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CC1120: Antenna design

Callum Bassie
Prodigy 20 points
Part Number: CC1120
Other Parts Discussed in Thread: CC-ANTENNA-DK2

Hi,

Is there a recommended antenna design for the CC1120 operating in the 433/434 band? A printed antenna is preferred. 

  • 0
    TI__Mastermind 29560 points

    Hi,

    Check out app note: https://www.ti.com/lit/swra730 

    Regards,

       Richard

  • 0 in reply to RGW
    Prodigy 20 points

    Hi Richard,

    I'm only looking for a single-band antenna.

    I have limited space in the X plane but I have a lot of space in the Y.

    I don't think I would be able to fit this design on my PCB.

    Is it better to have a straight line or should there be some bends?

    Do you have any application notes on single-band 433MHz antennas using the CC1120 chipset?

  • 0 in reply to Callum Bassie
    TI__Mastermind 29560 points

    Hi,

    The app note covers both single-band (page 15 for just 433 MHz) and dual-band.

    What is your maximum size for the antenna ?

    Regards,

       Richard

  • 0 in reply to RGW
    Prodigy 20 points

    Hi Richard,

    I have also looked into the application note SWRA496A which suggests that a helical antenna (board #4: 433-510 MHz PCB Antenna) is more efficient than the meander design shown in swra730 so I'm a bit unsure of what to use. 

    There is space for an inductor (Z64) on design note swra730 to utilize the 433 MHz antenna. Is there not a design available with the component and excess track removed to make a single antenna for 433 MHz?

    Is there a way for me to share my current design to show the permitted space?

  • 0 in reply to Callum Bassie
    TI__Mastermind 29560 points

    Hi,

    The PCB helical antenna in the CC-Antenna-DK2 (SWRA496, page 25) has an efficiency around 35 % and a bandwidth of 15 MHz. This antenna design is sensitive to PCB thickness tolerances due to the number of vias used in the antenna so keep this into account if you choose this antenna. The closer the antenna is positioned to GND, will also decrease the efficiency and bandwidth furthermore.

    SWRA730 antenna for a single-band at 433 MHz has a lower efficiency around 19 % but with a larger bandwidth of 23 MHz.

  • 0 in reply to RGW
    Prodigy 20 points

    Hi,

    If it is possible, is it not better to just create a straight line? Please refer to the attached screenshot.

    The green and red fill on the internal layers are copper keep-out zones.

    I'm intending on creating a four-layer board. I presume this will cause a problem with the SWRA496 as it's based on a two-layer board at 1.54mm.

  • 0 in reply to Callum Bassie
    TI__Mastermind 29560 points

    Hi,

    It is possible to create a straight line. You want to utilize the available area as much as possible for the best efficiency. 

    Make sure you include a pi-match for the antenna matching.

  • 0 in reply to RGW
    Prodigy 20 points

    Hi,

    Thank you for your advice.

    Would a straight line be optimal compared to the other designs?

    Would you expect a greater bandwidth or would this be due to matching and grounding?

  • 0 in reply to Callum Bassie
    TI__Mastermind 29560 points

    Hi,

    The bandwidth will be dependent on the loading to GND and the effective size of the antenna. I would make the antenna as long as possible for this area. When you receive your first prototype, measure the resonance with a 0 ohm resistor in the antenna match. Tune / cut the antenna length until you receive 433 MHz resonance. 

    If the antenna's resonance is too high in frequency (antenna too short); then this can be compensated in the antenna match or alternatively add a meandering structure in the antenna trace.