Search Pattern (Digital Demod)

Search Pattern sets the synchronization (sync) pattern that the demodulator uses when Constellation Sync Search is enabled.

Minimum length: 1 Symbol

Maximum length: 32 symbols

See Constellation Sync Search for more information.

Edit, Add, Delete Search Patterns

To edit a Search Pattern, click MeasSetup > Digital Demod Properties > Search tab > Edit button. Highlight the desired pattern and click the edit button. Make changes and click OK.

To add a pattern, click MeasSetup > Digital Demod Properties > Search tab > Edit button > New button. This opens the New Sync Pattern dialog box that add a new Search Pattern. The Search Pattern must be entered as binary data. The demodulator ignores all characters except ones (1) and zeroes (0).

To delete a Search Pattern, click MeasSetup > Digital Demod Properties > Search tab > Edit button. Highlight the desired pattern and click the delete button.

Default Search Patterns

The VSA remembers the Search Patterns that have been entered. These Search Patterns are preserved and loaded each time the 89600 VSA software is started. To view a list of remembered Search Patterns, click MeasSetup > Digital Demod Properties > Search tab > Pattern button. The VSA also provides several groups of default Search Patterns:

GSM Global System for Mobile Communications: Originally developed as a pan-European standard for digital mobile telephony, GSM has become the world’s most widely used mobile system. It is used on the 900 MHz and 1800 MHz frequencies in Europe, Asia and Australia, and the 1900 MHz frequency in North America and Latin America. - These patterns are midamble training sequences for the GSM cellular telephone formats. (8 choices)
EDGE Enhanced Data for Global Evolution: A technology that gives GSMA and TDMA similar capacity to handle services for the third generation of mobile telephony. EDGE was developed to enable the transmission of large amounts of data at a high speed, 384 kilobits per second. (It increases available time slots and data rates over existing wireless networks.) - These patterns are midamble training sequences for the EDGE cellular format. (8 choices)
APSK - These patterns are used for SOF (start of frame) synchronizing symbols in the APSK format. (2 choices)

Symbols and Search Pattern

The maximum Search Pattern that can be entered is 32 symbols and depends on the current modulation format. If the modulation format is 16-QAM, 32 symbols represents 128 bits (4 bits/symbol x 32 symbols); if the modulation format is QPSK, 32 symbols represents 64 bits (2 bits/symbol x 32 symbols).

The demodulator can search only for Search Patterns that are a multiple of the number of bits-per-symbol (see below).

The demodulator can only search for Search Patterns that are a multiple of the number of bits-per-symbol. Internally, the demodulator assembles the Search Pattern into an integer number of symbols. When the demodulator assembles the final bits in the Search Pattern, if there are not enough bits to form a symbol, the demodulator ignores the final bits.

For example, if the number of bits-per-symbol is 4 (as with 16 QAM Quadrature Amplitude Modulation), the number of bits in the Search Pattern should be a multiple of four. If the Search Pattern contains 18 bits, the demodulator ignores the last two bits. In other words, the demodulator uses only the first 16 bits during Constellation Sync Search.