Changes between Version 4 and Version 5 of WARPLab/AGC

Timestamp:

Nov 9, 2015, 11:45:55 AM (8 years ago)

Author:

chunter

Comment:

--

WARPLab/AGC

@@ -15 +15 @@
 == DC Offset Correction based on Received I/Q ==
 
-After 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.
+After 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.
 
 == Dependence on 802.11's STS == #waveformDependence
 
+The 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.
+
+||  [[Image(sts.png,width=800)]][[BR]]20 MHz STS Symbol  ||
+
+The above figure shows a single 20 MHz STS symbol for both a 20 MSPS system (as defined by the 802.11 standard) and a 40 MSPS system (e.g. WARPLab). When 2x oversampled in a 40 MSPS system, the STS itself is periodic in 32 samples, achieving the requirements for the DCO correction subsystem. The magnitude-squared ({{{I^2^ + Q^2^)}}}), however, is periodic in 16 samples. This achieves the requirements for the baseband gain refinement in the AGC.
+
+Even though the AGC is tuned for a 20 MHz STS, it is important to note that this does not limit the overall WARPLab design from dealing with wider-bandwidth waveforms. Even the 40 MHz 802.11n standard still uses 20 MHz STS symbols by forming two valid 20 MHz preambles that on neighboring 20 MHz channels. Doing so still meets the periodicity requirements of the AGC and DCO correction subsystems.
 
 == AGC Characterization ==
+
+||  [[Image(agc_calib.png,width=800)]][[BR]]AGC Characterization  ||