Fetches the group delay trace. Group delay is computed from the channel frequency response. When you set the RFMXWLAN_ATTR_OFDMMODACC_AVERAGING_ENABLED attribute to True, this function returns the mean of the group delay trace computed for each averaging count.

Syntax

int32 __stdcall RFmxWLAN_OFDMModAccFetchGroupDelayMeanTrace(niRFmxInstrHandle instrumentHandle, char selectorString[], float64 timeout, float64 *x0, float64 *dx, float32 groupDelayMean[], int32 arraySize, int32 *actualArraySize)

Remarks

Use "segment<n>/chain<k>/stream<<i>l</i>>" as the selector string to read results from this function.

Parameters

NameDirectionTypeDescription
instrumentHandle[in]niRFmxInstrHandle

This parameter specifies the RFmx session refnum. Instrument Handle In is obtained from the RFmxInstr_Initialize function or the RFmxInstr_InitializeFromNIRFSASessionArray function.

selectorString[in]char[]

This parameter specifies a Selector String comprising of the signal name, result name, segment number, chain number, and stream number. If you do not specify the signal name, the default signal instance is used. The default value is "segment0/chain0/stream0".

Example:

"segment0/chain0/stream0"

"signal::sig1/segment0/chain0/stream0"

"signal::sig1/result::r1/segment0/chain0/stream0"

"result::r1/segment0/chain0/stream0"

You can use the RFmxWLAN_BuildStreamString function to build the selector string.

timeout[in]float64

This parameter specifies the timeout for fetching the specified measurement. Set this value to an appropriate time, longer than expected for fetching the measurement. A value of -1 specifies that the function waits until the measurement is complete. This value is expressed in seconds. The default value is 10.

x0[out]float64 *

This parameter returns the starting subcarrier index.

dx[out]float64 *

This parameter returns the subcarrier increment value. This value is always 1.

groupDelayMean[out]float32[]

This parameter returns an array of group delay responses. This value is expressed in seconds.

arraySize[in]int32

Specifies the size of the array. Set the arraySize parameter to 0 to get the size of all the arrays in the actualArraySize parameter.

actualArraySize[out]int32 *

Returns the actual size of the array, if you pass NULL to all output array parameters, and set the arraySize parameter to 0.

Returns

Returns the status code of this operation. The status code either indicates success or describes an error or warning condition. Examine the status code from each call to an RFmx function to determine if an error has occurred.

To obtain a text description of the status code and additional information about the error condition, call the RFmxWLAN_GetError function.

The general meaning of the status code is as follows:

Value

Meaning

0

Success

Positive Values

Warnings

Negative Values

Errors