cic_analyse

This function computes and shows the frequency response of a CIC filter and then analyse the aliasing that occurs after decimation.

Espace de nom : tsd::filtrage

Prototype

CICAnalyse cic_analyse(const CICConfig &config, float Fe, float Fint=0)

Paramètres

config	Paramètres principaux (voir CICConfig)
Fe	Fréquence d'échantillonnage d'entrée
Fint	Fréquence où mesurer l'atténuation

Retourne

A tuple with :

Theorical transfert function (not taking into account the decimation),
Number of additionnal bits needed to implement the CIC filter

Description

This functions draws two plots:

The first plot shows the frequency response before decimation (both the global one, and one centered on the passband).
The second plot shows the effect of the decimation (aliasing in the baseband).

Also, this function computes the number of additionnal bits needed to implement the filter in fixed point / integer arithmetic. This is computed as (see http://www.tsdconseil.fr/log/scriptscilab/cic/cic-en.pdf): \[n_{bits} = N\cdot\log_2(R) - 1\]

Exemple

// 10 MHz input sample frequency
fe = 10e6;
// Decimation ratio = 16, 5 CIC stages
// (sample rate at output of CIC is 10 MHz / 16 = 625 KHz)
R = 16, N = 5, M = 1;
cic_analyse({R, N, M}, fe);

Voir aussi

design_cic()