Hi
Can I change the quasi Yagi antenna (double food) by 2 antennas patch. ????
This characteristic is exploited to form sum and difference radiation patterns by combining the outputs from each feed out of phase and inphase.
Probe-fed Rectangular patch.(lambda/2 x lambda /2 is the size).
The two probes are located on the orizontal simmetry axis and next to the patch edges. So the probes are about manbda/2 far to each other.
When their excitation is (1,0) we have a delta pattern (difference pattern).
When their excitation is (1,0) and (1,180) you have a sum pattern.. let's a cosine... There are also some other effects.
It's very simple.
Take a sqaured patch antenna, the size is lambda /2 x lambda /2 ok?
Then, consider an edge port (maybe it's simpler..) exciting the linear polarization ok? It's the tipical LP patch antenna configuration ok?
then repeat the edge port excitation in the opposite side of the patch..
U have a simmetirc structure.
If the inputs are in phase u have a "DELTA" pattern (difference),
if the inputs are in opposite phase u have a cos pattern (more or less, sum pattern)...