Active Probing with the VNA
You can use passive and active, single and differential probes with the VNA.
RF Probes are available from Keysight, including the U1818A/B active probe with a maximum frequency of 12 GHz. Learn more at the Keysight website.
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Note: The VNA does NOT have a probe power port. Therefore, order the U1818A/B with banana plugs (Opt 002) for powering with an external power supply, such as the Keysight E3620A Dual Output Power Supply or equivalent. |
See Also
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App Note 5990-4387EN: High Frequency Probing Solutions for Time and Frequency Domain Applications.
Procedure
Use the following general procedure to make VNA measurements with ONE U1818B active probe:
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Connect the U1818A/B banana plugs to an external power supply. Power requirements for the U1818A/B are +15V (at 42mA) and -12.6V (at 12 mA).
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Connect the U1818A/B to the VNA port 2 directly, or using an adapter or short cable.
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Connect your DUT input connector to the VNA port 1 directly, or using an adapter or short cable.
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On the VNA, press Preset.
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Press Meas > S-Param > S21 (transmission measurement).
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Press Freq, then select the Start and Stop frequency range of the measurement. The maximum frequency of the U1818B is 12 GHz.
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Connect the probe tips as close as possible to the DUT input connector (point A in the above image).
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Note: The probe tip has two pins:
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Press Cal > Other Cals > Smart Cal....
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This calibration removes the losses (from the VNA test ports to the DUT) from subsequent measurements. Learn more about VNA calibration.
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When correctly calibrated, the S21 measurement should show a flat response at 0 dB across the frequency range.
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Connect the probe tips anywhere in the DUT path to view the frequency response between the DUT input and the probe tips.
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To view the response in Time Domain, press Math > Time Domain > Transform. Learn about Time Domain measurements.