A Circular-Polarization Reconfigurable Meng-Shaped Patch Antenna
Ignoring the paper quality and concept itself...

Answering your question in the comment: 

D in that figure is the diameter of the probe feed, I think. If you look at the bottom part of figure 1, you see that the antenna is made by using two separate PCBs that are spaced a significant distance apart. Fv is the height of these feeding probes.

Skimming over the paper, the 'antenna' they present can do both LH and RH polarization. This is probably because it two modes where it resonates, and by changing where/how you feed the antenna, you can change which mode you excite, and thus which polarization is radiated. This is what the diode switches are for. By turning one of the sets on, they can control which feed is connected to the input.