Multipath Fading Measurements at 5.8 GHz for Backscatter Tags With Multiple Antennas

Multipath fading can be heavy for ultra-high frequency (UHF) and microwave backscatter radio systems used in applications such as radio frequency identification (RFID). This paper presents measurements of fading on the modulated signal backscattered from a transponder for backscatter radio systems that use multiple antennas at the interrogator and transponder. Measurements were performed at 5.8 GHz and estimates of the backscatter channel envelope distributions and fade margins were calculated. Results show that multipath fading can be reduced using multiple transponder antennas, bistatic interrogators with widely separated transmitter and receiver antennas, and conventional diversity combining at the interrogator receiver. The measured envelope distribution estimates are compared to previously derived distributions and show good agreement.