The RTG digitizes incoming signals and provides a sample-accurate, programmable digital delay.

Total delay is calculated as the sum of two main parts: 
Total Delay = System Minimum Delay + Digital Delay
The RTG system controls some, but not all, of these underlying components. The figure below illustrates the different contributions to the total delay.
Figure 2. Total Delay


  • System Minimum Delay—The system minimum delay is achieved by setting the digital delay to 0. System minimum delay is the sum of the External Delay and the System Delay.
    • External Delay—The round-trip delay outside the RTG system, including cabling and over-the-air transmission between the radar and the RTG. The RTG cannot measure this automatically; users must determine this value and configure the software to compensate for it.
    • System Delay—The internal processing time required to acquire and generate the RF signal, execute signal-quality DSP, and process the targets (delay, frequency shift, and amplitude control). Because this latency varies based on system settings, the RTG provides a built-in self-calibration routine to calculate it.
  • Digital Delay—The programmatic delay applied to up to four targets. Resolution is 800 ps for the PXIe-5830/5831/5832/5841 and 400 ps for the PXIe-5842. The application of this delay varies by personality, as shown in the following figures.
    Table 2. Digital Delay
    Pulse Aware Pulse Invariant




    • Common Delay (Pulse Invariant personality only)—This single block is shared by all targets.
    • Target-Specific Delay—The topology of target delays differs between RTG personalities. The Pulse Aware personality provides three targets with fully orthogonal delays. The Pulse Invariant personality provides four coupled targets that share a common base delay before splitting into three data streams, each with an independent delay window.
      Note For the Pulse Invariant personality, all four targets must fall within a single maximum range window of 52.4 µs (for PXIe-5830/5831/5832/5841 VSTs) or 26.2 µs (for the PXIe-5842 VST). As shown above, the RTG applies a shared common delay to position the earliest target at the beginning of this window. Because the individual target-specific delay blocks have limited capacity, they only provide offsets relative to this common base. Consequently, the time difference between the closest and furthest targets cannot exceed the hardware's maximum range window.