SNAA358A January   2022  – March 2022 LMX2820

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 Combining theory
    2. 1.2 Real-World Synthesizer Combining
  3. 2Measured Performance
  4. 3Summary
  5. 4Revision History

2 Measured Performance

The measured performance of combining two LMX2820 is completed on the TIDA-010230 reference design which incorporates two LMX2820 devices on the board. The devices share an external reference frequency. Figure 2-1 shows the block diagram of the set-up.

Figure 2-1 Combined LMX2820 Block Diagram

As an example, the LMX2820 is tuned to 5.6 GHz. This is a fundamental VCO frequency within the device. Figure 2-2 shows the phase noise plot of each LMX device independently and then summed together.

Figure 2-2 Combined LMX2820 Phase Noise Performance

To get a feel for the expected performance improvement, Table 2-1 shows the average phase noise improvement by decade.

Table 2-1 Average Phase Noise Performance Improvement by Decade
100 Hz - 1 kHz 0.27 dB
1 kHz - 10 kHz 1.15 dB
10 kHz -100 kHz 1.81 dB
100 kHz - 1 MHz 2.14 dB
1 MHz- 10 MHz 2.98 dB