Effect Of Nonlinear Capacitance Research Articles

Effects of nonlinear capacitance in feedback LC-tank on chaotic Colpitts oscillator

This manuscript presents modifications of the standard Colpitts circuit by replacing one of the capacitors in C1 − C2 potential divider by a pair of back-to-back connected diode varactor. This introduces a nonlinearity of diode varactor type in the feedback signal generation itself. The dynamic capacitance of the varactor pair varies nonlinearly with the output voltage. The proposed modification facilitates generation of enriched frequency components with enhanced power. Both C1 and C2 were alternately replaced by the diode varactor and results were compared with the standard oscillator with fixed-value capacitors. The analysis is based on basic numerical tools such as Lyapunov exponents, bifurcation diagram, phase trajectories and power spectra.

Effect of non-linear capacitance on a non-uniform transmission line

In this paper we derive a non-linear polarization electric field relationship in a dielectric by considering harmonics binding of the electrons to its nuclei. We apply this theory to a transmission line to model the non-linear, inhomogeneous frequency-dependent capacitance of the line and approximate an expression for the line current when the line is terminated by load impedance. We then suggest a method for estimating the inhomogeneous, frequency-dependent non-linear component of the line capacitance from the measurements of the far field electromagnetic field radiated by the line current. The far field magnetic vector potential is calculated from the line current by the standard Green’s function integration in free space.

Power harvesting in a helicopter rotor using a piezo stack in the lag damper

A piezoelectrically augmented helicopter lag damper has been simulated for the purpose of harvesting electrical energy within the rotor of the aircraft. This energy can then be consumed locally for sensing, processing, and transmission of data to the cockpit. An 8.15-m radius rotor is considered, and in-plane rigid lagging motion forms the prime excitation of the damper. The piezoelectric stack is installed within the rod of the damper in such a manner that the stack is submitted to all damper loads. MATLAB and Simulink are used to simulate a simplified blade model. A number of electrical harvesting circuits are investigated, and the piezo stack is optimized for each circuit. Also the effect of nonlinear capacitance of the piezo material is investigated revealing a profound effect. The important design parameters are identified and optimized resulting in a power output of 5.1 W for a steady 130-knot forward flight profile.

Investigation of the non-linear input capacitance in LDMOS transistors and its contribution to IMD and phase distortion

In this paper the mechanisms causing the capacitive, reactive non-linearities in a lateral double diffused MOS, LDMOS, transistor are investigated. The non-linear input capacitance under load-line power match is extracted and analyzed. Computational TCAD load-pull is used to analyze the effect of non-linear capacitance on two-tone intermodulation distortion and AM–PM conversion in class-A operation. High-frequency measurements have been made to verify the use of 2D numerical device simulations for the analysis. It is found that the input capacitance, Cgg, of the LDMOS transistor working under power match conditions is a strongly non-linear function of gate voltage Vg but with an almost linear initial increase in Cgg. The voltage dependence of Cgg is found to mainly affect higher order IMD products in class-A operation. Transient simulations however show that Cgg seriously contributes to the onset of AM–PM conversion well below the 1dB compression point.

Conversion Loss and Noise of Microwave and Millimeterwave Mixers: Part 1--Theory

An analysis is presented for the conversion loss and noise of microwave and millimeter-wave mixers. The analysis includes the effects of nonlinear capacitance, arbitrary embedding impedances, nonideality of microwave diodes, and shot, thermal, and scattering noise generated in the diode. Correlation of down-converted components of the time-varying shot noise is shown to explain the anomalous noise observed in millimeter-wave mixers. Part 1 of the paper presents the theoretical basis for predicting mixer performance, while Part 2 compares theoretical and experimental results for mixers operating at 87 and 115 GHz.