Design and simulation of L-band microwave waveguide circulator with increased efficiency and broad bandwidth

The industrial L-band WR975 circulators operating at a frequency range from 900 to 930 MHz have been designed and simulated. Commercially, an L-band circulator at \pmb896±10 MHz is available. However, for a wider bandwidth (~ 30 MHz) application, we would need two units operated in dual frequencies between 896 MHz and 915 MHz to cover the frequency range required. Through a Finite Element Method (FEM) simulation study, it was found that by reducing the height of the waveguide circulator in half a broader bandwidth can be obtained and this also leads to a reduction of overall fabrication cost. This paper discusses a detailed design and modeling of the L-broadband circulator operating at 915 MHz with a bandwidth of 43.5 MHz (892MZ to 935.5 MHz), an insertion loss of 0.25 dB for the entire bandwidth, and 0.22 dB at frequency of 915 MHz. For the entire bandwidth, the transmission efficiency is over 94.3% and it is more than 95% from 900 to 930 MHz of operating region which reduces power reflections for improving the performance and reliability of magnetrons. In addition, different ferrite materials are studied for optimizing this L-band waveguide circulator.