C.J.M. Verhoeven

A high-frequency electronically tunable quadrature oscillator

An architecture composed of mutually regenerative oscillators is introduced. It has been used to design a low-noise high-frequency voltage-controlled oscillator (VCO) capable of producing two output signals in quadrature with essentially identical properties. The phase relation between the quadrature outputs is frequency dependent and extremely stable. A novel way of coupling the regenerative oscillators is suggested in order to improve the frequency stability of the coupled oscillator system. Results obtained from a test chip have verified the viability of the oscillator concept. The oscillator circuit has been realized in a medium-frequency bipolar process. The tuning range extends to 500 MHz. At an oscillation frequency of 200 MHz, measured phase noise was -121 dBc/Hz at 1-MHz distance from the carrier. >

Analysis and Design of Quadrature Oscillators

The following are some features of Analysis and Design of Quadrature Oscillators make it different from the existing literature on electronic oscillators: (1) focus on quadrature oscillators with accurate quadrature and low phase-noise, required by modern communication systems; (2) a detailed comparative study of quadrature LC and RC oscillators, including cross-coupled LC quasi-sinusoidal oscillators, cross-coupled RC relaxation oscillators, a quadrature RC oscillator-mixer, and two-integrator oscillators; (3) a thorough investigation of the effect of mismatches on the phase-error and the phase-noise; (4) the conclusion that quadrature RC oscillators can be a practical alternative to LC oscillators when area and cost should be minimized (in cross-coupled RC oscillators both the quadrature-error and phase-noise are reduced, whereas in LC oscillators the coupling increases the phase-noise.

A new low-noise 100-MHz balanced relaxation oscillator

A novel fully balanced architecture for high-frequency, low-noise relaxation oscillators is presented. Differential operation is achieved with the use of two grounded capacitors utilizing the circuit parasitics. Bypassing of the regenerative memory function in the oscillator benefits both high-speed and low-noise operation. A detailed analysis of phase noise in relaxation oscillators is performed. Results obtained from a test chip have verified the viability of the new oscillator and the developed phase-noise theory. The oscillator circuit has been realized in a medium-frequency (f/sub tau /=3 GHz) bipolar process. The tuning range extends to 150 MHz. At an oscillation frequency of 115 MHz, measured phase noise was -118 dBc/Hz at 1-MHz distance from the carrier. >

Sinusoidal and Relaxation Oscillations in Source-Coupled Multivibrators

The paper considers the differential equation describing sinusoidal and relaxation oscillations of the source-coupled multivibrator. The transition from one form of oscillations to another, when the coupling capacitor is increasing, is explained by modifications in the shape of the central branch of the isocline of horizontal tangents on the phase plane of this differential equation. The formulas for amplitude and frequency calculations in sinusoidal operation are found. The calculations of transistor switching time and period for relaxation oscillations are provided as well. The results were verified in simulations.

Orbiting Low Frequency Array for radio astronomy

Recently new and interesting science drivers have emerged for very low frequency radio astronomy from 0.3 MHz to 30 MHz. However Earth bound radio observations at these wavelengths are severely hampered by ionospheric distortions, man made interference, solar flares and even complete reflection below 10 MHz. OLFAR is Orbiting Low Frequency ARray, a project whose aim is to develop a detailed system concept for space based very low frequency large aperture radio interferometric array observing at these very long wavelengths. The OLFAR cluster could either orbit the moon, whilst sampling during the Earth-radio eclipse phase, or orbit the Earth-moon L2 point, sampling almost continuously or Earth-trailing and leading orbit. The aim of this paper is to present the technical requirements for OLFAR and first order estimates of data rates for space based radio astronomy based on the proposed scalable distributed correlator model. The OLFAR cluster will comprise of autonomous flight units, each of which is individually capable of inter satellite communication and down-link. The down-link data rate is heavily dependent on distance of the cluster from Earth and thus the deployment location of OLFAR, which are discussed.

The design of low-noise bandgap references

The noise power of bandgap references is directly related to the current consumption of the bandgap reference. This paper describes the design of low-noise bandgap references. It is shown that for an idealized bandgap reference, a fundamental noise limit exists when the limited current consumption is a constraint. A design example is given of a 1 V bipolar bandgap reference with a current consumption of 5 /spl mu/A. The output voltage is 200 mV and the mean temperature dependency is /spl ap/20 ppm/K for 0/spl deg/C to 100/spl deg/C. The output noise density equals 166 nV//spl radic/Hz.

Oscillators and Oscillator Systems

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Charge pump for optimal dynamic range filters

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The Effect of Mismatches and Delay on the Quadrature Error of a Cross-Coupled Relaxation Oscillator

A controllable charge pump is presented that is able to accurately generate a voltage larger than the supply voltage. It operates on a 3 V supply. It is intended to be used to accurately bias MOS-transistors in the triode region, for use as tunable resistors in tunable time continuous filters. The charge pump has been realized in a BiCMOS process (f/sub T/=3 GHz).<<ETX>>

Single electron tunneling technology for neural networks

Cross-coupled relaxation oscillators can produce two highly accurate quadrature output signals (Verhoeven, 1992). We present a high-level model of these oscillators in terms of circuit parameters, from which we obtain explicit equations for duty-cycle, oscillation frequency, and quadrature error. They show the influence on the oscillator performance of component mismatches and other nonideal effects, such as delays. The results provide useful guidelines for the design of high performance oscillators. The theoretical results are confirmed by simulation and by measurements on a test chip.