Power integrity measurements with R&S®RTP oscilloscopes

Your task

Measuring noise and ripple on power rails with small voltages and increasingly tighter tolerances is a challenge for oscilloscopes. Fast clock and data edges can be coupled onto rails, requiring higher bandwidth oscilloscopes for power integrity measurements.

Using a standard 500 MHz passive probe with a 10:1 attenuation results in additional measurement noise, causing overstated peak-to-peak voltage measurements and masking signal details.

Such a probe does not have sufficient bandwidth to isolate coupled signals. The higher bandwidth of R&S®RTP oscilloscopes allows isolation of coupled signals as shown in the gated FFT image.

Our solution

The R&S®RT-ZPR20 and R&S®RT-ZPR40 power rail probes with a 1:1 attenuation ratio have very little noise and sufficient bandwidth to not attenuate critical signal content. Both probes are compatible with R&S®RTP oscilloscopes. The combination results in a measurement system that delivers high-bandwidth, accurate measurements:

• The probe’s 1:1 attenuation provides minimal noise for a system noise of less than 500 µV (at 1 GHz bandwidth and 10 mV/div)
• With ±60 V of built-in offset, users can center and zoom in a wide variety of DC rail voltage standards without worrying about how much built-in offset the scope has. Increased vertical sensitivity means less noise and that more of the oscilloscope’s ADC bits are used, resulting in a more accurate measurement. The offset eliminates the need to use AC coupling or DC blocking capacitors, which impede the ability to see true DC values and drift.
• High-frequency transients and coupled signals are isolated. The R&S®RT-ZPR40 has a typical 3 dB bandwidth of 4 GHz
• 50 kΩ DC input impedance minimizes loading, so DC values remain accurate
• An integrated 16-bit R&S®ProbeMeter provides a simultaneous five-digit readout of each power rail’s DC value, even if the waveform is not on the oscilloscope display