VCO Testbench

Validate voltage controlled oscillator (VCO) by measuring phase noise metrics or VCO characteristics

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  • VCO Testbench block

Libraries:
Mixed-Signal Blockset / PLL / Measurements & Testbenches

Description

The VCO Testbench block validates the VCO device under test (DUT) by measuring one of the two target metrics: phase noise, or voltage sensitivity and quiescent frequency. You can use the testbench to validate a VCO of your own implementation, or you can use the VCO block from the Mixed-Signal Blockset™.

The VCO Testbench block generates the stimulus (control voltage) to drive the device under test (DUT) from the Stimulus tab. The setup parameters for validating the DUT are defined in the Setup tab and the target validation metrics are defined in the Target Metric tab.

To take the full advantage of the VCO testbench capabilities by using autofill parameters options, use only two blocks, the VCO DUT and the VCO Testbench in the Simulink® model.

Examples

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Open Script

This example shows how to validate the phase noise profile of a VCO device under test (DUT) using a VCO Testbench.

Open the model ringOscVCOPhaseNoise. The model consists of a Ring Oscillator VCO block and a VCO Testbench.

model = 'ringOscVCOPhaseNoise';
open_system(model)


close_system(model)

The voltage sensitivity of the VCO is set to 1.25e6 Hz, and the free running frequency is 2e9 Hz. Check that Add phase noise parameter is enabled. Click the Estimate phase noise parameters button, then click Plot fit to see how the phase noise is fitted against the specification. In the attached model, the fit is good.

The testbencch is set to measure the Phase noise metric of the VCO in the Measurement option. The Control voltage provided to the input of VCO is 4 V. So, the VCO operates at 2.5 GHz frequency. Click the Autofill setup parameters button to automatically calculate the Resolution bandwidth (Hz), and No. of spectral averages. Click the Autofill target metric button to automatically import the phase noise target profile to the VCO Testbench.

Run simulation for 8e-4 s, as recommended in the Block Parameters dialog box.

sim(model);
open_system([model '/VCO Testbench'])

Double click the VCO Testbench block to open the Block Parameters dialog box. Click on the Plot measurement button.

The operating frequency matches the predicted frequency 2.5 GHz. The measured phase noise profile also matches the target profile.

Ports

Input

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Input signal, which flows from the output of the VCO DUT. This input signal is used to calculate either the phase noise metric, or the voltage sensitivity and free running frequency of the VCO, depending on the Measurement option chosen.

Data Types: double

Output

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Output signal, which provides control voltage stimulus to the input of VCO DUT.

Data Types: double

Parameters

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Determines which of the two given target metrics is being measured.

Select Phase noise if you want the testbench to measure and compare phase noise to a target phase noise profile.

Select Kvco and Fo if you want the testbench to compute voltage sensitivity (Kvco) and quiescent frequency (Fo) using a range of control voltages.

Programmatic Use

  • Use get_param(gcb,'MeasureOptions') to view the current Measurement option.

  • Use set_param(gcb,'MeasureOptions',value) to set Measurement to a specific option.

Click to set the Recommended min. simulation stop time (s) reported by the VCO Testbench block as the model stop time.

Dependencies

This button is only available when you select Phase noise as the Measurement option.

Plots the relevant VCO metrics based on the Measurement options.

Selecting Phase noise in Measurement plots phase noise profile of VCO.

Selecting Kvco and Fo in Measurement plots the VCO characteristics and Kvco.

Exports the relevant VCO metrics based on the Measurement options to an excel file.

Selecting Phase noise in Measurement exports the phase noise profile of VCO.

Selecting Kvco and Fo in Measurement exports the VCO characteristics and Kvco.

Stimulus

Control voltage provided by VCO Testbench, expressed as a scalar in V. The value specified in Control Voltage (V) flows through the to vco port that provides the input of VCO.

Dependencies

To enable this parameter, select Phase noise as the Measurement option.

Programmatic Use

  • Use get_param(gcb,'ControlVoltage') to view current Control Voltage (V) value.

  • Use set_param(gcb,'ControlVoltage',value) to set Control Voltage (V) to a specific value.

Data Types: double

Control voltage provided by VCO Testbench, expressed as a two-element row vector in V. This parameter specifies the minimum and maximum values of control voltage, which is used to generate ten control voltage value points, including the provided values. These ten values of control voltage are sent to VCO input to measure Kvco and Fo.

Dependencies

To enable this parameter, select Kvco and Fo as the Measurement option.

Programmatic Use

  • Use get_param(gcb,'ControlVoltageRange') to view the current Range of control voltage (V) values.

  • Use set_param(gcb,'ControlVoltage',value) to set Range of control voltage (V) to specific values.

Data Types: double

Setup

Click this button to automatically populate setup parameters ( Resolution bandwidth (Hz) and No. of spectral averages) for phase noise measurement.

If the DUT is a VCO from Mixed-Signal Blockset, the dsp.SpectrumEstimator System object™ used by the VCO Testbench block for phase noise measurement automatically calculates setup parameters based on the VCO specifications.

Dependencies

  • This button only works if the VCO DUT is a VCO block from Mixed-Signal Blockset.

  • This button is only available when you select Phase noise as the Measurement option.

Smallest positive frequency that can be resolved, specified as a real positive scalar. The Resolution bandwidth (Hz) is used to determine window length for spectral analysis using the Welch method. For more information, see Welch's Method of Averaged Modified Periodograms.

In general, Resolution bandwidth (Hz) should be less than or equal to the lowest offset frequency value.

If the DUT is a VCO block from the Mixed-Signal Blockset library, you can use the Autofill setup parameters button to automatically calculate Resolution bandwidth (Hz).

Dependencies

To enable this parameter, select Phase noise as the Measurement option.

Programmatic Use

  • Use get_param(gcb,'ResBandwidth') to view current Resolution bandwidth (Hz) value.

  • Use set_param(gcb,'ResBandwidth',value) to set Resolution bandwidth (Hz) to a specific value.

Data Types: double

Number of spectral averages, specified as a positive integer scalar. The dsp.SpectrumEstimator System object used by the Phase Noise Measurement subsystem inside the VCO Testbench block computes the current power spectrum or power density spectrum estimate by averaging over the number specified by No. of spectral averages.

If the DUT is a VCO block from the Mixed-Signal Blockset library, you can use the Autofill setup parameters button to automatically calculate number of spectral averages.

Dependencies

To enable this parameter, select Phase noise as the Measurement option.

Programmatic Use

  • Use get_param(gcb,'SpectralAverages') to view current No. of spectral averages value.

  • Use set_param(gcb,'SpectralAverages',value) to set No. of spectral averages to a specific value.

Data Types: double

Hold-off period, specified as a nonnegative scalar in s. Hold-off time delays measurement analysis by the specified amount of time to avoid corrupting simulation results due to transients.

Programmatic Use

  • Use get_param(gcb,'HoldOffTime') to view the current Hold-off time (s) value.

  • Use set_param(gcb,'HoldOffTime',value) to set Hold-off time (s) to a specific value.

Target Metric

Click this button to automatically populate the target phase noise metric from VCO specifications.

Dependencies

  • This button will only work if the VCO DUT is a VCO block from Mixed-Signal Blockset.

  • This button is only available when you select Phase noise as Measurement option.

The frequency offsets of phase noise from the carrier frequency, collected from the data sheet, specified as a real valued vector in Hz.

If the DUT is a VCO block from the Mixed-Signal Blockset library, you can use the Autofill target metric button to automatically transfer VCO phase noise frequency offset vector values to the VCO Testbench.

Dependencies

To enable this parameter, select Phase noise as the Measurement option.

Programmatic Use

  • Use get_param(gcb,'PhaseNoiseFreqOffset') to view the current Phase noise frequency offset vector (Hz) value.

  • Use set_param(gcb,'PhaseNoiseFreqOffset',value) to set Phase noise frequency offset vector (Hz) to a specific value.

Data Types: double

The phase noise power in a 1 Hz bandwidth centered at the specified frequency offsets relative to the carrier, collected from the data sheet, specified as a real valued vector in dBc/Hz. The elements of Phase noise vector (dBc/Hz) corresponds to relative elements in the Phase noise frequency offset vector (Hz).

If the DUT is a VCO block from the Mixed-Signal Blockset library, you can use the Autofill target metric button to automatically transfer VCO phase noise vector values to the testbench.

Dependencies

To enable this parameter, select Phase noise as the Measurement option.

Programmatic Use

  • Use get_param(gcb,'PhaseNoiseVector') to view the current Phase noise vector (dBc/Hz) value.

  • Use set_param(gcb,'PhaseNoiseVector',value) to set Phase noise vector (dBc/Hz) to a specific value.

More About

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References

[1] Banerjee, Dean. PLL Performance, Simulation and Design. Indianapolis, IN: Dog Ear Publishing, 2006.

Version History

Introduced in R2019a

See Also

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