In this paper, microstrip-based spiral structured artificial magnetic media (metamaterial) coupled with microfluidic channel is experimentally demonstrated for sensing applications. It is found that the resonant frequency and the amplitude changes due to dielectric loading from the introduction of chemical substances in the microfluidic channels. Different concentrations of water -methanol and water -isopropanol samples are used in the characterization of the sensor. For water -methanol mixtures, the resonant frequency shifts from 2.15 GHz to 2.0 GHz with change in dielectric constant from 25 to 75. Results show that the wave propagation in LH-media can be used for interrogation of minute volumes of samples with high sensitivity. IntroductionRapid characterization of chemical and biological samples is increasingly important in clinical, security, safety, drug discovery and industrial applications. Sensing approaches are needed that does not require tagging, (e.g., using fluorescent markers) in order to maintain the samples in their original form while under study. Along with rapid label-free characterization, interrogation of small sample volumes is critically needed in the areas of clinical diagnosis and drug discovery. In this paper, periodic media co-integrated with microfluidic leading to a novel RF near-field sensor is implemented to tackle these challenges. The proposed sensor is simple, cost effective, and can be used for label-free sensing and detection Spiral structured artificial magnetic media (metamaterial) designs have been widely used in the design of compact coplanar waveguides (CPW) and microstrip-based circuit topologies. Recently, split-ring based metamaterial structures that are edge-coupled to a microstrip line have been used in the sensing of biomolecules [1]. In this structure, the interrogation signal (RF) edge couples from a microstrip transmission line to a ring resonator. The biomolecules are made to bind onto the ring resonator. A direct approach of interrogation will be desirable which is more compact and provides improved sensitivity and yet still simple to fabricate and implement. To meet this goal, in this paper, metamaterial structure that is integral part of the microstrip line is employed for sensing application. A spiral based metamaterial transmission was recently introduced, [2 -3], and this design is implemented here for sensing applications.In spiral based metamaterial transmission lines, the periodic arrays of the spiral structure employ left-handed (LH) propagation properties and support backward waves at their fundamental resonance [2]. Motivated by the wave propagation phenomenon of this medium, a microfluidic sensor that interrogates samples in the near-field region is attractive to achieve high sensitivity using low-volumes of samples. This sensor is designed and implemented for
A technique for producing miniaturized tunable planar monopole antennas for wireless communication applications is introduced. Miniaturization is achieved by optimizing the geometry of a pixelated metallic patch surrounding the monopole antenna. Tuning of the antenna is implemented by varying the capacitance of a varactor diode loaded between the pixelated metallic patch and the ground plane. The result is an ultracompact, dual band, folded monopole antenna that fits into a hemisphere of radius λ0/20 at 2.1 GHz. Varying the capacitance of the varactor diode enables the two resonance frequencies to be tuned simultaneously, covering multiple frequency bands for different wireless applications. A prototype antenna has been fabricated and measured, confirming the feasibility of the proposed design.
Abstract.A passive harmonic radio frequency (RF) tag on the pipe with added sensing capabilities is proposed in this paper. Radio frequency identification (RFID) based tagging has already emerged as a potential solution for chemical sensing, location detection, animal tagging, etc. Harmonic transponders are already quite popular compared to conventional RFIDs due to their improved signal to noise ratio (SNR). However, the operating frequency, transmitted power and tag efficiency become critical issues for underground RFIDs. In this paper, a comprehensive on-tag sensing, power budget and frequency analyses is performed for buried harmonic tag design. Accurate tracking of infrastructure burial depth is proposed to reduce the probability of failure of underground pipelines. Burial depth is estimated using phase information of received signals at different frequencies calculated using genetic algorithm (GA) based optimization for post processing. Suitable frequency range is determined for a variety of soil with different moisture content for small tag-antenna size. Different types of harmonic tags such as 1) Schottky diode, 2) Non-linear Transmission Line (NLTL) were compared for underground applications. In this study, the power, frequency and tag design have been optimized to achieve small antenna size, minimum signal loss and simple reader circuit for underground detection at up to 5 feet depth in different soil medium and moisture contents.
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