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CC1120EM-420-470-RD: Differential input to pins 19,20 (LNA_N and LNA_P)

Part Number: CC1120EM-420-470-RD
Other Parts Discussed in Thread: CC1120

Hi

I wanted to ask whether there is any way in which I can directly connect a differential input from antenna to cc1120's LNA pins(19 and 20) without using the circuitry involved to convert single ended input to differential input?

Also can you provide the s1p files for the PA, LNA_N,LNA_P, and TRX_SW pins for fequency bands 164-192MHz and 410-480MHz?

Regards,

Juhi

  • Hi,

    Please refer to sections 4.5 and 4.6 of the CC1120 data sheet for Impedance specs. No, we don't provide any S1P files. We used Load-pull techniques to get the impedance.

    You can use Differential connection but please note that you need to match it properly.

    We recommend to use our Reference Design to obtain an optimum performance.

    Thanks,

    PM

  • Thanks for the reply. 

    Regarding differential input, I was trying to employ separate RX and TX links for CC1120 as in this example www.ti.com/.../cc112xsky65313em-rd    and wanted to know if I can reduce some circuit components by giving differential input from an antenna.

    So, can I consider a differential input from antenna followed by an impedance matching network  connected to cc1120 a sufficient arrangement to achieve good results?

    Regards

    Juhi

  • Hi,

    Please note that the LNA has a differential input and PA has single ended.

    Do you want to use Balun on LNA to convert to single-ended or straight to Antenna?

    If you match it properly then you may get more or less the same performance.

    I recommend yo use the proven circuit to avoid issues.

    You can post your Schematic in PDF for our review. We will help you.

    Thanks,

    PM

  • Hi

    I do not want to use the balun for LNA connections, instead I wanted to connect it straight to the antenna in order to reduce the number of components.

    In the 2nd case(straight to antenna) will I need to design a differentially fed antenna? Kindly help me with this.

    Attaching the schematic I am currently working on to test separate RX and TX paths for CC. 

    Regards

    Juhi

    ccshem.pdf

  • Hi,

    I observed you use 2 antennas for Tx and Rx paths separately. Do you really want to use 2 separate antennas?

    What is the application of this project?

    What do you want to use 2 separate antennas?

    Thanks,

    PM

  • Hi,

    As seen in the schematic one antenna(RX) will be used in the RX path and one(TX) in the TX.

    I want to use CC for transmitting at 145MHz and receiving at 437MHz. Hence I am trying to separate the RX-TX path so that each path can be used with its respective frequency. Hence the 2 antennae.

    Separate RX TX paths referred from this schematic