About the Symbol Table (Digital Demod)

Selecting the Syms/Errs trace data displays the symbol table. The symbol table shows the error summary data and the symbol data (binary bits) for each symbol.

Error Summary Data

The top half of this display shows the Error Summary data. The digital demodulation type determines which error summary data are shown. See Error Summary Data for more information.

Symbol Data

The bottom half of the symbol table shows the raw data symbol bits for each demodulated symbol. The first bit in the table corresponds to the first bit of the first symbol in the digital data stream.

When the symbol table marker is enabled, the trace marker highlights the data symbol bits for the selected symbol and the marker readout provides the symbol number and its value in decimal.

To make the table easier to read, the data bits are shown in groupings of eight characters followed by a space. The characters can represent a binary digit or a hexadecimal digit as specified by the Symbol Table Format parameter. The number to the left of each row indicate either the bit or symbol offset position depending the symbol table format as described below:

Binary Format: The symbol data bit format is binary and each character represents a binary digit. The number to the left of each row indicates the bit offset of the first bit in the row.

Hexadecimal Format: The symbol data bit format is hexadecimal and each character represents a hexadecimal digit. The number to the left of each row indicate the symbol offset of the first symbol in the row.

There must be at least 4 bits/symbol to use the hexadecimal format, that is, symbols that have less than 4 bits/symbol will only be displayed in binary format regardless of the Symbol Table Format setting.

For example, if the Symbol Table Format is Binary and 192 is displayed to the left of third row, the first bit in the third row is the 192nd bit in the digital data stream.

For 2-level FSK Frequency Shift Keying: A form of modulation using multiple carrier frequencies to carry the digital information. The most common is the two frequency FSK system using the two frequencies to carry the binary ones and zeros., a 1 (one) corresponds to a positive frequency deviation (frequency greater than the carrier).

The following tips will help use the Symbol Table:

The symbol data bits can be shown in either binary or hexadecimal format, see Symbol Table Format.
The Result Length parameter specifies the number of symbols shown in the table.
An easy way to identify symbol bits and their corresponding symbol points in the constellation diagram is to display the constellation diagram in one grid and the symbol table in another. Then turn on the markers for both displays and enable marker coupling. When the marker is placed on a point in the constellation diagram, the VSA highlights the corresponding symbol bits in the symbol table.
Marker Movement: Use the keyboard arrow keys or the mouse wheel to move the marker from one symbol to the next. Use the Marker Position - X Position parameter to move the marker to a specific symbol location.