RF powercombiners

can anyone tell about the workiing principle of RF power combiner. For Example 10dBm power is fed to the I/P of 4-way power combiner, what will be th power at the O/P port{a) If all other ports except I/P port is termibated by 50 Ohm impedance.(b) If all other ports are kept open.

http://www.macom.com/Application%20Notes/pdf/m561.pdf
http://www.minicircuits.com/pages/pdfs/pwr2-4.pdf

in 4 way power the i/p power=dBm
if 50Ω terminate all other ports,the o/p of port (a)=4dBm.
if all other ports open some more loss will come.

For a typical Wilkinson type power combiner, if your input power is 10dBm your output power(s) is 4dBm.

Loss = 10LOG(N) N=number of outputs

A resistive splitter will give 12dB loss, -2dBm.

Niether example includes additional losses due to mismatch, resistance, etc.

Rod