Prototype antenna
One of the first design challenges Pulse faced was how to integrate the feed structure into the constraint space. To start, an aperture coupling structure was selected because of its traditionally good port-to-port isolation characteristics due to the orthogonal port excitation resonant modes. However, because of the low operating frequency of 880-960 MHz, the physical size of the feeding aperture was deemed too large (exceeded constraint space requirement) if made symmetrical. Therefore an asymmetric configuration resulted: Port 1 feed aperture was of optimal length and Port 2 feed aperture was short, yet tuned to frequency by widening the arms at the end of aperture (Figure 2).