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Are Bistatic or Monostatic Readers More Effective?

Posted By RFID Journal, 05.24.2010
Which is better: An RFID interrogator with four bistatic antennas, or one with eight monostatic antennas?

—Name withheld

Bistatic antenna systems generally deliver better performance in passive ultrahigh-frequency (UHF) RFID systems, because they have separate, dedicated antennas to send and receive signals, while a monostatic system utilizes the same antenna to both transmit and receive. Monostatic readers emit a lot of energy to power up a tag, then must stop and start again in order to receive a weak signal back from the interrogator. Their sensitivity and dynamic range are generally not as good as those of a bistatic system.

The main reason for choosing a monostatic system over a bistatic system is cost. It is cheaper to use one antenna to send and receive than two. However, if your choice is between an eight-port monostatic reader, which has eight separate antennas, and a four-port bistatic reader, which also requires eight antennas, the expense is likely to be the same. So under most conditions, I would choose a four-port bistatic system over an eight-port monostatic system.

Of course, if the eight-port monostatic antenna can cover two dock doors or portals, and the four-port bistatic antenna can cover only one portal, then it might be more cost-effective to use the monostatic antenna system.

—Mark Roberti, Editor,
RFID Journal


M F 2013-07-17 07:56:58 AM
"The communication link between interrogators and tags is half duplex, meaning that Tags shall not be required to demodulate Interrogator commands while backscattering. A Tag shall not respond to a man datory or optional command using full-duplex communication."(from EPC Gen2 RFID Protocol for communication at 860-960MHz ver 1.2.0) Even when the communication between Tag and Interrogator is half duplex, will bi-static antenna configuration perform better?
edmilson moreira 2015-06-11 09:54:34 AM
Interrogation zones, like portals, presents a much more uniform power distribution with the use of mono-static readers. Bi-static readers also present a problem that is related with the use of 2 antennas to read one tag: The greatest read range for a tag in a mono-static configuration is the minimal in bi-static configuration and while one tag is closer to emitters antenna sweet spot(phi=0, theta=0) it is probably getting far away from the same region in receivers antenna, compromising link budget. The challenge in mono-static reader is present in their development but in general the better financially and technically than bi-static ones, especially in large tags densities seen in item level applications.

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