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  • Model: Analysis of wireless microphone products
  • Time: 2017-2-4 9:42:07
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1 wireless microphone
Wireless microphone, or wireless microphone, is the transmission of sound signal sound equipment, by the transmitter and receiver composed of two parts, often referred to as wireless microphone system.
The transmitter is powered by a battery, which converts the sound into an audio electrical signal, which, after processing the internal circuitry, sends a radio wave containing audio information to the surrounding space.
The receiver consists of electric power supply, the receiving antenna receives radio waves emitted by the transmitter, after processing the internal circuit to extract the audio signal, and the output signal line to the sound system, complete the wireless transmission of audio signals. A receiver usually contains 1 sets, 2 sets or 4 sets of the receiving circuit, respectively receiving 1 and 2 or 4 wireless microphone signals, which are called "one" and "one to two" or "four in one" model. Which one is the most common type of two.
A wireless microphone is essentially a unidirectional wireless communication system.
1.1.UHF band
The wireless microphone system is via wireless transmission of audio signal equipment, according to the wireless microphone and receiver transceiver frequency, which can be divided into different frequency bands, FM, VHF, UHF commonly used several bands.
FM band refers to the frequency band used by the public FM radio and its nearby frequency band, usually only a few simple wireless microphone products using the 88~108MHz.
VHF band, according to the international standard, refers to the 30~300MHz band, FM band described above is actually contained in the VHF band, but due to its proximity to the public broadcasting (FM) band, so called FM band. VHF band wireless microphone using the 170~260MHz band, often referred to as the VHF BAND (VHF HIGH).
UHF refers to the 300~3000 band, MHz band, 400~830MHz band wireless microphone is generally used, more than 830MHz of the band 830~960MHz band is less used, because GSM and CDMA mobile phone interference, frequency of more than 960MHz diffraction ability is getting worse, so currently the most popular UHF band 800MHz band (740~830MHz).
2 several noun terms
To understand the performance characteristics of wireless microphone, it is necessary to understand the basic terminology of wireless microphone and the specific meaning of the main performance indicators. In addition to the wireless microphone with a wired microphone the same audio indicators, there are some specific terminology and performance indicators, the following one by one.
Squelch: wireless microphone receiver without receiving the signal, or when the signal is weak, in order to avoid the noise output, the output signal will be cut off automatically, this function is called squelch (Squelch). If there is no squelch function, or squelch function when no signal is bad or weak signals, speakers will emit noise. Noise will affect the quality of sound effects, damage to the atmosphere, and even damage the sound amplification equipment.
Dead: also known as dead or blind. In the process of moving the wireless microphone, the signal received by the receiver will be strong or weak because of the distance, the relative position of the barrier or obstacles. Some positions in normal use in the range of the signal is too weak to squelch action within the receiver, cut off the output signal; and leave the position, then can normally receive and output. This position is called dead or blind. A wireless microphone in the near or above the effective distance, inevitably there will be dead, if the design is reasonable, the dead point, there was just no voice; if the design or manufacturing bad, is not only a normal voice, but a murmur.
 Diversity reception: refers to the wireless microphone receiver can receive the same wireless microphone signals from 2 antennas, select the use of a strong signal through the internal circuit. This way can greatly eliminate the receiving dead zone, avoid mute or dead noise. There are two ways of diversity reception: antenna diversity and diversity.
In the antenna diversity mode, there are two receiving antennas, a set of control circuit and a set of receiving circuit, when the work received signal is weak, the control circuit will automatically switch to use another antenna.
In the diversity mode, in addition to two antennas and a set of control circuit, there are two sets of complete receiver circuit, while the work, from the control circuit to track the switch, the output of a better audio signal. In this way, it is better to track the strong signal at any time, so the effect is better than the former one, but the circuit is complex and the cost is high. This diversity is often referred to as double tuning, true diversity, etc.. In live performances, studio and other important occasions, we must choose the double tuned true diversity products, to ensure that no dead point in practical operating range.
Multi channel: general wireless microphone, the carrier frequency is fixed, the user can not change the use of the process. Because the wireless microphone is transmitted by radio waves of sound signal, so when the external signal with the same or close to the carrier frequency in the work environment, there will be interference, the receiving distance decreases, the receiver output noise, and even received the microphone signal.
In view of this situation, manufacturers have developed a multi-channel wireless microphone system. The transmitter (wireless microphone) and frequency receivers are adjustable, so users can encounter interference frequency, changing the carrier frequency of the system, in order to avoid the interference signal and the normal work; in addition, if the multiple wireless microphone using the same venue, but also can easily be a microphone regulation at different operating frequencies, so that it does not interfere with each other, coordination. Large professional stage performances of the use of wireless microphones are mostly multi-channel system, there are 8, 16, or even more channels, the most common is the 16 channel. Multi channel systems generally use phase locked loop (PLL) frequency synthesis technology, microcomputer control technology and other related technologies. Its production technical requirements, equipment requirements, production costs and product performance, are much higher than other ordinary models.
Some of the products currently on the market, is a fixed frequency, but the same type of a batch of products, can also be produced into different frequency products, users can choose to buy, but after the purchase, can not adjust the work frequency in use, some manufacturers will also be the nominal "channel", "32 the channel can be arbitrarily selected", which is not accurate, or is intended to mislead consumers. This situation requires special attention, there are several methods that can be distinguished: one is to observe whether there is a switch or button to adjust the channel receiver panel; two is to see its propaganda or instructions marked "adjustable frequency" and "user adjustable channel"; three is the actual operation, to see whether the adjustable.
Signal to noise ratio (SNR): the ratio of the original audio signal to the noise signal in the output signal of a signal received by a receiver at a specified intensity (typically 60dB V) is expressed in decibels (dB). The greater the value, the more pure the signal, the better the performance of the machine.
Reception sensitivity: in a radio or walkie talkie, the receiver sensitivity is the minimum radio frequency signal that is required when the receiver outputs a signal to noise ratio. The smaller the value, the higher the receiver sensitivity. In the wireless microphone, should be expressed in the input RF signal receiver squelch the critical value, because when the input signal is lower than the static noise, the receiver in a mute state, the output signal is not.
For example, a product receiving sensitivity is labeled as "-90dBm", said that when the antenna input signal is lower than that of -90dBm (7 V), the receiver will enter the mute state, such annotation can accurately receive receiver response capability.
Some of the products, using the method of indicating similar radio, walkie talkie the sensitivity index, for example, labeled "2 V/12dB", which means when the antenna input signal is 2 V (-101 dBm), the signal-to-noise ratio of the receiver output signal can reach 12dB. However, the signal to noise ratio (SNR) of wireless microphone is much higher than that of 12dB, so this method can not accurately express the receiver's ability to receive.
RF output power: refers to the size of the wireless microphone transmitter to the space of the signal energy, usually with mW (mW) to say, generally between 5~50.
Effective working distance: the distance between the wireless microphone and the normal signal. This parameter is indicated on the general product, most of which is indicated in the open or ideal condition. Because the actual transmission distance of the wireless microphone, to be affected by the actual environment, can not be accurately marked. Only in open spaces or under ideal conditions can provide reference, and can be compared with each other.
In fact, the ability to measure the transmission of the wireless microphone, to look at the receiving sensitivity of transmission power and critical squelch the 2 indexes which are converted to the same unit, the bigger the difference is, the same environment the effective working distance farther. Combined with the receiver is the diversity, as well as what kind of diversity, we can clearly estimate and compare the effective transmission distance of different products. Generally speaking, the effective range of the diversity receiver is larger than that of the non diversity receiver.

Enping City Keith Electroacoustic Equipment Factory

Enping City Keith Electroacoustic Equipment Factory

Enping City Keith Electroacoustic Equipment Factory

Enping City Keith Electroacoustic Equipment Factory Enping City Keith Electroacoustic Equipment Factory Enping City Keith Electroacoustic Equipment Factory Enping City Keith Electroacoustic Equipment Factory