A High Power Harmonic Filter Realized via Optimized Waffle-Iron

Abstract

This letter proposes a beneficial design approach for a high-power reflective harmonic filter based on an optimized waffle-iron. With a non-equidistant periodic array cylindrical architecture, the optimized waffle-iron can reduce the passband transmission loss and suppress second, third, and so forth harmonic reflection. To match the WR137 standard waveguide port, a quarter-wavelength-loaded cylindrical structure's stepped impedance transformation is adopted. The simulation results are largely in agreement with the test results, which show a maximum insert loss of 0.15 dB in the pass-band of 7.1 GHz–7.25 GHz and a minimum harmonic suppression of 60, 65, and 50 dB for the second, third, and fourth, respectively. Heat dissipation analysis and power handling capabilities tests were also performed. With nitrogen filled at 0.12 MPa atmospheric pressure, the continuous wave(CW) power without breakdown is measured over 30 kW. To our knowledge, this is the highest power reflecting harmonic filter in the X-band.