Jens Vidkjær

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.

Analysis and design of wide-band SiGe HBT active mixers

The frequency response of SiGe HBT active mixers based on the Gilbert cell topology is analyzed theoretically. The time-varying operation of the active mixer is taken into account by applying conversion matrix analysis. The main bandwidth-limiting mechanisms experienced in SiGe HBT active mixers performing frequency conversion of wide-band signals is discussed. The analysis is verified by computer simulations using a realistic high-frequency large-signal SiGe HBT model. An active mixer design based on the Gilbert cell topology modified for wide-band operation using emitter degenerated transconductance stage and shunt feedback load stage is discussed. Experimental results are given for an active mixer implemented in a 0.8-/spl mu/m 35-GHz f/sub T/ SiGe HBT BiCMOS process.

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.

Large-Signal Modeling of High-Speed InP DHBTs using Electromagnetic Simulation Based De-embedding

We report on a consistent large-signal and small-signal modeling and parameter extraction method for high-speed InP DHBT valid to 110 GHz. Electromagnetic simulation is applied to predict the embedded network model caused by pad parasitics. Applying direct parameter extraction on the de-embedded device response leads to accurate small-signal model description of the InP DHBT. We have solved the problem of consistent transit time modeling by a two step process. A parameter extraction approach is described for the Agilent ADS2004A HBT model, which assures consistency between large-signal and bias-dependent small-signal modeling

Instabilities in RF-power amplifiers caused by a self-oscillation in the transistor bias network

This paper describes a self-oscillation in the bias network of an amplifier which is commonly used for the output stage in mobile transmitters. It is demonstrated how some often observed spurious oscillations may be related to the self-oscillation and a method for stabilizing the amplifier is derived and discussed.

Development of an airborne ice sounding radar front-end

This paper describes the design of an airborne P-band ice sounding radar. The ice sounder design features a microstrip antenna array with a relative operating bandwidth of 20%, compact RF components, a high efficiency high-power LDMOS power amplifier with >60% power-added efficiency across a relative bandwidth of 20% at a center frequency of 435 MHz, and a digital signal generation and acquisition unit. Furthermore, we demonstrate broadband performance of our left-handed/right-handed out-of-phase power dividers. In 2008 the first data acquisition campaign will take place in Greenland.

A describing function approach to bipolar RF-power amplifier simulation

A method for fast and accurate computations of the primary performance parameters such as gain, efficiency, output power, and bandwidth in class-C biased RF-power amplifier stages is presented. The method is based on a describing function characterization of the RF-power transistor where the terminal currents are assumed sinusoidal. The approximation comprises both the input and output properties of the transistor simultaneously and includes the effects of base widening, current saturation, and the most significant thermal dependencies. The method is verified through a series of experiments.

A Novel HBT Frequency Doubler Design for Millimeter-Wave Applications

In this paper we present a novel HBT frequency doubler design for millimeter-wave application. HBT frequency doubler theory is described which leads to accurate design equations for improved performance. The developed theory shows that a substantial improvement in the HBT frequency doubler operation can be achieved using a novel second harmonic feedback network. Preliminary measurements on a frequency doubler implemented in a high-speed InP DHBT technology demonstrates an increase in the maximum output power from -14 dBm to -11.5 dBm at an input frequency of 31.4 GHz due to the presence of the second harmonic feedback network. We demonstrate here that the 3 dB improvement in performance is directly due to the feedback mechanism

POLARIS: ESA's airborne ice sounding radar front-end design, performance assessment and first results

This paper addresses the design, implementation and experimental performance assessment of the RF front-end of an airborne P-band ice sounding radar. The ice sounder design comprises commercial-of-the-shelf modules and newly purpose-built components at a centre frequency of 435 MHz with 20% relative bandwidth. The transmitter uses two amplifiers combined in parallel to generate more than ≫128 W peak power, with system ≫60% PAE and 47dB in-band to out-of-band signal ratio. The four channel receiver features digitally controlled variable gain to achieve more than 100dB dynamic range, 2.4dB noise figure, 160 ns receiver recovery time and −46dBc 3rd order IMD products. The system comprises also, a digital front-end, a digital signal generator, a microstrip antenna array and a control unit. All the subsystems were integrated, certified and functionally tested, and in May 2008 a successful proof-of-concept campaign was organized in Greenland. The system detected the bedrock under 3 km of ice, and internal layers were mapped up to 1.3 km.

Design and performance assessment of an airborne ice sounding radar front-end

The paper describes the design and experimental performance assessment of the RF front-end of an airborne P-band ice sounding radar. The ice sounder design features newly developed components at a centre frequency of 435 MHz, such as, antenna 20% bandwidth at RL < 13 dB, compact high power in-phase and out-of-phase power dividers with a relative bandwidth of 20% and more than 75 W CW power handling, high power SPDT PIN switch with 90 W CW power handling and a 70 W CW high efficiency LDMOS power amplifier with >60% power-added efficiency. The system comprises also a digital signal generator, a digital front-end and a control unit. The system was functionally tested in March 2008 and had a first successful proof-of-concept campaign in Greenland in May 2008.