Radiated field of a microstrip patch antenna

Hi,

I am trying to understand the basic theory of the radiation field of a patch antenna: (please see the attached picture)

'If the fringing fields are resolved into its parallel and tangential components with
respect to the ground plane, the normal components will be out of phase with each
other and would cancel out each other. The tangential components are in phase with each other therefore the resulting tangential field components would combine to give maximum radiated field in a direction normal to the patch i.e., the broadside direction.'

Here is my question:
We know that the tangential components will combine as they are in phase. But, how to visualize that the tangential field components would give us a radiated field in normal to the patch? Can anyone please help by explaining in more details (perhaps by using some examples)?

Many thanks.

Regards,
Sim

I'm not good painter. but I think that what missing to your pict.
the 2 parts combine to one field and propagate normal to the patch.

hi plasma,
Thanks for your help. One thing to clarify here, when you are saying that the field is propagating normal to the patch, shouldn't the field pointed upward (instead of pointing toward the right)? Thanks.

zhiweisim said:

hi plasma,
Thanks for your help. One thing to clarify here, when you are saying that the field is propagating normal to the patch, shouldn't the field pointed upward (instead of pointing toward the right)? Thanks.

Click to expand...

in the far field, the poynting vertor, rather than the E field, points towards the normal direction outwardly.
i'm sure it will be of help if u take a look at the farfiled analysis of a patch from a "two equivalent magnetic current source" point of view. most antenna textbooks have this content.

hi drunkbear,

Can you briefly explain this :

'The resulting tangential field components would combine to give maximum radiated field in a direction normal to the patch'?

I am abit confused about this since the tangential field is the one field parallel to the patch (and not normal to the patch). How will we get maximum radiation field normal to the patch in this case? Sorry for troubling as I am quite new to EM stuffs.

Many thanks.

hi zhiweisim


regarding your question concerning max radiation normal to the patch. well the resultant electric field is parallel to the patch but the power or energy of wave is normal to E

you might know about TEM waves in which both E and H are perpendicular to each other and also to the direction of propagation

so the direction of wave propagation in case of patch antenna is normal to the patch as you know the direction of E field


i hope this helps

regards

zhiweisim said:

hi drunkbear,

Can you briefly explain this :

'The resulting tangential field components would combine to give maximum radiated field in a direction normal to the patch'?

I am abit confused about this since the tangential field is the one field parallel to the patch (and not normal to the patch). How will we get maximum radiation field normal to the patch in this case? Sorry for troubling as I am quite new to EM stuffs.

Many thanks.

Click to expand...

hi zhiweisim,
well, u know it's not easy to explain this with only a few words.
i suggest u examine the chapter that discribes antenna array(for ur questino, the basic two-element-array theory is enough) in any antenna textbook. it pays to do that and won't take much time.
good luck!