Temperature modeling and measurement of an electrokinetic separation chip

This work presents experimental [infrared (IR) thermography] and computational (finite element model) results of temperature distributions of an electrokinetic separation chip. Thermal characteristics of both the electrolyte solution and the polymer chip (SU-8) are taken into account in modeling temperature distributions during electrokinetic flow. Multiphysics and multiscale simulation couples electrostatics, heat transfer, and fluid dynamics. The accompanying IR thermography is a non-contact method, which can measure fractional temperature differences with sub-second time resolution. Any structures or temperature marker molecules interfering with the experiment are not needed. Nominal spot size in the IR measurements is 30 μm with a field of view of several millimeters enabling both local and chip-scale temperature monitoring simultaneously. As a result, we present a computer model for electrokinetic chips, which enables simulation of fractional temperature changes during electrophoresis under real operating conditions. The accuracy of the model is within ±1°C when the deviation in electrochemical processes is taken into account. The simulation results also suggest that the temperature on the chip surface qualitatively reflects the temperature inside the microchannel with an average offset of 1–2°C.     

Evaluating Off-Peak Traffic Signal Control Strategies

This article discusses the evaluation of flashing yellow as an off-peak traffic signal control strategy by establishing an interface between a real-time traffic simulation software HUTSIM (Helsinki University of Technology Simulation Model) and a standard NEMA (National Electrical Manufacturers Association) traffic signal controller. The analysis was performed as part of research dealing with evaluation of different off-peak traffic signal operation strategies and their relative impacts on delay, fuel consumption, vehicle emissions, and driver safety. Because of its widespread use, the main emphasis was on the flashing yellow signal control. Delay field study was performed to obtain and analyze real-world data and compare the efficiency of flashing yellow and fixed time control strategies. To widen the research effort and eliminate inaccuracies due to certain assumptions made during the field study, computer simulation was chosen as an effective tool for comparison of different control strategies. Four different strategies were evaluated: fixed time, fully and semiactuated, and flashing yellow. Flashing yellow was found to be the most efficient of the signal strategies. The impact of this type of off-peak signal control on driver safety also was studied, and a summary of results is presented.     

Antenna Effective Aperture Measurement With Backscattering Modulation

A scattering measurement method for antenna characterization is described. The antenna backscattering is modulated by an oscillator circuit. The modulation begins, when a known RF power is transferred to the oscillator circuit from the antenna. This enables the measurement of the effective aperture of the antenna, from which the antenna bandwidth and radiation pattern are obtained. A theory for antenna aperture measurement is developed using a simple circuit model for the antenna-oscillator system. A dipole and a PIFA with a reactive input impedance at the application frequency were measured. The antenna aperture was measured to an accuracy of 9%, and the measurements complied with simulated and measured references. The method provides simple and accurate bandwidth and radiation pattern measurements with the reactive load the antenna is designed to work with.     

Millimeter-Wave Identification—A New Short-Range Radio System for Low-Power High Data-Rate Applications

The radio-frequency identification (RFID) concept is expanded to millimeter-wave frequencies and millimeter-wave identification (MMID) in this paper. The MMID concept and a comparison with UHF RFID are presented, showing the limitations and benefits of MMID. Three feasible applications are suggested for MMID, which are: (1) wireless mass memory; (2) an automatic identification system with pointing functionality; and (3) transponder communication with automotive radar. To demonstrate the feasibility of the MMID system, experimental results for both downlink and backscattering-based uplink are presented at 60 GHz.     

UHF RFID Reader With Reflected Power Canceller

Reflected power imposes severe linearity problems to the receiver in radio frequency identification (RFID) readers. In this letter, the design and realization of a ultra high frequency RFID reader with a reflected power canceller circuit based on quadrature feedback are presented. Theory and measurements of the signal and noise in the receiver are presented as a function of incident carrier power. The receiver sensitivity is even better than without the canceller with high incident carrier power: A noise spectral density at the data band is -140 dBm/Hz at +12 dBm incident carrier power. At the same time, input compression point of +15 dBm is achieved. The dynamic range of the receiver is improved by 10 dB.     

Backscattering-Based Measurement of Reactive Antenna Input Impedance

A scattering technique for measuring reactive antenna input impedance is described. The antenna scattering is measured with three different loads: an open circuit, a conjugate match, and a reactive match. The load reactances tune the antenna into resonance at the measurement band. Theory and error considerations are presented, as well as measurement results of two ultra high frequency radio frequency identification antennas. The measurements were performed in a gigahertz transverse electromagnetic mode cell. The measured impedances are within about 10% of the simulated values for a dipole-like antenna. The results of a planar inverted-F antenna are somewhat more complex, but also supported by the presented simulations and the coaxial impedance measurement results.     

Planar inverted-F antenna for radio frequency identification

A small and low-cost antenna solution for radio frequency identification (RFID) tags is presented. The impedance of the antenna is designed to match directly to the impedance of the RFID microchip. Also, the impedance of the antenna is immune to the platform. Thus, the antenna is applicable in many different environments. The design and measurement results are reported and discussed.