With the development of KTV to scale and high-end, the application of wireless microphones in KTV is becoming more and more popular, and the corresponding technical problems are also more and more plagued by equipment suppliers and KTV operators, the most important of which is It is the problem of mutual interference between microphones. For this reason, microphone manufacturers have introduced various types of products to solve this problem. In terms of transmission schemes, they can be divided into three types: wireless FM microphones, infrared wireless microphones, and digital wireless microphones. Way. Let me talk about the advantages and disadvantages of these three ways and our latest
What is interference? In the field of wireless communication, interference is defined as the situation where useless radio frequency signals exist in the same channel or frequency band, that is, mutual interference, interrupting useful communication transmission, or increasing overall noise in transmission €€Volume, from the source of interference, one is the mutual interference within its own network, such as the intermodulation products of sending and receiving, and the interference caused by spurious emissions, which is called self-interference. Specifically, KTV is the wireless used in each room. Microphone interference is internal interference. Another type of interference caused by signals from other wireless networks to your own network is called external interference. Such as TV transmission signals, mobile phones, walkie-talkies, DVDs, karaoke machines, and other wireless microphones. The interference of the Internet and the plasma TV to the infrared microphone is external interference.
Infrared microphones use infrared transmission microphones, which take advantage of the straight-line propagation of light and the characteristics of being easily blocked. In each independent space of KTV, it effectively avoids mutual interference between rooms. In Japan, the birthplace of KTV, it is the Audio-Technica , BMB, Biodio, Marantz have successively launched infrared microphones for the KTV market. Taiwan and mainland manufacturers have also followed up with similar products. It is expected that they will show their skills in the KTV market, but after several years of market practice Although infrared microphones have a place in the KTV market, they have not achieved the expected success. The reason is that the advantages of infrared are also its biggest shortcomings. First of all, there are a lot of infrared radiation in nature, such as plasma TVs and energy-saving lamps. Fluorescent lights will interfere with infrared microphones. During use, the flow of people and the way the singer takes the microphone may block the infrared transmission path. Once a breakpoint occurs, the interference noise generated is difficult for customers to accept. With the scale and high-end of KTV, the space in the private room is getting larger and larger, and the infrared microphone needs to be arranged with more receiving probes, which causes more inconvenience to the engineering construction, and it is also easier to produce noise and sound interruption. Wireless FM microphone: (WIRELESS FM microPHONE), wireless FM is divided into VHF (160-260MHz) and UHF (500-960MHz) frequency bands. From the channel setting, it is divided into fixed frequency single channel and variable frequency multi-channel models.
The advantage of the single-channel model is that it is cheap. The biggest disadvantage is that it cannot be used when encountering strong interference. When it fails, it cannot be interchanged. It causes a lot of trouble for engineers and operators. Due to the UHF frequency band, the frequency range is wide. , Less interference, so UHF variable frequency models have become the first choice for KTV. However, in actual use, although each private room uses a different frequency, interference problems such as cross-frequency and noise will still occur. Why? Because the wireless transmission part is not completely linear and one-way transmission, other frequencies in the system The transmitted signal or external interference signal of a point is intermodulated by the transmission antenna stringing into the amplifier circuit of the transmitter. The more the serialized signal, the greater the intensity, the more and the stronger the intermodulation interference generated. These intermodulation products It radiates to the outside world through the transmitting antenna. This interference caused by the interaction of the transmitting signal with the transmitting circuit is called transmission intermodulation interference. On the other hand, for the receiver, all wireless microphones use superheterodyne receiving circuit , At least it includes the following basic circuits, high frequency filtering, amplification, local oscillator, mixing, intermediate frequency filtering, demodulation, and for variable frequency microphones, PLL, VCO, CPU and other parts. When a specific useful signal passes through high frequency When the band-pass filter enters the front stage of the receiver, other frequency signals in the band and external interference signals will also enter the front stage of the receiver from the antenna and enter the mixer. The mixer is a typical nonlinear component, except for the local oscillator. In addition to mixing with a specific high-frequency signal to produce a specific intermediate frequency signal, various interference signals meeting the same conditions will also be demodulated by the demodulation circuit and output noise. This kind of interference caused by multiple frequencies acting on the receiver is called receiving Intermodulation interference. Intermodulation interference generated by two signals. Intermodulation interference generated by three signals. It can be seen that transmission intermodulation and reception intermodulation are difficult to avoid, and the more frequency points used, the intermodulation interference component will become The increase of doubling, noise will be generated in the receiver at the intermodulation frequency point such as 1. 2.3.4. Because of this. It is difficult for domestic and foreign manufacturers to make a model that can be fully compatible in the same frequency band, and Use completely non-interference FM wireless microphones in dozens of private rooms. Digital wireless microphone (DIGITAL WIRELESS MICROPHONE) NH?s?q1 analog to digital is the trend of the entire electronics industry, and wireless microphones also have a trend towards digital development.