I. Introduction
Recent advances in high power radar systems call for high levels of isolation between the transmit and received RF signals within a broad bandwidth of operation. In order to meet these requirements, low-profile and broadband RF circulators need to be developed [1]. However, the majority of commercially-available planar-based circulators exhibit fractional bandwidths (FBWs) below 20% [2]–[4]. Alternative RF design techniques have been developed with the purpose of increasing FBW. These include, adding multi-section matching networks at the input/outputs of the ferrite-puck or by routing the RF signal between inter-coupled ferrite-loaded cavities [4]. However, these techniques result in large physical size and excess of RF loss.