Linearized Baseband PLL
(To be removed) Implement linearized version of baseband phase-locked loop
Linearized Baseband PLL 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 Linearized Baseband 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. Unlike the Phase-Locked Loop block, this block uses a baseband model method. Unlike the Baseband PLL block, which uses a nonlinear model, this block simplifies the computations by using x to approximate sin(x). The baseband PLL model depends on the amplitude of the incoming signal but does not depend on a carrier frequency.
This PLL has these three components:
An integrator used as a phase detector.
A filter. You specify the filter's 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 the sensitivity of the VCO signal to its input using the VCO input sensitivity parameter. This parameter, measured in Hertz per volt, is a scale factor that determines how much the VCO shifts from its quiescent frequency.
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's quiescent frequency.