| Summary: | 碩士 === 國立成功大學 === 電機工程學系專班 === 97 === In a radio-frequency front-end receiver, it includes low noise amplifier,
oscillator, and mixer. A low noise amplifier is the first stage of a receiver. It
can amplify the received signal and reduce the noise of whole system in order
to improve the accuracy of transmission. The amplified signal will be mixed
with a local signal in a mixer and then be down-converted into an
intermediate-frequency signal.
In this thesis, the primary research focuses on the design of low noise
amplifiers for WiMAX applications. They include a multi-band low-noise
amplifier using switching inductors, a dual-band current-reused low noise
amplifier and a dual-band low noise amplifier using biasing circuit of active
feedback.
A multi-band low-noise amplifier using switching inductors for WiMAX
applications is a cascaded circuit which input is a common-gate stage. That
means that this circuit consists of two common-gate circuits. In the circuit, the
configuration of switching inductors is composed of three inductors in series.
The two inductors in the configuration can individually be switched on or off
in order to operate in three frequency bands. S11 and S22 at 2.3~2.7, 3.3~3.8
and 5.1~5.8 GHz are lower than -10 dB. Gains are between 13.4 and 16.8 dB.
The circuit has P1dB greater than -18 dBm, IIP3 greater than -27 dBm for the
operation of the two frequency bands. The power consumption is 8 mW.
A dual-band current-reused low noise amplifier for WiMAX applications
uses LC resonating networks at input and output to simultaneously arrive at
the matching of reflection coefficient. S11 and S22 at 2.3~2.7 and 5.1~5.8
IV
GHz are lower than -10 dB. Maximum gains are 17 and 14.5 dB for the two
frequency bands, respectively. The circuit has P1dB greater than -16 dBm,
IIP3 greater than -8 dBm for the operation of the two frequency bands. The
power consumption is 8.1 mW.
A dual-band low noise amplifier using active feedback for WiMAX
applications is a current-reused configuration like as the chip mentioned
previously. The active feedback circuit is used to bias the amplifier and
implement the input matching simultaneously. In addition, a voltage divider at
the gate of the cascoding MOSFET is used to improve the noise and linearity.
S11 and S22 at 2.3~2.7 and 5.1~5.8 GHz are lower than -9 dB. Maximum
gains are 16.4 and 14.4 dB for the two frequency bands, respectively. The
circuit has P1dB greater than -13 dBm, IIP3 greater than -3 dBm for the
operation of the two frequency bands. The power consumption is 8.7 mW.
The design of these circuits is based on the TSMC 0.18μm CMOS
process. These chips have been fabricated by the support of CIC in Taiwan.
The second circuit topology has been measured.
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