The antenna is oneof the most important accessories for the RF transmitter and wireless modules, itsgood gain effect can greatly improve the transmission range and signal strengthfrom the wireless module. Therefore, it is very important to choose a suitableantenna for the wireless modules. But there are varies of antennas on themarket. How do we choose a antenna for the wireless module?
Every wireless module has working frequencyband, such as 433MHz, 868MHz, etc.; Theantenna has the same working frequency band too, the frequency band of theantenna must be the same as the frequency band of the wireless module when weselect an antenna. Otherwise, the gain effect of antenna will be very poor. Thedifference of frequency band cause smaller radiation range of the antenna and accordinglyit get a short transmission distance.
The gain value is a very importantparameter of the antenna. The unit is dBi and the gain value is positive. Thehigher the gain value, the higher the gain effect on the wireless module.Therefore, a higher gain value antennawould be selected without considering other parameters when selecting theantenna.
3. VSWR(Voltage Standing Wave Ratio):
VSWR is the ratio of the amplitudeof the standing wave and the voltage of the valley, which is also called thestanding wave coefficient and the standing wave ratio. It is mainly used todescribe the matching of the antenna. When the VSWR is equal to 1, it meansthat the impedance of the feeder and the antenna are completely matched, whichis the most ideal case. When the VSWR is higher than 1, it means that someelectric waves will be reflected back and become heat, hence the feeder is warmedup. And the reflected electric wave may generate a high voltage at the outputof the wireless module and the module will be damaged sometimes. However, mostof the antennas on the market have higher VSWR value than 1 and less than 1.5. Some bad quality antennas have a higher VSWR valuethan 1.5 or even higher. The higher the VSWR, the more the transmitting waves ,the higher the heat and the greater the chance to damage the module. Therefore,when we select an antenna, we must pay attention to the VSWR of the antenna. It’dbetter to check it by ourselves.
Each project has a differentworking environment, so the antennas used will be different. If the environmentis in harsh and many sources of interference. NiceRF recommend you to select ahigh-gain external antenna, such as rod antenna, sucker antenna and Yagiantenna. The high-gain antenna can increase the anti-interference ability. Ifyou need to consider installing the antenna together with the RF transceivermodule inside the device, spring antenna or FPC is a better choice. Thedifference between internal and external antennas can be referred as below linkfor details：https://www.nicerf.com/news_184_327.html
1. High-powerwireless modules can not usesmall-gain antennas, such as spring antennas, FPC antennas and other built-inantennas with small gains. Because the module signal radiation will not be transmittedif the high-powerwireless modules use small gain antennas, resulting inbad transmission effects and accordingly it cause problems such as shortdistance。
2. Low-powerwireless modules can use high-gain antennas, the higher the gain of theantenna, the better the performance of the module. For example: NiceRF 20mWRF4431 wireless module can also use the Yagi antenna or similar large-volumehigh-gain antenna。
3. The higherthe position of the antenna, the better the signal transmission and the longerthe transmission range will be. It should be kept open and far away from metals,buildings and other interference sources.