SBAA682 April   2025 AFE7728D , AFE7768D , AFE7769D

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Acronyms Used in This Document
  5. 2Distributive Antenna System
  6. 3Repeater System
  7. 4Goals of DAS and Repeater Design
  8. 5RF Repeater System Without FPGA/ASIC
  9.   10
  10. 6Overcoming Bandpass Filter Effects From Cable Dispersions and Multi-Path
  11. 7Summary

6 Overcoming Bandpass Filter Effects From Cable Dispersions and Multi-Path

With the ideal condition of signal propogation from the MU to RU, the signal characteristic has a proper pulse filter to maintain the waveform meets various regional spectral mask requirements. If the signals go through typical Ethernet or fiber channel, the channel characteristic can introduce dispersion factor that can potentially widen the effective shape of the signal. In the case of repeater system, the signal goes through multi-path effect. In essence, the fiber dispersion factor and the repeater multi-path effect create a bandpass behavior and distorts the original pulse shaping filter. Therefore, to overcome the bandpass behavior, the design does the following:

  • RX DDC: the designers choose the proper DDC filter within the AFE77xxD family to removal additional distortions due to the bandpass behavior.
  • RX analog front end filtering: the designers add analog RF bandpass filters to filter out the additional distortions to the waveform.