RFID Read Range - 6 Crucial Factors

Data is transferred between devices using radio waves in RFID technology. To exchange tags, both the tag and the reader must be within the acceptable read range.

What determines the RFID read range?

The RFID read range is affected by a variety of factors. An in-depth analysis of these factors is presented in this article.Find out more by reading on.

How does Read Range work?

An RFID tag can detect radio waves from an RFID reader up to a certain distance away. Whenever the tag is within this range, it becomes active and can be read by the reader.

As long as the tag is within the 10 cm read range, the reader will capture all the data.

A tag that moves away from the 10 cm (like 12 cm) will not capture radio waves and will not be able to transfer data.

How far can RFID be read?

RFID tags operate at different frequencies. As shown below, each operation zone has a maximum read distance:

Passive tags with low frequencies (125 kHz and 134.3 kHz)

Water and metal do not affect this frequency range. There is a maximum reading distance of 30 cm (approximately 1 foot). In some cases, LF tags can achieve a wider read range in special circumstances.

When using specially designed readers that allow 1-2 meters, for example. It is also possible to read tags up to two meters away by using a large tag.

Passive tags with a high frequency (13.56 MHz.)

It is possible to read HF tags from a distance of 1.5 meters or less. Using a multiport and customized antenna can extend the read range.

To achieve a distance of more than 1 meter, you will need a reader with a minimum of 1 watt RFID output power.

Passive Ultra-High Frequency Tags (860 - 960 MHz).

The maximum read distance of these UHF tags is over one meter (approximately three feet). With a full 4-watt reader, you can read more than 16 meters away!

Active tags with an ultra-high frequency (433 MHz.)

With these tags, the reading range can be adjusted from 30 cm to 3 kilometers. A high gain antenna and a 433 MHz reader are used.

2.45GHz super-high-frequency active tags.

There is a reading range of approximately 100 meters with these tags. Having real-time location information makes it ideal for tracking assets.

RFID Read Range Factors

Several factors affect the RFID read range, in addition to the frequency strength. Among them are:

Gain of antennas

In antenna gain, input power is converted into radio waves directed in a specific direction by a transmitting antenna.

In technical terms, you'll gain by:

Directivity x Efficiency = Antenna gain

It indicates how strong a signal can be sent or received by the antenna in a particular direction. The greater the antenna gain, the greater the reading range. The antenna gain should be low if you need to read RFID tags over a short distance.

The importance of antenna gain

You can regulate the read range using this parameter. It is not always necessary to have a long read range, contrary to popular belief. The following situations may require a low range read distance:

If you don't want the reader to capture data from other tags besides the targeted one

The reader captures data only from one tag located within a short distance of the antenna

A long read range would be useless in both situations. Due to this, you will use a low-gain antenna to perform the duties.

The size of low gain antennas is smaller than that of high gain antennas. You should consider both size preference and gain when making your choice.

Polarization of antennas

Magnetic and electric fields are perpendicular to the propagation direction of a radio wave. Electric fields oscillate when they pass through a medium. Antenna polarization describes the direction of oscillation.

In general, linear-polarized antennas have a wider read range than circular-polarized antennas if they are aligned to the antenna polarization. Conversely, circular-polarized antennas will have a better read range if the tags are not aligned with the polarization.

SOAP tag (Size/Orientation/Angle/Placement)

Size of the tag. A tag's size is directly proportional to its read range. The longer ones will have a larger read range than the shorter ones.

Tag orientation and read angle. Antennas with linear polarization are the only ones affected by tag orientation. When a tag is tilted, the reader's ability to capture the data is significantly diminished. You should position your reader so that it can read the tag within a given line of sight when it is mounted.

Placement of tags. As UHF RFID tags are affected by metal and water environments, this consideration is particularly important. When selecting the placement areas for tags, you should be careful. Tags should not be placed in metallic or aqueous environments unless the manufacturer specifies that they can.

Settings for the reader

Your RFID reader allows you to control the power going to the antenna when you buy it. The higher the power setting, the greater the reading range.

If you want to optimize the read range, make sure your reader has the highest receive sensitivity. When combined with full power, this setting will give you the best reading range.

Multiplexers, adapters, and cable lengths

Energy leaks are more likely to occur with longer cables. Make sure that the antenna cables are thick enough to prevent energy loss if they are long.

Adapters and multiplexers also contribute to energy loss. Consequently, you should remove any RFID adapters you don't need.

Factors related to the environment

There are several environmental factors that affect the read range significantly. Fluorescent lighting, water, metal, other radio waves, and large machinery will reduce the read range.

Various readers should be tested in different environments in order to determine whether your current environment affects the read range adversely.