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System Objects in DSP System Toolbox that Support Fixed-Point Design

Get Information About Fixed-Point System Objects

System objects that support fixed-point data processing have fixed-point properties. When you display the properties of a System object™, click show all properties at the end of the property list to display the fixed-point properties for that object. You can also display the fixed-point properties for a particular object by typing dsp.<ObjectName>.helpFixedPoint at the MATLAB® command line.

DSP System Toolbox System Objects That Support Fixed Point

dsp.SignalSource Import a variable from the MATLAB workspace
dsp.SineWaveGenerate discrete sine wave

Display vectors or arrays


Write audio samples to audio file

dsp.SignalSinkLog MATLAB simulation data

Display frequency spectrum of time-domain signals

timescopeDisplay time-domain signals
Adaptive Filters
dsp.LMSFilterCompute output, error, and weights using LMS adaptive algorithm
Filter Designs
dsp.CICCompensationDecimatorCompensate for CIC filter using a FIR decimator
dsp.CICCompensationInterpolatorCompensate for CIC filter using a FIR interpolator

Direct form FIR full band differentiator filter


Halfband decimator


Halfband interpolator


FIR or IIR highpass filter


FIR or IIR lowpass filter

Filter Implementations
dsp.AllpoleFilterIIR Filter with no zeros
dsp.BiquadFilterModel biquadratic IIR (SOS) filters
dsp.FIRFilterStatic or time-varying FIR filter
dsp.IIRFilterInfinite Impulse Response (IIR) filter
Multirate Filters
dsp.CICDecimatorDecimate inputs using a Cascaded Integrator-Comb (CIC) filter
dsp.CICInterpolator Interpolate inputs using a Cascaded Integrator-Comb (CIC) filter
dsp.FIRDecimatorFilter and downsample input signals
dsp.FIRInterpolatorUpsample and filter input signals
dsp.FIRRateConverterUpsample, filter, and downsample input signals
dsp.SubbandAnalysisFilterDecompose signal into high-frequency and low-frequency subbands
dsp.SubbandSynthesisFilter Reconstruct a signal from high-frequency and low-frequency subbands
dsp.FFTCompute fast Fourier transform (FFT) of input
dsp.IFFTCompute inverse fast Fourier transform (IFFT) of input
Signal Operations

Remove DC component


Delay input by specified number of samples or frames


Translate digital signal from Intermediate Frequency (IF) band to baseband and decimate it


Interpolate digital signal and translate it from baseband to Intermediate Frequency (IF) band


Polynomial sample rate converter with arbitrary conversion factor

dsp.NCOGenerate real or complex sinusoidal signals

Delay input by time-varying fractional number of sample periods


Delay input by time-varying integer number of sample periods


Zero crossing detector

Set System Object Fixed-Point Properties

Several properties affect the fixed-point data processing used by a System object. Objects perform fixed-point processing and use the current fixed-point property settings when they receive fixed-point input.

You change the values of fixed-point properties in the same way as you change any System object property value. See Configure Components. You also use the Fixed-Point Designer™ numerictype (Fixed-Point Designer) object to specify the desired data type as fixed-point, the signedness, and the word- and fraction-lengths. System objects support these values of DataTypeMode: Boolean, Double, Single, and Fixed-point: binary point scaling.

In the same way as for blocks, the data type properties of many System objects can set the appropriate word lengths and scalings automatically by using full precision. System objects assume that the target specified on the Configuration Parameters Hardware Implementation target is ASIC/FPGA.

If you have not set the property that activates a dependent property and you attempt to change that dependent property, a warning message displays. For example, for the dsp.FFT object, before you set CustomOutputDataType to numerictype(1,32,30), set OutputDataType to 'Custom'.


System objects do not support fixed-point word lengths greater than 128 bits.

For any System object provided in the Toolbox, the fimath settings for any fimath attached to a fi input or a fi property are ignored. Outputs from a System object never have an attached fimath.

Full Precision for Fixed-Point System Objects

FullPrecisionOverride is a convenience property that, when you set to true, automatically sets the appropriate properties for an object to use full-precision to process fixed-point input. For System objects, full precision, fixed-point operation refers to growing just enough additional bits to compute the ideal full precision result. This operation has no minimum or maximum range overflow nor any precision loss due to rounding or underflow. It is also independent of any hardware-specific settings. The data types chosen are based only on known data type ranges and not on actual numeric values. Full precision for System objects does not optimize coefficient values.

When you set the FullPrecisionOverride property to true, the other fixed-point properties it controls no longer apply and any of their non-default values are ignored. These properties are also hidden. To specify individual fixed-point properties, first set FullPrecisionOverride to false.

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