Use the Snap to Point mode and click on a measured load point to set the marker and update the marker information below the Smith plot.
Depending on the marker format, the information shown includes Znorm (the real/imaginary part of the normalized impedance at the selected point), Gamma (amplitude and phase of the reflection coefficient at the selected point), VSWR (voltage standing wave ratio and phase at the selected point), and the measured quantity at the selected point.
Device characterization test solutions
Mesuro Ltd. (UK) has launched a device characterization test solution that uses an envelope load-pull technique with the PXI hardware and LabVIEW system design software.
The new Rapid Load-Pull solution can replace traditional passive tuning networks within load-pull test systems, offering the customer significant improvements in testing speed, Mesuro said in a press release.
The way in which the Rapid Load Pull solution fits into the test environment allows for the existing measurement hardware to be re-used within the improved test station. The system can be supplied as a turnkey project to include, the NI portion with Mesuro Software/Coupler/Amplifier, or can be customer assembled. The system is currently available covering frequency ranges up to 4.4GHz.
The device output is measured on the receiver elements via the coupler, with the output then being down-converted to baseband. The loop algorithm, implemented in the LabVIEW FPGA Module, then calculates the required settings to form the reflected signal that is then presented to the device under test, based upon the requested impedance. The loop amplifier provides the active element to ensure that the loop can tune the impedance to any desired point on the Smith Chart. The NI PXI solution contains an embedded controller, on which the main Mesuro test software resides and operates. The system can perform all the required load pull tests and the data can be viewed within the measurement software or exported for use within EDA or other tools by the user.
The concept of load pull may not be that clear to many Design News readers since, while it does sort of have a mechanical equivalent, it has not been talked about by this name outside of the RF amplifier design realm very much.
Load pull is the effect on the amplifier output caused by chyanges in the downstream load impedance driven by the amplifier's output power. It may often be quite nonlinear, which makes modeling a bit more challenging. Also, the effect may work in both directions, making evaluation and analysis more complex and challenging.
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