SNAA361A april   2022  – may 2023 LMX2820

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Reference Frequency
  6. 3Standard LMX2820 Phase Noise Performance
  7. 4 Pre-multiplier Stage Performance
    1. 4.1 External VCO Loop Filter Design
    2. 4.2 Active Loop Filter Implementation
    3. 4.3 External VCO Performance Results
  8. 5External PFD Topology
    1. 5.1 External PFD Loop Filter Modification
    2. 5.2 External PFD Measurement Results
  9. 6Putting it Together in the Real World
    1. 6.1 Real-World Performance Results
    2. 6.2 Why use the Dual Approach?
  10. 7Conclusion
  11. 8Revision History

4 Pre-multiplier Stage Performance

shows a block diagram of the 3x pre-multiplier stage using the TRF37C75 amplifier. Figure 2-3 compares the phase noise performance of the pre-multiplier stage with that of the signal generator. Table 2-2 reports the integrated jitter performance for each configuration.

GUID-20220906-SS0I-83KZ-KSJC-MBZJ49QBJ9BX-low.svgFigure 4-1 3x Pre-multiplier Stage
GUID-20220906-SS0I-TLCR-RKQD-VC9HVFBGJTV8-low.pngFigure 4-2 Phase Noise Comparison of 1474.56 MHz Signal
As expected, the SMA100B provides the best output at 1474.56 MHz. The 3x multiplied Wenzel oscillator performance is also quite good. Its sweep is nearly identical to the ideal response when the input performance is degraded by 20 * log (n), where n = 3 as the multiplication factor. As before, the multiplied-up Wenzel approach is significantly better than the Agilent PSG.

Table 2-2: Integrated RMS Jitter at 1474.56 MHz

Frequency

Source

RMS Jitter

1474.56 MHz

R&S SMA100B

8.1 fs

Wenzel Osc - 3x

22.2 fs

Agilent PSG

35.4 fs