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maximum out-of-band power for CC1000?

Greg Mooney
Prodigy 90 points
Other Parts Discussed in Thread: CC1000

I'm using the CC1000 at 425 MHz in an application where it is sharing an antenna (through a passive diplexer network with a GSM radio operating in the 900 MHz and 1800 MHz bands. I need to know the maximum RF power in these bands that can be present on the 'RF_IN' pin without DAMAGE to the CC1000. I'd also like to know the maximum power in these bands above which PERFORMANCE of the CC1000 will be adversely affected (operating at 425 MHz).

In the 'Absolute Maximum Ratings' section of the CC1000 datasheet, the maximum input RF level is given as +10 dBm, but I assume this is an IN-BAND spec (whereas I'm interested in maximum OUT-OF-BAND power). The only thing I see related to out-of-band rejection is a 'blocking' spec in the 'Receive Section' portion of Table 3: "blocking = 40 dBc @ +/- 1 MHz", but this says nothing about the rejection at frequencies that are much further out.

Thank you.

  • 0
    TI__Mastermind 27145 points

    Hi,

    That +10dBm holds good for both in-band and out of band signals. The front-end of this chip is LNA and it doesn't have any filter infront of it. So, more than +10dBm signal may damage the LNA.

    You may better to use LPF at the input/out of CC1000. This will attenuate the GSM band signals as well as harmonics from CC1000 also.

    Thanks,

    PM

  • 0 in reply to PM
    Prodigy 90 points

    Thank you. That answers the question about the DAMAGE level of the CC1000: +10 dBm whether in-band or out-of-band. Does this answer change if the CC1000 is powered-down?

    As for the out-of-band RF signal level at which the PERFORMANCE of the CC1000 will be degraded (when operating at 425 MHz), I will be filtering (via a diplexer) the input/output RF signal as you suggest, but I need to know how much rejection of the 900 MHz GSM band (880-960 MHz) is required. Does the blocking spec that I referred to in my previous post apply here ("blocking = 40 dBc @ +/- 1 MHz")? I assume that spec means the CC1000 will reject an interferer +/- 1 MHz from the desired signal by 40 dB? If so, can you tell me what the rejection will be hundreds of MHz from the desired signal, or better yet - send me the wideband rejection characteristics of the CC1000? I can perform tests to determine the maximum tolerable out-of-band signal level, but I'd like to avoid that if possible.