Figures 3(b), 3(d) and 3(e) depict the radiating surface, aperture slot arrangement and feed line structure correspondingly.
As an EM wave travels from the source of the antenna to the feed line, aperture slots, radiating element and is excited in free space, the EM wave is encountered by a different impedance match at each interface.
A small aperture slot on the ground is oriented to excite the magnetic field between the feedline and patch.
Therefore, it is possible to allocate the aperture slot not exactly at the patch centre as long as it gives the maximum coupling and resonant at the desired frequency.
The H-shaped aperture slot on the ground plane is positioned at the centre with reference to the top patch while the I-shaped aperture slot is positioned at the centre with reference to the bottom patch.
The aperture coupled microstrip antenna has the flexibility in design parameters due to various shapes of aperture slot and patch which gives more freedom in antenna design.
f]) via a small aperture slot embedded on the ground plane (Figures 1(a)-(b)).
Some common feeding mechanisms such as probe feed, aperture slot
, microstrip line and coplanar line can be used with the DRAs .
The distance between the first slot and the edge of the microstrip line 'L' is chosen so that its reactance cancels out that of the aperture slot, and it can be calculated by using the expression found in :
The geometrical dimensions of the two aperture slots which excites the first and last CDRAs are [L.
On the other hand, an electromagnetic coupled structure such as reported by  will be very hard to switch because there is no specific coupling mediator between the patch and the feed line, unlike the aperture slot as proposed here.
A novel reconfigurable log periodic patch array has been proposed by inserting switches within the aperture slots coupling the patches to the feed line.