Factors that Affect RFID Read Range

Your RFID reader is connected to your RFID antennas, you’ve set your power too high and you’ve put your tags on the item, but you can’t read them. This post will help you troubleshoot some of the most common RFID read range pitfalls. Of course, the importance of testing cannot be stressed enough. Regardless of what is said here, you must always test, make appropriate adjustments, and then test again.

Some hardware is designed to allow the highest read values, while other hardware is designed to allow the lowest possible read values. You must ensure that your hardware and software requirements are met for your application. Here is an introduction to important hardware specifications and features.

Antenna size.

If you need a stronger signal, try using a higher gain antenna. If you need less gain, the antenna could use a lower antenna. If you have to study close up tags, use proximity antennas.

Details: Simply put, a higher gain antenna does the trick. If you want to be sure your antennas can reach farther, you need high gain antennas (e.g. 9 dBi, or higher). This question begs to be asked, “why would one want a low gain antenna?” It requires very controlled configuration for various situations. For example, a high gain antenna is not needed for systems where tags will always be within the short distance of the antennas. Some others require a scanning distance as short as fifteen centimeters. The higher the gain, the higher the band width, and vice versa. Also, lower gain antennas are smaller in size than high gain antennas; so, if your application has size restrictions on antennas, you can experiment with a low gain RFID reader.

Antenna Formulations:

If tags are aligned with antenna’s polarization, linear antennas will read farther than circular. If the antenna is not aligned with the polarization, then it will read further than linear polarized antenna.

The contents: Polarization refers to the wavelength the antenna is radiating. Linear polarization refers to light that moves along a single plane. A linearly polarized antenna beam is like swinging a sword straight up and down or side to side. The power from radar beams is spread across two axis so it can scan many planes at a time. The simplest way to imagine an RFID antenna’s field is to imagine a “tornado” emerging from the surface of the antenna. With linear antennas, tag orientation becomes much more critical because of the field. Because the power from the antenna is not split across multiple frequencies, the read range is longer.



Small tags will have shorter read ranges, and large tags will have longer read ranges. Make sure that the tag is fully facing the antenna when using a linearly polarized antenna and you should pay attention to tag orientation when using it. Lastly, when tagging objects with high liquid content, try RFID tags that are suitable for mounting on such objects.

New policy details:

The size of the tag range from inches to 50+ feet. Because of larger antennas, RFID tags can transmit signals longer.

To describe the tag orientation and read angle, let us picture an RFID tag lying flat on a stool. And then picture an RFID antenna facing downward above the stool. In this scenario, you can make an intelligent move.

Before scanning, rotate the tag 45 degrees anticlockwise. This point only matters for linear transmitters or receivers. If you have a circular polarized antenna, you don’t need to worry about the orientation of the tag. However, with linear antennas, antenna orientation is necessary. Imagine that the seat of the stool is the shape of a clock face. With a linear antenna, if the tag is correctly oriented from 8 o’clock to 12 o’clock and you are not receiving the tag signal, try switching the antenna to 6 o’clock to 12 o’clock. This is a quick test which can be applied to tags with a dipole emission (e.g. the Alien Squiggle). The dual dipole RFID tags which are capable of movement are to help offset this movement (e.g. the SMARTRAC Frog).

Turning the RFID chip on its side will impact the range at which RFID scanners can scan it. For the most energy possible from the RFID antenna, the tag should be directly facing the antenna. Take the example of naval warfare in the 19th century. In this imaginary scenario, the RFID tag is a small gunship, and the RFID antenna is an enfused 4 deck ship of the line with Lord Nelson on board. The antenna should be placed parallel to Lord Nelson in order to keep him at bay. If you like math, you can think of the antenna as an X and Y plane, while the tag corresponds to an X and Y plane. Two particles are separated by the same distance, and they never touch. In short, if you hold the tag face-on, the read-length will be longer. Some RFID tags, such as RFID wire tags, can work in 360 degree read range.

What you are tagging and where you place the tag is an easy topic to explain, but it is very crucial when it comes to read range. The uHF RFID tags are most affected by objects or liquids which contain metal (absorption of RF energy). If you do not use the right tag for the object you intend to tag, it is likely that you will not be able to tag it at all. The switches will have metal-mount RFID tag with special backing (or objects containing water). Metal tags will perform better on metal than they will off metal. Generally speaking, an RFID tag should not be applied to any object that is made of metal or water. Besides, the item will often contain a “sweet spot” that can maximise the scan range when the tag is placed within the item. To find sweet spots on specific products, one needs to carefully test them.

Higher power settings will result in longer range reading while lower power settings will result in shorter range reading. In order to maximize range on your reader, change its maximum receive sensitivity to its highest level.

Also, all RFID readers can limit how much power goes to the antennas on the cable. To know how far your reader can receive, you need to experiment with its settings. The power is doubled (or is cut in half) with every increase of 3dB. (or decrease). 27 dB is twice as strong as 24 dB and 30 dB is twice as strong as 27 dB. Although the power increase every three decibels that doesn’t mean the sensor’s read range will double. Lastly, check your reader’s receive sensitivity settings. Almost by default, these are set to maximum, and it’s worth checking these for sure. If the reader is set to maximum sensitivity, it will read tags that typically come from tags that are located farther away. End result: Maximize read range by ensuring that your reader is set to its highest sensitivity and power.

Coaxial Cable, Multiplexers, and Adapters:.

As the cable length increases, you introduce additional losses. In order to achieve maximum read range, install the antenna as close to the reader as possible and never use unnecessary connectors or add ons. Regardless of the length, you should always use a higher rated cable as a compensating factor.

New policy details:

The antennas which are connected to the RFID reader consume energy because of leakage of energy. The longer the cable, the more power, and energy it will lose, which eventually will result in the antenna not being sufficiently powerful to generate a strong magnetic field (regardless of the antenna gain). To maximize read range and the RFID reader is a significant distance away from the antenna (i.e. 20 feet or more), you should use a cable with higher wire strength. If your application doesn’t demand much bandwidth, a lower lossy cable will be suitable for longer cables.

Some adapters can be used to convert the end of an antenna cable from one type to another. However, this comes at the expense of using other devices. Multiplexers, such as Impinj antenna hub, split up one cable into many, but add more loss into the transmission. The Impinj network hub contains approximately 1 dB of loss. If you mostly use Wi-Fi, there could be no way to escape the loss of protection (which affects the read range). This is important in dollar-cost averaging.

Environment: Environment Factors

Many environment factors can affect detection. Make sure you account for read range degradation due to various forms of noise.

New policy details: There are many environmental conditions affecting the performance of UHF RFID systems. There may be adverse effects of water, metal, fluorescent lighting, large machinery, and competing frequencies on the UHF RFID read ranges. Taking measures to manage interference would provide better and improved results.

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