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Talking about the Three Performance Indexes of Tuner Frequency Tuner

Text:[Big][medium][small] time:2018/12/12 10:55:06    Views:    

       With the rapid development of science and technology, high-frequency head and television tuner and so on the product application is very wide, especially the application of high-frequency head, but in the practical application of the tuner, the tuner is So many users headache problem, then what is the performance of tuner frequency tuner what? The following by Baowei Li Electronics for everyone to briefly introduce.

       1, selectivity and pass band: Because the receiving antenna sensor a variety of electromagnetic signals, the tuner selected from the need to amplify the signal, and unwanted signal attenuation, in particular, to effectively inhibit the adjacent channel And mirroring interference, the tuner should have an appropriate pass band and good selectivity. To this end, the general requirements of the tuner total frequency characteristics of the bimodal curve, the top of the roughness of less than 20%, - 6dB bandwidth should be less than 11MHz. For the mirror interference and IF interference should have 40dB of the ability to suppress. Because the mirror frequency (equal to the local oscillator f0 plus IF frequency) frequency, it and the difference between the local oscillator is equal to the frequency, can successfully pass the circuit, so the high level can be suppressed as soon as possible.

       2, power gain and noise figure: Because the tuner is the front end of the entire TV receiver, so the receiver sensitivity and signal to noise ratio will mainly depend on his power gain and noise figure level. In order to ensure the purity of the image background, no snow-like interference, the general requirements of the tuner noise coefficient of less than 8dB. On the one hand to reduce the insertion loss of the circuit; the other hand, should use low noise tube and reasonable arrangements for the working state of the transistor to solve. In order to improve the receiver sensitivity and mess, the general requirements of the tuner power gain of 20 ~ 30dB, while requiring high and low channel gain difference should be less than 8dB. High-release tubes are required to be low-noise tubes.

       3, cross-modulation: If the signal near the channel is very strong, because the transistor device there is a certain non-linear, will want to receive the channel TV signal modulation, the results of two different images. This phenomenon is called cross modulation. So the tuner for the adjacent channel should be as large as possible to suppress.

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