Evaluating and Optimizing Tradeoffs in CMOS
RFIC Upconversion Mixer Design
by Dr. Stephen Long
University of California, Santa Barbara
It is not easy to design an RFIC mixer. Different, sometimes conflicting,
performance specifications must be prioritized, depending on the application.
Receive applications require a mixer to handle a wide range of input signal
levels, and maximum linearity under large signal conditions is often more
critical than the noise figure. Transmit applications have controlled signal
levels, so the design strategy shifts to tradeoffs between noise and intermodulation
distortion (IMD) behavior to achieve the largest useable dynamic range.
In this article, a transmit mixer is used to illustrate many of the design
tasks that go into the development of a quality RFIC. The design is an upconversion
mixer for a basestation transmitter using a Gilbert-cell MOSFET double-balanced
differential mixer with an input IF signal centered at 200 MHz and an output
of 1.8 GHz. This design example uses 0.35 mm MOSFETs with a default device
model parameter set. Other users would substitute their own verified device
models.
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