Figure 2-7 shows the phase noise is similar out to an offset frequency of 2.5 MHz, at which point the LMX1204 devices' measured phase noise begins to converge. The phase noise of the cascaded LMX1204 design follows what is measured on the LMX1204EVM up to an offset frequency of 100 MHz, at which point the cascaded design follows the variation produced by the SMA100B at an elevated noise floor.

The average difference measured beyond 2.5 MHz comes out as 0.4 dB, which predicts the amount of added phase noise generated by any additional cascaded LMX1204 devices in a system operating near 12.8 GHz. Refer to Section 2.5 for a comparison in high-speed converter performance.