SPVA068 July   2026 ADC3669

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2ADC366x Internal Rx Architecture
    1. 2.1 1.4GHz Wideband, High Performance and Low Power Direct RF Sampling
    2. 2.2 Integrated Digital Downconverter (DDC) and 32-Bit NCO
  6. 3 ADC366x Low Latency Mode
  7. 4IFF Pulse Processing Performance
    1. 4.1 ADC3669 Performance in Presence of a High-Power Signal Pulse
    2. 4.2 ADC3669 Performance in Presence of a Weak Signal Pulse
  8. 5Summary - Buying Back Time
  9. 6References

4.2 ADC3669 Performance in Presence of a Weak Signal Pulse

When a weak -60dBFS input signal is introduced, the raw time-domain peak-to-peak code spread expands from an idle baseline of approximately 110 codes up to 175 codes. This 175-code envelope represents the summation of the approximately 110 codes of thermal noise present within the 250MHz Nyquist bandwidth and the 65-code peak-to-peak amplitude of the weak input pulse.

As illustrated in Figure 4-3, the time-domain capture of the 2μS pulse at -60dBFS tracks at this steady 175-code peak-to-peak window highlighting very good linear performance of the ADC3669, proving its ability to resolve waveforms even at extremely small signal strengths.

Because the pulse envelope is currently embedded within the wideband noise floor at the full 500 MSPS sample rate, the internal Digital Downconverters (DDCs) can be engaged to filter out out-of-band quantization noise, thus tightening the baseline and rendering the actual pulse shape clearly visible for downstream timing logic.

Time-Domain Capture of a 2μS Pulse at 1090MHz at -60dBFS Figure 4-3 Time-Domain Capture of a 2μS Pulse at 1090MHz at -60dBFS
Frequency Domain Capture of a 2μS Pulse at 1090MHz at -60dBFS Figure 4-4 Frequency Domain Capture of a 2μS Pulse at 1090MHz at -60dBFS