A simplified nonlinear model is proposed for intermodulation (IM) analysis of MESFET gate mixers. The accuracy of the model has been verified experimentally using two different MESFET mixers at X-band. Both tests show...
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A simplified nonlinear model is proposed for intermodulation (IM) analysis of MESFET gate mixers. The accuracy of the model has been verified experimentally using two different MESFET mixers at X-band. Both tests show excellent agreement between measurement and simulated data for second- and third-order IM performance. The simplified model is based on modeling the derivative of the device transconductance by the sum of a Gaussian function and a linear function of the gate voltage. Drain bias dependence is ignored. The advantage of this model is that the fitting parameters can be easily determined from a nonlinear characterization of the device at low frequencies.< >
We introduce computer simulation results that illustrate performance trade-offs associated with the mixed priority queueing model (MPQ) for the initial introductory phase of switching and demultiplexing fabrics for AT...
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We introduce computer simulation results that illustrate performance trade-offs associated with the mixed priority queueing model (MPQ) for the initial introductory phase of switching and demultiplexing fabrics for ATM based high-speed multimedia networking services. We study the hierarchical shared memory ATM switch architecture in which the queues for all the switch output ports share space flexibly in a common buffer. Using computer simulation of this shared buffer ATM switch under both uniform and bursty traffic, we investigate the delay and cell loss probability (CLP) for the each class of traffic. Our finding supports the MPQ model as a worthwhile strategy for buffer management to improve the quality of service (QOS) in an ATM etwork.< >
Echo cancellation is common in full-duplex data transmission over pair-wire telephone lines. A well-designed hybrid circuit can lessen the echo canceller's burden as well as reduce the A/D converter's complexi...
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Echo cancellation is common in full-duplex data transmission over pair-wire telephone lines. A well-designed hybrid circuit can lessen the echo canceller's burden as well as reduce the A/D converter's complexity in a digital implementation. We formulate the task of hybrid design as an optimization problem where the objective function is a weighted average of post-cancellation echo power, echo canceller complexity, and A/D converter complexity. In contrast, prior work in this area appears to have not considered the effect of echo cancellation in problem formulation. We discuss proper forms for the objective function and employ one of them in a numerical study. The chosen objective function is a weighted sum-squares value of the transhybrid echo impulse response. We consider several simple balance network topologies for the hybrid. These networks range from a simple resistor to a fourth-order RLC circuit. The numerical results obtained show that there is significant advantage in using optimized higher-order balance networks, as compared to suboptimal balance networks or simple resistor balance, in terms of both echo cancellation efficiency and hardware complexity. Some topics for further study are indicated.
We present a numerical study of the GAMMA-X mixing in GaAs/AlAs/GaAs quantum well structures. A GAMMA-X mixing model proposed by Liu [Appl. Phys. Lett. 51, 1019 (1987)] is extended to include the effects of self-consi...
We present a numerical study of the GAMMA-X mixing in GaAs/AlAs/GaAs quantum well structures. A GAMMA-X mixing model proposed by Liu [Appl. Phys. Lett. 51, 1019 (1987)] is extended to include the effects of self-consistency and nonzero transverse momentum. In the present model, the coupled Schrodinger equations for GAMMA and X electron envelope wave functions are solved self-consistently with Poisson's equation to calculate the electron transmission probability and wave functions, which lead to the current-voltage (I-V) characteristics of single barrier and double barrier resonant tunneling diode structures. The quantum transmitting boundary method is employed in the model for numerical solution of the coupled Schrodinger equations, which proves to be very stable and efficient, even for large (> 2000 angstrom) structures. The features of GAMMA-X mixing, such as the resonance/antiresonance in the transmission probability and the virtual bound states, are clearly demonstrated. Additional physical features are observed in the transmission probability and the wave functions under applied bias conditions. Our work shows that inclusion of transverse momentum, variable effective mass, and the self-consistent potential is important in the realistic modeling of I-V characteristics for structures exhibiting GAMMA-X coupling.
In DESIRE process, silylation is probably the most critical step since the final resist profiles are mainly determined by the Si distribution between the exposed and unexposed areas of the upper part of the resist. In...
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A theoretical model for quantum well varactors is presented. The model is used to calculate the device C-V and I-V characteristics and very good agreement has been found between the calculated and measured results. Ba...
A theoretical model for quantum well varactors is presented. The model is used to calculate the device C-V and I-V characteristics and very good agreement has been found between the calculated and measured results. Based on the model, a triple barrier double well varactor has been designed and fabricated. A very high capacitance ratio within a very small bias range is achieved, as designed. Details of the design calculations and experimental results are presented.
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