DSP Blockset

Direct Rate Conversion

Rate conversion blocks accept an input signal at one sample rate, and propagate the same signal at a new sample rate. Several of these blocks contain a Frame-based mode parameter offering two options for adjusting the sample rate of the signal:

• Maintain input frame rate: Change the sample rate by changing the frame size (that is M_o  M_i), but keep the frame rate constant (T_fo = T_fi)
• Maintain input frame size: Change the sample rate by changing the output frame rate (that is T_fo  T_fi), but keep the frame size constant (M_o = M_i)

The setting of this parameter does not affect sample-based inputs.

Rate Conversion Blocks.   The following table lists the principal rate conversion blocks in the DSP Blockset. Blocks marked with an asterisk (*) offer the option of changing the rate by either adjusting the frame size or frame rate.

Block	Library
Downsample *	Signal Operations
Dyadic Analysis Filter Bank	Filtering / Multirate Filters
Dyadic Synthesis Filter Bank	Filtering / Multirate Filters
FIR Decimation *	Filtering / Multirate Filters,
FIR Interpolation *	Filtering / Multirate Filters
FIR Rate Conversion	Filtering / Multirate Filters
Repeat *	Signal Operations
Upsample *	Signal Operations

The following examples illustrate the two sample rate conversion modes:

• Example: Rate Conversion by Frame-Rate Adjustment
• Example: Rate Conversion by Frame-Size Adjustment

Converting Sample Rates and Frame Rates

Example: Rate Conversion by Frame-Rate Adjustment