0000000000073489
AUTHOR
E.f. Calandra
Analysis of bias-shift effects in free-running and injection-locked negative resistance oscillators
In this paper, the interaction between DC and RF in quasi-sinusoidal free-running and injection-locked oscillators is addressed. To account for and illustrate in a user-friendly manner the bias-shift related effects stemming from such interaction, a frequency-domain method of analysis has been developed for a rather wide class of negative-resistance circuits. Grounding on a first-approximation exact perturbation-refined approach, it permits computationally efficient simulation of the oscillator behavior directly in terms of the DC and RF signals evolutions (dynamical complex envelopes). In fact, it allows the investigation of both steady-state and transient operation of the shifting-bias dr…
Layout influence on microwave performance of graphene field effect transistors
The authors report on an in-depth statistical and parametrical investigation on the microwave performance of graphene FETs on sapphire substrate. The devices differ for the gate-drain/source distance and for the gate length, having kept instead the gate width constant. Microwave S -parameters have been measured for the different devices. Their results demonstrate that the cut-off frequency does not monotonically increase with the scaling of the device geometry and that it exists an optimal region in the gate-drain/source and gate-length space which maximises the microwave performance.
Microwave characterization and modeling of packaged HEMTs by a direct extraction procedure at cryogenic temperatures
In the present work we employ a direct extraction procedure to determine small signal equivalent circuit of microwave GaAs FETs by means of scattering (S-) parameter measurements down to cryogenic temperatures. The direct extraction procedure was tested on packaged AlGaAs/InGaAs HEMTs and good agreement between the simulated and measured S-parameters was obtained at different bias and temperature conditions. We employed a properly designed cryogenic set-up operating in our laboratory that allows to perform DC and RF characterization down to 30 K.
Necessary and sufficient conditions for frequency entrainment of quasi-sinusoidal injection-synchonised oscillators
A method is presented which permits the first-approximation exact analysis of the dynamical stability of fundamental-mode injectionsynchronized oscillators (FISO's) characterized by a quasi-sinusoidal quasi-static behavior. By combining small parameter and stroboscopic transformation techniques, the phase-lock stability investigation of an nth-order system is reduced to the simple Hurwitz test on an nth degree polynomial easily obtainable from steady state describing quantities. On this basis, equations for critical locking are also derived, which demonstrate the existence of a pair of limit curves (Locus and Boundary) already conjectured and looked for in the past, but only with partial su…
A Novel Approach to the Characterization and Modelig of Microwave Transistor Packages
A novel approach to the characterization and modeling of microwave transistor packages through dedicated VNA measurements is presented. By combining a multi-step partitioning method with the use of purposely realized - but technologically simple - "package style" test devices, the proposed technique permits to derive in a systematic manner an equivalent circuit for both the transistor package and the test-fixture mount employed for the characterization. Since it does not rely on the indirect, optimization-based, conventional extraction methods of the literature, nor on a simplified circuit structure for the overall parasitic fourport embedding the active device, it is able to provide a high…
A method for the investigation of high-order two-frequency asynchronous oscillators
A general method for analysing asynchronous high-order two-frequency oscillators is presented. the oscillator model is made up of a GC non-linear parallel group embedded in a linear lumped time-invariant network of any order. the approach devised rests on the identification of a pair of narrow-band impedance operators which permit one to derive first-approximation steady state and dynamic equations in the phasor domain—as well as stability criteria—in a simple and expressive manner. Previous results from averaging and perturbation treatments on fourth-order asynchronous oscillators are shown to be obtainable from this theory as particular cases. the sixth-order oscillator chosen as an appli…
Approach to the analysis of nonlinear feedback oscillators under large-signal injection
A method for the analysis of driven oscillators under high-level injection is presented. It applies to single-loop feedback systems with a memoryless nonlinear element and a second-order (high-Q) tank circuit. The analysis technique employed combines the classical block-diagram approach with an improved firstharmonic dynamic modelling to provide a couple of differential equations capable of accounting for the amplitude-dependence effects arising under large-signal operation. On this basis, first-and second-order approximate expressions are also derived, which allow a better understanding of the validity limits of previous theories on this subject. As an example of application, both the stea…
Graphene Field-Effect Transistors Employing Different Thin Oxide Films: A Comparative Study
In this work, we report on a comparison among graphene field-effect transistors (GFETs) employing different dielectrics as gate layers to evaluate their microwave response. In particular, aluminum oxide (Al$_{2}$O$_{3}$), titanium oxide (TiO$_{2}$), and hafnium oxide (HfO$_{2}$) have been tested. GFETs have been fabricated on a single chip and a statistical analysis has been performed on a set of 24 devices for each type of oxide. Direct current and microwave measurements have been carried out on such GFETs and short circuit current gain and maximum available gain have been chosen as quality factors to evaluate their microwave performance. Our results show that all of the devices belonging …
On the Theoretical Limits of Noise-Gain-Mismatch Tradeoff in the Design of Multi-Stage Cascaded Transistor Amplifiers
The problem of evaluating the limit performances of cascaded single-ended multi-stage transistor amplifiers is addressed. In particular, a theoretically rigorous approach is proposed for the determination of a family of optimal design curves (ODC's) which express the best (maximum optimal) noise-gain tradeoff that can be achieved - at each operating frequency - when a simultaneous constraint on amplifier input VSWR is accounted for.
Investigation on Metal–Oxide Graphene Field-Effect Transistors With Clamped Geometries
In this work, we report on the design, fabrication and characterization of Metal-Oxide Graphene Field-effect Transistors (MOGFETs) exploiting novel clamped gate geometries aimed at enhancing the device transconductance. The fabricated devices employ clamped metal contacts also for source and drain, as well as an optimized graphene meandered pattern for source contacting, in order to reduce parasitic resistance. Our experimental results demonstrate that MOGFETs with the proposed structure show improved high frequency performance, in terms of maximum available gain and transition frequency values, as a consequence of the higher equivalent transconductance obtained.
Computationally efficient dynamical analysis of optically driven injection-locked GaAs FET oscillators
A computer-aided simulation technique for the dynamical analysis of a class of GaAs FET optically-driven injection-locked oscillators (ODILO's) is presented. By combining a measurement-derived nonlinear model of the illuminated transistor with a phasor-domain analysis method, a first-approximation - but phenomenologically complete - differential model of the synchronized oscillator is derived. Since amplitude and phase of waveform evolutions are directly addressed and evaluated in a stroboscopic-time scale, the calculation of the transient response to modulated input signals can be done in a more user-friendly and computationally efficient manner than possible through conventional time-doma…
Radio frequency shielding of thin aluminized plastic filters investigated for the ATHENA X-IFU detector
Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. The X-ray Integral Field Unit (X-IFU) is one of the two detectors of the ATHENA astrophysics space mission approved by ESA in the Cosmic Vision 2015-2025 Science Programme. The X-IFU consists of a large array of transition edge sensors (TES) micro-calorimeters covering a field of view of 5' diameter, sensitive in the energy range 0.2-12 keV, and providing a spectral resolution…
On the dynamical stability of negative conductance free running oscillators
For a class of weakly nonlinear autonomous systems exhibiting both resistive and reactive nonlinearities, asymptotic orbital stability is investigated through a new narrow-band differential approach. The main result is the derivation of the exact characteristic polynomial associated with the local dynamics of the amplitude and phase of the free-running oscillation to be tested. For an nth-order circuit, (n - 1) necessary and sufficient stability conditions are then obtained, in an analytical explicit form suitable for computer implementation, by resorting to conventional Hurwitz test algorithms. A comparison with other differential stability criteria available in the literature is also carr…
A DRO-based X-band injection-locked amplifier without input non-reciprocal elements
Conventional design of injection-locked amplifiers (ILA's) implies the use of a non-reciprocal (ferrite, usually) element for separating the input signal from the synchronized output signal. In this paper a novel topological structure is proposed which permitted the realization of a wide-band, transmission-type, ILA with no need for separating input-port isolator or preamplifier. The prototype, realized in HMIC technology, while intended only as demonstrator of the newly proposed approach in the design of ILA's, shows quite satisfactory performances at X-band, with a simple, compact and low-cost structure.
On the optimal design of multi-stage cascaded transistor amplifiers with noise, gain and mismatch constraints
The problem of evaluating the optimal performances of cascaded, unbalanced, multi-stage transistor amplifiers is addressed. In particular, a theoretically rigorous approach is proposed for the determination of a family of Optimal Design Curves (ODC's) which express the best noise-gain tradeoff that can be achieved - at each frequency and device operating condition - when a simultaneous constraint on amplifier input VSWR is accounted for. Such curves can be used as a more meaningful starting point in practical amplifier design in place of the approximate calculations so far employed for target performance or optimization goals determination.
Employing Microwave Graphene Field Effect Transistors for Infrared Radiation Detection
In this work, we investigate the possibility of employing graphene field effect transistors, specifically designed for microwave applications, as infrared detectors for telecom applications. Our devices have been fabricated on a sapphire substrate employing CVD-grown transferred graphene. The roles of both the gate dielectric and the DC bias conditions have been evaluated in order to maximize the infrared generated signal through an experimental investigation of the signal-to-noise ratio dependence on the transistor operating point.
Subharmonic phase-lock criteria for a class of weakly non-linear high-order oscillators
Subharmonic frequency entrainment of high-order weakly non-linear oscillators is investigated. For the class of circuits considered, equations are first derived which provide the first approximation values for the amplitudes and phases of the two main spectral components of the steady-state waveform. Necessary and sufficient stability criteria are then derived in explicit from. The example worked out (a negative conductance double-tuned oscillator) shows the efficiency and ease of use of the proposed method.