Relationship of microstrip width and length

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Antenna94

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Hi!

This must be a pretty basic question, but I couldn't find the answer yet. Can a microstrip line's width be larger than its length? I am currently designing some LPFs and this problem came up.
Thank you for your answers!
 

Yes, it can. Microstrips like this are used in amplifiers all the time (outputs usually have a very low output impedance). If the geometry bothers you, you might try different types of filters, or orders. What is your design frequency?
 
It is a 3dB ripple Chebyshev low-pass filter with cut-off frequency of 6GHz for the output of a 4GHz oscillator. It doesn't bother me, but I worried that if a line is shorter than its width doesn't work as a transmission line. (I think I recall from my electromagnetic theory course that if length>>width isn't true then general field modelling must be used instead of the transmission line model.)
 

3dB is a lot of ripple. Is the oscillator a single freq, or is it a VCO? If it is a single freq, then 6GHz is probably too far out for the corner.

Have you simulated the resulting filter?
 

Yes, I realized meanwhile that it is not that good (I designed some filters previously for other uses and was just adjusting the frequency as a first approximation), but a Butterworth filter works fine now and also holds the l>>w relationship. Thank you for your insight!
 

if width is greater than length , still it acts as a transmission line. a patch antenna design is one example, for a rectangular patch width>length
 

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