As part of my research, I need to couple a loaded, custom-sized, rectangular, waveguide (in which a hybrid mode propagates at 8.5GHz) to either a) a coaxial transmission line or b) to a standard X-band waveguide.
I need to understand the design and optimization processes for both including impedance matching and/or mode conversion as required.
What is the best, most efficient way of approaching such a task?
Any useful resources on the topic would also be very much appreciated.
Kind Regards
Simon
if there is a hybrid mode in your waveguide it has presumably some part of the cross section filled with some material or the wall are corrugated .One very simple solution is to provide smooth a transition to a conventional waveguide and then use a standard coax-waveguide transition.
Fritz Caspers Hi, thanks for the response. The waveguide is loaded with complementary split-ring resonators. Regards a smooth transition I have tried tapering the waveguide up to a conventional waveguide dimension to no avail. The issue I have when using this technique is the impedance mismatch resulting in reflected power. To my knowledge, most waveguides have an impedance somewhere around 500 Ohms. The calculated complex impedance for my current system is Z1 = 10 +115i. Using a complex conjugate matching method I require a matching system with Z2 = 10-115i. I am unsure if this is possible with a waveguide. I know 10 Ohm cable is available. Would there be any way of designing a coupling system via a stub/loop within the loaded waveguide direct to coax?
ok I see ..some metamaterial..which definition for the "wave impedance" are you using.?.500 Ohm appears rather high to me and depends on the type of mode.For more detail you can consult the books by Pozar on microwave engineering
For the wave-impedance (often defined as ratio of transverse field components for conventional modes) you can check wikipedia. For hybrid modes keep in mind that they are also known as LSM and LSE modes and check via IEEE explore.
There you should also find something on waveguide to coax transition for this kind of modes..
As for the design of a waveguide to coax transition (which can be seen as a transformer) I would start with a classical version (i.e Pin coming in in the middle if the waveguide and about lamdg (g for guide) from the shorted andplate and then play with the parameters.Good luck
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