Trace Data Transfers

Internal Measurement Arrays

Figure 6-3

Internal Measurement Arrays

The following sections describe the sequence of math operations and the resulting data arrays as the measurement information flows from the raw data arrays to the display. This information explains the measurement arrays accessible via GPIB.

Figure 6-3 is a data processing flow diagram that represents the flow of

numerical data. The data passes through several math operations, denoted in the figure by single-line boxes. Most of these operations can be selected and controlled with the front panel CONFIGURE block menus. The data is stored in arrays along the way, denoted by double-line boxes. These arrays are places in the flow path where data is accessible via GPIB. While only a single flow path is shown, two identical paths are available, corresponding to measurement channels 1 and 2.

Numeric Data Flow Through the Network Analyzer

Raw Data Arrays

These arrays are linear measurements of the inputs used in the selected measurement. Note that these are pairs of complex numbers. The arrays are directly accessible via GPIB and are referenced as CH[1|2]AFWD ,

Programmer’s Guide 6-21

Table 6-4

Trace Data Transfers

Internal Measurement Arrays

CH[1|2]BFWD and CH[1|2]RFWD . Raw data for AUX INPUT is not available via GPIB. Use the corrected data array to access AUX INPUT data.

Raw Data Arrays

Selected Measurement Raw Arrays

A

B

Transmission (B/R)

Reflection (A/R)

B = CH[1|2]BFWD , R= CH[1|2]RFWD

A = CH[1|2]AFWD , R= CH[1|2]RFWD

A = CH[1|2]AFWD

B = CH[1|2]BFWD

R

Power (B*)

R = CH[1|2]RFWD

B*= CH[1|2]BFWD

Conversion Loss (B*/R*) B*= CH[1|2]BFWD , R*= CH[1|2]RFWD

R* R*= CH[1|2]RFWD

AM Delay (Y/X)

X

Y

Y/R*

Y/X, X/Y

Y = CH[1|2]BFWD , X = CH[1|2]RFWD

X = CH[1|2]RFWD

Y = CH[1|2]BFWD

Y = CH[1|2]BFWD , R* = CH[1|2]RFWD

Y = CH[1|2]BFWD , X = CH[1|2]RFWD

Ratio Calculations

These are performed if the selected measurement is a ratio (e.g. A/R or

B/R). This is simply a complex divide operation. If the selected measurement is absolute (e.g. A or B), no operation is performed.

Error Correction

Error correction is performed next if correction is turned on. Error correction removes repeatable systematic errors (stored in the error coefficient arrays) from the raw arrays. The operations performed depend on the selected measurement type.

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NOTE

Trace Data Transfers

Internal Measurement Arrays

Error Coefficient Arrays

The error coefficient arrays are either default values or are created during a measurement calibration. These are used whenever correction is on. They contain complex number pairs, are accessible via GPIB, and are referenced as CH[1|2]SCORR1 , CH[1|2]SCORR2 , CH[1|2]SCORR3 and CH[1|2]SCORR4 .

Error Coefficient Arrays Table 6-5

Selected Measurement Error Coefficient Arrays

Transmission (B/R) Response CH[1|2]SCORR1 Tracking

Transmission (B/R) Response & Isolation CH[1|2]SCORR1 Tracking

CH[1|2]SCORR2 Isolation Term

Transmission (B/R) Enhanced Response CH[1|2]SCORR1 Directivity

CH[1|2]SCORR2 Source Match

CH[1|2]SCORR3 Reflection Tracking

CH[1|2]SCORR4 Transmission Tracking

Reflection (A/R)

Broadband Internal

CH[1|2]SCORR1 Directivity

CH[1|2]SCORR2 Source Match

CH[1|2]SCORR3 Tracking

CH[1|2]SCORR1 R* Response

These arrays do not apply to Broadband External measurements.

Programmer’s Guide 6-23

Trace Data Transfers

Internal Measurement Arrays

Table 6-6

Forward

2-Port Error Coefficient Arrays

Direction Error Coefficient Arrays

CH[1|2]SCORR1 Directivity

CH[1|2]SCORR2 Source match

CH[1|2]SCORR3 Reflection tracking

Reverse

CH[1|2]SCORR4 Transmission tracking

CH[1|2]SCORR5 Load match

CH[1|2]SCORR6 Isolation

CH[1|2]SCORR7 Directivity

CH[1|2]SCORR8 Source match

CH[1|2]SCORR9 Reflection tracking

CH[1|2]SCORR10 Transmission tracking

CH[1|2]SCORR11 Load match

CH[1|2]SCORR1 2 Isolation

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Trace Data Transfers

Internal Measurement Arrays

Averaging

Averaging is a noise reduction technique. This calculation involves taking the complex exponential average of several consecutive sweeps.

This averaging calculation is different than the System Bandwidth setting. System Bandwidth uses digital filtering, applying noise reduction to the measured data before it is stored into the Raw Data

Arrays.

Corrected Data Arrays

The combined results of the ratio, error correction and averaging operations are stored in the corrected data arrays as complex number pairs. These arrays are accessible via GPIB and referenced as

CH[1|2]SDATA .

Corrected Memory Arrays

If the Data

−

>Mem or Normalize operations are performed, the corrected data arrays are copied into the corrected memory arrays. These arrays are accessible via GPIB and referenced as CH[1|2]SMEM .

Programmer’s Guide 6-25

Trace Data Transfers

Internal Measurement Arrays

Trace Math Operation

This selects either the corrected data array, or the corrected memory array, or both to continue flowing through the data processing path. In addition, the complex ratio of the two (Data/Memory) can also be selected. If memory is displayed, the data from the memory arrays goes through exactly the same data processing flow path as the data from the data arrays.

Electrical Delay

This block adds or subtracts phase, based on the settings of Phase Offset,

Electrical Delay, and Port Extension. The Electrical Delay and Port

Extension features add or subtract phase in proportion to frequency. This is equivalent to "line stretching" or artificially moving the measurement reference plane. (See your analyzer’s User Guide for more details on these features.)

Transform (Option 100 only)

This block converts frequency domain data into distance domain, or into an SRL impedance value when measuring fault location or SRL. The transform employs an inverse fast Fourier transform (FFT) algorithm to accomplish the conversion.

Formatting

This converts the complex number pairs into a scalar representation for display, according to the selected format (e.g. Log Mag, SWR, etc). These formats are often easier to interpret than the complex number representation. Note that after formatting, it is impossible to recover the complex data.

Formatted Arrays

The results so far are stored in the formatted data and formatted memory arrays. It is important to note that marker values and marker functions are all derived from the formatted arrays. Limit testing is also performed on the formatted arrays. These arrays are accessible via GPIB and referenced as CH[1|2]FDATA and CH[1|2]FMEM .

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Trace Data Transfers

Internal Measurement Arrays

Offset and Scale

These operations prepare the formatted arrays for display. This is where the reference position, reference value, and scale calculations are performed, as appropriate for the format.

Programmer’s Guide 6-27

Trace Data Transfers

Internal Measurement Arrays

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7 Using Graphics

7-1