In order to ensure the transmission efficiency of the antenna, the length of the antenna is about 1/4 of the wavelength of the electromagnetic wave, so the lower the signal frequency, the longer the wavelength, the longer the length of the antenna; the higher the signal frequency, the shorter the wavelength, the shorter the length of the antenna. The commonly used 2.4GHz frequency band has high frequency, short wavelength, and short antenna length. Internal antennas can be used, or external antennas can be used. Antennas made shorter, such as 1/8 wavelength or 1/16 wavelength, can also be used, but the efficiency will be reduced. Some devices will adopt the method of "short antenna + LNA", which can also achieve the receiving effect of long antenna. However, in order to achieve the transmission effect of a long antenna with a short antenna, it is necessary to increase the transmission power, so the walkie-talkie needs to transmit signals, which are all long external antennas, while the FM radio only receives and does not transmit, and has a built-in receiving antenna. For example, 2G (900MHz), 4G (700-2600MHz), WIFI and Bluetooth (2.4GHz), GPS (1.5GHz), these common IoT communication methods can be used as built-in antennas.
For small-sized products such as handsets, wearable designs, and smart homes, external antennas are rarely used, and built-in antennas are commonly used. The integration is high, the appearance of the product is more beautiful, and the performance is slightly weaker than the external antenna. The Internet of Things and intelligent hardware products all need antennas to transmit data online. The smaller the space and the more frequency bands, the more complex the antenna design. External antennas are generally standard products, buy the appropriate frequency band, no need to debug, plug and play. For example, express cabinets, vending machines, etc., generally use magnetic external antennas, which can be sucked on the iron shell. These antennas cannot be placed inside the tin cabinet, the metal will shield the antenna signal, so they can only be placed outside. The advantage is that it is easy to use and cheap, and the disadvantage is that it cannot be used on small-sized products.
Antenna Category
Then how to choose a 2.4GHz antenna suitable for your wireless transceiver equipment from many 2.4GHz antennas, and then introduce how to choose a 2.4GHz antenna through the classification and comparison of 2.4GHz antennas. Antennas used in the 2.4GHz frequency band mainly include ceramic antennas, PCB antennas and spring antennas. Ceramic antennas and PCB antennas belong to built-in antennas, while spring antennas belong to external antennas.
The advantages of ceramic antennas are that they take up less space and have better performance. The disadvantage is that it is difficult to achieve multi-band, so it is difficult to apply in 4G products. The clearance requirements for the circuit board are relatively high, and it is not suitable for particularly compact products.
PCB antennas are widely used in single-frequency module circuit boards such as Bluetooth modules, WIFI modules, and ZIGBEE modules.
The advantages are that it occupies less space, the cost is low, the antenna does not need to be assembled separately, it is not easy to be damaged by touch, and the whole machine is easy to assemble, but performance will be sacrificed. The disadvantage is that a single antenna field is difficult to be rounded, the insertion loss is high, the efficiency is relatively low, and it is easy to be interfered by the motherboard; at the same time, it is only suitable for a single frequency band, such as Bluetooth, wifi; different batches of PCB antenna performance will be certain deviation.
There are many types of external antennas, such as spring antennas, FPC antennas, short glue stick antennas, long bendable antennas, sucker antennas and other external antennas. The advantages of the external antenna are that the field pattern can be better controlled, the insertion loss is low, the direction of the signal is good, the efficiency is high, and the anti-interference ability is strong. The mismatch between the wireless transceiver equipment and the external antenna can also be solved by directly replacing the external antenna without replacing the PCB board; the disadvantage is that the cost is high and it is more troublesome to assemble.
2.4G Antenna Application
What is the difference between E73-2G4M04S1A, E73-2G4M04S1B, E73-2G4M08S1C, E73-2G4M04S1D? First of all, the four models use different chip solutions, the size and power of E73-2G4M04S1A, E73-2G4M04S1B and E73-2G4M04S1D are the same, E73-2G4M08S1C is slightly different; but under the same test conditions, but in terms of transmission distance, E73-2G4M08S1C has slightly better transmission distance than E73-2G4M04S1A, E73-2G4M04S1B and E73-2G4M04S1D. The power will also be slightly more.
In particular, the transmission power of E73-2G4M08S1C is 8dBm, which is higher than that of other Bluetooth modules, so the transmission distance is slightly longer than that of other Bluetooth products.
If you use the IPEX antenna interface to connect to the external antenna, the transmission distance will definitely be longer than that of the onboard antenna. Considering the requirements of volume and installation, and the transmission distance is also within the acceptable range, the on-board PCB antenna or ceramic antenna is more preferred. But determining a wireless transceiver is not only the parameter of transmission distance, but also the performance of the product and different applications in different usage environments. Therefore, whether it is for the E73 series or other Bluetooth, ZigBee, and GPRS products of Chengdu Ebyte, there is a necessary environment for use, and different 2.4GHz antennas can be selected according to the needs of their own projects.
