Electrical measurement of the junction temperature and thermal resistance of HBTs

A simple method is proposed to derive the junction temperature and the bias- and temperature-dependent thermal resistance of heterojunction bipolar transistors (HBTs) using a radio frequency (RF) signal. The method exploits the thermal dependence of the current gain of a transistor whose dissipated power is modified by applying an RF signal. The new method is used to derive the junction temperature and thermal resistance of a power HBT. The results are compared with state-of-the-art techniques

A new technique for thermal resistance measurement in power electron devices

A simple technique is proposed for the thermal resistance measurement of electron devices. The new approach is based on the standard measurements which are normally carried out for the electrical characterization of power devices, without requiring special-purpose instrumentation and/or physics-based temperature-dependent electrical device models. Experimental results, which confirm the validity of the new method, are provided

A nonlinear dynamic model for performance analysis of large-signal amplifiers in communication systems

A new nonlinear dynamic model of large-signal amplifiers based on a Volterra-like integral series expansion is described. The new Volterra-like series is specially oriented to the modeling of nonlinear communication circuits, since it is expressed in terms of dynamic deviations of the complex modulation envelope of the input signal. The proposed model represents a generalization, to nonlinear systems with memory, of the widely-used amplitude/amplitude (AM/AM) and amplitude/phase (AM/PM) conversion characteristics, which are based on the assumption of a practically memoryless behavior. A measurement procedure for the experimental characterization of the proposed model is also outlined

Implementation and performance evaluation of a broad-band power spectrum analyzer

A new technique for power spectrum analysis is introduced, theoretically evaluated, and experimentally verified with a prototype. This technique is based on the estimate of the autocorrelation function for different delays. The proposed sampling strategy is random in the time domain and equally spaced, synchronous with the signal, in the delay domain, It is shown that the estimate of the power spectral components is asymptotically unbiased, and the experimental results are also give

A nonlinear dynamic S/H-ADC device model based on a modified Volterra series: identification procedure and commercial CAD tool implementation

A nonlinear, dynamic empirical model, based on a Volterra-like approach, was previously proposed by the authors for the time-oriented characterization of sample/hold (S/H) and analog-to-digital conversion (ADC) devices. In this paper, the experimental procedure for model parameter measurement is presented, as well as techniques devoted to the implementation of the model in the framework of the main commercial CAD tools for circuit analysis and design. Examples of simulations, performed both in the time and frequency domain on the model obtained for a commercial device, are proposed, which show the model's capability of pointing out the dynamic nonlinear effects in the S/H-ADC response

A broad-band power spectrum analyzer based on twin-channel delayed sampling

This paper describes a power spectrum analyzer whose bandwidth is not limited by the mean sampling time. The procedure is based on the estimation of the spectral components of the autocorrelation function of the input signal through the simultaneous random sampling of the given input signal and its randomly “delayed copy”. The samples are therefore randomly taken in a double-dimension space, time, and delay. By using a random process in the time domain with a recursive mean previously introduced by the authors in order to avoid any bandwidth limitation due to the sampling strategy, it is shown both theoretically and through simulation that the estimate of the power spectral components is asymptotically unbiased on the unique hypothesis of a synchronized random sampling in the delay domain, i.e., the sampling delays are uniformly distributed in an interval equal to the period of the input signal. The simulation results confirm the theoretical finding

Hardware implementation of a broad-band vector spectrum analyzer based on randomized sampling

A hardware prototype of vector spectrum analyzer, which is based on a randomized sampling strategy and associated alias-free digital signal processing (DSP) algorithms, has been fully designed and implemented. The instrument exploits a couple of identical independently programmable digital data acquisition channels, whose synchronization allows to sample the input signal at instants that can be very close along the time axis (tens of picoseconds), against a maximum single-channel average throughput rate of 250 ksamples per second (kSa/s). This architecture has shown to be suitable for the accurate implementation of the randomized periodic sampling with uniform jitter on which the instrument is based. In addition, the design solutions adopted for the sampling command generators, which exploit the interaction between a digital gate signal and a phase-controlled sinusoidal wave, together with the particular analytical definition proposed for the spectral estimators, have allowed to make practically negligible the quantum time according to which the sampling instants are generated. Experimental results are provided, which validate both the alias-free spectrum analysis technique and the capability of the architecture proposed of reliably implementing the analytical benefits deriving from the randomized sampling strategy adopted

A modified Volterra series approach for nonlinear dynamic systems modeling

This paper describes a modeling approach for nonlinear dynamic systems based on a modified Volterra series; by comparing the truncation error of this series with that of the classical Volterra one, we outlined that, under the assumption of short-term nonlinear memory effects, the modified series enables a single-fold nonlinear convolution integral to be adopted also in the presence of strong nonlinearities. The measurement-based identification of the first terms of the modified Volterra series is described; experimental and simulation results which confirm the theoretical considerations are also provided

Accurate pHEMT nonlinear modeling in the presence of low-frequency dispersive effects

Low-frequency (LF) dispersive phenomena due to device self-heating and/or the presence of "traps" (i.e., surface state densities and bulk spurious energy levels) must be taken into account in the large-signal dynamic modeling of III-V field-effect transistors when accurate performance predictions are pursued, since these effects cause important deviations between direct current (dc) and dynamic drain current characteristics. In this paper, a new model for the accurate characterization of these phenomena above their cutoff frequencies is presented, which is able to fully exploit, in the identification phase, large-signal current-voltage (I-V) measurements carried out under quasi-sinusoidal regime using a recently proposed setup. Detailed experimental results for model validation under LF small- and large-signal operating conditions are provided. Furthermore, the I-V model proposed has been embedded into a microwave large-signal pseudomorphic high electron-mobility transistor (pHEMT) model in order to point out the strong influence of LF modeling on the degree of accuracy achievable under millimeter-wave nonlinear operation. Large-signal experimental validation at microwave frequencies is provided for the model proposed, by showing the excellent intermodulation distortion (IMD) predictions obtained with different loads despite the very low power level of IMD products involved. Details on the millimeter-wave IMD measurement setup are also provided. Finally, IMD measurements and simulations on a Ka-band highly linear power amplifier, designed by Ericsson using the Triquint GaAs 0.25-/spl mu/m pHEMT process, are shown for further model validation