9.2.1.1 Design Requirements

For high-performance devices, limitations of the equipment can affect phase-noise measurements. The noise floor of the equipment is often higher than the noise floor of the device. The real noise floor of the device is probably lower. It is important to understand that system-level phase noise measured at the DUT output is influenced by the input source and the measurement equipment.

For Figure 11 and system-level phase noise plots, a Rohde & Schwarz SMA100A low-noise signal generator was cascaded with an Agilent 70429A K95 single-ended-to-differential converter block with ultra-low phase noise and fast-edge slew rate (>3 V/ns) to provide a low-noise clock input source to the LMK00804B-Q1. An Agilent E5052 source signal analyzer with an ultra-low measurement noise floor was used to measure the phase noise of the input source (SMA100A + 70429A K95) and system output (input source + LMK00804B-Q1). The light blue trace shows the input source phase noise, and the dark blue trace in Figure 11 shows the system output phase noise.