NI 5442 FIR Filter Type: Root Raised Cosine

NI Signal Generator

NI 5442
FIR Filter Type: Root Raised Cosine

Alpha Values: 0.1 to 0.4

This lowpass filter is commonly used in communications applications. The passband of the root raised cosine filter stops at 0.5 × (1 − α) of the IQ Rate. The stopband of the root raised cosine filter begins at 0.5 × (1 + α) of the IQ Rate. The transitionband of the root raised cosine filter (in dB) follows the following formula:

where

S = 0.5 × (1 − α)

f = Frequency (fraction of the IQ Rate)

Use the Root Raised Cosine Filter Alpha property or the NIFGEN_ATTR_OSP_FIR_FILTER_ROOT_RAISED_COSINE_ALPHA attribute to set the α value.

The following diagram shows an ideal root raised cosine filter response with an α of 0.5. The frequency axis is scaled as a fraction of the value of the IQ Rate property or the NIFGEN_ATTR_OSP_IQ_RATE attribute.

Ideal Root Raised Cosine Filter Response (Alpha = 0.5)