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CC1200: receive sensitivity between CC1125 vs CC12xx

Marvel52
Prodigy 200 points
Part Number: CC1200
Other Parts Discussed in Thread: CC1125, , CC1101

What is the comparable difference in receive sensitivity between CC1200 and CC1125 in 4-FSK applications from 10-50Kbps assuming minimum CHF and best modulation index for given rates?

The LNA gain looks the same. I’m aware of the narrower CHF in the 1125 but I don’t think it applies for my rates. The blocking and selectivity look slightly better in cases where the CHF is extremely narrow. Not sure about NF or other factors that may contribute to 1125 having better sensitivity but the 1125 specs list “Mobile Radio” in the list of applications and CC1200 does not. This makes me think there might be some RX performance advantages in using CC1125 that I am not yet aware of.

Looking at the spec sheets for both 1200 and 1125, the sensitivity specs around the rates I am using are not shown specifically enough for me to make an informed decision.

Example from spec sheets:

CC1200: –122 dBm 1.2 kbps 2-FSK, DEV=4 kHz CHF=11 kHz

CC1125: –123 dBm 1.2 kbps, DEV=20 kHz CHF=50 kHz

[This lead me to think the CC1125 could have some significant RX performance advantages at rates higher than 1.2 while using a wider CHF]  

My application is a NLOS mobile environment with lots of multipath/fading.

As an example:

I’m currently testing using two TXREB and CC1200em (one TX and one RX) at 902-928Mhz with cable and attenuator calibrated to within 1db. On the bench the CC1200 sensitivity checks out as follows:

Mod=4-FSK, Data Rate = 10Kbps, Deviation = 4K, CHF= 16.5Khz, FEC(CC1101), whitening, PN, Viterbi:

Usable RX sensitivity (ber ~3%) = -114dbm

1. I would like to know how the CC1125 would perform with the parameters above (minus FEC which I can code into the MCU if I decide to use the CC1125).

2. Is there a performance breakdown between CC1200 and CC1125 for 4-FSK with data rates from 10-50Kbps other than those on the respective spec sheets?

3. What are the recommended parameters or register settings for optimum RX sensitivity at 10,20,30,40, and 50Kbps for the CC1200 and CC1125?

4. Besides a range extender or lowering the data rate, what other settings and techniques can be implemented to raise sensitivity and or mitigate multipath/fading?

5. Is the SMA-LNA pin loss on the CC1200em significant (>1db)?

  • 0
    TI__Mastermind 36375 points

    Marvel52,

    I am not going to be able to answer all your questions, however I will say the the main difference between the CC1125 and the CC1200 are the two IF data converters used for sampling the I and Q data. The CC1125 are slower, but slightly better linearity and lower noise. So if you are targeting a system with lower than 100KHz RX bandwidth the CC1125 is a great device. But if you are planning on going above 100KHz, then the CC1200 is better. The reason is that the CC1125 switching to Zero-IF at above 100KHz RX bandwidth where the CC1200 does not.

    1. I would like to know how the CC1125 would perform with the parameters above (minus FEC which I can code into the MCU if I decide to use the CC1125).

    - the CC1125 is going to be marginally better in sensitivity.

    2. Is there a performance breakdown between CC1200 and CC1125 for 4-FSK with data rates from 10-50Kbps other than those on the respective spec sheets?

    • No, but in general about 1-2dB improvements for low data and then as you get closer to 50Kbps it because almost identical.

    3. What are the recommended parameters or register settings for optimum RX sensitivity at 10,20,30,40, and 50Kbps for the CC1200 and CC1125?

    • Please use SmartRF Studio to generate the recommended values.

    4. Besides a range extender or lowering the data rate, what other settings and techniques can be implemented to raise sensitivity and or mitigate multipath/fading?

    • I have seen customer have multiple receivers to achieve good antenna diversity.

    5. Is the SMA-LNA pin loss on the CC1200em significant (>1db)?

    • No, and the numbers in the datasheet at measured with a reference at the SMA connector on the exact same boards that we have in distribution.

    Regards,

    /TA

  • 0 in reply to TA12012
    Prodigy 200 points

    ,

    Thank you for responding to my questions.

    I am clear on all but #3.

    3. What are the recommended parameters or register settings for optimum RX sensitivity at 10,20,30,40, and 50Kbps for the CC1200 and CC1125?

    • Please use SmartRF Studio to generate the recommended values.

    More specifically. I do use Smart RF Studio for register setting when testing.  What I'm looking for is optimum modulation indexes along with receive filter bandwidths Etc for CC1200 that could be used as the input parameters for Smart RF Studio in order to obtain maximum RX sensitivity at those rates mentioned.

    Regards,

    Marvel52

  • 0 in reply to Marvel52
    TI__Guru**** 317180 points
    A modulation index = 1 will in most cases be optimal. Lower index gives a signal that is harder to demodulate, higher increase the noise bandwidth due to higher RX BW requirement.

    Note that: Required RX filter bandwidth can be approximated as :Signal BW + 4*ppm xtal*Frequency of operation