In microstrip quasi TEM mode sustains.For practical purposes, which mode TEmn or TMmn is to be considered?
A microstrip has no cutoff frequency. It conducts all the way down to DC. Did you mean to ask what is the cutoff frequency of the second-order mode?
It has a dominant mode and it is the quasi-TEM mode that exists all the way to DC. BTW, you can only get true TEM modes in homogeneous waveguides. The microstrip is inhomogeneous due to the substrate and air. Most of the field is confined in the substrate so it is still close to TEM, thus called quasi-TEM.
Dear researcher.
A microstrip antenna has dominant modes. theses modes can be predicated for a rectangular patch (whose dimensions are w L and h) by using the cavity model .
These dominant modes are for this case:
If L > W > h, the mode is TM010 :
If L > W > L/2 > h,we have TM001;
If L > L/2 > W > h, we have TM020;
and If W > W/2 > L > h, we have TM002 :
for more details and schemae, I join this 2 word pages.
The micro-strip line is the quasi-TEM mode (similar to parallel plate) and therefore has no cut off frequency.
What about the higher order cut off frequency in Microstrip line? Is there any concept of higher order modes in MSL?
The microstrip does have higher-order modes. The cutoff frequency of the second-order mode is sometimes what people mean when they ask about cutoff frequency. Typically you do not want to operate the microstip as a multimode waveguide so there is an upper frequency cutoff above which it becomes multimoded.
Thanks Raymond. Could you please refer me to some research article as how to calculate that. I need to make sure that in my design I am not running into higher order modes. My range of frequency is 1 to 5 GHz. Thanks.
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