With the rapid development of wireless data transmission, the application ofwireless modules is becoming more and more extensive. The wireless module is widelyused in the fields of remote control, wireless meter reading, identification,electronic price tag, biosignal acquisition, etc., and thus the communicationdistance of the wireless module is also higher.
The transmission distance of the wireless module is mainly affected by factorssuch as power, receiving sensitivity, and antenna. This paper mainly discussesthe influence of antenna on the communication distance of wireless module fromtwo aspects of antenna index and classification.
An antenna is a transducer that transforms a guided wave propagating on atransmission line into an electromagnetic wave propagating in an unboundedmedium (usually free space), or vice versa. A component used to transmit orreceive electromagnetic waves in a wireless communication device. Engineeringsystems such as radiocommunication, broadcasting, television, radar,navigation, electronic countermeasures, remote sensing, radio astronomy, etc.,all use electromagnetic waves to transmit information, relying on antennas towork. In addition, the general antenna is reversible, that is, the same antennacan be used as both a transmitting antenna and a receiving antenna. The samecharacteristic parameters of the same antenna as transmitting or receiving arethe same. This is the reciprocity theorem of the antenna.
3. Antenna indicators
The indicators of the antenna mainly include frequency band range, frequencybandwidth, gain, polarization, impedance, standing wave ratio, andfront-to-back ratio.
In terms of impedance, usually the antenna is made to a standard 50Ω, and theimpedance of the wireless module is also designed according to 50Ω, so that theimpedance between the antenna and the wireless module is more compatible withthe transmission efficiency. In theory, the higher the matching degree betweenthe module and the antenna, the easier the communication distance isguaranteed.
Antenna gain refers to the ratio of the power density of the signal generatedby the actual antenna and the ideal radiating element at the same point inspace under the condition of equal input power. It quantitatively describes theextent to which an antenna concentrates the input power. For example, a modulewith an output power of 20 dBm is transmitted through an antenna with a gain of3 dBi. The total energy emitted by the module is the sum of the module powerand the antenna gain. Theoretically, the larger the total energy sent by themodule, the farther the module transmits.
Antenna polarization is a parameter that describes the spatial orientation ofthe radiated electromagnetic wave vector of an antenna. Since the electricfield has a constant relationship with the magnetic field, the spatialdirection of the electric field vector is generally used as the polarization directionof the electromagnetic wave radiated by the antenna. It is often said that thepolarization direction has vertical polarization and horizontal polarization,because the vertical polarization mode is not easy to generate polarizationcurrent, thereby avoiding the large attenuation of energy, ensuring theeffective propagation and transmission distance of the signal, so in thewireless communication system In the middle, the vertical polarizationpropagation mode is generally adopted.
Standing wave ratio is called voltage standing wave ratio, also known as VSWRand SWR, which is short for English Voltage Standing Wave Ratio. Refers to theratio of the amplitude of the standing wave and the voltage of the valley, alsoknown as the standing wave coefficient and the standing wave ratio. When thestanding wave ratio is equal to 1, it means that the impedance of the feederand the antenna are completely matched. At this time, the high-frequency energyis completely radiated by the antenna, and there is no reflection loss ofenergy; when the standing wave ratio is infinite, it means total reflection,and the energy is completely radiated. . It can be seen that the closer thestanding wave ratio of the antenna to the standing wave ratio of the module,the better, so as to ensure the output power and communication distance.
4. Influence of antennas of different classifications on communication distance
There are many types of antennas. For the convenience of discussion, theantennas are mainly divided into package types: flexible (FPC) soft antennas,on-board PCB antennas, glue stick antennas, suction cup antennas, etc. Theantenna used in this comparison is the TX433-NP-4310, TX433-JK-20, andTX433-XP-100 antennas sold by Chengdu Ebyte. For detailed parameters of the antenna, pleasevisit:
The influence ofthe antenna on the communication distance of the wireless module
The flexible (FPC) soft antenna in Figure 1 has the characteristics of beingbendable and small in size, but it can also be seen that its gain is 2dBi andthe gain is low, so its communication distance will also be affected.
In Fig. 2, the bendable glue stick antenna has a wide angle of theomnidirectional antenna, a gain of 3dBi, and a standing wave ratio of 1.3, sothe communication distance is farther than that of the flexible soft antenna.
In Figure 3, the suction cup antenna is used to place the antenna on a largeiron plane, such as a car roof. The antenna has the characteristics of highgain and wide angle. Therefore, the communication distance has more performancethan the glue stick antenna, but the installation environment is limited by theglue stick, and the flexible antenna is flexible.
There are many factors affecting the communication distance of the wirelessmodule. The antenna is only one of them. We want to optimize the antenna toachieve better communication. So the choice of the antenna should be optimalwith the module, but this is not absolute. In actual applications, we may alsohave a slightly lower performance antenna communication distance may befarther, so the choice of antenna should also be flexible and applicable.