I have gone through so many papers on planar LWAs based on CRLH. They say that unit cell length is less than guided wavelength/4. But when i calculate the unit cell length is greater than the above mentioned condition. I am bit confused. please help me on this????
I think this condition is for microstrip based LWA. As in case of SIW some of the paper do not satisfy this conditions..
hope this will clear your confusion a little bit
Well, you just met some examples which slightly violates the rule. It doesn’t mean they can’t realize good antennas. This quarter wavelength rule is more like a soft requirement. If your unit cell’s period is shorter than that, your unit cell is closer to an artificial material. If it is longer, as long as it is still shorter than half wavelength, you are free from grating lobe problems and the design shouldn’t be problematic.
Are you designing a material or an LWA? If the answer is the latter, violating this rule is not that serious.
Sir,
But they clearly mention that unit cell length is less than guided wavelength/4 .
Are "they" the author of the paper you are looking?
Make sure you didn't get "them" wrong.
How did you check their calculation?
By calculating the free space wavelength according to the broadside frequency. Then i divide the free space wavelength by its dielectric constant to get guided wavelength. Then i divide it by four to check.
First, make sure you use the square root of the relative dielectric constant εr when doing the division.
It will look like (λg)=(λ0)/sqrt(εr), where λ0 is your free space wavelength.
Second, the above calculation is only an approximation of λg. Since the wave is not fully bounded in the PCB material, λg should be somewhere between (λ0)/sqrt(εr) and (λ0), so some errors can possibly arise.
Third, If I have successfully synthesized a "metamaterial" and put it in free space. I will try to compare the difference between the "metamaterial" and the background free space.
Wait, it seems like i don't need to know εr if I found the effective εs and μs (permeability) of this "effective material".
In short, I suggest you simply use the free space wavelength when comparing. At least the meaning is much clearer in this case.
Thanks a lot for the support sir...
Can i message for some other queries...
It looks like you need to take solid courses on electromagnetics and on antenna theory, Rahul
Sir,
Can you please suggest me some courses on electromagnetic and antennas theory
Your question surprises me, Rahul, as an Institute where somone considers undertaking research in a field, ought to offer the right courses in that very field; don't you think?
Hello,
Go through some standards books, which may clear all confusions.
Some papers are attached for the help.
Thanks,
Those papers might appeal to the engineer want-to-be who is too greedy for results (and 2nd-class manuscripts) to take the time to learn and thus save time in the long run, Smrity.
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