What are the Bluetooth modulation methods?

The following is the modulation method and operation of Bluetooth brought by Bian Xiao, hoping to bring you some help. Thank you for watching.

Methods/steps

1/6 Step by step reading

FSK modulation is a modulation method in which the carrier frequency is proportional to the information symbol. When the information symbol 1 is sent, the transmission frequency is shifted by fdHz, and when the information symbol-1 is sent, the transmission frequency is shifted by fdHz.

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Sudden frequency switching will lead to large out-of-band spectral sidelobes. In order to reduce instantaneous phase transition and thus reduce out-of-band radiation, information symbols are usually pre-modulated by filters and then frequency modulated. In addition, there is the problem of how to choose the appropriate frequency offset.

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Modulation index: For the frequency offset of GFSK modulation, a variable is introduced to represent the normalized frequency offset, which is called modulation index.

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Without considering the modulation shaping filter, it can be seen that the phase of a symbol signal changes π/2 when the modulation index is 0.5; When the modulation index is 1, the signal phase of a symbol changes π. After the above analysis, we can easily think that the frequency offset interval should be as large as possible, so that the receiver can easily distinguish different frequencies.

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The voltage converter is used to convert the external power supply voltage into the voltage of 1.8V required by the power supply input pin of Bluetooth chip1.8v. Specifically, it may include the XCL210d181gr-g voltage converter.

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XCL2 10 series is a low-power step-down voltage converter, which integrates the control IC (integrated circuit) with the coil and realizes miniaturization.

Matters needing attention

The above is the key for Bian Xiao to take you to operate.