Linearization Techniques for VCO-Based Delta-Sigma Modulator
Date Issued
2012
Date
2012
Author(s)
Hsu, Shou-Chen
Abstract
This thesis presents two calibration techniques to address the linearity issue in VCO-based delta-sigma modulator. Unlike conventional delta-sigma modulator, the VCO-based delta-sigma modulator operates in a open-loop manner which avoids the stability and excess loop delay (ELD) issues. However, the non-linear effect is not suppressed by the loop as it affects output directly. Among all the non-linear effects, the harmonic distortion from VCO is the worst and needs to be addressed.
The first technique utilizes the foreground calibration to recover the distorted output signal. The nonlinearity is detected by sending a fixed input pattern. In the second technique, the background calibration is presented. The nonlinearity of VCO is corrected based on the additional reference ADC.
These two techniques are implemented in a TSMC 90-nm CMOS process. The system bandwidth is designed 10 MHz with 500 MHz sampling frequency. The implemented modulator dissipate 20 mW and 12 mW respectively from a 1.2-V supply.
Subjects
VCO
Delta-Sigma Modulator
Type
thesis
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