Compact mode-matched excitation structures for radar distance measurements in overmoded circular waveguides

[摘要] This contribution deals with guided radar level measurements of liquidmaterials in large metal tubes, so-called stilling wells, bypass or stillpipes. In the RF domain these tubes function as overmoded circular waveguidesand mode-matched excitation structures like waveguide tapers are needed toavoid higher order waveguide modes. Especially for high-precision radarmeasurements the multimode propagation effects need to be minimized toachieve submillimeter accuracy. Therefore, a still pipe simulator isintroduced with the purpose to fundamentally analyze the modal effects.Furthermore, a generalized design criterion is derived for the spurious modesuppression of compact circular waveguide transitions under the constraint ofspecified accuracy levels. According to the obtained results, a promisingwaveguide taper concept will finally be presented.

[学科分类] 电子、光学、磁材料