| Summary: | 碩士 === 國立清華大學 === 電機工程學系 === 96 === This research works on the circuit development with noise and linearity improvement for
wideband RF front-end circuits. The driving vehicle is mobile TV standards, such as DVB-H
system at UHF band from 470 to 890MHz. This system presents many technical challenges
especially low noise and high linearity over wide bandwidth. The power consumption is of
great concern due to the limited battery capacity for handheld receivers, and the use of low
cost CMOS is desirable.
In this research three different circuits are developed. First is a LNA with multiple gain setting
and noise cancellation. With the wideband nature of shunt feedback structure, the input
matching over a wide bandwidth can be sustained. Second is a LNA with a new noise reduction
strategy. Instead of using feedforward cancellation, this work uses a feedback topology for
noise suppression. With the signal-nulling feature, the linearity constraint of feedforward cancellation
technique can be broken. Third is the noise and linearity improvement for wideband
LNA and mixer integration. The proposed circuit configuration can apply both feedforward
noise cancellation and multi-gate distortion cancellation. With the breakthrough of the tradeoff
between power consumption and linearity, a good noise and linearity performance can be
obtained under decent power dissipation for a front-end design.
These techniques developed in this research can be applied to different front-end circuit
topologies to achieve a better noise and linearity performance.
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