Multiplexer
HardwareHardware device that allows a single RFID reader to connect to and switch between multiple antennas beyond its built-in ports.
Multiplexer
An RFID multiplexer (mux) is a hardware switching device that allows a single RFID reader to connect to and sequentially switch between more antennas than the reader's built-in antenna ports support. This expands coverage area and read-zone flexibility without requiring additional reader hardware.
Why Multiplexers Are Needed
Most fixed UHF RFID readers have 2 to 8 built-in antenna ports. However, many installations require more antennas than ports available:
- A warehouse portal reader system may need 12-16 antennas across multiple dock doors but only deploy 2-4 readers.
- A conveyor tunnel might require 8 antennas (top, bottom, left, right at two positions) connected to a 4-port reader.
- A smart shelf deployment with 32 shelf-level antennas connected to a single reader via a 32-port mux cascade.
How Multiplexers Work
The mux sits between the reader's antenna ports and the antenna array. It contains RF switches (typically PIN diode or GaAs FET based) that route the reader's transmit/receive signals to one antenna at a time. Switching is coordinated with the reader's inventory cycle through GPIO triggers or LLRP commands.
| Parameter | Typical Values |
|---|---|
| Port count | 8, 16, 32, or 64 output ports |
| Insertion loss | 0.5 - 2.0 dB per stage |
| Switching speed | 1 - 10 ms per port |
| Isolation | > 30 dB between ports |
| Cascade | Multiple muxes for higher port counts |
Impact on Performance
Multiplexing trades time for coverage. Since only one antenna is active at a time, the effective dwell time per antenna decreases as port count increases. A 4-port reader with a 16-port mux spends only 1/4 of the time on each antenna group compared to a dedicated reader. This affects read rate and may reduce detection probability for fast-moving items.
The insertion loss of the mux also reduces the RF power reaching each antenna, directly impacting read range. A 1.5 dB insertion loss reduces range by approximately 15%. This loss must be accounted for in the link budget.
Deployment Best Practices
Engineers should size the multiplexer based on the slowest acceptable scan cycle time and minimum required reads per tag. For high-speed conveyors, dedicated reader ports (no mux) on critical antennas are preferred. For static inventory (shelving, storage), multiplexed antennas with longer dwell times are cost-effective.
See also: Portal Reader | Link Budget | Read Rate
الأسئلة الشائعة
The RFID glossary is a comprehensive reference of technical terms, acronyms, and concepts used in Radio-Frequency Identification technology. It is designed for engineers, system integrators, and project managers who work with RFID and need clear definitions of terms like EPC, backscatter, anti-collision, and ISO 18000.
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