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It looks like a simple monopole over a reference earth strip.
The monopole varies in width and is very broad on the top. This adds distributed capacity to the monopole and makes the b/w larger.
The horiz strip is some extension "capacitive hat" I guess.
I think performance might leave some things to be desired though.
What is the brandname/type ?
hmmm......... one should analyse in Ansoft Designer planar or HFSS to get a better feel on it.
I analyzed the antenna for you with MWS. I assumed a FR-4 basematerial with an er of 3.8 and 1.6mm thickness.
The antenna has an impedance of about 150Ohms and is usable starting from about 600MHz. At 900MHz you will have a gain of about 4dBi. The main direction of the farfield is the y-axis (antenna lies in xy plane). The FB ration is about 8dB.
The stub in the right upper corner removes a sharp resonant point at 2.3GHz and increases gain and directivity.
This antenna is the two dimensional approximation to a conic monopole (called discone) over a ground plane. Notice that it works like a high pass filter. As you go higher in frequency the radiation pattern breaks up into peaks and nulls just like a wire dipole that is several wavelengths long.
The angle of the "cone" determines the impedance and the length determines the "cutoff" frequency.
The dipole version of this antenna is called a 'bow tie" for obvious reasons.
In the three dimensional case the shape of the large end has some effect and spheres and cones are sometimes used. The two dimensional case would then have a curved or pointed broad end.
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