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Where To Find This Example

Select Help > Open Examples... from the menus and type either the example name listed above or one of the keywords below.

Or in Version 13 or higher you can open the project directly from this page using this button. Make sure to select the Enable Guided Help before clicking this button.

Design Notes

IQ modulator with Phase Noise

Click Analyze to update MWO measurements and Run/Stop System Simulators for VSS measurements.

This example illustrates the use of a subcircuit to represent an IQ modulator in the system as one block.

To see the basic blocks that are used to construct the IQ modulator select the subcircuit in the system diagram then right hand click and from the menu chose Edit Subcircuit.

An I/Q modulator and quadrature mixer make up the subcircuit. The I/Q modulator generates the pulse shaped IQ baseband signal used to drive the quadrature mixer.

You can control parameters of the underlying blocks of the IQ modulator subcircuit through the parameter page of the subcircuit.

The VSS OSC_S block is used to extract the phase noise characteristics of an oscillator design in MWO. The OSC_S block automatically extracts the power level, phase mask and frequency of the oscillator. The OSC_S block allows for simulations with and without phase noise. For more information on the OSC_S block please read its online help.

The VSS phase noise spectral density (in brown) aligns with that generated by MWO (in red). The VSS phase noise is measured using the VSS PHS_NOISE measurement.

You can find the OSC_S block under the RF Blocks/Sources/Simulation Based node. The PHS_NOISE measurement can be found under System/Noise.

The graph “Local Oscillator” shows frequencies on the x-axis relative to the center frequency (25MHz). The blue spectrum is a power spectrum plot and shows the power of the LO to be approximately 5dBm. The black spectrum is a power spectral density plot (Pwr/Hz). Thus, you can measure the delta from the peak of the blue spectrum to that of the black spectrum and verify that VSS is accurately replicating the spectral mask.

System Diagram - System

Schematic - Oscprobe_Crystal_Osc

Graph - Spectrum

Graph - Local Oscillator

Graph - IQ

Graph - MWO and VSS Phase Noise Mask