Design and Simulation of an L-band Ferrite Waveguide Circulator for Industrial Applications

Commercial L-band circulator (WR975) at
$\mathbf{896}\pm \mathbf{10}\ \ \mathbf{MHz}$
is available on markets. 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. A Finite Element Method (FEM) simulation study found that a broader bandwidth can be achieved by reducing the height of the waveguide circulator in half. This also leads to a reduction in overall fabrication cost. This paper discusses a detailed design and modelling of the L-band circulator operating at 915 MHz with a wide bandwidth of 55 MHz (895MZ to 950 MHz), an insertion loss of 0.195 dB for the entire bandwidth, and 0.173 dB at 915 MHz for a uniform applied bias field. The average transmission efficiency within the bandwidth is > 95.59% in the operating region, which reduces power reflections for improving the performance and reliability of magnetrons. This paper also discusses a realist magnetic circuit design for the proposed model to simulate a non-uniform applied bias for more accurate simulation results.