Showing papers by "Giorgio Vannini published in 2007"

Design of Low Phase Noise Dielectric Resonator Oscillators with GaInP HBT devices exploiting a Non-Linear Noise Model

Abstract: This paper presents the design, implementation and characterization of two dielectric resonator oscillators (DRO) at 7.61 GHz. The circuits consist of a negative resistance monolithic bipole coupled in a series feedback configuration with a ceramic dielectric resonator. The two circuits exploit different sizes for the active device. The adopted monolithic process is a commercially available GalnP HBT with very good low frequency noise performance. The measured phase noise performance of the two circuits are -120 dBc/Hz and -135 dBc/Hz @ 10 kHz from the carrier respectively, which represent to the authors' knowledge state-of-the-art performance for this technology and resonator type. These excellent results have been obtained by means of a proper large signal design technique and exploiting the predictive capability of a non-linear cyclostationary noise model, which proves its excellent predictive capability for these very low phase noise levels.

Scalable equivalent circuit PHEMT modelling using an EM-based parasitic network description

Abstract: Electron device modelling requires the accurate identification of a suitable parasitic network accounting for the passive structures which connect the intrinsic electron device to the external world In conventional approaches, the parasitic network is described by a proper topology of lumped elements As an alternative, a distributed description of the parasitic network can be conveniently adopted In particular, the latter solution is the better choice when dealing with device scaling and very high operating frequencies In this paper the parasitic network is described by means of a suitable distributed network identified through electromagnetic simulations of the device layout It is shown how the adoption of a distributed instead of a lumped description leads to a more accurate equivalent-circuit-based electron device model The good scalability properties of the approach are also presented through experimental results

Electron Device Model Parameter Identification Through Large-Signal-Predictive Small-Signal-Based Error Functions

Abstract: Empirical electron device models based on lumped equivalent circuits are usually identified through nonlinear optimization procedures, which are based on the best fitting between the extrinsic model behavior and measurements carried out under multibias static and small-signal excitations. In this paper, a new error function is proposed for equivalent circuit model parameter optimization. Although still being defined through standard static and small-signal measurement data, the new error function can be configured so as to obtain models tailored to specific large-signal applications. Experimental results, which confirm the validity of the proposed identification approach, are provided for a GaAs microwave pseudomorphic HEMT model aimed at the design of highly linear power amplifiers.

Hybrid High Power Amplifiers for L-Band Space Application

Abstract: This paper describes the design and implementation of 2 hybrid high power amplifiers at L band for a space application. Indeed, the amplifiers represent prototype test vehicles for a larger hybrid amplifier to be used as the final power stage in the transmitting chain of a T/R module of an L-band SAR antenna for earth observation. The amplifiers described in this paper exploit a discrete bar of a commercial 0.35 mum pHEMT process as active device. The first amplifier, featuring a single discrete device, delivers 12 Watts with 56.5% PAE and 12.3 dB gain at 2 dB compression. The second amplifier exploits 4 discrete pHEMT bars using input/output microstrip splitter/combiner and lumped wire bonding/ceramic MIM capacitor output matching networks. It delivers 42 watts with 50% PAE and 13 dB gain at 2.5 dB compression. Since it is a space application, these performances have been achieved with the required de-rating on break-down voltages, current densities and operating channel temperature. The latter has been evaluated by means of a 3-D device model implemented in the framework of a finite differences numerical thermal simulator. In spite of the constraints due to space de-rating rules, the obtained output power densities are 1 W/mm and 0.875 W/mm for the single-discrete and the 4-discrete amplifiers, respectively, which represent a value very close to the state of the art for pHEMT processes.

Empirical Investigation on Time Dispersion of Microwave Electron Device Characteristics under Nonlinear Dynamic Operating Conditions

Abstract: In this paper, a measurement set-up is described for the investigation on microwave electron device characteristic time dispersion (or "walkout"), occurring in nonlinear dynamic operation. The stress procedure is carried out by applying a large-amplitude excitation signal at moderately high frequency at either the input or the output port of the device. The corresponding forward or reverse mode of operation can be easily configured by means of a switch manipulation, exploiting the symmetrical, dual-channel architecture of the system. The walkout of the device characteristics, which can be either a bipolar-or a field effect-transistor, can be observed both at the end of the stress test and in real-time during the test execution.

Low-frequency dynamic drain current modeling in AlGaN-GaN HEMTs

Abstract: Low-frequency dispersive effects in AlGaN/GaN HEMTs are here modeled above their cutoff frequencies by adopting a modeling approach developed for GaAs PHEMTs. To this aim, a new identification procedure is proposed, which allows to obtain very accurate predictions of the pulsed drain currents, even in the presence of strong kink effects in the DC characteristics. In addition, a dedicated algorithm of data extrapolation is used, in order to make the model more computationally efficient.

Empirical Investigation onTimeDispersion ofMicrowave Electron Device Characteristics underNonlinear DynamicOperating Conditions

Abstract: Inthis paper, ameasurement set-up isdescribedfor the investigation onmicrowave electron device characteristic time dispersion (or"walkout"), occurring innonlinear dynamic operation. Thestress procedure iscarried outbyapplying alarge- amplitude excitation signal atmoderately high frequency ateither theinput ortheoutput portofthedevice. Thecorrespondingforward orreverse modeofoperation canbeeasily configured bymeansofa switch manipulation, exploiting thesymmetrical, dual-channel architecture ofthesystem. Thewalkout ofthedevice characteristics, whichcanbeeither abipolar- orafield effect-transistor, canbe observed both attheendofthestress test andinreal-time during the test execution.