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CC2530-CC2592EM-RD: SAW Filter for LTE Coexistence

Dave Eypper
Prodigy 120 points
Part Number: CC2530-CC2592EM-RD
Other Parts Discussed in Thread: CC2592, CC2530, CC3200

Hi, does anyone have experience/recommendations with using a SAW/BAW filter with the CC2530/CC2592 reference design? My questions are specifically:

1. Will reflection of harmonics back into the PA damage the CC2592?  Or significantly increase current consumption?  e.g. for reasons mentioned here: 

processors.wiki.ti.com/.../CC26xx_Optimal_Load_Impedance

2. Are there any components added for filtering that could be eliminated from the TI reference design if we use a SAW/BAW filter?  We're working off this design:

www.ti.com/.../tidra40a.pdf

3. Are Bluetooth/WLAN filters (e.g. Qualcomm B39242B8840P810) bidirectional for both RX and TX?  All seem to be specified with an "input" and "output" pin, however reference designs (e.g. CC3200 LaunchPad) use them bi-directionally...

We are considering this filter because of likely interference from cellular base-stations in the 2305-2360MHz and 2495-2690MHz bands.  I don't think the filter in the TI reference design has steep enough roll-off to attenuate these bands significantly, also we are using a wide-band antenna (TI design SWRU120C).  We can "punch through" the interference by turning the CC2592 up to ~22dBm, however would prefer a lower-power and more selective design for SAR exposure, compliance, and battery-life reasons.

Thanks,

Dave

  • 0
    TI__Mastermind 27145 points
    Hi,

    You can put the SAW Filter after the Harmonic Filter ( in between L3104/C3105 Junction and C3110 of the Ref Design).

    As SAW filter doesn't have enough attenuation to the Harmonics, Harmonic filter is required.

    Yes, SAW filter is Bi-Directional.

    Please note that when you use SAW Filter at the Front-End, it degrades the Rx Sensitivity and Transmit power because of Insertion Loss of SAW Filter.

    Also please refer to the CC2530 Data sheet (SWRS081) for Blocking, Channel and Adjacent/Alternate channel Rejection specs of CC2530 to use in your system design calculations.

    Thanks,
    PM