High-Sensitivity Liquid Dielectric Characterization Differential Sensor by 1-Bit Coding DGS.

This paper presents two devices to detect the liquid dielectric characterization. The differential method was used to enhance the robustness and reduce tolerance. A basic sensor based on defected ground structure (DGS) was designed and the optimization for the squares of the DGS via adaptive genetic algorithm was applied to enhance the performance of the microwave sensor, which was shown by the difference of the two resonant frequencies. Furthermore, the electric field distribution was enhanced. Glass microcapillary tubes were used to hold samples to provide an environment of non-invasive. The optimized device exhibited the sensitivity of 0.076, which is more than 1.52 times than the basic structure. It could be considered a sensitive and robust sensor with quick response time for liquid dielectric characterization.

Microstrip triband bandstop filter with sharp stop band skirts and independently controllable second stop band response.

This paper presents a compact planar triband bandstop filter (TBBSF) with compact size and high selectivity. The structure of the filter incorporates two folded trisection stepped-impedance resonators (TSSIRs). One of these resonators is designed to operate at the first and third center frequencies and the other resonator is designed to operate at the second center frequency of the proposed filter. To achieve a compact size filter, alternating impedance lines of the resonators are folded widthwise and also one resonator is embedded within another. Theoretical analysis and design procedures are described, including the synthesis equations for each resonator. The main advantage of the proposed method is that the filter provides flexibility to tune the second center frequency and control the corresponding bandwidth without changing the first and third stop band response. Additionally, several reflection zeros (RZs) are introduced in the pass band to improve its flatness. To demonstrate the feasibility of the proposed design method, both the first and second order TBBSFs were designed, simulated, and fabricated, with center frequencies of 1.92 GHz, 3.55 GHz, and 5.5 GHz.

Multiparameter Microwave Characterization and Probing of Ultralow Glucose Concentration Using a Microfabricated Biochip.

This paper presents a planar biochip consisting of electromagnetically coupled, symmetric, square open loops for the multiparameter microwave characterization of deionized water, a phosphate-buffered saline solution, and a fructose-deionized water solution. The characterization additionally includes the probing of an ultralow glucose concentration in a very small volume of human sera and in solutions of d-glucose powder and deionized water. The interaction between the coupled electromagnetic field and the aqueous solution sample translates into a predictable relationship between the electrical characteristics of the biochip (magnitude and phase of S-parameters, attenuation, phase constant, group delay, characteristic impedance, and effective complex permittivity) and the physical properties of the solution. Owing to the microfabrication technology used for fabricating the proposed microbiochip, it is possible to develop robust, compact square open loops with a microsized coupling gap that characterizes a very small volume (1 µL) of the sample. Additionally, the biochip's impedance peaks at its resonances were modeled using glucose-level-dependent coupling capacitance between folded square open loops and mutual inductance between center-loaded T-shaped stubs. These peaks linearly shifted in frequencies and markedly varied in impedance. Consequently, a physiologically relevant amount of glucose (50⁻400 mg/dL) with a high sensitivity (up to 2.036 Ω/(mg·dL-1)) and an ultralow detection limit (up to 4.8 nmol/L) was linearly detected.

Rapid, sensitive, and reusable detection of glucose by a robust radiofrequency integrated passive device biosensor chip.

Tremendous demands for sensitive and reliable label-free biosensors have stimulated intensive research into developing miniaturized radiofrequency resonators for a wide range of biomedical applications. Here, we report the development of a robust, reusable radiofrequency resonator based integrated passive device biosensor chip fabricated on a gallium arsenide substrate for the detection of glucose in water-glucose solutions and sera. As a result of the highly concentrated electromagnetic energy between the two divisions of an intertwined spiral inductor coupled with an interdigital capacitor, the proposed glucose biosensor chip exhibits linear detection ranges with high sensitivity at center frequency. This biosensor, which has a sensitivity of up to 199 MHz/mgmL(-1) and a short response time of less than 2 sec, exhibited an ultralow detection limit of 0.033 µM and a reproducibility of 0.61% relative standard deviation. In addition, the quantities derived from the measured S-parameters, such as the propagation constant (γ), impedance (Z), resistance (R), inductance (L), conductance (G) and capacitance (C), enabled the effective multi-dimensional detection of glucose.