In this thesis we present an analysis of the load modulation of the SAL14
sensor tag from ams AG. The sensor tag and crucial standard specifications are
presented in the introduction. Principles of load modulation and voltage limiting
were analysed on a simple mathematical model. Further, load modulation amplitude
(LMA) of SAL14 was measured according to NFC standard. In some cases
LMA exceeded the defined boundaries. Conclusions from mathematical analysis
and measurements were used for a new load modulator design in CMOS 180 nm.
Voltage limiter and rectifier were also redesigned in CMOS 180 nm to ensure correct
operation of load modulator. The new load modulator automaticly adapts
level of LMA according to the current in the voltage limiter. Reference NFC
devices were modelled to ensure correct simulation of the new load modulator.
Models were verified by simulating measurements done on SAL14. The new load
modulator generates LMA well within NFC defined boundaries.
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