This engine is a similar in principle with the ramjet engine. The main difference is that the flow inside the engine remains supersonic and the shockwaves contributes sustantially in the overhaul compression ratio.
It is very difficult to sustain a flame front under these flow conditions and most engines are still in the early experimental stage (like NASA/Boeing's X-43 and Qinetiq's HyShotIII).
If however they reach operational status scramjets can operate efficiently in hypersonic velocity (~10+mach) and high altitudes while scramjet equipped aircraft can be lighter in comparison to the equivalent rocket powered because there is no need for onboard oxidiser as the scramjet receives oxygen from the atmosphere