Specs on microwave power divider/combiners

I'm thinking that something like this:
http://www.mini-circuits.com/pdfs/ZN2PD-9G+.pdf ...is a multi-stage Wilkinson
divider internally. I'm curious how they decide to specify its frequency
range... anyone know? Based on this data *** and others I've looked at, I'm
thinking that the low-end (1.7GHz) is spec'd based on the isolation between
the split/combined ports becoming "unreasonably" low (20dB, or thereabout),
whereas the high-end (9GHz) is based on the insertoin loss becoming
"unreasonably" high (~1dB over theoretical minimuum).

If you're just using a Wilkinson like this as a splitter and have a very good
match on the output ports, presumably you can use it to much lower
frequencies? At DC, for a 50-ohm 2-way Wilkinson, the input is looking at 25
ohms (=VSWR of 3:1=return loss of -9.5dB, still acceptable in some cases) and
(since at this point it's just a resistive splitter, really) the overall
insertion loss is also 9.5dB or 6.5dB over the minimum.

---Joel


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