1. Polar Envelope Predistortion (“PEP”) for RF Power Amplifier Linearization
Prototyping Status
September 11, 2012
Kathleen Tokuda & Prof. J. Stevenson Kenney
Communication Systems Technology Lab
School of Electrical and Computer Engineering
Georgia Institute of Technology
Atlanta, GA 30332

2. Amplitude & Error Measurement
Preliminary tests indicate wide-band level shifter is functional on system board
WCDMA3 test of level shifter on standalone testboard properly shifted output of envelope detector using a dummy load (matched to log amp input impedance)
Open loop test on system board: Full 4V range in error signal output is attained with a 20-dB variable attenuator in feedback path
Debugging closed loop test (observed excessive loss in feedback path likely due to a short or broken connection)

3. Amplitude Feedback Subcircuit Schematic

4. Attenuation Subcircuit Schematic

5. Phase Detection & Error Measurement
Real-time measurements on MC100EP140 digital phase-frequency detector completed previously
Functional for WCDMA3 test signals at carrier frequencies less than 1500 GHz
Modification A: reduce the input signal frequency ( 2 or  4)
Modification B: clean up the input edges to properly trigger detector
Dividers/prescalers tested (MC12095 works for a 2.1 GHz carrier)
Subcircuits to clean up input edges
Inverter w/ Schmitt trigger tested (logic levels require high power inputs)
Expedited PECL comparator evaluation board to arrive 9/14 (on backorder)
Successful test of CML comparator evaluation board at low frequency using internal voltage offset of function generator (Offset is required to translate to CML input levels.)
Re-purposing voltage level shifter to offset WCDMA signal at 2 GHz (requires a modification to mini testboard to compensate for loading effects)

6. Phase Detector & Error Measurement Subcircuit Schematic
Prescaler
Vref
Phase Ref
Comparator
Phase FB
Phase Detector & Error Measurement Subcircuit Schematic
Proposed modifications:
Prescaler (frequency divider)
Reduce frequency by ½ or ¼
Tested successfully 1-tone
Comparator
Clean up inputs
Building testboard
Both subcircuits are “add-ons”

7. MATLAB Simulink® Model of an Ideal Analog Predistortion System