(To be removed) Implement phase-locked loop to recover phase of input signal
Phase-Locked Loop will be removed in a future release. To design voltage-controlled oscillators (VCOs) and phase-locked loops (PLLs), use the Phase-Locked Loops (Mixed-Signal Blockset) blocks.
Components sublibrary of Synchronization
The Phase-Locked Loop (PLL) block is a feedback control system that automatically adjusts the phase of a locally generated signal to match the phase of an input signal. This block is most appropriate when the input is a narrowband signal.
This PLL has these three components:
A multiplier used as a phase detector.
A filter. You specify the filter transfer function using the Lowpass filter numerator and Lowpass filter denominator parameters. Each is a vector that gives the respective polynomial's coefficients in order of descending powers of s.
To design a filter, you can use functions such as
cheby2in Signal Processing Toolbox™ software. The default filter is a Chebyshev type II filter whose transfer function arises from the command below.
[num, den] = cheby2(3,40,100,'s')
A voltage-controlled oscillator (VCO). You specify characteristics of the VCO using the VCO quiescent frequency, VCO initial phase, and VCO output amplitude parameters.
This block accepts a sample-based scalar input signal. The input signal represents the received signal. The three output ports produce:
The output of the filter
The output of the phase detector
The output of the VCO
For more information, Phase-Locked Loops.
- Lowpass filter numerator
The numerator of the lowpass filter transfer function, represented as a vector that lists the coefficients in order of descending powers of s.
- Lowpass filter denominator
The denominator of the lowpass filter transfer function, represented as a vector that lists the coefficients in order of descending powers of s.
- VCO input sensitivity (Hz/V)
This value scales the input to the VCO and, consequently, the shift from the VCO quiescent frequency value. The units of VCO input sensitivity are Hertz per volt.
- VCO quiescent frequency (Hz)
The frequency of the VCO signal when the voltage applied to it is zero. This should match the carrier frequency of the input signal.
- VCO initial phase (rad)
The initial phase of the VCO signal.
- VCO output amplitude
The amplitude of the VCO signal.
For more information about phase-locked loops, see the works listed in Selected Bibliography for Synchronization.