Digital up conversion VS IQ modulation using a wideband arbitrary waveform generator

Abstract

In many applications, including radar, EW and SIGINT, the modulation bandwidth requirements are constantly increasing, but at the same time excellent signal fidelity is necessary and distortions have to be kept at a minimum. Traditional signal generators can provide the required signal purity, but most of them offer modulation bandwidths of only about 100 MHz. External arbitrary waveform generators and IQ modulators can achieve a much larger bandwidth, but the downside to their use is carrier feed-through and images. Another alternative is the digital I/Q modulation inside the arbitrary waveform generator (AWG). This paper presents a solution using a wide-bandwidth, high-precision AWG to generate waveforms with 2 GHz or more of modulation bandwidth and discusses the pros and cons of the different alternatives.