Differences between ARB and RealTime modes of vector signal generator

      From the knowledge of communication principles and digital signal processing, we know that the general process of signal source generating signal can be represented by the figure below. The data undergoes channel coding, framing, oversampling, and is converted into an analog signal by DAC, and then up-converted and output by the RF module.

      The main difference between ARB and RT is the different ways of generating signals. The ARB mode is implemented on the PC before the DAC through the corresponding software (these software can be Agilent signal studio, Matlab, Visual), and the data is encoded and stored in the RAM of the signal source in the form of a waveform file. The waveform file is played in a loop by the signal source. In the RT mode, the signal generation process is implemented in the hardware. When the user gives the data information, the data encoding, modulation, framing and other signal processing processes are all implemented on the DSP chip inside the signal source. Therefore, RT is a real-time signal generation method. At this time, no waveform file is needed, only the data information to be transmitted needs to be sent. The more commonly used data sequences, such as the PN9 sequence, can be directly generated by the internal hardware of the signal source, but users often need specific self-generated data sequences. To meet the special needs of some users, users can generate data blocks by themselves and then store the data in the signal source RAM.

ARB and RT modes have their own characteristics, so they are suitable for different application scenarios. ARB is flexible in application and can generate arbitrary waveforms by users. It is easy to implement signal processing in software, so the development cycle is short. If the user only needs a few frames of test signals and the signal waveform is short, we recommend that users use the ARB mode. You only need to generate the waveform file you want, download it to the RAM of the signal source, and then play it in a loop to complete the relevant tests. Since the Real time mode generates waveform sequences in real time with full hardware, it requires the use of internal DSP and FPGA. Therefore, the cost is higher, but if the user needs to frequently change the configuration of signal processing during the R&D stage, and the generated waveform file is large, in order to reduce the R&D time and make it more convenient for users to configure, we recommend using the RT mode.

      In short, ARB and RT modes are two technical routes for modern vector signal generation, each with its own advantages and applicable environments. The two modes can be used together to provide customers with more effective signal generation solutions and shorten their R&D cycle.