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How does the multimode receivers work with a single IF filter?

Shamsher Singh
Prodigy 160 points

How does the multimode receivers work with a single IF filter?

  • 0
    TI__Mastermind 37500 points

    The digital radio devices are after the analog ADC conversion.  multiple signals of the same bandwidth or different bandwidths can be combined into a wider band signal.  The wider band signal can be mixed to a common IF.

    The IF filter at the ADC input usually encompasses the wider band signal, so a single IF wider filter accomodates several carriers. 

    The digital radio part has multiple Down converter and Upconverters to tune, filter eacj carrier.

    Note: of your question is about different modulator/ demodulator designs, the digital radio does not contain modulation and demodulation logic, strictly DDC/DUC first stage radio channels, and second stage digital IF streams.

    Regards,

    Radio Joe

  • 0 in reply to Radio-Joe
    Prodigy 160 points

    Thanks RJ. You exactly understood my question and thanks for the answer. I have one more query that when in multimode receivers when other network signal is selected, do we need to change samling frequency by some factor to effect the bandwidth of the IF filter?

    Regards,

    Khushbir

  • 0 in reply to Shamsher Singh
    TI__Mastermind 37500 points

    Hello,

    The IF filter is an analog design, that preselects the input to the ADC.  It is designed for the widest expected bandwidth.  Some radios have selectable pre-selector filters.  

    The Digital Down Conversion that has a block down converter  followed by DDUC, can provide portions of the digital IF filtered and decimated, this is more of a DDUC number of channel requirement, than a selectable bandwidth. 

    Regards,

    Radio Joe