The proposed slot design technique is able to provide a compact structure with a large operating bandwidth, without occurring in undesired cross-polarization effects strongly affecting the useful radiation
Microstrip antennas have enjoyed proliferate use in many circularly polarized applications due to their low-profile light weight and useful radiation
characteristics (Bao & Ammann, 2007).
Especially, to get generally useful radiation
patterns and acceptable gain for different frequencies in one structure, the proposed antenna makes advantages over the conventional combination of the individual 2 GHz antenna and the individual 2.4 GHz antenna, because a 2 GHz antenna has its harmonic 4 GHz and it can not hold a slot for 2.4 GHz resonance whose size exceeds the 2 GHz patch.
The useful radiation
results from the currents which distribute along the right edges of the ground plane.
Figure 1(b), however, which superimposes the normalized average plant response curve (McCree's average relative quantum efficiency curve)--representing the portion of the radiant output that is actually useful for photosynthesis--clearly shows that the radiometric measurement substantially deviates from the measurement of photosynthetically useful radiation
, represented by the area under the plant response curve.