Microwaves&RF, an electronics engineering trade magazine is running a two-part series on receiver basics. Part 1 discusses noise figure, direct-conversion receivers, and single-conversion superheterodyne receivers.
Part 2 covers dual-conversion superheterodyne receivers and direct RF sampling receivers (shown below). There’s also a short discussion of the performance characteristics of each type of receiver.
This discussion is pertinent because advances in analog-to-digital converter technology is allowing manufacturers to direct RF sampling receivers. The Elecraft KX3, Flexradio transceivers, and the new and much-touted ICOM IC-7300 all have direct RF sampling receivers.