How to understand relationship betwwen EM field and circuit more intuitvely?

Hi,
All nicy guy.
I try to understand relationship betwwen EM field and circuit for a long time, But I still have some problems that can not understand.
We learn from the textbook that plane wave is a TEM wave. and we also learn that the wave between two parrellel plates is TEM plane wave. then my question:
Can the plane wave transmit into the two parrellel plates? If it can, why we use antenna?
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plane wave----->
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I guess some guy will say that depends the wavelenth. But how to explain intuitvely? They are all plane TEM wave outside and inside the two parrellel plates.

I also can not understand the bend tansmission line can guide the wave to bend. e.g. if the stripline of the pcb has a angle, then the wave also change the transmission direction. I guess some guy will explain the current change the direction, so the wave also change the direction. But how to explain form the point of view of EM filed or wave? You know there is no any explaination of the direction change of wave transmission excpet the reflection and refraction in textbook.

Thanks in advance!

If I got your first part of the question, it translates to the need of having wireless communication as over wired communication. parallel-plates support TEM waves in general, and also higher order modes in other circumstances. Waveguides which are single conductor transmit TE or TM waves..But all these structures, waveguides, parallel plates, transmission lines are guiding structures or transmission structures. The main aim is to guide the energy and not to radiate. So a good guiding structure should be a bad radiator.
On the other hand, antennas are radiating structures, which aids in wireless form of communication. Say for instance you want to have ionospheric wave propagation, or you want to have satellite communication, you can't opt for a guiding structure. You need antennas..you need antennas for mobile communication etc. Not only that, antennas are needed for defence purposes for radar-based detection, microwave imaging purposes, bio-medical imaging of tissues inside human body etc. There are hell lot of applications where they are used.

As far as second question is concerned, the analogy can be explained from charges and currents. Though you want to avoid it, still we have to assume from first principles that electric fields emanates from a positive charge and terminates at a negative charge (or infinity). It is as if when you are applying a source to the stripline, positive charges reside on top conductor and negative on the ground..This produces E-field from top to ground.and in the next cycle the polarity reverses. And in this way the charges traverse on a transmission line. . Now this Charge configuration changes, hence E-field changes with time, generating H-field from Maxwell's eqn. and vice-versa. This phenomena generates a TEM wave in a transmission line..Also certainly I didn't mention that moving charges will result in current, also to support the H-fields in the structure.. When the bends occur, the charges cant go out of the conductor, nor the currents.The fields as a result of these charges and currents have to bend accordingly.. However, in the sharp bends there are sudden charge accumulation at corners resulting in stray radiation from the structure.