Novel Quadrature Modulator Balancing Method

Smith, Robert J. M.S.E., Purdue University, May 2012. Novel Quadrature Modulator Balancing Method. Major Professor: Abdullah Eroglu. Quadrature modulators are ubiquitous in modern communication systems due to the flexibility they provide. By simply generating an in-phase and quadrature-phase signal, nearly any type of modulated waveform can be created with a quad modulator. Although these devices are simple to use, they produce relatively large amounts of unwanted carrier and image signals. In many cases, they need to be calibrated before operation, or operated in a closed-loop to adjust the stimulating signals and null the undesired emissions. There have been many methods developed to iteratively find the appropriate correction factors needed to improve the spurious performance of these devices. In the following thesis, a method for rejecting the image and carrier leakage is proposed which solves for the correction factors directly from a limited number of measurements. This method is proven through simulations in Agilent’s Advance Design System (ADS) and Matlab/Simulink.