Electrical Design Methodology Research Articles

Processing gain and noise in multi-electrode impedance cytometers: Comprehensive electrical design methodology and characterization

We introduce a novel technique for minimizing false positives and improving the fidelity of signals detected with impedance cytometry. We make use of interdigitated multi-finger electrodes for introducing redundancy and robustness in impedance based detection of micro- and nanoparticles. Multi-electrode impedance sensors provide multiple peaks and unique signatures for single cells and particles, and can be used in conjunction with match filters to provide processing gain. This approach is particularly useful in minimizing false positives, which is particularly difficult for signals with low signal-to-noise ratio. The unique signature provided by multi-electrode sensors results in higher signal-power compared to single electrode pair sensors, and can also result in more fidelity in distinguishing particles from noise. This technique holds the potential of using micro-scale channels for detection of nanoscale particles such as viruses and even individual proteins. Previous work has shown extraction of signal from noise using multi-electrode sensors. To the best of our knowledge, this manuscript presents the first comprehensive attempt to characterize processing gain improvement and system noise in multi-electrode sensors by directly comparing simultaneous measurements obtained from sensors fabricated along the same channel. By measuring simultaneously the electrode pairs along a single channel, consistency in flow rate and buffer conditions is ensured, while other experimental assay-to-assay variations are minimized. We achieve high SNR for particles as small as 1um in a 30μm wide by 10 diameter tall pore. SNR and noise measurements for different electrode configurations and excitation frequencies is thoroughly studied. The results of this study demonstrated that while increasing number of electrodes resulted in increased processing gain, noise levels also increased with larger number of electrode fingers, thus total SNR remained relatively unchanged. Our investigations showed that this increase in noise is likely due to electrochemical reactions at the surface of the electrode dominating the total noise.

Fundamental Electrical Design Method for Superconducting Synchronous Generators

A fundamental electrical design methodology using electrical equations for superconducting synchronous generators, taking into consideration the size of the machine components and the performance of the superconducting field winding, has been developed. A fundamental electrical design of a 70 MW superconducting generator developed as part of the Super-GM project was conducted and it was found that the design predictions were in good agreement with the test results.

Electrical design and simulation of high density printed circuit boards

High density interconnect printed circuit board technology enables significant board size and layer count reduction. Thinner inner layer dielectric materials, reduced line widths, and closer spaced components inherent in high density board technology require a change in electrical design methodology. Most notably, the thinner dielectric thickness significantly impacts the electrical performance of the circuit board with respect to crosstalk, board capacitance, via inductance, and controlled impedance. Via inductance is significantly reduced as mechanically drilled through hole vias are replaced with microvias. Distributed capacitance will tend to increase because of the thinner dielectric layer and crosstalk between signal traces run on adjacent layers may also increase. Using either FR-4 type epoxy (diel, cnst.=4.0) or higher performance materials (diel, cnst.=2.8) conventional controlled impedance structures such as a stripline, microstrip, and coplanar waveguide are possible to design using current manufacturing capabilities. A 50 /spl Omega/ impedance can be achieved by a microstrip or a coplanar waveguide using either dielectric material. The stripline can only achieve approximately 35 /spl Omega/ with the higher performance material and 25 /spl Omega/ with the FR-4 type epoxy material. A 500 mW radio frequency receiver and transmitter module operating at 467 MHz was successfully fabricated using a three layer build-up high density circuit board. The circuit board construction had one build-up layer fabricated with a liquid epoxy material. The circuit board electrical design incorporated microstrip, stripline, and coplanar waveguide controlled impedance structures. The results of the electrical performance measurements indicated that transmitted power, receiver sensitivity, and frequency specification performance were similar to a six layer board manufactured with conventional technology.