[evla-sw-discuss] setting gains on the station board

[Barry Clark]

I think there should be an option for doing requantizer only.

Sonja Vrcic wrote:
> Please disregard my previous message, I accidentaly prresed 'send' before the message was 
> complete. See my comments below.
> Sonja
> 
> 
> Ken Sowinski wrote:
>> Getting the station board gains, especially the requantizer gain,
>> right will be important for the three bit samplers.  I talked with
>> Bruce about this yesterday and summarize are conclusions and questions
>> here.
>>
>> 2.  We must decide how to communicate to the statino board when and how
>> to do this.  The obvious solution is for the executor to send a VCI
>> 'modify' document specifiying when to begin the adjustment, and what
>> to do.  In addition to an activation time one might want to include
>> set points, integration time and, perhaps, desired ALC strategy.
>> this depends on implenting the VCI modify funtion.  Is there any need
>> for an alternate path which might be available sooner?
> 
> 
>  From the point of view of CM this should not be difficult to implement. Most work will be 
> implemented on CMIB. CM would simply pass instructions to Station Boards. To speed up 
> implementation it is important to define requirements.
> 
> 
> Here is my attempt to capture requirements (based on requirements for the Filter Gain 
> panel in Station Board GUI):
> 
> 1. Target filter gain (and other related parameters) to be specified (and set) for each 
> subband independently, i.e. for each subband of each baseband pair (or baseband singleton).
> 2. Parameters are specified per subband and apply for all the antennas (stations) in a 
> subarray (as VCI "modify subarray").
> 3. Alternatively, as for other parameters, user can specify a subset of antennas 
> (stations) to be configured.
> 4. Activation time assigned per subarray (in the same fashion as when creating a new 
> subarray).
> 
> List of parameters that can be specified for each subband of each baseband:
> a. Desired RMS (mandatory)
> b. Desired RMS for re-qunatizer (mandatory)
> c. Number of integrations (for power measurements) to be used to calculate RMS (optional, 
> if not explicitly specified = 100)
> d. Number of integrations to discard between the measurements for different stages 
> (optional, if not specified it is ON, number of integrations to discard=100). GUI allows 
> user to turn this on/off and to specify number of integrations. That was required in 
> experimental phases. Is there a need to keep this as externally specified parameter(s) or 
> should it be hard-coded in CMIB software ?
> 
> Then there is a question of units: in GUI, one can select whether RMS is displayed in 
> computer units or normalized units. Which one should be used in VCI. Is there a need to 
> implement both options. If possible, it would be nice to simplify interface and 
> implementation.
> 
> This is just the first attempt, please modify the list as needed.
> 
> Sonja
> 
> -------------------------------------------------------------------------------------
> Here is a copy of the "user help window" for the Station Board GUI - Filter Gain.
> 
> Commands:
> Refresh reads from hardware and displays:
> Filter ID and status
> Station/Baseband/Subband IDs inserted in the output data stream (subband)
> RFI Detect Level
> Scales for used filter stages and for re-quantizer
> Number of bits for re-quantizer
> 
> Set RFI detect level sets RFI detection level in the filter FPGAs (as specified in the table)
> 
> Measure RMS calculates RMS based on the power counts
> 
> Adjust filter scales to get desired RMS optimizes RMS as close as possible to the desired 
> RMS (specified by user)  RMS is calculated as follows:
> RMS = sqrt(powerNdOn + NdOff) / numberOfIntegrations)
>   Use normalization units applies to RMS. If selected, RMS is normalized:
> normRMS = (RMS / (2^(numberOfBits - 1) - 1))
>   For stages 1 to 4, numberOfBits = 16. For re-quantizer, number of bits is obtained from 
> the Filter FPGAs (and displayed in the table).
> 
> Save/Load Configuration to/from File on the "Main" menubar allows you to optionally save 
> or load "RFI Detect Level" (column RFI) and "Desired RMS" (columns D_RMS and D_RQ_RMS). 
> Only the filters with their "Select" box checkmarked will be saved.
> When loading, the "Select" checkbox will be used to indicate which filters were updated.
> 
> RMS Units:
> RMS displayed in computer units can be converted to normalized units. Conversion from 
> normalized units to computer units is not performed. If "Use normalization units" not 
> selected, columns for measured RMS are filled with blanks, and desired RMS is set to the 
> default values.
> 
> RMS is calculated for the stages that are used (see the Filter GUI's "Format" box, Primary 
> Signal) and for the re-quantizer.
> 
> When the Start button is clicked, the following is performed:
> Get filter status, scales and number of bits for re-quantizer;
> For each stage {
>      Configure all the (green) filters for stageX;
>      Collect power counts (for all the filters);
>      For each filter {
>          Calculate RMS;
>          Display RMS;
>          If (adjustScales is selected) {
>              Calculate new scale;
>              Configure filter for the new scale;
>          }
>      }
>      If (adjustScales is selected) {
>          Collect power counts (for all the filters);
>          For each filter {
>              Calculate RMS;
>              Display RMS;
>          }
>      }
> }
> 
> Get RFI and scales from hardware;
> Number of power counts integrations used to calculate RMS:
> User can specify the number of power count integrations used to calculate RMS.
> By default, this number is the same as the power count integration factor obtained from 
> hardware; which means that, by default, one report (table) is used to calculate RMS.
> 
> Delay between stages:
> RMS is calculated for one stage at a time. Before calculating RMS for each stage, filter 
> configuration is slightly modified. To ensure that the power counts used to calculate RMS 
> are only for the data processed after the configuration change, the power counts received 
> immediately after the filter configuration change should be discarded.  By default, the 
> number of integrations to be discarded is the same as the power counts integration factor 
> set in hardware; which means that the first report (table) received after the 
> configuration change will be discarded. This feature can be disabled.
> 
> -------------------------------------------------------------------------------------------
> 
> 
> 
> 
> 
> 
> 
>> 3.  We must decide how the executor knows when to tell the correlator
>> to set gains.  Is it explicitly in the scripts?  Should the executor
>> understand enough about the meaning of the script to discern when to
>> send the cause a gain setting?  Getting this right will interact with
>> setting up the antenna, setting downconverter gains, and antenna motion.
>>
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>