Spurious-Free Dynamic Range (SFDR)

Spurious-free dynamic range (SFDR) is two-thirds the difference between the 2-tone, third-order intercept point (IP3) and the minimum discernible signal (MDS). Referring back to Figure 1, it can be seen that the 3rd-order product line has a 3:1 slope while the fundamental output line has a 1:1 slope. Therefore, the 3rd-order products are always three times as far from the IP3 as the fundamental output. If you use the SFDR as the power of the output tones (dBm) and plug it into the equation for IP3 calculation from the Intercept Points (IP3 & IP2) section of the RF Cafe web site, the power of the 3rd-order products will be right at the MDS power level.

Spurious-Free Dynamic Range chart plot - RF Cafe Website

Figure 1

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a lady's voice announced "You've Got Mail" when a new message arrived...