Active Differential Probes U1818A/B
Technical Overviews
The Keysight Technologies, Inc. U1818A/B active differential probes provide high differential input impedance from 100 kHz to 7 or 12 GHz. Suitable for those in R&D and quality assurance who are performing RF/ Microwave and high-speed digital design and validation work in wireline, wireless communications and aerospace and defense industries. Designed to be directly compatible with Keysight’s network, spectrum and signal source analyzers, these probes enable you to quickly find and fix defects while taking full advantage of the instruments capability.
The U1818A/B active differential probes are available with a variety of probe heads for different application needs. They can also be used with most of Keysight’s probe accessories including extreme temperature extension cable, in-line attenuator kit, minimum loss attenuator pad, DC blocking capacitors, probe positioners and others to achieve accurate measurements.
Key Features and Benefits:
Broad bandwidth with flat frequency, +/- 1.5 dB, which ensures excellent measurement accuracy and helps users achieve the best product specifications.
Low noise floor, less than -130 dBm/Hz at 10 MHz to 12 GHz, which allows measurements to be made at a low signal amplitude.
Convenience biasing from Keysight’s RF and microwave instruments probe power port or bench top power supply for user flexibility
Using a Network Analyzer with Active Differential Probes
Below is an application showing the U1818A/B with a network analyzer measuring step response in a high-speed digital design. In this application, the network analyzer provides the signal at one end while the active differential probe is used to measure the insertion loss between the DUT at the other end. The network analyzer will automatically transform the output signal from frequency domain to time domain for the frequency sweep selected. After the conversion of the signal, you will be able to identify the rise time, fall time or overshoot values which is essential in verifying the PCB design. The in-circuit measurement method of using the active differential probe with a network analyzer will provide accurate measurements with bigger dynamic range.
Using a Signal/Spectrum Analyzer with Active Differential Probes
In this application, the active differential probe is used with a Keysight signal/spectrum analyzer for RF troubleshooting. As shown in the diagram below, the active probe is connected to the spectrum analyzer and the signal source is provided by the DUT itself. The method begins by probing the component at each stage one at a time and the values are measured in terms of power or harmonics. Users will be able to identify the problem area through the measurement reading on the spectrum analyzer.
Using signal source analyzers with active differential probes
Other important parameters are phase noise and/or jitter when designing a high-speed digital PCB. The phase noise and jitter value can be accurately measured with the active differential probe and a signal source analyzer. Similar with the application shown in the diagram above, the signal source is provided by the DUT itself and the probe is used to measure the value at each stage at one time. The spectrum analyzer will show the value of the phase noise and jitter stage by stage. The difference between the parameters will easily enable you to identify the problem area during the design of the PCB. This application provides an accurate measurement with a broad dynamic range where jitter and phase noise can be measured down to a few femto-seconds.