Interference Factors in Wireless Intercom Systems

Radio interference in a wireless walkie-talkie system refers to electromagnetic waves that enter wireless communication devices through direct or indirect coupling. Radio interference will directly affect the reception of available signals, reducing its performance, deteriorating signal quality, causing communication blockage, increased transmission data errors or even loss. Common interference phenomena include co-channel , adjacent frequency, out-of-band and intermodulation interference.1. Interference factor in the wireless intercom system: adjacent frequency interferenceWhen the wireless signal is in the radio frequency band or near the passband of the receiver, the interference caused by entering the intermediate frequency band after frequency conversion becomes adjacent frequency interference. And this kind of interference will also reduce the signal ratio of the receiver and reduce the sensitivity, but it is different from co-channel interference. The adjacent frequency interference is mainly due to the technical indicators of the wireless communication equipment itself not conforming to the national technical standards. Adjacent channel interference can also occur if the receiver's IF filter performance is poor.Another situation is that when the user leaves the station, the radio wave of one channel received by the base station is strong, and the radio wave of another channel may affect the quality of the wireless intercom system itself.2. Interference factor in the wireles intercom system: intermodulation interferenceTwo or more signals are adjusted in a nonlinear transmission circuit to generate a combined frequency close to the same available signal frequency, thereby interfering with the wireless intercom system, which is intermodulation interference.Transmitter intermodulation, receiver intermodulation, and intermodulation are three reasons cause external effects.Intermodulation interference should satisfy three conditions at the same time:(1) There is a certain spacing relationship between several interfering frequencies and the nominal frequency of the interfering receiver;(2) The interfering signal should have a sufficient range;(3) All jammers and jammer receivers should work simultaneously.Transmitter intermodulation refers to the coupling of two transmitters to each other to form interference. Receiver intermodulation means that when two or more strong interfering signals enter the front-end circuit of the receiver, due to their nonlinear effects, the interfering signals are mixed with each other, resulting in intermodulation products that can fall into the passband of the receiver. Its size depends on factors such as the size of the interfering signal. Intermodulation caused by external effects refers to the poor contact between the transmitter's high-frequency filter and antenna fasteners or the phase interference of metal components, which can be avoided as much as possible.3. Interference factor in the wireless intercom system: out-of-band interferenceOut-of-band interference refers to the wireless interference caused by the spurious radiation of the transmitter of wireless communication equipment and the spurious response of the receiver. And this is also a common interference problem affecting wireless communication caused by the poor quality of the wireless intercom system itself.Crystal oscillators are mainly used in transmitters of ultra-short wave radios to obtain higher frequency stability. The oscillator is multiplied to obtain the desired operating frequency. If the frequency multiplier of the transmitter has poor filtering characteristics, spurious radiation waves are generated at the transmitter output stage, which can interfere with the receiver at that frequency.Spurious response of the receiver: In addition to receiving available signals, the receiver will also receive unwanted signals of other frequencies. This responsiveness to other unwanted signals has become the receiver's spurious response, which is related to the frequency purity of the receiver itself. Both stray radiation and stray response are strictly regulated in relevant national standards, and manufacturers should design products according to this index. In the production process, the quality control of the products should also be strictly sured, and the products that pass the inspection can be launched on the market.In fact, the essence of wireless intercom system interference is electromagnetic interference. Therefore, in order to solve this problem, we should understand and analyze electromagnetic interference to find available methods to protect wireless walkie-talkies, while taking into account the relevant measures of electromagnetic compatibility.