Internet of Things, intelligent hardware products, need to have antenna.
The smaller the space, the more frequency bands, the more complex the antenna design.
Commonly used antennas, according to the use scenario classification, there are several more species:
Large size product with an external antenna
The external antenna is generally standard, and the frequency section is suitable, no debugging, plug and play.
For example, a courier cabinet, a vending machine, generally using a magnetic external antenna, which is absorbed on the iron shell.
These antennas cannot be placed inside the iron cabinet, and the metal will block the antenna signal, so it can only be placed outside.
The advantage is to use, the price is cheap, and the disadvantages cannot be used on small size products.
↑ 图. Magnetic external antenna, SMA connector
Low frequency communication, an external antenna
The length of the antenna is about 1/4 of the electromagnetic wave wavelength, so the lower the signal frequency, the longer the length of the antenna.
Therefore, the FM radio of 100 MHz requires a long rod antenna, a walkie-talkie around 400MHz, and it is also necessary to use an external long rod antenna. 433MHz wireless serial ports commonly used in the Internet of Things, usually also used an external antenna.
The antenna is shorter, such as 1/8 wavelength or 1/16 wavelength, it can be used, but efficiency will decline. Some devices use "short antenna + LNA" way, and can also reach the reception effect of the long-day line.
However, the short antenna should reach the emission effect of the long-day line, and it is necessary to increase the transmit power, so the walkie-talkie needs to transmit the signal, which is a long external antenna, and the FM radio is only not sent, and there is a built-in receiving antenna.
High frequency signal can be used with a built-in antenna
For example 2G (900 MHz), 4G (700-2600 MHz), WiFi and Bluetooth (2.4 GHz), GPS (1.5GHz), these commonly used Internet of Things communication can be built-in antenna.
For hand-held machines, wear design, smart home and other small-sized products, rarely use an external antenna, and a built-in antenna is commonly used.
High integration, more beautiful appearance, and performance is slightly weak than the external antenna.
↑ 图. Mobile phone built-in antenna (yellow part)
Mainstream built-in antennas, types and features
The built-in antenna mainly include: ceramic antenna, PCB antenna, FPC / steel antenna, LDS antenna
Ceramic antenna
Ceramic antennas, the most used in Internet of Things products, is GPS antenna and Bluetooth antenna.
The advantage is that the occupied space is small and the performance is better.
The disadvantage is that it is difficult to do multi-band, so it is difficult to apply in a 4G product. It is relatively high for board clearance and is not suitable for special compact products.
↑ 图. GPS, Bluetooth and GSM ceramic antenna
PCB antenna
Tell it above, the antenna is a wire of a specific length. This line can also draw on the PCB board, which is the PCB antenna. The golden serpentine portion is shown below.
The PCB antenna is widely applied to the Bluetooth module, the WiFi module, the Module board of a single band, such as the ZigBee module.
Advantages: Almost no cost, no need to debug again at a time.
Disadvantages: Only suitable for a single band, such as Bluetooth, WiFi. Different batch of PCB antenna performance will have a certain deviation.
↑ 图. Onboard antenna of the Bluetooth module (golden snake part)
FPC / steel antenna
Steel sheets and FPCs are equivalent to pulling out the antenna line on the PCB board, and the antenna is made with other external metals.
Usually used in a complex medium and low-end mobile phones and intelligent hardware products.
Advantages: Suitable for almost all small electronic products, you can do more than 10 frequency bands such as 4G, good performance, and low cost.
Disadvantages: It is necessary to debug according to each product.
↑ 图. Steel sheet antenna and FPC antenna
LDS antenna
The LDS antenna is an evolutionary version of the FPC antenna. The spatial utilization is extremely high.
The steel sheet antenna is stamped, and it must be flat and cannot be stamped out of the complex shape.
The FPC antenna is a flat plane, although it is bent, but it can't be done too complicated.
In the 4G mobile phone era, the antenna band is very much, the internal space is very compact, it is difficult to find a large flat plane to the antenna. So the LDS antenna was born: engrave the graphic of the antenna by laser.
Advantages: A variety of irregularities in the three-dimensional space can be taken to make full use of the various irregularities of the stereo space.
Disadvantages: expensive. A number of quantities than the FPC antenna. And there are many special requirements for the process of the outside of the product.
↑ 图. LDS antenna
Summarize
Cost: PCB antenna. 1881. Steel sheet antenna
Performance: external antenna < Built-in antenna (similar to various built-in antenna performance)
Space: LDS minimum, largest external antenna
The appropriate antenna should be selected based on the frequency band requirements, appearance requirements, cost requirements of the Internet of Things and intelligent hardware products.
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