11: Multirate Systems
• Multirate Systems
• Building blocks
• Resampling Cascades
• Noble Identities
• Noble Identities Proof
• Upsampled z-transform
• Downsampled z-transform
• Downsampled Spectrum
• Power Spectral Density
• Perfect Reconstruction
• Commutators
• Summary
• MATLAB routines
11: Multirate Systems
DSP and Digital Filters (2016-9045)
Multirate: 11 – 1 / 14
Multirate Systems
Multirate systems include more than one sample rate
11: Multirate Systems
• Multirate Systems
• Building blocks
• Resampling Cascades
• Noble Identities
• Noble Identities Proof
• Upsampled z-transform
• Downsampled z-transform
• Downsampled Spectrum
• Power Spectral Density
• Perfect Reconstruction
• Commutators
• Summary
• MATLAB routines
DSP and Digital Filters (2016-9045)
Multirate: 11 – 2 / 14
Multirate Systems
Multirate systems include more than one sample rate
Why bother?:
• May need to change the sample rate
e.g. Audio sample rates include 32, 44.1, 48, 96 kHz
11: Multirate Systems
• Multirate Systems
• Building blocks
• Resampling Cascades
• Noble Identities
• Noble Identities Proof
• Upsampled z-transform
• Downsampled z-transform
• Downsampled Spectrum
• Power Spectral Density
• Perfect Reconstruction
• Commutators
• Summary
• MATLAB routines
DSP and Digital Filters (2016-9045)
Multirate: 11 – 2 / 14
Multirate Systems
11: Multirate Systems
• Multirate Systems
• Building blocks
• Resampling Cascades
• Noble Identities
• Noble Identities Proof
• Upsampled z-transform
• Downsampled z-transform
• Downsampled Spectrum
• Power Spectral Density
• Perfect Reconstruction
• Commutators
• Summary
• MATLAB routines
Multirate systems include more than one sample rate
Why bother?:
• May need to change the sample rate
e.g. Audio sample rates include 32, 44.1, 48, 96 kHz
• Can relax analog or digital filter requirements
e.g. Audio DAC increases sample rate so that the reconstruction filter
can have a more gradual cutoff
DSP and Digital Filters (2016-9045)
Multirate: 11 – 2 / 14
Multirate Systems
11: Multirate Systems
• Multirate Systems
• Building blocks
• Resampling Cascades
• Noble Identities
• Noble Identities Proof
• Upsampled z-transform
• Downsampled z-transform
• Downsampled Spectrum
• Power Spectral Density
• Perfect Reconstruction
• Commutators
• Summary
• MATLAB routines
Multirate systems include more than one sample rate
Why bother?:
• May need to change the sample rate
e.g. Audio sample rates include 32, 44.1, 48, 96 kHz
• Can relax analog or digital filter requirements
e.g. Audio DAC increases sample rate so that the reconstruction filter
can have a more gradual cutoff
• Reduce computational complexity
FIR filter length ∝ fs
Lower fs ⇒ shorter filter + fewer samples ⇒computation ∝ f 2
s
∆f where ∆f is width of transition band
DSP and Digital Filters (2016-9045)
Multirate: 11 – 2 / 14
Building blocks
Downsample
y[m] = x[Km]
11: Multirate Systems
• Multirate Systems
• Building blocks
• Resampling Cascades
• Noble Identities
• Noble Identities Proof
• Upsampled z-transform
• Downsampled z-transform
• Downsampled Spectrum
• Power Spectral Density
• Perfect Reconstruction
• Commutators
• Summary
• MATLAB routines
DSP and Digital Filters (2016-9045)
Multirate: 11 – 3 / 14
Building blocks
Downsample
y[m] = x[Km]
Upsample
v[n] =(u n
0
K K | n
else
11: Multirate Systems
• Multirate Systems
• Building blocks
• Resampling Cascades
• Noble Identities
• Noble Identities Proof
• Upsampled z-transform
• Downsampled z-transform
• Downsampled Spectrum
• Power Spectral Density
• Perfect Reconstruction
• Commutators
• Summary
• MATLAB routines
DSP and Digital Filters (2016-9045)
Multirate: 11 – 3 / 14
11: Multirate Systems
• Multirate Systems
• Building blocks
• Resampling Cascades
• Noble Identities
• Noble Identities Proof
• Upsampled z-transform
• Downsampled z-transform
• Downsampled Spectrum
• Power Spectral Density
• Perfect Reconstruction
• Commutators
• Summary
• MATLAB routines
Building blocks
Downsample
y[m] = x[Km]
Upsample
Example:
v[n] =(u n
0
K K | n
else
Downsample by 3 then upsample by 4
w[n]
0
DSP and Digital Filters (2016-9045)
Multirate: 11 – 3 / 14