On A Method for Automatic Image Balancing in IQ Mixer Based Software Defined Receivers

摘要

Over the past four years while working on a software defined radio core, DttSP, with Frank Brickie, and applying it to real world I/Q mixer based radios (2-5), the problem of find the right algorithm to insure equal amplitude and the proper phase relationship to achieve perfect quadature between the I and Q channels in these radios has been a source of constant work. My favorite author of for sale amateur radio software is Alex Shovkoplyas, VE3NEA(1). He has been doing wonderful work in many areas but specifically his work in software defined radio has been inspirational. He did an automatic image cancellation algorithm for his Rocky SDR as well as other interesting software defined radio and dsp work (6,7). His web page gives a tantalizing hint at the basis for the algorithm but does not express a complete derivation of the detector or show how to apply the results in the end. We will do that here.