Brilliant Instruments’ BI401 synthesized clock generator—a PXI-based instrument module for ultra-low phase-noise squarewaves up to 4.1 GHz—features phase noise of ‒120 dB at 1 GHz with 10-kHz offset. Jitter in the time domain is less than 0.5 ps—a key factor for high-speed analog-to-digital converters (ADCs). In addition, jitter remains constant even with low-frequency outputs. Frequency resolution is 20 digits (translating to less than 20 ps of accumulated drift per year) and phase resolution measures 0.3 ps regardless of the output frequency (1 µHz to 4.1 GHz). Phase switching is guaranteed to be smooth, and frequency switching runs less than 250 µs. Two outputs include a differential with 65-ps rise time and 1 V p-p (max), and a single-ended output with 6 V p-p (max). The outputs also can be set to precision dc levels with 1-mV accuracy. The standard timebase is a 2-ppm TCXO (a 0.02-ppm oven oscillator is optional). The clock generator consumes 14 W and occupies a single hybrid or legacy PXI slot. Applications range from semiconductor test (ATE), reference clocks for PLL testing, and sampling clocks for ADCs to radar systems, ultrasonics, pulsed lasers, oscillators/crystals, magnetic/optical data storage, and nuclear physics.