Step Width Tolerable For Offset Of The Aperture In A Millimeter-wave Transducer Between Post-wall And Hollow Standard Waveguides

摘要

A transducer with a wide step from a post-wall waveguide to a hollow waveguide width is proposed which is tolerant against the aperture offset. The modes in the step width of about 1.50 wavelengths are stable for the aperture offset and the fields are not so perturbed while in the conventional stepped structure with step width of about 1.00 wavelength, the higher evanescent mode of TE_(30) is excessively enhanced by the aperture offset. The operation of the transducer with the wider step is robust for the fabrication errors in the millimeter wave band. It is also suggested that the anti-symmetrical TE_(20) mode which is excited only by non-zero offset or the misalignment of the aperture exists in both structures and can not be the dominant factor for the improvement. The transducers are designed and fabricated at 61.25 GHz using PTFE substrate with glass fiber of ε_r=2.17. The bandwidth for the reflection lower than -15 dB is almost unchanged (6.30-6.60 GHz) for the offset from -0.2 mm to 0.2 mm, while it is degraded in the conventional stepped structure, from 7.65 GHz for no offset to 3.30-5.70 GHz for the same range of the offset.