Torsten Djurhuus

Oscillator Phase Noise: A Geometrical Approach

We construct a coordinate-independent description of oscillator linear response through a decomposition scheme derived independently of any Floquet theoretic results. Trading matrix algebra for a simpler graphical methodology, the text will present the reader with an opportunity to gain an intuitive understanding of the well-known phase noise macromodel. The topics discussed in this paper include the following: orthogonal decompositions, AM-PM conversion, and nonhyperbolic oscillator noise response.

Nonlinear analysis of a cross-coupled quadrature harmonic oscillator

The dynamic equations governing the cross-coupled quadrature harmonic oscillator are derived assuming quasi-sinusoidal operation. This allows for an investigation of the previously reported tradeoff between close-to-carrier phase noise and quadrature precision. The results explain how nonlinearity in the coupling transconductances, in conjunction with a finite amplitude relaxation time and de-tuning of the individual oscillators, cause close-to-carrier AM-to-PM noise conversion. A discussion is presented of how the theoretic results translate into design rules for quadrature oscillator ICs. SPECTRE RF simulations verify the developed theory.

Theory of Injection-Locked Oscillator Phase Noise

The paper describes the development of a model for the calculation of noise-driven phase response of an injection-locked oscillator perturbed by Gaussian white sources. Being based on the state space formalism the framework is unified encompassing all circuit topologies and methods of unilateral coupling. We thus avoid reverting to the kind of simplified block-diagram description that one finds in previously published works on the topic and our approach furthermore allows for all the main results and model parameters to be derived numerically based on the netlist description of the circuit. To our knowledge this constitutes the first attempt at an ILO phase-noise description not relying on block diagrams or other such phenomenological modelling strategies.

Numerical analysis of stochastic resonance in a bistable circuit.

Summary The paper documents the construction of a novel nonlinear model of a noise-driven, multi-dimensional, bistable circuit employing stochastic resonance. Simulations are performed in order to characterize the various relevant device performance measures and their sensitivity to parameter values. The numerical results are considered in the context of nonlinear energy harvesting, and it is explained how the developed simulation tools could prove useful for the development of such devices. The topic of reduced-order modelling is discussed, and it is shown that this approach leads to incorrect results. Copyright

A Generalized Model of Noise Driven Circuits with Application to Stochastic Resonance

The paper presents a novel simulation tool which can be used for numerical analysis of nonlinear circuits and systems forced by strong noise sources and perturbed by weak periodic signals. The methodology, which is based on linear-response theory, is universal in scope and can be applied to all topologies without restraints on the dimensionality of the structure or the size of the parameter set. The main purpose of the developed algorithm is to enable efficient numerical analysis of nonlinear noise-driven circuits and systems with emphasis on stochastic resonance. Currently, computationally expensive Monte-Carlo methods often constitute the only other option available for simulation in these cases. Linear-response models have previously been developed for the 1-dimensional canonical scenario but it will be shown that these specialized formulations can not be directly adapted to higher dimensional systems. Compared to a simple Monte-Carlo integration scheme, the computational efficiency following from the proposed algorithm is improved by several orders of magnitude.

Physical based Schottky barrier diode modeling for THz applications

In this work, a physical Schottky barrier diode model is presented. The model is based on physical parameters such as anode area, Ohmic contact area, doping profile from epitaxial (EPI) and substrate (SUB) layers, layer thicknesses, barrier height, specific contact resistance, and device temperature. The effects of barrier height lowering, nonlinear resistance from the EPI layer, and hot electron noise are all included for accurate characterization of the Schottky diode. To verify the diode model, measured I-V and C-V characteristics are compared with the simulation results. Due to the lack of measurement data for noise behaviors, simulated noise temperature is compared with the experimental data found from the open literature.

Wideband monolithic microwave integrated circuit frequency converters with GaAs mHEMT technology

We present monolithic microwave integrated circuit (MMIC) frequency converter, which can be used for up and down conversion, due to the large RF and IF port bandwidth. The MMIC converters are based on commercially available GaAs mHEMT technology and are comprised of a Gilbert mixer cell core, baluns and combiners. Single ended and balanced configurations DC and AC coupled have been investigated. The instantaneous 3 dB bandwidth at both the RF and the IF port of the frequency converters is /spl sim/ 20 GHz with excellent amplitude and phase linearity. The predicted conversion gain is around 10 dB. Simulated results are supported by experimental characterization. Good agreement is found between simulations and experiment is found after adjustment of technology parameters.

Millimeter-Wave Integrated Circuit Design for Wireless and Radar Applications

This paper describes a quadrature voltage-controlled oscillator (QVCO), frequency doubler, and sub-harmonic mixer (SHM) for a millimeter-wave (mm-wave) front-end implemented in a high-speed InP DHBT technology. The QVCO exhibits large tuning range from 38 to 47.8 GHz with an output power around -15 dBm. The frequency doubler is based on a novel feedback network and demonstrates an output power of -11.5 dBm at an input frequency of 31.4 GHz. The SHM shows a maximum conversion gain at 45 GHz of 10.3 dB with an LO power of only 0 dBm. The mixer is broad-band with more than 7 dB conversion gain from 40-50 GHz. To the authors knowledge the QVCO, frequency doubler, and SHM presents the first mm-wave implementations of these circuits in InP DHBT technology

Ultra-broadband Nonlinear Microwave Monolithic Integrated Circuits in SiGe, GaAs and InP

Analog MMIC circuits with ultra-wideband operation are discussed in view of their frequency limitation and different circuit topologies. Results for designed and fabricated frequency converters in SiGe, GaAs, and InP technologies are presented in the paper. RF type circuit topologies exhibit a flat conversion gain with a 3 dB bandwidth of 10 GHz for SiGe and in excess of 20 GHz for GaAs processes. The concurrent LO-IF isolation is better than -25 dB, without including the improvement due to the combiner circuit. The converter circuits exhibit similar instantaneous bandwidth at IF and RF ports of >7.5 GHz and >10 GHz for SiGe BiCMOS and GaAs MMIC, respectively. Analysis of the frequency behaviour of frequency converting devices is presented for improved mixer design. Millimeter-wave front-end components for advanced microwave imaging and communications purposes have also been demonstrated. Analysis techniques and novel feedback schemes show improvement to the traditional circuit design. Subharmonic mixer measurements at 50 GHz RF signal agree very well with simulations, which manifests the broadband operating properties of these circuits.