Analysis of the four major interference problems of wireless communication wireless microwave, in the process of wireless communication information transmission, network interference has always been a big problem in the wireless transmission process, in the wireless transmission process, there are many factors, sometimes from external noise, sometimes from The surrounding environment, but as long as we find out the cause of the interference, we can find a solution. The following small make up for several interference phenomena that you often encounter in the process of wireless microwave transmission, I hope to help you!
Before explaining, we need to briefly introduce the nature of radio interference. In the process of wireless communication, the interference signal enters the electromagnetic wave of wireless communication through direct or indirect coupling, thereby affecting the reception of the signal, reducing its performance, deteriorating the signal quality, blocking the communication, increasing or even losing the transmitted data error. In the face of high-frequency ultra-short waves, the interference factors are generally artificial interference, and the interference phenomena are co-channel interference, adjacent-frequency interference, external interference, and mutual adjustment interference. We will introduce these interferences below, I hope you can understand the interference according to the actual situation and reduce the impact of interference on the communication.
Co-channel interference
Refers to the wireless interference of other wireless signals of the same frequency entering the collector. When the interference signal and the desired received signal enter the collector in the same way, when the carrier frequency difference between the two signals occurs, beat interference will occur; when the two signal conditioning systems are not large, distortion interference will occur; when Distortion interference occurs when there is a phase difference between two signals.
This phenomenon may be due to the effect of co-frequency devices being too close to each other, or from illegal radio stations, or because the frequency reuse distance of legitimate radio stations without designated frequencies is relatively close, and this type of interference source is easier to detect.
adjacent channel interference
When the wireless microwave signal is in the radio frequency band of the receiver or close to the receiving band, the interference caused by frequency conversion into the intermediate frequency band is called adjacent frequency interference, which can lead to a decrease in the received signal ratio and affect its sensitivity. Different from co-channel interference, adjacent-channel interference is generally caused by unqualified wireless communication equipment technology. Theoretically, when the two signals are different, there is no interference, but assuming that the frequencies of the two signals are close to each other, a wireless communication device is unqualified, the stability of the transmission frequency is poor, the modulation is too large, and the transmission spectrum is too wide, there may be platform jumping Phenomenon. Of course, the performance of the receiver IF filter can also cause this phenomenon. Secondly, the strong channel of the base station interferes with the weak channel. Therefore, in order to avoid this situation, during the installation process, the quality of the equipment itself should be further tested to reduce the occurrence of similar situations.
out-of-band interference
The wireless interference caused by the spurious radiation of the transmitter of wireless communication equipment and the spurious response of the receiver is called out-of-band interference. Like adjacent channel interference, this phenomenon is also an interference problem caused by the poor quality of the equipment itself. In ultra-short microwave transmission, the transmitter generally uses a crystal oscillator to obtain higher frequency stability. The oscillator is multiplied to obtain the desired operating frequency. If the transmitter's frequency multiplier has poor filtering characteristics, spurious radiation waves are generated at the transmitter output stage, which can interfere with receivers operating at that frequency. At this time, if the receiver spurious response of the receiver is poor, the spurious response will appear. In addition to receiving useful signals, the receiver can also receive unwanted signals of other frequencies, which is related to the frequency purity of the receiver's local vibration. The stray radiation and stray response are generally produced with strict standards stipulated by the state. On the one hand, before putting it on the market, it must pass the test of the national testing center before it can be put on the market, but there are also bad merchants who do not put it on the standard.
Intermodulation interference
Two or more signals are adjusted in a nonlinear transmission circuit to generate a combined frequency close to the frequency of the useful signal, thereby causing interference to the wireless transmission system, which is called mutual interference. There are three reasons for mutual adjustment, namely, mutual adjustment of transmitters, mutual adjustment of receivers, and mutual adjustment of external effects. Of course, the interference of mutual adjustment must be satisfied at the same time. There is a certain interval relationship between several interfering frequencies and the nominal frequency of the interfered receiver, and the interfering signal must have sufficient range.
For mutual adjustment of receivers, all interfering and interfering receivers must work simultaneously. Transmitter mutual adjustment refers to the interference formed by the mutual coupling of two transmitters. The mutual adjustment of the receiver means that when two or more strong interference signals enter the front-end circuit of the receiver, due to their nonlinear effects, the interference signals are mixed with each other, resulting in mutual adjustment products that can fall into the passband of the receiver. Its size depends on the size of the interfering signal and other factors. Mutual adjustment caused by external effects refers to the high-frequency filter and antenna feeder caused by poor contact of the receiving plug-in fasteners or corrosion of metal components, which play a mutual adjustment role in the strong radio frequency electric field and form an interference radiation source, which can completely avoid this external effect. Mutual adjustment interference.
In fact, the essence of wireless interference is electromagnetic wave interference. In most practical situations, in order to solve the interference problem, it is necessary to understand the causes of electromagnetic interference, so as to take effective protective measures against the interference and propose targeted solutions.
