You cannot do this with Radio, you must find another solution. Radio is a little more complicated then you think, and poor topology would render your system useless. Remember, most fm antennas are omnidirectional..
Please take advice and move on to ultrasonics, sound, or infrared.. This approach would still offer a challenge, believe me
Mostly because the highs and lows are different with every sweep..
If I were to do this, I would probably use a fast 16-bit microcontroller (mps430), 16-bit-10bit ADC, and a high resolution absolute optical encoder or a high resolution stepper motor 400step/rev..
You would need to get a sample for each position from information from the encoder or from the stepper. The next part is tricky,, should someone compare each sample with the next sample? or should they gather all samples and process them? I suppose that the first solution would be best, but there would need to be an algorithm taking place. The second is easy, but there might not be enough processing time to keep up with the scanning.
This method would allow more flexibility rather then using comparators and etc., which wouldn't allow for change. For example, if the light or whatever is close, then the photoreceiver could be saturated over a large degree, giving no direction.
There are some things to think about
Steve
P.S. not gates and etc. are the least of your worries.. the process is more important