Look at the rate of change in potential across the antenna for the standing RF. Where are the current maximal and minimal?
The Maxwell–Faraday equation states that a time-varying magnetic field always accompanies a spatially varying (also possibly time-varying), non-conservative electric field, and vice versa.
Because this is a resonant antenna, a energy feed into it creates a stationary standing wave pattern at that frequency because there are discontinuity reflections at the ends.Hello Nsaspook, for half wavelength,current will be zero on the edges.
but why voltage is +-Vmax on edges and0 in the middle?
A half wave long patch operates in what we call the fundamental mode: the electric field is zero at the center of the patch, maximum (positive) on one side, and minimum (negative) on the opposite side. These minima and maxima continuously change side like the phase of the RF signal. The electric field does not stop abruptly near the patch's edges like it would in a cavity: the field extends beyond the outer periphery. These field extensions are known as fringing fields and cause the patch to radiate. Some popular analytic modeling techniques for patch antennas are based on this leaky-cavity concept and the fundamental mode of a rectangular patch is often denoted using cavity theory like the TM10 mode. This TM notation often leads to confusion and here is an attempt to explain that: Figure 1 uses a Cartesian coordinate system, where the x and y axes are parallel with the ground-plane and the z-axis is perpendicular to it.
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by Jake Hertz
by Jake Hertz
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