Minimum Phase noise of an LC oscillator: Determination of the optimal operating point of the active part

International audienceIn this paper, we describe an original method for determining the optimal operating point of the active part (transistor) of an LC oscillator leading to the minimum phase noise for given specifications in terms of power consumption, oscillation frequency and forgiven devices (i.e.,transistor and resonator). The key point of the proposed method is based on the use of a proper LC oscillator architecture providing a fixed loaded quality factor for different operating points of the active part within the oscillator. The feedback network of this architecture is made of an LC resonator with coupling transformers. In these conditions, we show that it is possible to easily change the operating point of the amplifier, through the determination of the turns ratio of those transformers, and observe its effect on phase noise without modifying the loaded quality factor of the resonator. The optimal operating point for minimum phase noise is then extracted from nonlinear simulations. Once this optimal behavior of the active part is known and by associating the previous LC resonator, a design of an LC oscillator or VCO with an optimal phase noise becomes possible. The conclusions of the presented simulation results have been widely used to design and implement a fully integrated LC differential VCO on a 0.35µm BiCMOS SiGe process

2.4 GHz antenna array using vector modulator based active phase shifters for beamforming

International audienceThis study presents the analysis and the experimental results of a 2.4 GHz antenna array using vector modulators working as active phase shifters for beamforming. With the use of such an active phase shifter, a continuously controlled 360° phase shifting range can be achieved leading to an efficient beamforming architecture. To show the robustness of this system, a theoretical analysis is first performed in order to quantify the impact of vector modulators I/Q mismatch on the obtained gains and phase shifts. In the same way, the impact of the vector modulators noisy command voltages is also quantified by system simulations. The experimental results of the 2.4 GHz vector modulators show a maximum relative gain error close to 2.5% and an absolute phase error less than 3°. The measured 1 dB output compression point is -6 dBm. Measurements of the prototype including an array of four 'patch' antennas controlled by the vector modulators were also performed in an anechoic chamber. The results show good agreement between measured and theoretical radiation patterns

A 2.4 GHz active phase shifter architecture for smart antennas control

International audienceThis paper aims at developing the bases of a smart radio-communication prototype, able to modify the radiation patterns, both on emission and reception, according to the needs of the communication. Smart antenna is a well-known concept, allowing to increase the quality of the transmission and spectral efficiency. To control the radiation patterns, algorithms used in smart antenna techniques require precise amplitudes and phases generation. In this paper, vector modulators working as active phase shifters will be used in order to synthesize such amplitudes and phases. A theoretical analysis will be performed in order to quantify the impact of vector modulators mismatches on the synthesized amplitudes and phases. Furthermore, measurements of radiation patterns generated by a prototype at 2.4 GHz will be presented

Analysis of the Frequency Locking Region of Coupled Oscillators Applied to 1-D Antenna Arrays

International audienceDuring the past decade, coupled oscillators have shown their efficiency as simple methods for phase control in microwave antenna arrays, and hence as alternatives to conventional electronic beam steering methods. In this paper, a new writing of the nonlinear equations proposed by R. York to describe the oscillators' locked states is presented. This has allowed the elaboration of a CAD tool which provides, in a considerably short simulation time, the frequency locking region of the coupled oscillators. This region is plotted versus the oscillators' tunings referred to the resonant frequency of the coupling circuit. A prototype circuit consisting of a five oscillators array is currently under test to validate the theory

Commande d'un réseau d'antennes actives par couplage d'oscillateurs

National audienceDans les domaines des radiocommunications, le contrôle conjoint de l'orientation et de la formation des diagrammes de rayonnement augmente considérablement la qualité de la communication. En effet, des points clés tels que la répartition de la puissance émise et le rapport Signal/Bruit sont améliorés. Cette commande de l'orientation est réalisée en contrôlant la phase injectée sur chacun des éléments rayonnants qui constitue le réseau. Une des techniques consiste à coupler des oscillateurs entre eux, et ce papier présente la conception d'un prototype ainsi que les résultats expérimentaux qui valident un outil de CAO développé au sein de notre laboratoire

Analysis and Design of an Array of Two Differential Oscillators Coupled Through a Resistive Network

International audienceThis paper considers the analysis and the design of an array of two NMOS differential oscillators coupled through a resistor. A new writing of the nonlinear equations proposed by R. York to describe the oscillators' locked states but limited for the specific case of a resistive coupling is presented. The new system permits the calculation of the free-running frequencies of the oscillators when a specific phase shift is desired. This has led to the modeling of the two coupled NMOS differential oscillators as two coupled differential Van der Pol oscillators, with a resistive coupling network. A good agreement between the circuit, the model and the theory was found, giving some design considerations for a network of two differential oscillators coupled through one resistor

Conception de VCOs 15 GHz à très faible bruit de phase intégrés sur technologie BiCMOS SiGe 0,25μm

National audienceCe papier présente les résultats issus de l'étude de deux topologies d'oscillateurs contrôlés en tension entièrement intégrés sur une technologie BiCMOS SiGe:C 0,25μm, développée par NXP Semiconductors (QUBiC4X). La principale caractéristique analysée porte sur les performances en terme de bruit de phase. Les topologies retenues sont des architectures reconnues comme étant parmi les plus performantes dans les bandes L ou S. Il nous a donc semblé intéressant d'évaluer leurs performances dans la bande Ku pour laquelle les technologies III-V sont généralement utilisées

Design and Implementation of A 6-GHz Array of Four Differential VCOs Coupled Through a Resistive Network

International audienceThis paper presents the design and the implementation of a fully monolithic coupled-oscillator array, operating at 6 GHz with close to zero coupling phase, in 0.25 μm BICMOS SiGe process. This array is made of four LC-NMOS differential VCOs coupled through a resistor. The single LC-NMOS VCO structure is designed and optimized in terms of phase noise with a graphical optimization approach while satisfying design constraints. At 2.5 V power supply voltage, and a power dissipation of only 125 mW, the coupled oscillators array features a simulated phase noise of -127.3 dBc/Hz at 1 MHz frequency offset from a 6 GHz carrier, giving a simulated phase progression that was continuously variable over the range -64° < Δphi <64 ° and -116° < Δphi < 116°. This constant phase progression can be established by slightly detuning the peripheral array elements, while maintaining mutual synchronization

Modeling and characterization of oscillator circuits by Van Der Pol model using parameter estimation

International audienceIn this paper, we present a new method for the modeling and characterization of oscillator circuit with a Van Der Pol (VDP) model using parameter identification. We also discussed and investigated the problem of estimation in nonlinear system based on time domain data. The approach is based on an appropriate state space representation of Van der Pol oscillator that allows an optimal parameter estimation. Using sampled output voltage signal, model parameters are obtained by an iterative identification algorithm based on Output Error method. Normalization issues are fixed by an appropriate transformation allowing a quickly global minimum search. Finally, the proposed estimation method is tested and validated using simulation data from a 1 GHz oscillator circuit in GaAs technology

Conception et implémentation d'un réseau composé de quatre VCOs couplés oscillant à 6 GHz

National audienceCe papier décrit la conception et l'implémentation d'un réseau d'oscillateurs couplés totalement intégré en technologie BiCMOS SiGe 0,25 μm. Ce réseau est constitué de quatre VCOs NMOS différentiels couplés au moyen d'une résistance. Pour une tension d'alimentation de 2.5V, une puissance consommée de 125 mW à une fréquence d'oscillation de 6 GHz, le réseau présente un bruit de phase de -127dBc/Hz à 1MHz de la porteuse et un déphasage qui varie de façon continue entre -64° et +64 ° et entre -116° et +116°