of the proposed system.