Preliminary Technical
Data
Rev. PrA | Page 65 of 82
CLGC MEASUREMENT
The CLGC measurement cycle is common to both passive loop gain measurement and active loop gain control modes. In active
loop gain control mode, the Tx attenuation is also adjusted by the CLGC algorithm. The Tx attenuation adjustment is covered in
the next section.
The CLGC measurement relies on the sample batch size, the power level of the samples and the SNR of the observed data. The
CLGC captures samples in batches specified by the parameter clgcMeasurementBatchTime_us defined in the data structure
adi_adrv9025_ClgcConfig_t. The user is required to tune the measurement batch size based on the signal characteristics that they
are most likely to encounter. Please refer to the section Case Study For Configuring Clgc Batch Sampling Period which goes
through an example case study for determining the optimum batch measurement size. The list of parameters used to determine a
successful capture is listed in Table 37.
Table 37. CLGC Measurement Configuration
Parameter Description User Configuration Access
Capture Batch Time
This parameter determines the duration of samples
to be captured per batch specified in microseconds.
A maximum of 65536us can be configured
adi_adrv9025_ClgcConfig_t.
clgcMeasurementBatchTime_us
Maximum No. of batches
The CLGC measurement continues to capture
samples in batches until the required SNR criteria is
met OR the no. of batches exceeds 512. If the no. of
batches captured exceeds 512, and the requisite SNR
criteria is not met, then an error is flagged, and the
CLGC aborts calibration.
Fixed value of 512, not user configurable
Tx Qualifying Threshold
If the captured Tx samples are below this user
configured threshold, then the samples are
discarded.
adi_adrv9025_ClgcConfig_t.
clgcTxQualifyingThreshold_dBFS
ORx Qualifying Threshold
If the captured Orx samples are below this user
configured threshold, then the samples are
discarded.
adi_adrv9025_ClgcConfig_t.
clgcOrxQualifyingThreshold_dBFS
Tx and ORx qualifying threshold
As described in Table 37, the CLGC samples are required to meet the threshold criteria in order to be considered for loop gain
estimation. The thresholds are configured by the user through the API adi_adrv9025_ClgcConfigSet() using the parameters
clgcTxQualifyingThreshold_dBFS, clgcOrxQualifyingThreshold_dBFS that are part of adi_adrv9025_ClgcConfig_t data structure. If
either one of Tx or ORx samples do not meet the criteria, then the entire batch of Tx and ORx captured data is discarded. Shown
below is an example scenario in which the Tx/ORx signals meet the threshold criteria in Batch 1, where as the RMS power in
batch 2 fails to meet the threshold criteria. Therefore, samples in Batch 2 are discarded and not considered for measurement.
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