Project Goal

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Project Goal

• Architectural issues
• -- Wideband, highly linear requirement for
  COGUR mandates
• adventurous exploration and meticulous
  investigation at system level
• -- Looking for an appropriate simulation
  platform to facilitate the top-down
• design flow
• -- Verilog-A proves a good candidate for this
  task
• Linearization schemes under investigation
• -- Existing ones in the transmitter side
  provide a fertile body of innovation.
• Due to the lack of data information
  beforehand, feedback control is ruled
• out. Feedforward and envelope injection
  are adopted because of their
• open-loop property
• -- Trying out more eccentric idea?
  Dithering, a DSP technique, shows great
• potential for receiver linearization

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Verilog-A Behavioral Modeling
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(1) Envelope Injection

• Inject the envelope of the input signals into the
  receiver path by choosing the amplitude and
  polarity (0o or 180o) of G1/G2
• The envelope mixes with the signals in the main
  path to produce new IM3 terms which act to cancel
  out with the receivers intrinsic IM3
• More than 20 dB suppression of IM3 reported
• The need for automatic tuning for proper values
  of G1/G2 is difficult to achieve

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(2) Feedforward Linearization

• Nonlinearities from LNA is calculated with the
  aid of a mixer-alone reference path and
  subtracted from the main path
• Peak detector monitors the gain/phase mismatch
  between two paths and modifies the VGA/phase
  shifter accordingly
• Most of signal processing is done at baseband
• E.g. LNA IIP3-5dBm, S2118dB Mixer
  IIP325dBm, conversion gain -3dB
• ? IM3 improves by more than 25dB

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(3) Dithering Linearization

• Amplifier 3rd order nonlinearity coefficient
  possesses inverse polarity along the bias axis
• Large dither signal at higher frequency is
  applied at input to operate the amplifier back
  and forth between two regions such that the
  averaging a3 is close to 0

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IM3 Measurement

• Two tones_at_ 250/249M, Dithering tone _at_ 1.1GHz
• Mini-circuits amplifier ZJL-6G,
  Bandwidth20M6GHz, typical gain13dB, IP324
  dBm , NF4.5dB

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Side Effects

• Gain loss due to averaging effect, maximal 5dB in
  the region of interest
• High frequency dither signal raises entire band
  noise floor, max increase in NF by 12dB

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Measurement Results
1, ratio of the dither frequency to the signal
frequency 2, out of amplifiers BW 3, with
respect to no dithering 4, 0, 3 for two-tone
input power between 03dBm, dither power varies
between constant 5.5, 7.5, 9.5dBm 5, at regions
of interested dither and input power level 6,
out of noise meters operatable input power limit
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Summary of Work

• Generating a full array of RF behavioral modeling
  in Verilog-A. Building blocks include LNA, mixer,
  oscillator, filter,etc, all specified and
  examined by end RF metrics
• Proposing/modifying linearization schemes from
  conventional ideas or other disciplines. Using
  behavior models to expedite functionality check
• Envelope injection technique is less favored due
  to the requirement of gain and phase tuning
  control on the injection path
• Measurement results from dithering scheme reveal
  an intriguing venue for further understanding the
  tradeoff between IM3 improvement and gain/noise
  degradation. The same exploration effort shall
  apply to feedforward scheme as well