##

Second order Loop Filter for PLL type 2 block

This block realizes a continuous second order loop filter defined by the following electrical circuit :

**Figure ****1:** Passive second order loop filter

Because this circuit can be explicitly expressed with linear ordinary differential equations,
it is able to be described by a tranfert function.

The transfer function of this filter is :

where the zero and the poles
are computed according to the dialogue parameters and with the hep of the Scilab macro **calcul_3eme_ordre**.
The interfacing function of this block also allows to plot the different Bode diagrams of the linear model of a third order type 2 PLL.

This can be useful for the calibration of the the attenuation at cut-off frequency of the closed-loop transfert function.

**Natural loop frequency (Hz)**

The cut-off frequency of the closed-loop transfert function.

Type 'vec' of size 1.

**Phase Margin (rad)**

The phase margin at the cut-off frequency.

Type 'vec' of size 1.

**Linear VCO gain (Hz/V)**

The local sensitivity of the VCO when loop is in lock.

Type 'vec' of size 1.

**Charge pump current (A)**

The maximal output current of the charge pump.

Type 'vec' of size 1.

**Nominal divider value (integer)**

The value of the feed-back frequency divider of the loop.

Type 'vec' of size 1.

**Plot open loop transfert function (0=No) ?**

Plot the Bode diagram of the open loop transfert function in a scilab window.

Type 'vec' of size 1.

**Plot closed loop transfert function (0=No) ?**

Plot the Bode diagram of the closed loop transfert function in a scilab window.

Type 'vec' of size 1.

**Plot fm response transfert function (0=No) ?**

Plot the Bode diagram of the the frequency modulation response transfert function (viewed as the input of the VCO) in a scilab window.

Type 'vec' of size 1.

**always active:** yes
**direct-feedthrough:** no
**zero-crossing:** no
**mode:** no
**regular inputs:**

** - port 1 : size [1,1] / type 1**

**regular outputs:**

** - port 1 : size [1,1] / type 1**

**number/sizes of activation inputs:** 0
**number/sizes of activation outputs:** 0
**continuous-time state:** yes
**discrete-time state:** no
**object discrete-time state:** no
**name of computational function:** *csslti*

- MODNUMCOS/macros/scicos_blocks/Pll/SOLOOPFILTER_f.sci [view code]

A. Layec