9-PIM distorton by steer-2.pdf

NC STATE UNIVERSITY Passive Intermodulation Distortion, Part 2 Michael Steer with Greg Mazzaro and Josh Wetherington 1 Copyright 2009 to 2011 by M. Steer, G. Mazzaro, and Josh Wetherington Not to be posted on the web or distributed electronically without permission. NC STATE UNIVERSITY Outline ? Background ? Passive Intermodulation Distortion (2 parts) – Part 1, PIM effects, Electro-Thermal PIM ? Test Equipment, Microwave Circuits / Antennas – Part 2, PIM effects ? Non Electro-Thermal PIM, Filter PIM ? Behavioral Modeling – Behavioral model – Measurement Equipment ? Simulation and Modeling of Large Systems – Part 1, New circuit concepts – Part 2, fREEDA 2 NC STATE UNIVERSITY PIM Measurement System (Analog Canceller) 3 NC STATE UNIVERSITY Problem ? Need to measure small signals in the presence of large signals. – E.g. GPS receiver, radar, distortion measurement 4 NC STATE UNIVERSITY Cancellation Theory ? Sum with equal amplitude/anti-phase signal of original signal 5 Vector Modulator With 16 bit ADC NC STATE UNIVERSITY Cancellation Theory ? Amplitude Measurements Only ? Non Newton-Based Iteration Cancellation Errors ? Phase error: – Mostly result of errors in β and α in θS equation – Dependent on phase separation of signals – Can be minimized in iteration ? Amplitude error: – Results from path non-linearities – Dependent on phase, frequency, time – More sensitive than phase errors due to sole reliance on amplitude measurement – Minimized through path amplitude calibration 6 NC STATE UNIVERSITY Amplitude Calibration ? Standard (baseline): Generate calibration matrix: Ampl. vs. Freq. – Occurs pre-test – Does not capture time-dependent or phase-dependent effects – Only needs to be done once (ideally) – Speed depends on density of matrix – Inherent interpolation error ? In-line: Perform calibration on-the-fly – Occurs during cancellation – Minimizes time-dependency – Very fast: single measurement