An antenna is a core part of the radiofrequency chip. It is very important when selecting the best antenna for Long Range (LoRa) devices. LoRa devices that transfer and receive data in the radiofrequency band need an antenna. Examples of such LoRa devices are LoRaWAN gateways and LoRa nodes.
The performance of the antenna takes up a crucial position in Long Range IoT. In reality, it is believed that LoRa antenna A has a longer range and performs much better than LoRa antenna B. What makes antenna A to perform better than LoRa antenna B is yet to be known. Therefore, there is no direction to choose from the application.
In this article there are some parameters that affect the performance of the LoRa PCB antenna. Some of these parameters include frequency bandwidth, VSWR, impedance, frequency, and other parameters. However, the question remains what are the functions of the LoRa PCB antenna and how do choose the best antenna for LoRa. Here, we will be explaining a few different parameters.
What is LoRa PCB Antenna?
LoRa PCB antenna is a high performance antenna specially designed for LoraWan and LoRa node. Basically, there are four different components for the LoRa network. These components include the gateway/ base station, the cloud, the terminal (with built-in LoRa module), and the server. Furthermore, the LoRa network enables the bidirectional transmission of application data.
The communication range of the LoRa PCB antenna is about 15 km and the connection budget is about 157 dB. However, this depends on the environment. The LoRa coverage will amount to about 2 Km radius in urban areas if the gateways are installed on mobile base stations that has a transmit power of 20 dBm. On the other hand, the coverage will rise to a 10 Kn radius in rural areas featuring low building capacity. With this connectivity range, smart grid applications can be easily facilitated in large compounds.
Considerations for LoRa PCB Antenna Design
The LoRa PCB antenna design is very important. Designers usually encounter problems with the radio frequencies. However, once you take note of a few points, you can achieve the best performance LoRa PCB antenna design.
Circuit design matching
The designer must reserve a π-type matching circuit between the antenna pin of the module and the antenna connector during the schematic diagram design. There are certain factors that impact the antenna’s impedance. Some of these factors include the installation angle, the housing, and the PCB.
It is crucial to reserve the π-type matching circuit for correction when the antenna moves away from 50 ohms. The impedance of the antenna should be close to 50 ohms according to the default settings.
When some special cases happen like the small size of the antenna, the inside of the antenna installation mold, or how to increase the strength of the suppression of high-order harmonics, it is crucial to adjust some matching components.
In theory, regardless of the value of the antenna impedance, it is possible to match 50 ohms via a π-type matching circuit. The point here is that components like capacitors and inductors feature internal resistance. In cases like this, the internal resistance will suck the energy. It won’t be ideal to match the antenna impedance to 50 Ohms if it is too small or too large. This is because the matching element’s internal resistance has consumed most of the energy. The antenna impedance is small when it is only a few ohms and it is large when it is thousands of ohms.
Microstrip line routing rules
The microstrip line is the PCB trace from the LoRa module’s antenna pin to the antenna connector. The module’s internal impedance is usually designed with 50 ohms, the microstrip line’s characteristic impedance is 50 ohms and the antenna impedance is 50 ohms, therefore, these three parameters are best matched.
It is possible to achieve a microstrip line of almost 50 ohms. In this case, the designer can increase the impedance processing requirements to the PCB (antenna). The PCB antenna manufacturer is capable of regulating the trace impedance via the line width based on the parameters of the board. Meanwhile, the PCB antenna manufacturer can obtain the board after the software has calculated parameters such as the line width and the dielectric constant. This will help in regulating the impedance within the expected range.
The characteristic impedance would be almost 50 Ohms if the FR4 board is integrated when the line width is more than the distance from the microstrip line to the reference layer. For instance, in a double layer PCB, the line width will be 1.7 mm if the thickness of the board is 0.8mm.
However, it is crucial to understand that the ground must be complete. Also, one must set the distance between the copper paving and the microstrip line based on the results given by the impedance calculation software. Furthermore, it is crucial to ensure the ground pads on the two sides of the module antenna pins are properly grounded.
PCB floor requirements
The three major parameters associated with communication distance includes antenna, transmitting power, and receiving sensitivity. The distance impacting the communication the antenna parameter, and these parameters will change as a result of the motherboard of the user.
Antenna installation specifications
The hardware parameters need to be adjusted. After this, the antenna will need to be installed. The installation of the antenna is a crucial step since the radiation of the antenna is directional, and the energy radiated in every direction isn’t equal. This is similar to our voice. When we speak, some directions produce strong sounds, while the sound in some directions is weak.
Also, it is crucial to align the antenna’s direction with the strongest radiation during the installation of the antenna. This will help the receiving antenna to achieve the best received signal. You can achieve this if you know the direction of the antenna’s radiation.
Placing the LoRa PCB Antenna
The positioning of the LoRa PCB antenna will determine its performance. The antenna is a crucial part of the communication device. In LoRa technology, the sensitivity of this device poses a major issue. Here are tips on how to position the LoRa antenna:
- Ensure the antenna is placed far away from the ground. Also, avoid using your hands to touch the LoRa antenna while testing. Ensure the antenna stays more than 2 meter away from the ground. It is easy to avoid contact with the antenna since the human body is over 2 meter away from the antenna.
- The LoRa antenna should be placed far away from large metal objects. Avoid placing it near the river in order to reduce obstacles that may occur between the antennas
- Avoid placing the antennas skewed or flat on the ground. The best way to place it is in an upright position. Also, keep the antennas of the two communication parts on a level surface.
You need to match various ISM/Lora frequency bands with various antennas. Therefore, in the mechanical design, you need to take some factors into account based on the product in order to correctly place the antenna. This will help in preventing any closed interference with the product.
Parameters in LoRa PCB Antenna
The LoRa antenna’s performance is impacted by some basic parameters. These parameters are responsible for the functioning of the antenna. Below is a brief description of a few different parameters:
Impedance
The input impedance is a crucial parameter in a LoRa antenna’s design. It is simply the ratio of the input current to the input voltage at the antenna’s feed side. Although, the impedance value of the majority of the current market standards is 50Ω, this depends based on the requirement and convention.
VSWR
VSWR describes the travelling wave coefficient’s reciprocal. The value of this parameter is between 1 and infinity. When you have a VSWR of 1, it means a perfect match. However, commercially available antennas have a VSWR <1.5.
Gain
The antenna gain is an important parameter than determines how the LoRa PCB antenna performs. This parameter measures the capability of the LoRa antenna to transmit and receive signals in a specific direction. The antenna gain is crucial for selecting a base station antenna. The antenna gain performs better when it is higher.
Frequency band
There are a wide range of frequency bands in LoRa antennas. These frequency bands include 915 MHz 169 MHz, 433 MHz, 315 MHz, 868 MHz, and more. Each of these frequency bands are ideal for use in different applications.
In practice, the LoRa antenna A offers better performance than LoRa antenna B. Also, the antenna A features a longer range compared to antenna B. LoRA PCB antennas feature a wide range of frequency bands. These antennas support a range of frequency bands. For instance, the antenna’s performance will reduce if it is integrated outside its frequency band. This helps in achieving a good transmission effect.
Factors to Consider When Integrating LoRa Antennas
LoRa antennas are ideal for use in a number of applications. These antennas perform well when used in equipment. However, it is vital to pay attention to certain factors when integrating these antennas in equipment.
- There must be an antenna in the Lora node/Lora gateway regardless of its proximity to the receiving end (module or gateway). The data may not be received if otherwise.
- Every connection of antenna may result in signal attenuation. This could include the feeder line of the antenna, the suction cup antenna line’s length, and the U.FL to SMA connector transfer line. You need to pay attention to the attenuation impact of the wire especially when there is a long line.
- LoRa’s signal coverage is non-linear at a long distance. Due to some factors like terrain and construction, some areas will feature blind areas. In such cases, testing is important.
We have looked into some core data for choosing antennas. Antennas are categorized as omnidirectional antennas, panel antennas, and directional antennas.
Basically, LoRa antennas are known to be omnidirectional antennas. Antennas have many key parameters. However, many parameters need professional equipment to measure. You must consider some core parameters when choosing a model.
One of the most crucial parameters is gain of the antenna. The antenna gain has some parameters which are dBd and dBi. The gain which is relative to the point source antenna is dBi. The majority of LoRa antennas available in the market basically have the dBi marking. In the same scenario, when there is a higher antenna gain, the distance of the radio wave propagation is usually longer.
The standing wave ratio is another factor to consider. The antenna has better effect and greater efficiency when the standing wave ratio is closer to 1.
Other factors to consider
- Also, the center frequency is factor that must remain consistent with the frequency the module selected.
- It is advisable to choose a professional antenna manufacturer to help in achieving the best transmission distance of LoRa. The manufacturer will help with antenna matching, particularly the built-in antenna. The transmission distance is impacted by a well-matched antenna.
- The antenna gain’s strength will interrupt the capability of the antenna to receive signals in a communication system. The wireless signal will move farther and faster if the gain is higher. Ensuring the LoRa PCB antenna is far away from the ground is crucial. Also, this antenna shouldn’t be close to large metals.
- Furthermore, the LoRa antenna should integrate an actual frequency at the range of the frequency band it supports.
Conclusion
The LoRa antenna’s performance is impacted by some basic parameters. These parameters are responsible for the functioning of the antenna. Below is a brief description of a few different parameters. The communication range of the LoRa PCB antenna is about 15 km and the connection budget is about 157 dB. However, this depends on the environment. The performance of the LoRa antenna is very crucial. Therefore, it is crucial to allow a device operates based on the frequency the antenna supports.
