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CC3100MOD: TX power does not meet the spec

Shuyang Zhong
Expert 4890 points
Part Number: CC3100MOD
Other Parts Discussed in Thread: CC3100

Hi dear team,

A customer is testing the performance of CC3100MOD and found that the TX power appeared lower than expected, would you please help review their design and see if anything is missing? Thanks.

1. Running OTA test on CC3100MOD, the result of TX power is 12dB, which is lower than the expected power(17dB - (2~3dB) for antenna efficiency). To compare, the test result of another wifi module(Realtek RTL8710) which has the same 17dB TX power is above 14dB.

The test results also match the max distance in filed test, CC3100MOD will lose the connection with a distance > 80m, while the other module for comparison can stay connected at 100m range.

What could cause this result? Is there any suggestion to extend the range of CC3100?

2. CC3100MOD's TX power is 13.5dBm at 54OFDM according to the datasheet, which is significantly lower than the 17dBm at DSSS or CCK, could this be the reason for the test results in OTA test? If so is there a way to set CC3100MOD to use 802.11b only to maximize the TX power?

3. Is there a way to add PA on CC3100 or other simplelink wifi products? Does the voltage of power supply (e.g from 3.3V to 3.6V) has anything to do with TX power? Is there any other suggestion to maximize the range of CC3100MOD?

Please find the PCB of customer's module as attached, thanks.

CC3100MODULE-WF_V0.1.PcbDoc.zip

Best regards,

Shuyang Zhong

  • 0
    TI__Mastermind 46861 points

    Shuyang,

    The 17 dBm TX Power you see in the datasheet is from a conducted measurement and not radiated. The customer should do a conducted measurement using Radio Tool and compare the output power against the datasheet by soldering a pigtail SMA connector to the R1 pad. The range is greatly influenced by the wireless access point and the connection used, i.e. b,g,n. and also the antenna used.

    In connected mode (STA, AP), the modulation is handled by the CC3100MOD itself. There is no API for set modulation in connected mode.

    Since the 2.4GHz only has a single output pin, it is also not possible to add and external PA to get better power as this is the RX/TX pin. Note that Table 8.9.2 in the datasheet is when VBAT = 2.3 to 3.6V, so higher VBAT will not result in higher TX power. What is the gain of the antenna being used? 

    BR,

    Seong

  • 0 in reply to Seong Kim
    Prodigy 100 points

    Hello,Seong Kim

    Any other suggestions to increase the communication distance to an AP when CC3100MOD is configured as a STA?

    Thanks!

  • 0 in reply to Seong Kim
    Prodigy 100 points

    Hello,Seong Kim

    The gain of the antenna is 2-3db.And which register to set the gain for CC3100MOD?

  • 0 in reply to Seong Kim
    TI__Expert 4890 points

    Hi Seong,

    Thanks for the reply. Cen() is the engineer working on this, as he said, the antenna gain is 2-3dB. Cen will also help run conducted test to compare with the datasheet and will get back to you soon.

    I have one more question to discuss with you: since the b/g/n mode can't be set manully, and CC3100MOD's TX power is only 13.5dBm at 54OFDM (against 17dBm at 1DSSS), could it be the reason of the low TX power in the OTA that CC3100MOD had switched to OFDM without knowing? If that is the case, is there anyway to make CC3100MOD stay in 11b mode, e.g. some sort of setting from the AP end?

    Best regards,

    Shuyang

  • 0 in reply to Shuyang Zhong
    TI__Mastermind 46861 points

    Shuyang,

    Please keep in mind that in order to use the module's certification, the antenna gain cannot exceed 2.14dBi. 

    Yes, the range will decrease if the TX power is lower.

    You're not able to on typical APs. On Cisco APs, you do get this configurability to use only certain modulations.

    BR,

    Seong

  • 0 in reply to user6462792
    TI__Mastermind 46861 points

    Cen,

    You can vary the TX output power level by using the "sl_WlanSet()" API with the "WLAN_GENERAL_PARAM_OPT_STA_TX_POWER" parameter.

    For further details you can refer to the CC3100 programmers guide.

    BR,

    Seong

  • 0 in reply to Seong Kim
    TI__Expert 4890 points

    Hi Seong,

    Thanks for clarify this.

    If putting the certification limit aside, can CC3100MOD support the use of higher gain antenna?

    Best regards,

    Shuyang

  • 0 in reply to Shuyang Zhong
    TI__Mastermind 46861 points

    Shuyang,

    Yes, the CC3100MOD can support the use of a higher gain antenna.

    BR,

    Seong

  • 0 in reply to Seong Kim
    TI__Expert 4890 points

    Seong,

    If a higher gain antenna is used, do I need to set the antenna gain in software accordingly? I didn't find the API in the programmer's guide.

    BR,

    Shuyang

  • 0 in reply to Shuyang Zhong
    TI__Mastermind 46861 points

    Shuyang,

    No there is nothing you need to configure in the SW according to the gain of the antenna.

    BR,

    Seong