I recently set up my own RTL-SDR-based ADS-B receiver. I live in a Manhattan high-rise with an eastern view, so I do not get any signals from behind the building (almost: I get the occasional reflection). A simple (azimuth-) omni antenna is a waste, nothing is coming from inside my apartment! Similarly, there are no planes flying below my window (if there are, I'll hear them :) ), so I am only interested in the upper half of the radiation lobe. The receiver has an SMA connector.
Searching around I have found lots of omni designs for ADS-B receivers, but none that fit these requirements. The last time I thought about antenna design was in my undergraduate class on antenna design, >35 years ago; can someone please point me to some appropriate resource? Ideally, something that I can render on PCBs and tape it to my window?