Design of a VCO-based ΣΔ-modulator

The principle of ΣΔ-modulation has experienced an impressive evolution during the past decades and allows to realise high-performance linear Analog-to-Digital Convertors (ADC). The technique makes clever use of high clock rates and digital signal processing to obtain noise shaping and a reduced sensitivity to the mismatch of analog components.

Current research towards new architectures/techniques attempts to reduce the analog complexity in the -modulators by shifting its focus to the digital domain. The VCO-based (Voltage Controlled Oscillator) -modulator realises this transition by means of an alternative implementation of the quantiser (see Figure 1). By encoding the valuable information in the frequency/phase domain, the performance of the modulators is less influenced by technological miniaturisation and the speed and accuracy of digital electronics can be fully exploited.

VCO-based ΣΔ -ADC

Figure 1: VCO-based  ΣΔ-ADC. The modulator consists of a continuous-time loop filter , a VCO-quantiser and a DAC in a closed loop configuration.

The aim of this thesis is to build a VCO-based  ΣΔ-modulator. You will start by investigating the whole circuit on the system-level using behavioral models. From this phase, specifications on the sub-blocks are obtained and each of the sub-blocks can be designed separately. The design will take place in Cadence and will use a 180nm CMOS process. After the design and testing of the separate blocks, everything is put together for the final verification of the design. If time is left, a lay-out of the chip can be made and the chip can be processed to confirm the simulation results by measurements.

During this thesis you will

  • become an expert in the working principle of  -modulators, both at system and circuit level,
  • learn to design CMOS integrated circuits using your engineering skills and algorithms,
  • use Cadence to simulate, design and layout microelectronic circuits.

 

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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