Traditional RF instruments such as vector signal generators and vector signal analyzers use standard RAM (Random Access Memory) as a mechanism for waveform storage. As a result, maximum generation and acquisition sizes for these RF instruments are typically limited to several hundred megabytes at best.
However, the combination of a high-speed data bus and RAID technology enables longer acquisition rates. Moreover, for RF signals, an RF analog front end and digital signal processing technologies enables efficient generation and acquisition of signals using superheterodyne upconversion and downconversion. A high-level system diagram of a typical system is illustrated in the figure below.
Figure 1. Several core technologies enable RF stream-to-disk.
As a result of each of these components, instrument memory can be supplemented with high-speed RAID (Random Array of Inexpensive Disks) hard drive configurations. In this scenario, data can be transferred from the instrument to hard disk at rates that exceed the rate of acquisition. Thus, the maximum waveform size is no longer limited by size of onboard memory, but by the size of available hard disk space. Using external RAID hard drive configurations, the waveform storage can be expanded to up to several terabytes of data.
Overview of RF Stream-to-Disk Applications
The ability to generate or acquire up to several terabytes of continuous data enables PXI instruments to solve new applications that were once only possible with custom hardware. In this paper, we will describe four common applications which significantly benefit from the use of sustained continuous RF generation or acquisition. These applications are:
- Spectrum Monitoring
- Packet Sniffing
- Wireless Receiver Design, Validation, and Verification
- Digital Video Broadcast BER Tests
In each of the applications listed above, the ability to continuously stream data to disk for extended periods of time is either essential, or provides substantial benefits.