Are you stable enough?

Oscillators are the beating heart of many electronic and communication systems. Without them, there would be no radio, no television, no Wi-Fi ... They produce the periodic, oscillating electronic signal (sine or square wave) which is needed for high-frequency carrier generation, clock signals used by data processing equipment, as well as the reference signals for special-purpose systems.

Oscillators based on the LC-tank topology are very popular (see Figure 1). This specific topology makes use of a nonlinear element  to compensate for the resistive losses present in the non-ideal LC-tank.
The most challenging task when designing an oscillator is to make sure that the produced oscillation remains stable. The presence of the nonlinearity  makes this analysis difficult. Methods like the Describing Functions or the Best Linear Approximation exist which allow to approximate the nonlinearity with a linear model such that well-known linear system techniques involving Bode or gain-phase plots can be used again.

Negative resistance LC-tank topology

Figure 1: Negative resistance LC-tank topology.

This thesis will start by investigating the general operation of oscillators. The Describing Functions will be introduced such that the influence of the considered topology on the performance/stability can be checked. Using the obtained knowledge from the previous stages, an oscillator will be designed using Simulink/ADS. The designed oscillator will also be realised on a PCB and validated using measurements.

During this thesis you will

  • become an expert in the working principle of oscillators, both at system and circuit level,
  • learn to use the Describing Functions to analyse the behaviour of oscillators,
  • design your own oscillator using Matlab/Simulink/ADS and obtain practical experience by building and validating your own design.

Interested? Don't hesitate to contact us!

Depending on your own background, the thesis objectives can be altered such that they perfectly match your interests.

Contact: dries.peumans [at] vub.ac.be, gerd.vandersteen [at] vub.ac.be

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