IoT Antenna Technologies and Factors Affecting Antenna Selection
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IoT applications rely heavily on wireless connectivity to communicate with IoT gateways and other devices in the ecosystem, especially those applications where wired connectivity is nearly impossible. This connectivity is enabled by a range of antennas that support various types of networks.
IoT platforms have evolved dramatically over the past decade, shrinking in size and incorporating advanced wireless technologies. These developments have had a huge impact on the evolution of antenna technology and IoT antenna design, resulting in ultra-compact antennas that are efficient and performant. Embedding multiple antennas in high-performance, small-form-factor IoT designs has become a standard requirement, creating significant challenges for IoT product developers.
Some of the popular wireless technologies used in IoT applications are Wi-Fi, Bluetooth, WLAN, and ZigBee, which operate in the frequency band from 2.4GHz to 5GHz. These wireless standards are capable of handling high data rates over short distances. Wireless standards such as LoRa (operating in the RF band from 169 MHz to 915MHz) and SigFox (operating in the RF band from 868MHz to 928MHz) are used for applications that require relatively longer distances and much lower data rates. The emergence of LPWANs such as NB-IoT and LTE Cat-M that provide low-bandwidth data connectivity, higher bandwidth, high throughput, low latency, and battery usage are also having a huge impact on IoT designs by providing cost-effective solutions. 5G is the fifth generation of wireless technology and is expected to further revolutionize the development of IoT and related technologies.
IoT Antenna Technology
This section briefly describes the various types of antennas commonly used in IoT devices.
Patch Antenna
Chip antennas are compact and have relatively low bandwidth. They perform better with large ground planes, which can increase the challenges of integrating high component density boards. Chip antennas have limited range, making them ideal for small IoT devices that use low frequency bands, such as computers, satellite radios, GPS devices, etc.
Wired Antenna
Wire antennas are more economical compared to other IoT antennas such as Chip and Whip. The size of a wire antenna is inversely proportional to its frequency, i.e. the size of the antenna increases as the frequency decreases, which can pose a design challenge. Wire antennas are either fixed to the PCB via a ground plane or connected via a coaxial cable that provides good RF performance. These antennas come in various patterns and shapes such as dipole, loop, and spiral and are commonly used in connected cars, smart building solutions, etc.
Whip Antenna
Whip antennas are one of the best performing IoT antennas and are also likely to be the most expensive of the commonly used antennas. They are usually located outside the device housing and physically connected to the PCB via a coaxial connector. Whip antennas are a common monopole antenna that is well suited for wireless connectivity in ISM, LoRa, LPWAN based applications. Whip antennas are well suited for designs that use multiple transceivers such as handheld radios, routers, gateway intercoms, Wi-Fi enabled devices, vehicles, etc.
Antenna on PCB
As the name implies, Antenna over PCB (AoPCB) is an antenna or antenna pattern embedded on a PCB using modern manufacturing techniques – typically copper traces on the board. PCB antennas are cost-effective and offer great flexibility in design as developers can integrate antenna designs at an elementary level. One disadvantage of antennas on PCB is that it takes up space on the board, which can present significant challenges for ultra-compact or complex designs with a large number of sensors and components. These antennas are ideal for USB dongles, automotive, and robotics applications.
Factors Affecting Antenna Selection for IoT Applications
Several factors influence the choice of antenna for IoT design - frequency band, size, range, accuracy, deployment area, etc. Usually, IoT antennas are designed in the unlicensed ISM band (Industrial, Scientific, Medical) . Each antenna is designed for a specific frequency band, keeping in mind a specific application. For example, Wi-Fi or Bluetooth may be a good choice for portable devices, wearables, gaming devices, webcams, etc., while industrial applications such as smart cities, Industry 4.0, and smart agriculture require the use of LPWAN, LoRa, SigFox, or NB-IoT.
The selected antenna should match the aesthetic requirements of the product packaging. A perfectly positioned small size antenna is more likely to provide the best performance. However, it must provide the expected coverage with the lowest possible power consumption. Sometimes, it is not only the size of the antenna that matters, but also the antenna topology. Antenna topology affects the bandwidth, radiation pattern, gain, and overall efficiency of the antenna.
One question that may come to the mind of the reader is whether to consider using a standard off-the-shelf antenna or a custom designed antenna! An off-the-shelf antenna that meets the performance requirements of the product is certainly a cost-effective solution, however, designers may face challenges in packaging such an antenna in an extremely compact design. The rigidity of the design may further affect the antenna performance. In such cases, a custom designed antenna is an ideal choice to ensure superior performance.
Another important factor to consider when selecting an IoT antenna is the regulatory standards in various regions around the world. In addition to SAR requirements, developers should also check standards such as the Radio Equipment Directive (RED), electromagnetic compliance, and FCC Class A and Class B rules.
In short, the key parameters to consider when choosing an antenna are,
Antenna Type
Working frequency band
Coverage/Range and FoV
Radiation Pattern
Antenna gain
Antenna shape and size
cost
Several design points for antenna placement in IoT devices
Choosing the right antenna is critical in IoT designs, however, this alone does not provide a solution for achieving high RF performance. It is important to note that antenna performance is a key factor in determining device battery life. Factors such as the proximity of other electronic components, the use of ground planes, signal interference, packaging materials, and proximity to the human body (learn more about the impact of the human body on antennas in the Wearable Antennas blog) greatly affect antenna performance. Therefore, developers must pay close attention to these factors during the design process.
Here are some design points for antenna placement in wireless IoT designs,
Place the antenna in a corner of the PCB to ensure that there is enough shielding area for the antenna on the PCB.
Use a ground plane with ideal width and ground clearance for maximum antenna efficiency
Avoid placing the antenna near plastic (Plastic ID) during packaging. Plastic has a higher dielectric constant than air and may affect the resonant frequency of the antenna.
The antenna must not be covered by a metal casing
The antenna orientation should match that of the final product to ensure maximum radiation in the desired direction.
in conclusion
Ultra-compact, high-gain, ultra-efficient antennas are revolutionizing the way wireless IoT devices are designed and developed. Despite this, IoT antenna design or choosing the right type of antenna remains one of the main design challenges. A great antenna ensures excellent performance, wide range, and low power consumption. Although a wide range of off-the-shelf antennas are available at frequencies suitable for IoT applications, developers may have to consider custom antenna designs to achieve optimal size and performance parameters. Designers should also understand the impact of other components in terms of design, industrial design (ID), ID materials, antenna tuning, positioning, and EMI/EMC regulations.
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