An Alternate Dual-moded Dlds Utilizing the Te01° and Te02° Modes

In recent designs for multi-moded delay line distribution systems, the waveguide modes of choice have been TE01° and one or both polarizations of TE12° [1,2]. For the highly overmoded waveguide diameter of 4.75" (and out to ~7") at X-band, these are the modes with lowest theoretical ohmic loss. Considerable experience with the use of TE01° has been gained in pulse compression development [3] over the past decade, and recent transmission experiments [4] have demonstrated the feasibility of using TE12°. There may, however, be certain advantages to substituting TE02° for TE12°. In the past, this mode has been passed over largely because ideas for selective launching and extracting depended on modes being distinguishable by the azimuthal variation of their fields. The new design approach, however, of manipulating modes in overmoded rectangular waveguide [5] and transitioning to circular waveguide via special tapers, suggests that we could work instead with the rectangular TE20 and TE40 modes. We present reasons to consider a TE01°/TE02° system and describe waveguide circuits for launching and directing the above rectangular modes.