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VCO

Model voltage controlled oscillator

  • Library:
  • Mixed-Signal Blockset / PLL / Building Blocks

  • VCO block

Description

VCO or voltage controlled oscillator is a voltage to frequency converter. It produces an output signal whose frequency is controlled by the voltage at the input vctrl port. The frequency of the output signal, F is determined either by:

F=(KVCO·Vctrl)+Fo

where:

  • Kvco = voltage sensitivity (in Hz/V)

  • Vctrl = control voltage (in V)

  • Fo= free running frequency (in Hz)

or from linear interpolation using the mapping:

F=interp(Fout(Vcntl))

where:

  • Vctnl = vector of control voltages (in V)

  • Fout= vector of corresponding output frequencies (in Hz)

Ports

Input

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VCO control voltage used to control the output frequency of the VCO. In a phase-locked loop (PLL) system, vctrl is the output of the Loop Filter that contains the phase error information.

Data Types: double

Output

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Output signal of VCO. In a PLL system, vco out is the output clock generated by the PLL. It is also fed back to the PFD block through a clock divider to complete the control loop.

Data Types: double

Parameters

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Parameters

Define how VCO output frequency is specified:

  • Select Voltage sensitivity to specify output frequency from Voltage sensitivity (Hz/V) and Free running frequency (Hz).

  • Select Output frequency vs. control voltage to interpolate output frequency from Control voltage (V) vector versus Output frequency (Hz) vector.

Programmatic Use

Block parameter: SpecifyUsing
Type: character vector
Values: Voltage sensitivity | Output frequency vs. control voltage
Default: Voltage sensitivity

Measure of change in output frequency for input voltage change, specified as a positive real scalar with units in Hz/V. This parameter is also reported as VCO voltage sensitivity in the Loop Filter tab and is used to automatically calculate the filter component values of the loop filter.

Dependencies

To enable this parameter, select Voltage sensitivity in Specify using in the Parameters tab.

Programmatic Use

Block parameter: Kvco
Type: character vector
Values: positive real scalar
Default: 100e6

Data Types: double

Frequency of the VCO without any control voltage input (0 V), or the quiescent frequency, specified as a positive real scalar in Hz.

Dependencies

To enable this parameter, select Voltage sensitivity in Specify using in the Parameters tab.

Programmatic Use

Block parameter: Fo
Type: character vector
Values: positive real scalar
Default: 2.5e9

Data Types: double

Control voltage values of the VCO, specified as a real valued vector in volts.

Dependencies

To enable this parameter, select Output frequency vs. control voltage in Specify using in the Parameters tab.

Programmatic Use

Block parameter: ControlVoltage
Type: character vector
Values: real valued vector
Default: [-5 0 5]

Data Types: double

Output frequency of the values of the VCO, corresponding to the Control voltage (V) vector, specified in Hz.

Dependencies

To enable this parameter, select Output frequency vs. control voltage in Specify using in the Parameters tab.

Programmatic Use

Block parameter: OutputFrequency
Type: character vector
Values: positive real valued vector
Default: [2e9 2.5e9 3e9]

Data Types: double

Maximum amplitude of the VCO output voltage, specified as a positive real scalar.

Programmatic Use

Block parameter: Amplitude
Type: character vector
Values: positive real scalar
Default: 1

Data Types: double

Select to enable increased buffer size during simulation. This increases the buffer size of the Variable Pulse Delay block inside the VCO block. By default, this option is deselected.

Number of samples of the input buffering available during simulation, specified as a positive integer scalar. This sets the buffer size of the Variable Pulse Delay block inside the VCO block.

Selecting different simulation solver or sampling strategies can change the number of input samples needed to produce an accurate output sample. Set the Buffer size to a large enough value so that the input buffer contains all the input samples required.

Dependencies

To enable this parameter, select Enable increased buffer size.

Programmatic Use

Block parameter: NBuffer
Type: character vector
Values: positive integer scalar
Default: 10

Data Types: double

Impairments

Select to introduce phase noise as a function of frequency to the VCO. By default, this option is selected.

The frequency offsets of phase noise from the carrier frequency specified as a positive real valued vector in Hz.

Dependencies

To enable this parameter, select Add phase noise in the Impairments tab.

Programmatic Use

Block parameter: Foffset
Type: character vector
Values: positive real valued vector
Default: [30e3 100e3 1e6 3e6 10e6]

Data Types: double

The phase noise power in a 1 Hz bandwidth centered at the specified frequency offsets relative to the carrier specified as a negative real valued vector in dBc/Hz. The elements of Phase noise level corresponds to relative elements in the Phase noise frequency offset.

Dependencies

To enable this parameter, select Add phase noise in the Impairments tab.

Programmatic Use

Block parameter: PhaseNoise
Type: character vector
Values: negative real valued vector
Default: [-56 -106 -132 -143 -152]

Data Types: double

More About

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References

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

Introduced in R2019a