Source Phase Control (Opt 088)

Option 088 allows you to control the phase of a PNA source or an external source. Two sources are required.

• Overview

• Features and Limitations

• Phase Control Use-Cases

• How to make Phase Settings

• Calibration and Phase Control

• Active Load Pull Examples

See other 'Setup Measurements' topics

Overview

The Source Phase Control feature provides a specific phase difference between two sources. The phase difference can be fixed (for example, at 90 degrees), or swept between two arbitrary phase values (for example, from 0 to 360 degrees).

This feature is allowed on ALL PNA-X models, and any N522xA model with either two internal sources or an external source and configurable test set.

Any combination of PNA internal or external sources may be used. One source is selected as the controlled source and the other source is the reference source. You select the two sources by selecting the ports at which the sources are available. The choice of ports is limited for you on the Phase Control dialog. Learn about these limitations.

In addition to selecting source ports, you also select the receivers to be used to measure the phase for the sources. This can be test port receivers or the reference receivers for the specified source ports. The receivers measure the relative phase of the sources, then adjust the phase of the controlled source, then remeasure until the phase difference is within the tolerance that you specify.

Phase can also be set without using any receivers. This is called 'Open Loop' mode. In this mode, the phase of the controlled source is set once, and iterations are not done, resulting in phase that is less accurate and stable compared to using receivers to measure and set phase. Use Open Loop mode when you need to use the receivers to measure other parameters.

The phase of the controlled source can be swept relative to the reference source. The phase difference between the controlled and reference source is incremented and iterated on consecutive data points. Before starting the Phase Control dialog, select Sweep Type = Phase Sweep. Learn how.

When the phase of a source is controlled, the power of that source is also controlled using Receiver Leveling. Instead of the normal receiver-leveling mode where only one receiver is used, when phase control is active the ratio of two receivers is used to level the power of the controlled source. This is useful for making active load-pull measurements as described below. In Open Loop mode, neither the phase nor the power of the source is controlled.

Features and Limitations

• Phase Control is allowed ONLY in a standard S-parameter channel.

• Phase Control can be used with Wideband pulse measurements - NOT in narrow-band pulse mode.

• Point Averaging is NOT allowed.

• External sources are supported. Learn how to Configure an External Device. Phase can be controlled on Keysight MXG, PSG, ESG and EXG sources. The external source must be routed through the rear panel so that a reference receiver can measure its phase. Use the Path Configuration dialog to make switch settings and enable FOM mode.

• Remote commands are available that allow the phase and power of each point to be set individually, much like in source power calibration. Use these commands if you need to create a specific pattern of amplitude/phase states, such as characterizing the load-pull of an amplifier.

Phase Control Use-Cases

Phase control and phase sweep is useful in the following applications:

Active load control

Provide a controlled, electronically-settable impedance to the output port of a DUT under fixed or swept-frequency conditions. Some examples are: measuring the gain and output power of an amplifier with a known load, and measuring the output from a directional detector with a known load.

The reference source is applied to the DUT input port, and the controlled source is applied to the DUT output port as a reverse input wave. The phase and power level of the controlled source is set relative to the forward output wave of the DUT (which is determined by the reference source), so that any arbitrary load impedance (gamma) can be set.

Optionally, the phase of the controlled source can be swept with a constant frequency, so that the phase of gamma rotates while the magnitude of gamma remains constant. The ratio of reverse input wave and forward output wave as viewed on a Smith chart or polar display would appear as a circle. This capability can be combined with external load-pull software to create traditional load-pull power contours.

Phase-controlled sources

Set the phase and magnitude of one source relative to a reference source, to provide differential, quadrature, or arbitrary phase-offset signals at a fixed or swept frequency. Typically, another instrument, receiver, or detector would be required to measure the response of the DUT.

Calibration and Phase Control

Calibrate only those ports that are used for a phase control measurement. For example, if using ports 1 and 3 for phase control, then do NOT calibrate all four ports. If other ports are calibrated, then even ports 1 and 3 may not yield acceptable results.

After performing calibration, the phase is aligned and the power is accurate at the calibration plane.

Active Load Control Example (4-port PNA-X

See setup using a 2-port 2-source PNA-X.

1. Select the Phase Control parameters in the above Phase Control and Phase Control Setup dialogs.

2. Setup a measurement with the same receivers that are selected on the Phase Control Setup dialog. In this example, on the 'Receivers' measurement tab, select 'a4/ b4' as in the following image:

3. Select Format, then either Phase or Smith Chart.

4. If you continually see Phase leveling warning: power not settled, then on the Power and Attenuators dialog, clear Port Powers Coupled (independent port power), then add attenuation to the controlled port. This happens because of additional power being measured from both sources.

Active Load Control with 2-Port 2-Source PNA-X Models

1. Connect a rear-panel jumpers cable from J8 to J1.

2. On the Phase Control Setup dialog, select Port 2 as the controlled source and Port1 Src 2 as the reference source.

3. On the Path Configuration dialog, on the Configuration box, select 2- port dual source.

4. Select the Control Parameter (receivers) a2 / b2.

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