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antenna for cc2530

strongleg strongleg
Intellectual 605 points
Other Parts Discussed in Thread: CC2530

1st question:may i use the IFA specified in DN0007 for CC2530? document AN058 said it's better than MIFA

2nd question: i made a test with 2 cc2531board: one have a whip antenna and controlled by Packet Sniffer to function as a sniffer; another board can select between whip antenna and MIFA, controlled by SmartRF Studio to send some packet. distance between 2 board is about 1.5m, results are:

Antenna      Whip              MIFA

TX power     4.5     -22     4.5     -22

RSSI             -60    -87      -71    -96

TX power is set in SmartRF studio, RSSI is read in Packet sniffer. Is this result normal?

  • 0
    TI__Genius 14940 points

    Yes, the IFA is slightly better than the MIFA.  This is due almost entirely to the size of the aperture of the two antennas.  Since the MIFA aperture is slightly smaller than the IFA, its radiating efficiency will be slightly less.

    The numbers you are showing are reasonable.  They do appear slightly low so you may need to do some more tuning of the component values in the RF path to optimize this.  Also, what kind of insertion loss does your selection circuitry contribute to the overall circuit.

    Jim Noxon

  • 0
    TI__Expert 4435 points

    The Inverted F antenna is designed for a 50 ohm imput and has a pattern of omni-directional.   Which means in 2 directions you will see a circle with maximum range dependent upon the efficiency of the antennna.  The antenna efficiency is set by the dimension of the antenna and the size of the ground plane.   As long as you keep the same layer stacking,  antenna dimensions and ground size your antenna will have >90% efficiency and have maximum pattern when the PCB board is in the correct direction with ground.   The 3rd direction will work but with slightly less range due to the null of the antenna. 

    Try repeating the your test and you should get 2 directions which read close to the same as the whip and one that is slightly less.  Then when you mount the antenna make sure it is orientated for maximum direction.

    Regards,

  • 0
    Intellectual 605 points

    this is the layout. R6 and R8 is used to select MIFA or Whip antenna,  i think that's why the performance is not good. U3 is JTI balun 2450BM15A0002

    the following is the new design, use IFA and 2450BM15A0002. PCB is 2 layers 1.6mm FR4. Any suggestions about this layout? May i expect some improvement with this design? thanks

  • 0 in reply to strongleg strongleg
    TI__Expert 4435 points

    It is hard to tell from limited picture size all the issues of this layout but I'll mention the ones that can be seen in your snapshot.

     

    1)   Unless you validated the antenna input is 50 ohm then you should include a PI network as close to the Antenna input to handle impedance errors.

    2)  Impedance errors occur when the trace from the balun is not a 50 ohms,  antenna in not 50 ohms or the balun is not 50 ohms.

    3)  If you use 2-layer or more with ground fill on the top.  You need to connect all layer grounds by vias spaced at the wavelength of 1/10 of 2.45GHz.    Wavelength is given in meter/sec. 

    4) Before connecting to the antenna you can using a coax measure the output power into 50 ohm termination of a spectrum analyzer to make sure the power you program is the what is being delivered to the antenna.   

    5)  Then connect the antenna.  At this point you can take a TI reference board with a whip antenna,  add a whip antenna on the input of the spectrum analyzer and compare the referenece design power and your baord power at 1 to 3 meter separation.   This is an approximate reading since it includes multipath but gives a good indication everything is working close or same as the reference design. 

    Regards,