How to Select RFID Antenna

An RFID antenna is a necessary part of any RFID system. Unless the antenna is embedded into a reader, you will need to select and purchase the right antenna for your application. There are many options to choose from. Selecting the right RFID antenna can depend on several factors, such as the application, frequency band, read range, and mounting requirements.

Here are some general steps you can follow to select an RFID antenna:

1. Frequency Band:

Ensure that the antenna operates in the same frequency band as your RFID tags. RFID systems operate in different frequency bands, such as low frequency (LF), high frequency (HF), ultra-high frequency (UHF), and microwave.

2. Antenna Type:

There are various types of RFID antennas, including linear, circular, patch, and near-field antennas. Choose an antenna that is compatible with your application and the shape and size of your tags.

3. Read Range:

The read range of an RFID system is the distance between the reader and the tag, and it depends on the antenna type and the frequency band. Smaller antennas within the same frequency band will have a shorter read range, and vice versa. The antennas with the shortest read range for UHF technology are near-field antennas, which utilize near-field as opposed to far-field like regular UHF RFID antennas. These are often used for item tracking and where short ranges are required for item singulation and/or security purposes.

4. Frequency Region:

This will depend on the country of operation and will affect only the UHF frequency. Due to regulations, the frequency bands for UHF RFID slightly differ between the US, Europe, and other regions. Most UHF antennas are specified as global, and they are tuned for operation between 860 to 960 MHz. You can also find antennas that are specifically tuned for each region, which can slightly improve their performance in that region. For instance, an 865 - 868 MHz antenna will perform better when deployed in Europe than a global antenna, although this may not be distinguishable in most applications. A global antenna will work well for most applications; however, you can choose a region-specific antenna for difficult deployments (long read ranges, RF challenging environments) or where a global option is not available.

5. Antenna Gain:

Antenna gain refers to the ability of the antenna to transmit or receive signals in a specific direction. Choose an antenna with appropriate gain to achieve the desired read range and performance. Antenna gain affects read range and beam width. Antennas with higher gain will have a longer read range but a narrower beam. Antennas with lower gain will have a shorter read range and a wider beam width. Select antenna gain based on the shape of your interrogation zone and coverage needs. The most common gain is 6 dBi, but you can find antennas with 1 dBi (low gain) and 11 dBi (high gain).

6. Polarization:

Consider the polarization of the antenna. RFID antennas can be linearly polarized or circularly polarized. Choose an antenna that matches the polarization of your RFID tags to ensure optimal performance. Depending on your requirements, you can select between circular and linear polarization. Circularly polarized antennas will have a shorter read range but will be less sensitive to orientation. You can choose between right-hand circularly polarized antennas (RHCP) or left-hand circularly polarized antennas (LHCP). Sometimes, you may encounter dual circularly polarized antennas that have both left-hand and right-hand polarization.Linearly polarized antennas will provide a longer read range and a more focused beam but will only read tags that have antennas parallel to the plane of the wave. If your tag orientation is not fixed, especially when using single dipole tag antennas (which are the most common), you should select a circularly polarized antenna.

7. VSWR:

Voltage Standing Wave Ratio (VSWR), also known as return loss, refers to the mismatches in impedance within the connector, which can cause some of the signals to be reflected. The ratio of the input signal to the reflected signal is called the Voltage Standing Wave Ratio (VSWR). This ratio can also be measured in dB and expressed as return loss. The VSWR signifies antenna design efficiency; the lower the VSWR, the smaller the return loss, and the better the antenna (an ideal VSWR is 1:1).

8. Beam Width:

Select the elevation beam width (vertical, up, and down) and azimuth beam width (horizontal, left to right) based on the desired coverage of an interrogation zone. Wider beamwidth antennas will provide broader coverage without the need for additional antennas; however, the read range may be shorter (which is often desired to avoid reading tags outside the portal or door).

9. Axial Ratio:

The axial ratio is the ratio of orthogonal components of an E-field. A circularly polarized field consists of two orthogonal E-field components of equal amplitude, which are 90 degrees out of phase. Because these components are of equal magnitude, the axial ratio is 1 or 0 dB. Axial ratios are often specified for circularly polarized antennas. The axial ratio tends to degrade away from the main beam of an antenna; therefore, in the spec sheet for an antenna, you may sometimes see information such as: “Axial Ratio:

10. Antenna Connectors:

There are several common types of connectors used with RFID antennas. They can be male or female and can be regular or reverse polarity. Each manufacturer prefers certain connectors. In general, the connectors do not affect performance; some are smaller and less bulky, making them suitable for tight spaces or easier to hide, while others work better with thin cables. On the other hand, larger and bulkier connectors are sturdier and compatible with thicker cables and harsher environments. You must know what connector your antenna has, as well as your reader so that you can purchase a cable that will pair with them. The most common connectors are N-type, RP-TNC, and SMA (the least bulky). Don’t forget that you must pair female and male connectors.

11. Mounting Requirements:

Check the mounting requirements of the antenna, such as the type of connector, mounting orientation, and mounting location. Ensure that the antenna can be mounted in the required location and orientation.

12. Interference:

Check for potential sources of interference in your environment that may affect antenna performance. Choose an antenna designed to minimize interference. Identify any causes of interference in your environment, such as metal objects or other RFID systems, that may impact antenna performance.

13. Profile Width:

If you are short on space or have aesthetic considerations, you may need to look for low-profile antennas that have a side connector or a side pigtail.

14. Front to Back Ratio:

This ratio indicates the ratio of forward-to-backward signal transmission. Most, if not all, antennas also radiate to the back of the main beam, which is often due to the signal bending from the main beam. You want this ratio to be as large as possible unless you plan to utilize the back beam (which is not usual).

15. Environmental Protection and Ruggedness:

Select an antenna with a suitable IP rating and made of materials that will withstand the environment in which it will be installed. Most antennas are enclosed in hard plastic, but there are also all-metal antennas (suitable for very harsh environments or where they may suffer impact) or antennas encased in rubber (for mounting on the ground).

We carry a wide range ofRFID antennas of various form factors and sizes so that you can pick the perfect one for your application. Select from linearly polarized and circularly polarized RFID antennas, as well as RFID antennas that are either global or tuned for a specific region (USA or EU). We also carry UHF near-field RFID antennas and HF and NFC options. If you are unsure which RFID antenna would work best for your project, contact us. We would be happy to help!

Antenna Selection Criteria Review:

1. Frequency: This will depend on your tags; choose between LF, HF, UHF, or microwave frequency.
2. Antenna Type: These include RFID antennas such as linear, circular, patch, and near-field antennas.
3. Read Range and Size: Smaller antennas within the same frequency will have a shorter read range, and vice versa.
4. Frequency Region: Global, USA, EU, or country-specific; use global or per region.
5. Antenna Gain: Gain affects read range and beam width. Antennas with higher gain will have a longer read range but a narrower beam. Antennas with lower gain will have a shorter read range and a wider beam width.
6. Polarization: Choose between circular, dual circular, or linear polarization.
7. VSWR: Look for a VSWR as close to 1:1 as possible.
8. Beam Width: Select based on your application and need for coverage.
9. Axial Ratio: Aim for an axial ratio as close to 1 or 0 dB as possible.
10. Antenna Connectors: Common types include N-type, RP-TNC, and SMA. Consider your space and mounting; some connectors are bulkier than others, with SMA being the smallest.
11. Mounting Requirements: Check the mounting requirements of the antenna, including the type of connector, mounting orientation, and mounting location.
12. Interference: Choose an antenna designed to minimize interference.
13. Profile Width: If you are short on space or have aesthetic reasons, consider low-profile antennas that have a side connector or a side pigtail.
14. Front-to-Back Ratio: You want this ratio to be as large as possible unless you plan to utilize the back beam (which is not usual).
15. Environmental Protection and Ruggedness: Select an antenna with a suitable IP rating and made of materials that will withstand the environment in which it will be installed.

Conclusion: How to Select an RFID Antenna

Selecting the right RFID antenna is essential for the success of your RFID system. Antennas play a crucial role in determining the performance and efficiency of your RFID applications. By considering factors such as frequency, antenna type, read range, polarization, and environmental conditions, you can ensure that you choose an antenna that meets your specific needs.

It's important to remember that the right antenna can significantly enhance the reliability and effectiveness of your RFID system. Whether you require a low-profile design for space constraints or a rugged antenna for harsh environments, understanding the selection criteria will help you make an informed decision.