What is RFID and how does it work? Tag, reader and antenna explained

At the shipping gate a pallet moves slowly forward. Nobody scans the cartons one by one, yet the count on the screen next to it rises by itself, and as the pallet leaves the gate, the products expected to ship and those read stand side by side. Someone seeing the scene for the first time might take it for magic; in fact it is a few small parts working together. The same logic can count garments on a rail, cartons on a shelf or parts on a production line. This article explains from start to finish what those parts are, how they talk to one another and in which situations RFID can cause problems.

RFID, short for Radio Frequency Identification, is the technology that lets the identity on a tag attached to an object be read by radio waves, without contact or line of sight. Unlike a barcode, the reader does not need to look at the tag, and many tags can be read at the same time.

What parts make up an RFID system?

• Tag: made of a small chip and an antenna connected to it; in most applications it carries only an identity number.
• Antenna: the part that sends out the reader’s radio signal and collects the tag’s reply; its direction and position determine the read zone.
• Reader: the device that drives the antennas and collects the identities coming from the tags. It can be a fixed gate, a tunnel or a handheld terminal.
• Edge computer: runs right next to the reader, cleans up repeated reads of the same tag and applies simple rules.
• Software: matches the identity to a product, batch, serial or location record and passes the result to the ERP, warehouse or production system.

How does an RFID tag work?

How a tag works depends on where it gets its energy. A passive tag has no battery of its own; with the tiny amount of energy it takes from the field the reader emits, it wakes its chip and answers with its identity. It is the type most used in warehouses, retail and production. An active tag has its own battery and can send a signal by itself; so it can be seen from farther away, but it is bigger, more expensive and limited by battery life.

The tag itself usually does not know “what it is”; it only says “who it is.” It carries an identity number, and which product, carton or batch that number belongs to is kept in the software. The step of matching the tag to the product record is therefore the foundation of the system.

How does an RFID reader work?

1. The reader emits a radio signal through the connected antenna and creates a read zone.
2. Passive tags entering the zone take energy from this signal and wake up.
3. Each tag answers with its identity; even if the answers arrive at the same time, the reader applies a collision management that tells the tags apart one by one.
4. The reader can see the same tag many times during the read; these raw reads are sent to the edge computer.
5. The edge layer weeds out the repeats, compares them with the expected product and location, and produces a clean result.
6. The software shows the result on screen and passes the approved movement to the central system.

How does a read turn into a product movement?

Picture the goods-receiving gate of a fictional warehouse. As tagged cartons from a supplier pass through the gate, the reader collects the identity of each tag. The edge computer reduces repeated reads of the same carton to a single record, compares them with the cartons expected on the order list and puts three groups on the screen: those that match, those on the list but not read, and those read but not on the list. The operator looks at the missing or extra cartons, confirms the result, and the software sends that confirmation to the central system as a stock movement. A tag says nothing on its own; the value comes from the read meeting a record and a rule.

RFID advantages and disadvantages

RFID is not the answer to every problem. The table below puts next to each advantage the cost that comes with it.

Where is RFID used?

• Warehouse and goods receiving: comparing incoming and outgoing cartons with the expected list.
• Shipping: counting the pallet as it leaves the gate and spotting missing or extra products before dispatch.
• Retail and hanging products: counting products on shelves or rails without opening the box.
• Production tracking: following at which station and in which operation a work order is, through tag movement.
• Fixed assets and equipment: recording the location and history of vehicles, equipment or crates on pallets.
• Archives and documents: finding and counting files and folders on shelves.

What these uses have in common is that many objects need to be counted in a short time and matched to a record. If you are tracking only a few items, RFID’s setup and tag cost is mostly unnecessary; if there are hundreds of movements every day, the time and error risk of manual counting come to the fore.

Why does an RFID read sometimes fail?

The technology is not flawless; most problems come from the field. Metal surfaces reflect the signal, products containing liquid absorb it, the orientation or position of the tag may not match the antenna field, tags stacked on top of one another shadow each other, and other readers or machines nearby can create interference. If the read power is turned up too far, this time the tags in the next aisle are read too. That is why a sound installation first measures the site, then sets the read zone to cover only the target area. The success of a read is tested not in a laboratory or a brochure but where the products really pass; the same tag may read without trouble on a cardboard box and not at all inside a metal crate.

Where do barcodes, paper and Excel fall short for counting?

For a small number of items and a slow flow, a paper list, barcodes and Excel are enough; they cost little and are easy to learn. The problem starts as the number of items and the speed rise: cartons are scanned one by one, counts take days, and the difference between the list and physical stock is understood only after the count. A barcode helps with fast reading but requires the reader to look at each tag in line of sight. This is where RFID comes in, but only if the tagging arrangement, the product type and the flow suit it. RFID is unnecessary for every product; the practical rule is that it makes sense as counting volume and the cost of error rise.

How do the YazSis RFID Tunnel and handheld terminal fit into this chain?

YazSis RFID & IoT systems focuses on building this whole architecture in the field. The RFID Tunnel, with the readers and antennas inside it, counts tagged products in cartons, on hangers or on pallets in bulk as they pass through, and shows the result live on a connected laptop. The RFID handheld terminals do mobile counting without opening cartons or while products are on hangers or shelves, and show progress on the terminal screen. The data that is read can be passed in real time to a computer, the organization’s server or a cloud infrastructure.

The four principles of the chain are: measure the site, calibrate the read zone, validate at the edge layer, connect to the system. Matching the tag to the product or batch record, weeding out repeated reads and validating against expected product and location rules are on the software side. The scope of integration is set per project.

The general advice is to start with a single flow: for example, choosing only the shipping gate or only one product group and trying it with real products is far less risky than converting the whole warehouse at once. If the results are good, the flow is widened; if not, the tag, position or read-zone setting can be changed at low cost.

To see whether RFID makes sense in your own product flow, you can start from the RFID & IoT systems page and discuss your counting scenario together with real products.