Tracking a radio signal

[Al Skierkiewicz]

Theoretically you could have a shuttered antenna array such that multiple dipoles backed by reflectors would keep antennas from receiving in multiple directions at the same time. A simple RF switch would then allow one receiver to sense signals from different directions based on the switching. The tough part is scaling down an antenna array at this frequency. A dipole is still over one foot long. I suppose you could effectively couple from something smaller, saya few inches. So the device looks like pie segments from the top. A dipole is fit into each corner so that it effectively can only receive in 90 degree increments for a four section assembly. Four dipoles gives you four separate directions. If you sense data and position the platform so that your are flying/receiving from the correct transponder, while the others transponders could be used for stabilizing the path.
You might also take a cue from instrument flying. There are high gain antennas pointed straight up at specific distances from the target that can only be received when directly overhead. (you might remember the phrase "I'm over the outer marker now" in some flying movies) This system would allow you to know distance to target with another receiver.
Remember that RF in free space is essentially traveling at the speed of light. Phase over short distances at the speed of light are extremely difficult.