wilkins power combiner

hi i have to design a wilkinson circuit for 400-500 mhz using an Er<10 could u please tell me which is the best circuit that gives less losses at this frequency? and could u please tell me the formula as to how the thickness and the height of the dielectric can be found out

I also wanted to know what would happen if power was sent only in one arm of the wilkinson combiner and if there are losses is there any method to overcome it

The S-parameter matrix of a wilkinson divider/combiner clarifies, that half of the input power is absorbed, if you feed only one arm. Wilkinson power divider - Wikipedia, the free encyclopedia
This behaviour is by design and can't be changed. I assume, that you want a lossless power combination independent of the signal magnitudes (and phase?). As far as I know, this isn't feasible without tuning.