360 Keysight EXG and MXG X-Series Signal Generators User’s GuideCustom Digital Modulation (Option 431)Custom ModulationCustom ModulationFor creating custom modulation, the signal generator offers two modes of operation: the ARBcustom modulation mode and the real-time custom modulation mode. The ARB custommodulation mode has built-in modulation formats such as NADC or GSM and pre-definedmodulation types such as BPSK and 16QAM that can be used to create a signal. It also provides theflexibility to modify the digital format’s attributes. The real-time custom modulation mode can beused to create custom data formats using built-in PN sequences or custom-user files along withvarious modulation types and different built-in filters such as Gaussian or Nyquist.Both modes of operation are used to build complex, digitally modulated signals that simulatecommunication standards with the flexibility to modify existing digital formats, define or createdigitally modulated signals, and add signal impairments.ARB Custom Modulation Waveform GeneratorThe signal generator’s ARB Custom Modulation mode is designed for out–of–channel testapplications. This mode can be used to generate data formats that simulate randomcommunication traffic and can be used as a stimulus for component testing. Other capabilities ofthe ARB Custom Modulation mode include:— configuring single or multicarrier signals. Up to 100 carriers can be configured.— creating waveform files using the signal generator’s front panel interface.The waveform files, when created as random data, can be used as a stimulus for component testingwhere device performance such as adjacent channel power (ACP) can be measured. TheAUTOGEN_WAVEFORM file, that is automatically created when you turn the ARB Custom Modulationon, can be renamed and stored in the signal generator’s non–volatile memory. This file can later beloaded into volatile memory and played using the dual ARB waveform player.For more information, refer to “Waveform File Basics” on page 187 and “Modes of Operation” onpage 3.Real-Time Custom Modulation Waveform GeneratorThe real-time mode simulates single-channel communication using user-defined modulation typesalong with custom FIR filters, and symbol rates. Data can be downloaded from an external sourceinto PRAM memory or supplied as real-time data using an external input. The real-time I/Qbaseband mode can also generate pre-defined data formats such as PN9 or FIX4. A continuousdata stream generated in this mode can be used for receiver bit error analysis. This mode is limitedto a single carrier. The real-time custom modulation mode:— has more data and modulation types available than the ARB waveform generator mode— supports custom I/Q constellation formats— has the capability to generate continuous PN sequences for bit error rate testing (BERT)— needs no waveform build time when signal parameters are changed.
