build swr meter

Hi...all,

I want to build swr meter for vhf band using pcb fr4,substrate thickness 1,24mm
i have some pic of directional coupler design..and confuse about it...

my question is
1. can some one give me some formula to design ?
2. what the difference of two pic ? are same design ?

The difference is what you see. The small picture shows a 6-port coupler, the large a standard 4-port. SWR meters are often using a 6-port coupler, because it's directivity is nearly unaffected by mismatching of the detector outputs.

can u or some one give some formula or reference to design 6 port coupler ?

Check out Mongia's book on couplers. Very good.

Might I suggest you look at a dual directional coupler instead? These are commonly implemented for SWR measurements.