Kahtan A. Mezher

Comparison of nonlinear MESFET models for wideband circuit design

The Curtice quadratic, Materka, Statz, and Rodriguez nonlinear models are compared from DC, CV, and RF points of view, to determine which is the most suitable for nonlinear wideband circuit design. For this comparison, GaAs MESFETs of various sizes are employed. These include devices of varying gate widths, gate lengths, number of fingers, and pinch-off voltages. >

Noise and sensitivity optimization in the design of second‐order single‐amplifier filters

Simultaneous optimization of the sensitivity and noise performance of second-order single-amplifier RC filter sections resolves a long-standing discrepancy and reveals practical trade-offs. the influences of controlled gain, component spread and design choice are elucidated for both bandpass and lowpass complementarily symmetrical circuits.

The dynamic range of second-order continuous-time active filters

Analysis of both the output noise and the large-signal harmonic distortion in terms of block diagrams allows the total dynamic range of active filters to be predicted theoretically. This leads to optimization and comparison of single and multiple-amplifier RC and OTA-C second-order bandpass filter circuits. The results are confirmed experimentally throughout. Increased design frequency or selectivity reduces dynamic range which is also often related to active sensitivity. Available OTA-C circuits appear to pay for their higher-frequency performance in terms of more restricted signal-handling capability.

Improved junction capacitance model for the GaAs MESFET

An empirical equation for simulating the bias dependency of the junction capacitances of the GaAs MESFET is presented and compared with existing techniques. It provides increased accuracy over a wide range of silicon and GaAs devices for microwave circuit design applications and up to 72% savings in CPU execution speed over existing techniques. >

Noise analysis of continuous-time active filters

A rigorous and flexible direct-referral procedure for analyzing the noise performance of analog active networks is proposed. Based on an equivalent noise block diagram, it allows consistent comparisons of noise levels in active-RC, active-R, and OTA-C configurations. In each case, the measured results agree closely with theory. The state-variable operational-amplifier circuit appears to offer the best dynamic range.<<ETX>>

Optically controlled 2.4GHz MMIC amplifier

In this paper a 2.4GHz MMIC amplifier for mobile applications is used to demonstrate the significant control that can be achieved in the amplifiers performance using optical illumination. The results presented show a 15dB variation in the amplifiers S21 figure and a 6 to 10dB variation in the input and output return loss when the incident optical power is varied.

Noise-flow-graph analysis of OTA-C filters

Canonical and noncanonical second-order OTA-C filter circuits are analysed by means of noise flow graphs, leading to generalisation of configurations. The noise performances of specific cases are compared theoretically and experimentally. For high-Q circuits, the number of active devices is shown not to determine the output noise.

Energy saving in tunnels lighting using shading structures

This paper introduces a constructive proposal to save energy in tunnels lighting using shading structures. These structures aim at the reduction of sunlight levels at tunnels portals. Accordingly, such sunlight reduction will reduce the artificial lighting requirements at the entrances and exits and hence provide further energy saving without additional smart intervention using control methods. The aesthetic appearance of shading structures needs to be considered without sacrificing the traffic safety requirements. The energy saving in addition to initial costs reduction render shading structures as a good candidate for permanent installations with low maintenance requirements compared to conventional lighting installations. Our proposal could be applied equally at the design stage of new tunnels and underpasses, or as a retrofit for existing roads structures to turn them into green energy facilities. Renderings and payback calculations predict flourishing future for the proposed tunnel lighting energy conservation by shade structures. This study shows that up to 50% saving in the lighting electrical load can be achieved.

Computationally efficient and accurate capacitance model for the GaAs MESFET for microwave nonlinear circuit design

A new equation for simulating the bias dependency of the gate-source and gate-drain capacitances of the GaAs MESFET is presented and compared with existing techniques. It provides increased accuracy for microwave circuit design applications and substantial savings in CPU execution speed over existing techniques. The new empirical relation is applied successfully to a wide range of silicon and GaAs devices. >

Complete dynamic range for second-order analogue active filters

Analyzing both the output noise and the large-signal harmonic distortion allows the total dynamic range of active filters to be predicted. This leads to optimization and comparison of single and multiple-amplifier RC and OTA-C second-order bandpass filter circuits. The results presented enable recommendations to be made for the choice of filter circuit in a specific signal-handling application.<<ETX>>