Pratt and Whitney J58-P4 - Blackbird SR-71 - Duxford
If you need to sustain Mach 3, then look no further than the Pratt and Whitney J58-P4, which flew on the Blackbird SR-71 from 1964 to 1998. (SR stands for Strategic Reconaissance).
The SR-71 P&W engine was essentially a hybrid, with a turbojet inside a ramjet. The engine developed a static thrust of 32,500 Ibs and functioned at high speeds, basically, with air compressed by variable spikes mounted on the intake, which bypassed straight to the afterburners through six tubes on the exterior of the engine.
At slower speeds, traditional compression was used, with air passing through the core, mixed with fuel, then burnt in the combustion chamber.