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How to choose and use WiFi antennas for IoT devices

Category: Wireless

08/10/2024

How to choose and use WiFi antennas for IoT devices

Introduction to WiFi antennas and their applications

Wi-Fi is a versatile technology used in a wide variety of sectors and applications such as home automation, business, public spaces, industry and transportation, among many others.

Wi-Fi technology has revolutionized connectivity by providing wireless, convenient and reliable access to numerous applications. Its widespread adoption continues to drive innovation and improve productivity, convenience and connectivity in a variety of industries.

When choosing the right Wi-Fi antenna for an IoT application, several factors must be considered to ensure optimal performance and reliability. This article explains the key considerations.

 

Antenna application.

Wi-Fi antennas can be classified as internal and external antennas.

Internal antennas are commonly used to save space. For example, laptops, smart home devices and phones. Some routers use them for a more compact appearance. These antennas are suitable for relatively small signal coverage areas or indoor environments such as homes and offices. 

Figure 1. Internal Wi-Fi antenna, JCW406 - from JC Antennas.

 

External antennas are used to obtain an optimal signal. For example, high-performance routers and access points use them to improve coverage and signal strength. IoT devices that require larger coverage areas and stronger signals use external antennas.

They are suitable for applications where the device may have protruding parts. They are used outdoors or in large indoor areas such as; factories, warehouses or large offices.

Figure 2. External WiFi antenna, JCW406 - from JC Antennas.


Size, form factor and location.

The size and shape of the antenna must fit the constraints and installation of the IoT device. Antenna performance and small size must strike a balance, these two factors are always constraining factors.

Location is critical to the electromagnetic (EM) wave radiation performance of the Wi-Fi antenna. It is important to avoid obstacles, to help better signal propagation and to keep the antenna away from devices that may cause interference.

 

Frequency bands

The frequency band for Wi-Fi communication includes the 2.4GHz and 5GHz bands. The electromagnetic wave of the 2.4GHz band can propagate farther than the 5GHz band. However, the 2.4GHz Wi-Fi band has a narrow bandwidth. According to Shannon's theorem a narrow bandwidth leads to a lower data rate.

The 2.4 GHz band spans the frequency from 2.4 GHz to 2.4835 GHz. There are 13 channels in this band, each channel covering the 20 MHz frequency band. The distance between the center frequency of each channel is 5 MHz, as shown in Figure 3. Channels 1, 6 and 11 are separated so that their frequency bands do not overlap.

 

Figure 3. Channels in the 2.4GHz band.

 

The 5 GHz band covers frequencies from 5.15 GHz to 5.35 GHz, and from 5.725 GHz to 5.85 GHz. There are also 13 channels, and each channel is not overlapped, as shown in Figure 4.

Figure 4. Channels in the 5GHz band.

 

Types of antennas

Based on radiation characteristics, there are omnidirectional antennas and directional antennas.

Omnidirectional: They radiate signals in all directions and are suitable for general coverage in IoT applications where devices are distributed around a central point. Figure 5 shows the radiation pattern for an omnidirectional antenna.

Figure 5. Omnidirectional radiation pattern.


Directional: Focuses the signal in a specific direction, providing longer range and higher signal strength in that direction, ideal for point-to-point communication or when devices are aligned in a specific orientation. Image 6 shows the radiation pattern for a directional antenna.

Figure 6. Directional radiation diagram.

Gain

The gain of a Wi-Fi antenna is a measure that indicates the efficiency with which an antenna can transmit or receive radio waves in a specific direction compared to an isotropic antenna (a theoretical antenna that radiates power uniformly in all directions). The gain of an antenna is usually expressed in (dBi). The definition is: the ratio of the power radiated in the direction of the strongest signal to the power radiated by an isotropic antenna in all directions. High gain antennas concentrate more of the signal in a particular direction, which extends the range in that direction, but reduces the beamwidth. They are useful for long distance point-to-point communication. Higher gain antennas provide longer range and stronger signals, but reduce the coverage area.

Low gain antennas distribute the signal more evenly in all directions. They are useful for covering large areas. The directional antenna usually has higher gain, but a relatively narrower coverage area. So it is difficult to have an antenna with high gain and a larger coverage area, coverage area and gain are usually two opposing factors. It is recommended to choose the gain based on the coverage area and the distance required by the application.

 

Polarization

Matching the antenna polarization (vertical, horizontal or circular) to the device requirements ensures better signal reception and transmission. As for the polarized Wi-Fi antenna, the transmitting antenna and receiving antenna must have the same polarized direction. As for circular polarized antenna, there is no strict requirement for electromagnetic wave polarization.

 

Environmental considerations

It must be ensured that the antenna is suitable for the environmental conditions in which it will operate, such as indoors or outdoors, and that it can withstand factors such as temperature, humidity and physical impacts.

Wi-Fi communication signals easily interfere, are blocked by barriers, scattered by surrounding objects, due to the complex and versatile application environment. EM wave propagation behavior includes absorption, reflection, refraction, scattering, diffraction, path attenuation and multipath phenomenon.

Taking these environmental factors into account, the deployment of Wi-Fi antennas can be optimized to achieve better coverage, signal strength and overall network performance.

 

Integration and compatibility

Selecting the right Wi-Fi antenna is necessary to ensure reliable and efficient communication in IoT applications. Integrating Wi-Fi antennas into systems involves ensuring compatibility with the hardware and software of the devices to which they connect. Proper integration improves performance, coverage and reliability.

Understand antenna types and use cases. Including radiation direction type, antenna shape and antenna location.

Hardware compatibility. Including connector type, antenna port, frequency range of Wi-Fi systems and impedance matching.

 

MIMO (Massive Input and Massive Output) applications for Wi-Fi technology.

MIMO is a technology used in Wi-Fi networks to improve performance, reliability and coverage. This technology uses multiple antennas on both the transmitter (e.g. router) and receiver (e.g. laptop) to send and receive more data simultaneously. The electromagnetic field of the multiple antennas can be coupled and achieve the desired radiation direction.

The advantages of MIMO antennas are:

  • Increased data transmission: By transmitting multiple data streams simultaneously, MIMO significantly increases data transmission speed.
  • Increased reliability: Multiple antennas improve signal reliability through diversity gain, mitigating the effects of interference and fading.
  • Better coverage: MIMO improves coverage by using beamforming and spatial diversity to direct signals where they are needed most.


In conclusion, MIMO antennas provide significant improvements in data throughput, reliability and coverage. Leveraging multiple antennas at both the transmitter and receiver enables more efficient use of the wireless spectrum and improves overall network performance.

Understanding and implementing MIMO technology is essential for deploying high-performance Wi-Fi networks in a variety of applications, from home and enterprise networks to public Wi-Fi and IoT devices.

 

Figure 7. Non-beamform compatible antenna and beamform compatible antenna.

 

JC Antennas Wi-Fi antenna solutions

Eurotronix offers different Wi-Fi antenna solutions from the manufacturer JC Antennas, which specializes in developing solutions for sectors such as vehicle fleet management, aircraft networks, power grids or intelligent transportation, among others.

It has a large R&D team that develops all its products and has its own laboratory for testing all solutions.

Eurotronix Product Managers and FAEs provide full support in your projects, advising you on the right antenna for any of your applications.

Eurotronix