With the popularization of Internet of Things products, PCBA boards with 4G communication functions are becoming more and more widely used. After many customers get the 4G version of the PCBA model, they often encounter such phenomena: equipment is occasionally dropped, networking is slow, indoor signal is weak, and the network cannot be directly found in the ba*t/metal enclosure environment. The first reaction of many people suspected that it was a quality failure of the PCBA board and the 4G module itself. However, after a large number of projects from our Ningbo Chaojing Electronics, we measured that most of the 4G signals were poor. The root cause was not the motherboard circuit, but the selection, installation, and matching debugging of the 4G antenna were not done properly.
Ningbo Chaojing Electronics started from the MCU single-chip microcomputer solution. Since 2019, it has undertaken the production of large quantities of pcba IoT control boards. It has been exposed to signal problems of a large number of IoT terminals and small home appliances intelligent networking equipment. Today, we share our practical experience with you and help you. It will be a solution!!
1. Which phenomena have a high probability of causing signal problems caused by antennas???
The bare board is placed on the desktop to test that the signal is normal, and the signal becomes significantly worse after being placed in the product shell.
Some sites are connected stably, and the network is frequently disconnected under metal shells, closed shells, and metal structures inside the equipment
The module displays the registered network, but uploading data is slow, latency is high, and packet loss is serious.
The same set of 4G PCBA, change the antenna, and the signal strength will be improved immediately
When the problem described above occurs, there is a high probability that it is an antenna problem, so don't keep holding on to the circuit board.
2. So what are the 4G signal problems???
1. Antenna selection and frequency band mismatch
The 4G module supports multiple frequency bands. If the selected antenna working frequency band does not cover the actual frequency band used by the equipment, even if the antenna looks intact, the receiving and transmitting capabilities will be greatly reduced. Many customers directly purchase universal cheap antennas without matching the corresponding module frequency bands. No matter how excellent the hardware is, it cannot achieve performance.
2. The antenna installation position is unreasonable
The antenna is closely attached to metal parts, batteries, cable cables, and large-area copper foil on the motherboard. The metal will directly shield RF signals. When designing the structure of many products, the 4G antenna is pressed behind the battery and pasted on the inside of the metal shell. This is the most common mistake in IoT products. The antenna needs to reserve a clearance area to avoid metal blocking.
3. Antenna feeder and joint loss
The feeder line is too long, the wire quality is poor, and the IPEX joint is virtual. The RF signal is lost during the cable transmission process, which directly reduces the receiving sensitivity of the whole machine. The internal routing of small size equipment, the feeder length and wiring method need to be evaluated.
4. The antenna matching debugging was not done well
Even if the antenna and hardware are fine, the impedance mismatch between the motherboard RF port and the antenna will also cause signal reflection and lower radiation efficiency. Batch products cannot be directly applied based on models, but need to be tuned and matched by real machines.
Note: Of course, there are also module soldering and motherboard RF routing process problems, but in our large number of 4G In PCBA mass production projects, antenna-related problems account for a much higher proportion than failures of the motherboard itself.