Phase Discriminator Design

Anyone know what the block diagram is of the inside of one of these phase discriminators, like an Anaren 20757:

http://i90.photobucket.com/albums/k2...PHDiscriml.jpg

It has two inputs and TWO SETS of I/Q outputs? Why two sets of outputs? I would think one set of I/Q outputs would be sufficient to measure the phase difference between the two inputs. I am having trouble figuring out what the block diagram of the internal guts is, and what the actual output signal is--detected output (video) or I/Q IF frequency or ?

I would guess that it is a frequecny discriminator with 2 IQ discriminators.
One with a short delay line for coarse measurement and one with a longer delay line for finer measurement. The longer delay line will give an ambiguous readout that can be resolved with the output of the short delay line.
Ouput is video.

It is the same size as a frequency discriminator, except that it has two inputs. I do not see how you can use an internal delay line with two differenct (phase coherent) inputs.