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A Study on the Aliasing-image Problem in I/Q Modulators Employing RF-DACs
Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
2013 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In today’s world of high-speed communication, data-converters are playing a vital role. The purpose of this project is to analyze the aliasing image problem that occurs in quadrature I/Q modulators utilizing radio frequency digital-to-analog converters (RF-DACs). The RF-DAC is considered to be high-speed DAC that operates in higher GHz region. These high performance DACs are becoming the most essential part of the upcoming future communication devices like next generation radars and telecommunication systems. Some I/Q modulators are implemented in this thesis. The aim is to identify the unwanted signal that is trying to distort the desired output.

In this thesis, the work is divided into two main parts. First is the aliasing image verification and second is the implementation of the I/Q modulators. Begin with the assessment of the aliasing image through sketching the spectrum using Matlab tools. Also mathematically the calculation is derived to support the flow. In the next part, four different architectures are implemented focusing on image rejection ratio (IRR) calculation while the maximum achievable rejection ratio is 119 dB using the RF-DAC. Lastly the effect of discrete local oscillation (LO) is shown. A comparison plot is drawn, comparing the effect of a discrete-LO at different bit levels vs. IRR variation. It shows a nice picture of IRR dependence on the perfect matching and not on the signal shaping. 

Place, publisher, year, edition, pages
2013. , 97 p.
Keyword [en]
RF-DAC, DAC, Image Rejection Ratio (IRR), Aliasing Image, I/Q modulators
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:liu:diva-113386ISRN: LiTH-ISY-EX--13/4673--SEOAI: diva2:781574
Subject / course
Electrical Engineering
2013-06-12, NOLLSTÄLLET, University of Linköping, Linköping, 15:00 (English)
Available from: 2015-01-19 Created: 2015-01-16 Last updated: 2015-01-19Bibliographically approved

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Khan, Muhammad Awais
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