无线话筒的技术是怎样开展的？关于这一点很多人会有许多疑问，就来给大家说一说这些问题。

       1. Simple FM transmission and reception

      At that time, in order to get rid of the fetters of the microphone cable, people thought of the transmission acceptance principle similar to FM broadcast, through the microphone's energy exchange principle and audio → modulation → amplification → transmission process, and then through the FM radio or special reception machine (special frequency point) to accept and play. It can be expected that its sound quality, stability and anti-interference ability can not meet the needs of practical application.

       2. Frequency modulation emission and acceptance of quartz oscillation

       Due to the RC or LC oscillation produced by electronic circuits, the stability of the oscillation frequency is greatly affected by the environment, and the frequency can not be very high, generally only under two or three hundred megahertz, in such a frequency band, it is very easy to be interfered with other signals, at this time, it presents the emission and acceptance circuit using quartz oscillators. As we all know, the oscillation frequency of quartz crystal is very stable, composed of wireless microphone transmitter and receiver, work more stable, at the same time, its operating frequency can be in the V segment (30MHZ-250MHZ), U segment (200-1000MHZ), the external interference signal is not serious, to the use of wireless microphone has brought better results.

       In use, because the oscillation frequency of the quartz crystal is not adjustable, so for a set of wireless microphone, its acceptance and emission frequency is fixed, and the request is corresponding one by one, it is not convenient, assuming that there is interference at this frequency point in a certain place, the wireless microphone can not be used.

       3. Use PLL accepted wireless microphone

      PLL is the English acronym for frequency phase locked loop. In the transmission acceptance of wireless microphones, the frequency synthesis method can be used to accept signals in a frequency band, and in this frequency band, the working channel can be arbitrarily switched. In theory, in a 24MHZ frequency band, if the channel resolution is 1MHZ, 25 channels can be switched; If it is 125KHZ, 193 channels can be switched, and the number of channels is related to the bandwidth and channel resolution of the receiving machine. In practice, it is necessary to coordinate various elements, but it is certain that the wireless microphone using PLL technology, its acceptance channel is adjustable, and more than one, which brings great sensitivity to the use of the transmitter and the receiver can also be combined at will, as long as in a bandwidth range, the working channel can be switched at any time to prevent interference.

       At present, the first type of wireless microphone on the market has been eliminated, and it is only used in ordinary experiments. The second type also exists only in low-end products or old products, and a large number of wireless microphones using PLL technology are used.

      4. Diversity acceptance

    Because the wireless microphone is used for frequency modulation technology, its working frequency band in the V segment or U segment, the waves are transmitted in a straight line, when encountering obstacles, can only reflect, can not diffraction. Therefore, there will be a shadow or dead Angle, affecting the use of the microphone effect (light sound, frequency modulation noise, etc.), in order to prevent this situation, at present, in the high-end wireless microphone, the use of diversity acceptance technology, the so-called diversity acceptance, that is, in a system needs to have the same two acceptance installation, a signal issued by the transmitter, At the same time, it is amplified by two FM receivers by frequency discrimination and low frequency, respectively, and added to the annexer, which is actually a selector, and chooses a strong acceptance signal as an output signal at each instant, which can effectively improve the acceptance effect.