Design of Dual-Band Microstrip Circulator for X and Ku Bands

With the rapid development of mobile communications, there has been a demand for wideband or dual-band capabilities in antennas and RF devices to meet the requirements of multiple communication systems, reduce interference between antennas operating at different frequencies, and lower costs. This paper presents a dual-band microstrip circulator designed for X-band (9 GHz) and Kuband (16.5 GHz) communication system. The design results are as follows: for the X-band frequency, the operational bandwidth is 3 GHz, isolation <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\geq \mathbf{18\ {dB}}$</tex>, insertion loss <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\leq \mathbf{0.3}$</tex> dB, and VSWR <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\leq 1.25$</tex>. For the Ku-band frequency, the operational bandwidth is 300 MHz, isolation <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\geq 18 \text{dB}$</tex>, insertion loss <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\leq \mathbf{0.5\ {dB}}$</tex>, and VSWR <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\leq \mathbf{1.25}$</tex>.