Biasing

About: Biasing is a research topic. Over the lifetime, 29422 publications have been published within this topic receiving 301035 citations.

Broadband Frequency-Selective Rasorber With Varactor-Tunable Interabsorption Band Transmission Window

Abstract: In this paper, we present a frequency-selective rasorber with tunable transmission window located within the absorption band. The rasorber maintains a low reflectivity, which is less than −10 dB in broadband during the tuning process. An equivalent circuit model is provided as a guideline for the tunable rasorber design. Based on the model, a varactor-tunable rasorber composed of three stacked metallic layers is constructed and investigated. These layers include a frequency selective surface (FSS) loaded with resistors and varactors, a wire grid and a varactor-loaded bandpass FSS. The wire grids in the middle and bottom layers in combination with metallic vias provide the bias and grounding for the varactors, respectively. This configuration avoids using two separated bias networks for varactors on different layers, thus, averting undesirable responses associated with having more bias grids. A tunable rasorber prototype was fabricated and measured, showing that the passband can be tuned from 2.2 to 3.3 GHz by changing bias voltage from 4 to 22 V, with an insertion loss between 6.6 and 3.3 dB. A wide low-reflectivity band under normal incidence for double polarizations from 1.9 to 5.4 GHz is realized. This tunable rasorber has promising applications in broadband stealth facilities with integrated hopping communication functionality.

A variable delay cell with a self-biasing load

Abstract: A variable delay cell with a self-biasing load (40) suitable for the implementation of a voltage controlled oscillator and other functions. Because the invention employs current steering (60) between symmetric loads and fully differential voltage control (CTL), it is very fast relative to conventional methods and has reduced jitter and improved power supply noise rejection. Additionally, since the load (40) is self-biasing, the need to externally generate a bias current for the load is eliminated. This significantly simplifies design. Also as the load readily self biases in response to changes in the bias current of the biasing transistor (55), desirable functionalities can be achieved merely by appropriately changing the bias current into the biasing transistor. Notably, the slew rate of both the rising and falling edge can be controlled in this way. Because the load provides a fully differential output, noise immunity as well as a 50 % duty cycle is readily achieved.

Ballisticity of nanotube field-effect transistors: Role of phonon energy and gate bias

Abstract: We investigate the role of electron-phonon scattering and gate bias in degrading the drive current of nanotube field-effect transistors (FETs). Optical phonon scattering significantly decreases the drive current only when gate voltage is higher than a well-defined threshold. For comparable electron-phonon coupling, a lower phonon energy leads to a larger degradation of drive current. Thus in semiconductor nanowire FETs, the drive current will be more sensitive than in carbon nanotube FETs because of the smaller phonon energies in semiconductors. Acoustic phonons and other elastic scattering mechanisms are most detrimental to nanotube FETs irrespective of biasing conditions.

Method and system for self-convergent erase in charge trapping memory cells

Abstract: A process and a memory architecture for operating a charge trapping memory cell is provided. The method for operating the memory cell includes establishing a high threshold state in the memory cell by injecting negative charge into the charge trapping structure to set a high state threshold. The method includes using a self-converging biasing procedure to establish a low threshold state for the memory cell by reducing the negative charge in the charge trapping structure to set the threshold voltage for the cell to a low threshold state. The negative charge is reduced in the memory cell by applying a bias procedure including at least one bias pulse. The bias pulse balances charge flow into and out of the charge trapping layer to achieve self-convergence on a desired threshold level. Thereby, an over-erase condition is avoided.

High-frequency modulation characteristics of red VCSELs

Abstract: The authors have measured small- and large-signal modulation response characteristics of a red VCSEL (λ = 670 nm). A small-signal 3 dB bandwidth of 11 GHz was recorded at a bias current of 16 mA. The small-signal response for each bias current was fit to an analytic model to determine the resonance and damping factor. From these data the differential gain coefficient and K-factor were estimated. Large signal digital measurements were conducted showing suitability of this device for data communication applications. An open eye diagram at the receiver output is presented with no pre-bias current applied and the VCSEL modulated at 155 Mbit/s demonstrating the possibility of direct logic-level drive.