The problem...
Running from a 2.2 GHz clock and squeezing power, I'm using T-flops (toggle-flops).
I DIV2 on positive edge to get 1.1GHz I also DIV2 on negative edge to get 1.1GHz but shifted +/- 90°
Continuing with the dividing I get down also to...
137.5MHz and 137.5MHz, angle +/- 90I want to mix the 1.1GHz and 137.5MHz signals to get either 1.2375GHz or 962.5MHz in a image-reject mixer
The snag...
The sum/difference depends on phasing of each component, but, since each of the final components started out from toggle flops the final sign of the 90° is unknown.
Anyone have clever ideas to determine whether each component is + or -
90° ??If I can determine phase I can flip to the correct phase thru a PECL inverter.
If I can solve this then the system can simply call for high or low sideband and be assured its the right one.
Right now it's random :-(
This is on an ASIC, so I must DESIGN the circuit, NOT buy something off-the-shelf which consumes more power than this whole WiFi chip.
...Jim Thompson