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Difference in using modulation format of MSK & AM in place of GFSK

stefan 12
Expert 1780 points
Other Parts Discussed in Thread: SIMPLICITI

Hello, 

I am using Ti's simpliciTI code with the CC111F32 as trasmitter and receiver circuit matching the Transmitter section wiht the following things

1)Channel spacing of 115Khz 2)RF frequency of 869.5 Mhz 3)Modulation technique as GFSK

Can someone explaine what can(will) the difference observed if

a)Minimum shift keying(MSK) 

b)Amplitude Modulation -OnOff Keying (OOK) and Amplitude Shift Keying(ASK)  

are used in place of GFSK modualtion fromat.

can someone explain me the difference in using the above.

Thanks.

  • 0
    TI__Mastermind 39860 points

    MSK = GFSK with modulation index = 0.5 (i.e 2 x deviation / symbol rate = 0.5). Lower mod index will give degraded sensitivity for the same RX filter BW. However, if you decrease deviation you can also decrease RX filter BW and thus gain some of the sensitivity back. 

    For new systems we generally do not recommend OOK/ASK as it is not very spectrum efficient. One advantage of OOK/ASK is average TX current which will lower compared to GFSK. 

  • 0 in reply to Sverre
    Expert 1780 points

    Thanks Sverre.

    I didn't get this  "For new systems we generally do not recommend OOK/ASK as it is not very spectrum efficient". Can you please explain a bit more about this.

     

  • 0 in reply to stefan 12
    TI__Mastermind 39860 points

    The signal bandwidth for OOK will generally be wider than for a GFSK signal of the same data rate