To answer your question, I reached out to RFID4U, a training and consulting company. CEO Sanjiv Dua says there are several approaches and commercial, off-the-shelf products available.
“Many UHF [ultrahigh-frequency] readers, such as Motorola‘s FX9500, can support up to eight antennas,” Sanjiv states. “The CSL 468 can support up to 16 readers (CSL’s multiplexer is an external unit). With Impinj‘s Antenna Hub (multiplexor), you can support up to 32 antennas with one reader. RFID Span offers a UHF reader that supports up to 256 read points. SkyeTek offers the SkyePlus MXH antenna multiplexor for HF readers and SkyePlus MXU antenna multiplexer for UHF reader antennas. Each can support up to eight antennas. If your reader is looking at custom design, we can help in creating that.”
—Mark Roberti, Founder and Editor, RFID Journal