The interface specifications for the N and many other connectors are referenced in MIL-STD-348. Originally, the connector was designed to carry signals at frequencies up to 1 GHz in military applications, but today's common Type N easily handles frequencies up to 11 GHz.
The coupling has a 5/8-24 UNEF thread. The center coaxial contacts are identical to TNC and BNC connectors.
The peak power rating of an N connector is determined by voltage breakdown/ionization of the air near the center pin. The average power rating is determined by overheating of the center contact due to resistive insertion loss, and this is a function of frequency.