content: It is not a repeater it is different: WiFi backscatter PDF: https://homes.cs.washington.edu/~gshyam/Papers/wifibackscatter.pdf You still need your normal powered wifi (T1) that is your transmitter. This radio energy gets absorbed by the passive Wifi device (P1) and used as energy source. Now here comes the key, a second wifi device listens (L1) to T1, but the P1 device will either absorb the T1 energy or not absorb the T1 energy so that the L1 device will detect a very tiny variation in T1 energy. And that is the information.  The equivalent would be that you put a loud speaker in one room (T1), and a microphone at another room (L1) and the passive wifi device  (P1) would open or close a shutter somewhere in the room that cause more or less absorption of the sound.  Or another way to see it could be a light (T1) in one place and a light detector (L1) in another place and you have a device (P1) that absorbs more or less light. And P1 gets powered by the light of T1.