I'm working on a phased array radar design, and I'm trying to work out the best way to combine the different receive signals from various antenna. I'm also trying to reduce cost as much as possible, so reducing the number of RF switches, active components etc is important.
The frequency range of interest is 2-3GHz, and the signal will be narrow band (that sweeps 2-3GHz).
Each element is a transmit and receive module (TRM) and can be switched from one to the other by serial control. This means I need to be able to selectively combine any number of RX signals from the total (for the sake of argument 16).
Simply connecting all signals into large combiner or cascade of combiners is going to lead to the situation where some of the input ports are driven and some are floating, connected to a length of copper that is unterminated at the end. Will this cause issues and am I likely to loose power up the floating track of the unused input port? Will the port-port isolation help alleviate this?
Is there a particular type of combiner that is most suitable to this kind of scenario? Something that can be realized by PCB etch and passives would be absolutely ideal.
I can add in a switch to a short terminated stub so that unused input ports are terminated, but that's a lot of extra RF switches that I'd rather avoid if possible.