QuinStar Technology‚ QMF series Mode Filters provide a solution to the critical need for mode purity when using TE01 mode circular waveguide. Due to the similarities between the TE01 and TM11 modes, even the slightest irregularities in the circular waveguide cause mode conversion from TE01 to TM11. The large waveguide diameters will readily propagate TEM1 modes, which degrade the purity of the TE01 signal. Extraneous TEM1 and TEMN modes cannot be reconverted to the TE10- rectangular mode ‚Äì they show up as large spurious losses. Each QMF series mode filter consists of a section of lossy wall waveguide. Because the higher order modes (TMM1,TEMN) have wall currents, they are sharply attenuated and do not propagate. Although the energy transferred to these modes is minimal, mode filters must be placed periodically along the transmission line. The TE01 mode, which does not have wall currents, passes through this section unaffected. The QMF series mode filters are available in circular waveguide sizes from 12.4 to140 GHz. The QMF series mode filters are used to prevent TE01 conversion to higher order modes. By attenuating unwanted TEM1 modes, the QMF series filters allow for the low loss transmission of TE01, TE02 modes in circular waveguide, and eliminate unwanted resonance; it is recommended that the QMF series filters be placed at least every 10 feet apart.
Model Number: QMF - ABC 000
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