The LMX1204 device multiplies the 1474.56 MHz by 4 × to achieve the final output sampling frequency of 5898.24 MHz. Figure 2-4 shows the performance of the sample clock phase noise compared to the test equipment sources.

Figure 2-4 Phase-Noise Comparison of 5898.24-MHz Signal

The multiplier circuitry does introduce some phase-noise degradation, particularly evident at the higher frequency offsets beginning at around 1-MHz offset. The performance is still good and still surpasses the Agilent PSG for offsets below the 300-kHz offset. With the multiplier (and the phase-noise contribution of the multiplier) the absolute performance of the source becomes diminished; the performance using the LMX1204 multiplier with the SMA100B as the source versus the pre-multiplier as the source is nearly the same. Table 2-3 reports the integrated jitter performance.