Changes between Version 8 and Version 9 of WARPLab/AGC


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Timestamp:
Nov 9, 2015, 3:17:31 PM (8 years ago)
Author:
chunter
Comment:

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  • WARPLab/AGC

    v8 v9  
    1717After the final gain adjustments are made, the AGC core can optionally subtract any detected DC offset. This also produces an [#waveformDependence waveform dependence] -- the transmitted I and Q waveforms must be zero mean over a period of 32 samples. A series of 20 MHz-wide 802.11 STS symbols meets these requirements.
    1818
    19 == Dependence on 802.11's STS == #waveformDependence
     19== Waveform Dependence == #waveformDependence
    2020
    2121The periodicity requirements of the AGC and DCO correction systems can be achieved by many different waveforms. One common waveform that meets the requirements is the 802.11 short training symbol. This 20 MHz-wide waveform is used by 802.11 for the purposes of AGC and DCO correction. It can be used as a WARPLab preamble even if the proceeding waveform has no relation to 802.11.
     
    3434
    3535The above image shows that the AGC performs adequately over the entire 90 dB range, roughly keeping the resulting I/Q magnitude flat at the ADCs.
     36
     37== Altering the AGC Behavior ==
     38
     39The [wiki:WARPLab/Reference/Baseband/Buffers#BasebandCommands Baseband Buffers] module contains many commands for modifying behavior in the AGC. The three most useful commands for users are:
     40
     411. [wiki:WARPLab/Reference/Baseband/Buffers#agc_target agc_target] - This command adjusts the target gain of the AGC. A lower (i.e. "more negative") value will produce a smaller signal at the ADCs and vice versa.
     421. [wiki:WARPLab/Reference/Baseband/Buffers#agc_dco agc_dco] - This command can enable or disable the DC offset correction. Depending on the waveform being used, it may make more sense to implement DC offset correction in MATLAB after a reception has occurred.
     431. [wiki:WARPLab/Reference/Baseband/Buffers#agc_reset_per_rx agc_reset_per_rx] - This command will configure the AGC to either reset on each trigger of the the receive state machine or to trigger once and leave the selected gains indefinitely until configured to do otherwise. This can be useful in experiments where correct gains are a priori unknown but changing gains over the course of the experiment could lead to anomalous results.