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DC blocking Capacitor CC1101

Gregorio Tovar
Prodigy 240 points

Other Parts Discussed in Thread: CC1101

Hi everybody,

 

In the Design Note DN025 (Johanson Technology Matched Balun Filter optimized for CC1101 868/915 MHz) mentions: "The DC block is only needed when there is a DC path in the antenna".

 

 

Q1. Can I remove the DC Blocking Capacitor (C124) if I am using a Meander Monopole Antenna?

Q2. Where can I find information about the DC Blocking Capacitor?

 

Regards,

Gregorio

 

 

 

  • 0
    TI__Mastermind 39860 points

    There is no dc path when using the meander monopole antenna so the dc block cap can be omitted.

    When you make your design it is good design practice to add placeholders for a PI network close to the antenna for impedance matching. If impedance matching is not needed (but most likely it will be), you simply do not mount the shunt components and use a 0 ohm resistor for the series component. See AN058 for more details on antennas and matching

     

  • 0 in reply to Sverre
    Prodigy 240 points

    Dear Sverre,

     

    Thank you for your answer.

     

    Regarding to good design practices,  I am carefully following all the specs, I do not want tune the circuit and place extra components on the board but apparently it is something I can not avoid.

     

    Thanks for your time and help,

    Gregorio

  • 0 in reply to Gregorio Tovar
    TI__Mastermind 39860 points

    Antenna performance is sensitive to the environment in which it is to operate (e.g plastic enclosure, hand held, metal casing,......). For optimum performance you do need to tune the antenna length (can be done by cutting the length or through external passive components - series inductor will make the antenna to appear electrically longer) and most likely also you need to do impedance matching.

  • 0 in reply to Sverre
    Prodigy 240 points

    Dear Sverre,

     

    It could sound as a complain, but due to the lack of equipment (VNA and Spectrum Analyzer) I am limited to achive the optimum performance at the first chance using the minimum of components. Nevertheless, I will follow your advice of the placeholders for 2 shunt and 1 serie element.

    I really appreciate your time and help, again thank you.

    Regards,

    Gregorio