Small-Signal Admittance of Forward-Biased a-Si:H p+-i-n+ Diodes by Time Domain Analysis

1998 ◽  
Vol 507 ◽  
Author(s):  
F. Lemmi ◽  
N. M. Johnson
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Forward Bias ◽  
Transient Current ◽  
Frequency Variation ◽  
Displacement Current ◽  
Current Response ◽  
Small Signal ◽  
Low Frequencies ◽  
Dc Bias

ABSTRACTIn order to study the observed frequency variation of small-signal admittance of forward- biased amorphous silicon (a-Si:H) p-i-n diodes, we performed time-resolved measurements of currents induced by application of a small voltage step superimposed on a constant DC bias. The small amplitude ensures a linear behavior of the system under study. The transient current response includes all the details necessary to explain the stationary response to small sine-wave excitation. Details are obtained through a Fourier transform of the transient current. The real and imaginary parts of the resulting complex current are related to the capacitance and conductance spectra. This approach can explain phenomena taking place in the stationary regime such as negative capacitance values measured at low frequencies.In the frequency domain, measured capacitances do show negative values, as well as a clear dependence on the applied forward bias voltage. Namely, higher voltages extend the region in which the phenomenon occurs to higher frequencies of the probe signal. In the time domain, all measured transient currents exhibit common features such as an initial decay after the displacement current and, for higher DC biases, a gradual increase. A physical explanation of the current transient is proposed which accounts for the dependence on applied DC bias. A mathematical model is used to show how a delayed increase in the current leads to a modulation of the capacitance and conductance in the frequency domain, the two being related to each other. This finally allows the comprehension of the observed frequency domain behavior.

Frequency Domain Design for Maximizing the Allowable Size of a Step Disturbance in Linear Uncertain Systems

1994 ◽  
Vol 116 (4) ◽  
pp. 635-642
Author(s):  
Suhada Jayasuriya ◽  
Massoud Sobhani
Keyword(s):  
Transfer Function ◽  
Frequency Domain ◽  
Time Domain ◽  
Design Procedure ◽  
Control Input ◽  
Low Frequencies ◽  
Loop Shaping ◽  
Loop Transfer Function ◽  
Step Disturbance ◽  
Domain Constraints

A design methodology is developed for a linear, uncertain, SISO system for maximizing the size of a step disturbance in the presence of hard time domain constraints on system states, control input, output and the bandwidth. It is assumed that the system dynamics can be represented by a combination of structured uncertainty in the low frequencies and unstructured uncertainty in the high frequencies. The design procedure is based on mapping the time domain constraints into an equivalent set of frequency domain constraints which are then used to determine an allowed design region for the nominal loop transfer function in the plane of amplitude-phase. Once such a region is found, classical loop shaping determines a suitable nominal loop transfer function. The pole-zero structure of the compensator is a natural consequence of loop shaping and is not preconceived. An illustrative example demonstrates the trade-off between controller bandwidth, or the cost of feedback, and the tolerable size of step disturbance.

Time Domain Transfer Function of the Induction Motor

2014 ◽  
Vol 1 (2) ◽  
pp. 1
Author(s):  
N N Barsoum
Keyword(s):  
Transfer Function ◽  
Frequency Domain ◽  
Induction Motor ◽  
Time Domain ◽  
Inverse Laplace Transform ◽  
Dynamic Mode ◽  
Small Signal ◽  
Small Signal Stability ◽  
Static Mode ◽  
Signal Stability

Small signal stability of electrical machines at frequency domain has been shown by toque coefficients and eigenvalue of motional impedance matrix in state space form. The relation of damping, synchronizing and total synchronizing torque coefficients with the eigenvalue or the roots of the characteristic equation of the perturbed machine shows that the instability occurs at 2 different modes. Static mode represented by real root at over load condition, and dynamic mode represented by complex root at the condition when the total synchronizing coefficient exhibits zero value within the negative range of the damping torque coefficient. However, small signal instability details at time domain are not given in the literatures. This paper discusses with figures the time domain signals of the induction motor perturbation variables under hunting condition, and presents the differences observed between inverse Laplace transform and Fourier transform in time domain response, based on the transform of the transfer function from the frequency domain, The figures demonstrate and confirm the machine small signal stability performance given in frequency domain.

JOINT INTERPRETATION OF AIRBORNE ELECTROMAGNETIC DATA IN THE TIME DOMAIN AND FREQUENCY DOMAIN

2018 ◽  
Vol 12 (7-8) ◽  
pp. 76-83
Author(s):  
E. V. KARSHAKOV ◽  
J. MOILANEN
Keyword(s):  
Fourier Transform ◽  
Frequency Domain ◽  
Time Domain ◽  
Frequency Interval ◽  
Single Spectrum ◽  
Simultaneous Inversion ◽  
Homogeneous Half Space ◽  
Time Domain Data ◽  
The Time Domain

Тhe advantage of combine processing of frequency domain and time domain data provided by the EQUATOR system is discussed. The heliborne complex has a towed transmitter, and, raised above it on the same cable a towed receiver. The excitation signal contains both pulsed and harmonic components. In fact, there are two independent transmitters operate in the system: one of them is a normal pulsed domain transmitter, with a half-sinusoidal pulse and a small "cut" on the falling edge, and the other one is a classical frequency domain transmitter at several specially selected frequencies. The received signal is first processed to a direct Fourier transform with high Q-factor detection at all significant frequencies. After that, in the spectral region, operations of converting the spectra of two sounding signals to a single spectrum of an ideal transmitter are performed. Than we do an inverse Fourier transform and return to the time domain. The detection of spectral components is done at a frequency band of several Hz, the receiver has the ability to perfectly suppress all sorts of extra-band noise. The detection bandwidth is several dozen times less the frequency interval between the harmonics, it turns out thatto achieve the same measurement quality of ground response without using out-of-band suppression you need several dozen times higher moment of airborne transmitting system. The data obtained from the model of a homogeneous half-space, a two-layered model, and a model of a horizontally layered medium is considered. A time-domain data makes it easier to detect a conductor in a relative insulator at greater depths. The data in the frequency domain gives more detailed information about subsurface. These conclusions are illustrated by the example of processing the survey data of the Republic of Rwanda in 2017. The simultaneous inversion of data in frequency domain and time domain can significantly improve the quality of interpretation.

MESFET large-signal model based on small-signal measurements for time-domain CAD

1988 ◽  
Vol 24 (15) ◽  
pp. 973 ◽  
Author(s):  
A. Ouslimani ◽  
G. Vernet ◽  
J.C. Henaux ◽  
P. Crozat ◽  
R. Adde
Keyword(s):  
Time Domain ◽  
Small Signal ◽  
Large Signal ◽  
Signal Model ◽  
Model Based
Sign in / Sign up

Export Citation Format

Share Document