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Does ADRV9025's Hard Clipper clip all the peaks above the threshold?

Category: Datasheet/Specs
Product Number: ADRV9025
Software Version: 5.1.0.27

Hi,

On page 71 of the "ADRV9029 DPD and CFR User Guide", the paragraph just before the figure 83 says "The CFR block within the transceiver consists of three cascaded CFR engines followed by a hard clipper to clip the few peaks that are skipped by all three CFR engines.". What I understand from it is the HardClipper does NOT clip all peaks above the H/C threshold but clips some peaks. Am I right? In all cases, cfrHardClipperThreshold is set to (cfrPeakThreshold + 0.1).

Thanks,

  • Yes,your understanding is correct.Ideally the CFR engines should clip all the peaks above the threshold.The CFR hardclipper is used to make sure no peaks beyond threshold reach Power amplifier.Hard clipper doesn't clip all the peaks,it comes into play only incase of the peaks got skipped by 3 CFR engines.

  • Got it, but what I expected was that if the hard clipper is enabled with a proper cfrHardClipperThreshold, the PAPR of the DPD input (pre) signal, dpdPeakTuPower - dpdMeanTuPower, would be near the cfrHardClipperThreshold. However, the many unclipped peaks flow into the DPD engine and cause the DPD saturation.

    If so, is there any way to implement stable DPD operation without backoff for RF signals containing many peaks?

    Thanks,

  • However, the many unclipped peaks flow into the DPD engine and cause the DPD saturation.

    That's not the case with hard clipper, Hard clipper makes sure that no unclipped peaks flow into the DPD actuator above the threshold value.And also we prefer to operate dpdPeakTuPower 3-5dB backoff from the maximum full-scale power to provide headroom for DPD mechanism to pre-distort the signal based on the PA output without stability error.