I. Introduction
Unmanned aerial vehicles (UAVs) have been widely used across the world for civilian, commercial, as well as military applications [1], [2]. Among applications of UAVs, UAV swarm-based spectrum sensing is gaining ever-increasing popularity due to the highly controllable maneuverability, on-demand coverage and line-of-sight (LoS) links. In such scenario, a group of UAVs equipped with precise receiving antennas and intelligent sensors collaborate to perform sensing tasks to the interested targets. Due to these desirable features, the UAV swarm-based sensing has recently drawn considerable interests from both civil and defense applications [3].