M. Prigent

Amplitude and phase noise of magnetic tunnel junction oscillators

The microwave emission linewidth of spin transfer torque nano-oscillators is closely related to their phase and amplitude noise that can be extracted from the magnetoresistive voltage signal V(t) using single shot time domain techniques. Here we report on phase and amplitude noise studies for MgO based magnetic tunnel junction oscillators. The analysis of the power spectral densities allows one to separate the linear and nonlinear contributions to the phase noise, the nonlinear contribution being due to the coupling between phase and amplitude. The coupling strength as well as the amplitude relaxation rate can be directly extracted.

An efficient design method of microwave oscillator circuits for minimum phase noise

In this paper, we describe a newly developed design method of high-Q microwave oscillator circuits leading to the minimum phase noise for a given transistor and resonator. The key point of the method is the maximization of the energy stored in the resonator and its transfer to the controlling input voltage port of the transistor. The proposed method has been applied to two experimental oscillators setups with pseudomorphic high electron-mobility transistors (PHEMTs). A state of-the art phase noise of -50 dBc at 10-Hz offset from carrier with a 1/f/sup 3/ slope has been measured at room temperature with a 9.2 GHz oscillator. The efficiency of this design method and its ease of use represent, in our opinion, a real breakthrough in the field of low noise transistor oscillator circuit design.

A new approach to nonlinear analysis of noise behavior of synchronized oscillators and analog-frequency dividers

An original theory of phase noise in synchronized oscillators is outlined through the phase-locked loop (PLL) approach. The phase-noise spectrum obtained first by the analytical PLL theory and then by a simulator have been compared with very good accuracy. This new approach permits the best understanding of noise conversion in synchronized devices.

Low-Frequency Noise Measurements of Bipolar Devices Under High DC Current Density: Whether Transimpedance or Voltage Amplifiers

Different setups for the measurement of the low-frequency noise of semiconductor devices have been proposed in the literature, based on the use of either low-noise voltage amplifiers (VAs) or, more recently, transimpedance amplifiers (TAs). This paper aims to address the applicability and physical limit of each configuration, when they are applied to measure the LF noise of HBTs or diodes at moderate to high DC current densities. Extracted noise curves issued from different setups are analyzed. Noise data collected from recent low-noise technologies shows that physical limits are being systematically approached

A Methodology to Characterize the Low-Frequency Noise of InP Based Transistors

This paper describes a methodology to measure the low-frequency noise of InP-based transistors. These transistors have demonstrated transition frequencies (ft) greater than 200 GHz, generally achieved at current densities in excess of 200 kA/cm2. Depending on the DC current gain, this may represent base currents of some mA. For the first time, curves of Sib, Sic and Sibic for base currents of up to 3 mA are demonstrated, in excellent agreement with those obtained from one-port measurements. This is only possible with an accurate experimental characterisation of the small-signal parameters of the transistor, which are frequency-dependent due to self-heating.

A low power, low phase noise 10 GHz MIC oscillator

This paper presents the design and the fabrication of a compact MIC 10 GHz single-transistor oscillator. It includes a packaged SiGe HBT (Infineon BFP740F) along with a low-Q coupled line resonator and only consumes 5 mA from a 3V power supply for an output power of -6 dBm. Its phase-noise has been measured at -117 dBc/Hz @100 kHz offset. Such performance is the result of a careful modeling process. The two most challenging aspects of the design were the stability analysis of the 10 GHz oscillator in hybrid technology and phase-noise optimization.

Impact of self-heating in LF noise measurements with voltage amplifiers

Voltage Amplifiers have been used to characterize the low-frequency noise of Heterojunction Bipolar Transistors (HBTs). They generally feature not only a lower noise floor, but also have less impact on simultaneous (two-port) measurements than Transimpedance Amplifiers, when moderate to high DC current regimes are considered. However, when the Device Under Test (DUT) is characterized under these regimes, common concepts such as unilateralism and frequency-independent small-signal parameters are no longer valid due to the frequency-dependent thermal response of the DUT (self-heating). It will be shown that depending on the conditions under which the measurements are carried out, the experimental data may vary for some orders of magnitude, leading to an incorrect characterization if the effect is disregarded.

Experimental characterization of the cyclostationary low-frequency noise of microwave semiconductor devices under large signal operation

his paper presents a detailed experimental analysis of the cyclostationary properties of low-frequency (LF) noise sources of microwave bipolar devices, in order to improve the LF noise description in compact models. Such models are used to help designers on predicting circuit performances such as phase and amplitude noise in oscillators. We start by reviewing the most relevant experimental and simulation results on the subject, and then investigate the model of conductance fluctuations proposed to explain the 1/f noise of carbon resistors. This simple linear case serves as a basis for understanding the complex case of a non-linear device under large-signal periodic operation. We then present the large-signal small-signal analysis of a pumped junction, focusing on the process of converting the fundamental LF noise process, a current fluctuation, into voltage fluctuations. We show why a stationary noise model would lead to an increase of the voltage noise observed around DC when the device is pumped, while the voltage noise would decrease if a cyclostationary model was used. A great amount of experimental data is presented not only to support our analysis, but also as a mean to distinguish between the two noise processes under consideration: stationary or cyclostationary. The goal of our noise measurement technique was to maximize the difference between those two concepts. Throughout the paper, we revisit some known concepts and show how some experimental results may lead to misinterpretations.

A new experimental method to characterize cyclostationary noise models of bipolar devices

This paper presents an experimental method that can be used to determine the cyclostationary properties of the low-frequency noise of bipolar transistors and diodes. The noise is measured while the device works in nonlinear regime, pumped by a low-noise signal source. To measure the noise around carrier (as close as 1 Hz offset from the carrier), bridge circuits are used to balance the pump out. By applying the proposed method to evaluate the low-frequency noise of a SiGe transistor in open collector configuration, it is shown that the 1/f like noise of the device is entirely attributed to fluctuations of its conductance.

Méthodes de simulation du comportement dynamique des circuits non linéaires

This paper presents analysis methods of non-linear circuits. These simulators must be capable to predict the non-linear behaviour of complex circuits such as frequency analog dividers and injection locked oscillators. Based on the harmonic balance technique, this paper presents two extensions of this method. It provides complete information on the non-linear behaviour of the device. In particular, synchronization bandwidths as well as power ranges for which the circuit can be synchronized are obtained from the stability loci drawn in the parameter space. Second, a noise analysis based on the frequency conversion technique is discussed. This analysis relies upon a description of linear or non-linear noise generators by means of correlation matrices and of circuit non-linearities by their conversion matrices. Two circuits examples are given to illustrate the great interest of these simulators.RésuméCet article présente les méthodes d’analyse et de simulation non linéaires du comportement dynamique des circuits. Basé sur l’application de l’équilibrage harmonique, deux extensions sont présentées. La première permet l’analyse des circuits autonomes, synchronisés ou libres tels que les oscillateurs et diviseurs de fréquence. Elle est basée sur une recherche des bifurcations et permet le calcul non linéaire des bandes de synchronisation d’un oscillateur ou l’analyse de la stabilité globale de ce même type de circuit. La deuxième présente la simulation des caractéristiques en bruit (spectres de bruit, facteur de bruit) de ces circuits. Elle est basée sur la représentation des non-linéarités par leurs matrices de conversion et des sources de bruit par leurs matrices de corrélation. Enfin deux exemples de circuits analysés par ces méthodes sont donnés.