Emerging Trends in Radar: Harmonic Radar Systems With mmWaves

In contrast to conventional radar, harmonic radar systems utilize two different frequencies for transmission and reception. Therefore, a desired target is equipped with a tag that includes a frequency doubler. It exclusively reflects the signal at twice the originally sent out frequency, making this specific target unique. Thus, enabling the key advantage of harmonic radar systems: clutter rejection. However, the range equation of such a system deviates significantly from conventional radar. This is mostly due to the power transfer function of the required doubler. Therefore, achieving sufficient range to satisfy a desired application is challenging. In this article, the measures with which state-of-the-art systems address those challenges are reviewed and explained with the help of this deviating range equation. Furthermore, this article highlights the potential of utilizing active tags as well as other research to increase realizable ranges and the frequencies of harmonic radar into the mmWaves, respectively.