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The utility of the ([La.sub.0.67],[Sr.sub.0.33])Mn[O.sub.3] (LSMO) ferromagnetic thin-film materials as microwave tunable enabling technology is discussed. Interdigited capacitor structures are formed on the top of LSMO materials that have displayed a wide tunable resistance with low bias.

This paper describes a novel technique to model the transient, steady state, and phase-noise behavior of microwave oscillators in the hardware description language VHDL-AMS. It can be applied to a large variety of both single-ended and differential voltage-controlled oscillators independently of their architecture. The model is derived from data obtained by a more complex circuit-level model. As opposed to input-output models of a microwave two-port, where the output follows more or less the applied input signal, the output of an oscillator depends mainly on its former state. Thus, approaches developed for input-output modeling cannot be applied. The technique proposed in this paper approximates the dynamics of the oscillator by a system of two first-order ordinary differential equations. The oscillator's nonlinear characteristics are reproduced by a multilayer perceptron neural network. In addition to reproducing the oscillator's large-signal waveform, its phase-noise characteristic in the 1/[f.sup.2] and flat region is emulated. Finally, a VHDL-AMS implementation of the model is proposed and associated issues are addressed. The suitability of the model for oscillators at millimeter waves is demonstrated by examples working at 60 GHz. Index Terms--Behavioral modeling, multilayer perceptron (MLP), nonlinear, VHDL-AMS, voltage-controlled oscillator (VCO).

The integration of K-band (20-40 GHz) full wavelength square wire- and slot-loop antennas on low resistivity (11-70 [OMEGA]cm) silicon substrates is addressed. By the use of polymer or silicon oxide/nitride membranes to support the slot or wire loop over micromachined trenches the efficiency of the antennas is enhanced while the majority of the bulk silicon within the apterture of the antenna is preserved to enable the integration of active devices. A 3.6 x 3.6 [mm.sup.2] large slot loop antenna chip with 200 [micro]m micromachined trench width yields 1.5 dBi gain at 29.5 GHz, while 1.0 dBi gain,is obtained at 24 GHz for a wire loop antenna on a 4.5 x 4.5 [mm.sup.2] large chip with 360 [micro]m wide trenches. Index Terms--Loop antennas, micromachining, silicon, slot antennas.

The kinetic of dielectric charging in capacitive RF microelectromechanical systems (RF MEMS) is investigated using an original method of stress and monitoring. This effect is investigated through a new parameter: the shift rate of the actuation voltages. We demonstrate that this lifetime parameter has to be considered as a function of the applied voltage normalized by the contact quality between the bridge and the dielectric. We also demonstrate that this phenomenon is related to Frenkel-Poole conduction, which takes place into the dielectric. We finally propose a model that describes the dielectric charging kinetic in capacitive RF MEMS. This model is used to extract a figure-of-merit of capacitive switches lifetime. Index Terms--Dielectric charging, figure-of-merit (FOM), Frenkel-Poole conduction, reliability, RF microclectromechanical systems (RF MEMS).

Telecommunication equipment manufacturers face their biggest challenge in improving phase-noise performance of microwave sources and the design of sapphire resonator oscillators for metrology. The electrical and noise performances of a 0.8 Mu silicone germanium transistor (SiGe) optimized for design of low phase-noise circuits and the design of a low phase-noise C band sapphire resonator oscillator are reported.

An original technique, based on a full noise characterization, to discriminate the low-frequency noise sources in modern sub-micron bipolar devices, is presented. It is demonstrated that the correlation resistance can reveal the presence of excess noise sources located in the extrinsic base region of the transistor.

An experimental design for the direct full low-frequency noise characterization of Si/SiGe heterojunction bipolar transistors is presented. This design is based on current/voltage conversion through transimpedance amplifiers.

The burn-in effect in microwave GaInP/GaAs heterojunction bipolar transistors for various dc current stresses is studied. Results show that the burn-in effect is caused by reduced surface recombination at the extrinsic base surface around the emitter parameter. Defects at the passivation/semiconductor interface are also associated with the recombination centers and that these centers are passivated by hydrogen atoms released from C-H complexes under stress. In addition, it is shown the reliability and electronic performance of ledge passivation technology is better compared to SiN passivation technology.

This paper presents an extensive electrical characterization of Si/SiGe/Si heterojunction bipolar transistors (HBT's) grown by molecular beam epitaxy (MBE). These devices are designed for microwave and millimeter-wave applications since they present a maximum oscillation frequency in the 40-GHz range. The processing technology, featuring a high-quality oxide passivation, results in ideal Gummel plots and an input noise corner frequency of 250 Hz at lowest. A dielectric resonator oscillator (DRO) at 4.7 GHz has, therefore, been realized. The measured phase-noise level of this oscillator is below -135 dBc/Hz at 10kHz offset frequency, which is at least 10 dB better than the best FET or HBT state-of-the-art DRO's. Index Terms - Dielectric resonator oscillators, Ge-Si alloys, heterojunction bipolar transistors, low-frequency noise, microwave oscillators, noise, 1/f noise, phase noise, SiGe alloys, silicon.

The conversion process of the low frequency noise into phase noise in field-effect transistors (FET) oscillators is investigated. First, an evaluation of the baseband noise contribution to the oscillator phase noise is provided from the analysis of the baseband noise and the frequency noise spectra. A distinction is made within the different components of the low frequency noise contributions to close-in carrier phase noise. Next, the frequency noise of the oscillator circuit is analyzed in terms of the FET's low frequency noise multiplied by the oscillator's pushing factor. Though this product usually provides a good evaluation of the phase noise, experimental results presented here show the inaccuracy of this method at particular gate bias voltages where the pushing factor decreases to zero. To account for these observations, a new nonlinear FET model involving at least two noise sources distributed along the channel is proposed.

A new noise model, developed for microwave heterojunction bipolar transistors (HBT), is based on pi-network. The noise behavior of Si SiGe HBT at different bias voltages is described very well using this model. Minimum noise figure, for a device working at a low injection level, increases due to current leakage at collector-base junction. Results of the study conducted for ideal and nonideal junctions are discussed.

The noise behavior of pseudomorphic high electron mobility transistors (HEMT) are compared to the noise properties of metal semiconductor field effect transistors and GaAlAs/GaAs HEMTs during operation at low and microwave frequencies between 10Hz-150MHz and 4-18GHz, respectively. The devices are shown to possess the unusual characteristic of having good microwave and low frequency noise performance.

The influence of the algorithm used for noise parameter fitting on the accuracy of the microwave noise parameter measurements is investigated. Five different commonly used algorithms are compared by statistical analysis including instrument accuracy specifications. Some of these algorithms are found to be more efficient in terms of available accuracy and computer-time. The best predicted available accuracies reported between 4 and 20 GHz for each noise parameter compare well with observed accuracies on noise parameter measurements performed with a dedicated test-set on a noise standard made of a passive two-port. The accuracy on minimum noise figure is found to be 0.1 dB maximum.

This paper addresses the influence of cooling on the phase noise of HEMT and MESFET oscillators. The initial measurements of the device dc characteristics and low frequency noise (0.1 kHz-100 kHz) under cooling give indications on the suitability of a given device for use in low phase noise cooled oscillators. Cooled pseudomorphic AlGaAs/GaInAs/GaAs HEMT's (PHEMT's) turn out to be particularly well-suited as they are free of collapse and they are free of g-r noise in the frequency range of interest. We report on 4 GHz oscillators operated at 110 K and featuring a phase noise below - 100 dBc/Hz at 10 kHz from the carrier in spite of a very modest loaded Q (160). It is suggested that high temperature superconductor resonators could greatly enhance the spectral purity of PHEMT's oscillators.