Interpolate digital signal and translate it from baseband to Intermediate Frequency (IF) band
Signal Operations
dspsigops
The Digital UpConverter (DUC) block converts a complex digital baseband signal to a real passband signal.
The DUC block upsamples the input signal using a cascade of three interpolation filters. The block frequency upconverts the upsampled signal by multiplying it by the specified center frequency of the output signal. This block designs the interpolation filters according to the filter parameters that you set in the block dialog.
This block brings the capabilities of dsp.DigitalUpConverter
System
object™ to
the Simulink^{®} environment.
The DUC block consists of a FIR interpolator, a CIC compensator, and a CIC interpolator. You can bypass the FIR interpolator, depending on how you set the DUC block parameters.
For more information on the structure that the DUC block uses,
including the flow of fixedpoint input, see the Construction section
in dsp.DigitalUpConverter
.
Interpolation factor, specified as a positive integer scalar,
or as a 1by2 or 1by3 vector of positive integers. The default
is 100
.
When you set this parameter to a scalar, the block chooses the interpolation factors for each of the three filtering stages.
When you set this parameter to a 1by2 vector, the block bypasses
the first filter stage and sets the interpolation factor of the second
and third filtering stages to the values in the first and second vector
elements, respectively. Both elements of the Interpolation
factor must be greater than 1
.
When you set this parameter to a 1by3 vector, the ith
element of the vector specifies the interpolation factor for the ith
filtering stage. The second and third elements of Interpolation
factor must be greater than 1
, and the
first element must be 1
or 2
.
When you select this check box, the block designs filters with the minimum order that meets the requirements specified in these parameters:
Passband ripple of cascade response (dB)
Stopband attenuation of cascade response (dB)
Two sided bandwidth of input signal (Hz)
Source of stopband frequency
Stopband frequency (Hz)
When you clear this check box, the block designs filters with orders that you specify in Order of first filter stage, Order of CIC compensation filter stage, and Number of sections of CIC interpolator. The filter designs meet the passband and stopband frequency specifications that you set in Two sided bandwidth of input signal (Hz), Source of stopband frequency, and Stopband frequency (Hz). By default, this check box is selected.
Order of the first filter stage, specified as an even positive
integer scalar. When you specify Interpolation factor as
a 1by2 vector, the block ignores the value of Order of
first filter stage because the block bypasses the first
filter stage. This parameter applies when you clear the Minimum
order filter design check box. The default is 10
.
Order of the CIC compensation filter stage, specified as a positive
integer scalar. This parameter applies when you clear the Minimum
order filter design check box. The default is 12
.
Number of sections in the CIC interpolator, specified as a positive
integer scalar. This parameter applies when you clear the Minimum
order filter design check box. The default is 3
.
Two sided bandwidth of the input signal, specified as a positive integer scalar. The block sets the passband frequency of the cascade of filters to half the value that you specify in this parameter. The default is 200 kHz.
Source of the stopband frequency, specified as Auto
or Property
.
The default is Auto
.
When you set this parameter to Auto
, the
block places the cutoff frequency of the cascade filter response at
approximately F_{c} = SampleRate/2
Hz, and computes the stopband frequency as F_{stop} = F_{c} + TW/2. SampleRate is
computed as 1
/ Ts, where Ts is
the sample time of the input signal. TW is the
transition bandwidth of the cascade response, computed as 2×(F_{c}–F_{p}),
and the passband frequency, F_{p},
equals Bandwidth/2.
When you set this parameter to Property
,
specify the source in Stopband frequency (Hz).
Stopband frequency, specified as a doubleprecision positive
scalar. This parameter applies when you set the Source of
stopband frequency to Property
. The
default is 150
kHz.
Passband ripple of the cascade response, specified as a doubleprecision
positive scalar. When you select the Minimum order filter
design, the block designs the filters so that the cascade
response meets the passband ripple that you specify in Passband
ripple of cascade response (dB). This parameter applies
when you select the Minimum order filter design check
box. The default is 0.1
dB.
Stopband attenuation of the cascade response, specified as a
doubleprecision positive scalar. When you select the Minimum
order filter design check box, the block designs the filters
so that the cascade response meets the stopband attenuation that you
specify in Stopband attenuation of cascade response (dB).
This parameter applies when you select the Minimum order
filter design check box. The default is 60
dB.
Oscillator type, specified as one of the following:
Sine wave
(default) —
The block frequency upconverts the output of the interpolation filter
cascade using a complex exponential signal obtained from samples of
a sinusoidal trigonometric function.
NCO
— The block
performs frequency up conversion with a complex exponential obtained
using a numerically controlled oscillator (NCO).
Center frequency of the output signal, specified as a doubleprecision
positive scalar. The value of this parameter must be less than or
equal to half the product of the SampleRate times
the total interpolation factor. SampleRate is computed
as 1
/ Ts, where Ts is
the sample time of the input signal. The block up converts the input
signal so that the output spectrum centers at the frequency you specify
in Center frequency of output signal (Hz). The
default is 14
MHz.
Number of NCO accumulator bits, specified as an integer scalar
in the range [1 128]
. This parameter applies when
you set Type of oscillator to NCO
.
The default is 16
.
Number of NCO quantized accumulator bits, specified as an integer
scalar in the range [1 128]
. This value must be
less than the value you specify in Number of NCO accumulator
bits. This parameter applies when you set Type
of oscillator to NCO
. The default is 12
.
When you select this check box, a number of dither bits specified
in Number of NCO dither bits applies dither to
the NCO signal. This parameter applies when you set Type
of oscillator to NCO
. By default, this
check box is selected.
Number of NCO dither bits, specified as an integer scalar smaller
than the number of accumulator bits that you specify in Number
of NCO accumulator bits. This parameter applies when you
set Type of oscillator to NCO
and
select the Dither control for NCO. The default
is 4
.
When you select this check box, sample rate is computed as N
/ Ts,
where N is the frame size of the input signal,
and Ts is the sample time of the input signal.
When you clear this check box, the block’s sample rate is the
value specified in Input sample rate (Hz). By
default, this check box is selected.
Input sample rate, specified as a positive
scalar. The value of this parameter multiplied by the total interpolation
factor must be greater than or equal to twice the value of the Center
frequency of output signal (Hz). The default is 30
MHz.
This parameter applies when you clear the Inherit sample
rate from input check box.
Opens the Filter Visualization Tool FVTool and displays the magnitude/phase response of each stage as well as the cascade of stages in the Digital UpConverter. The response is based on the block dialog box parameters. Changes made to these parameters update FVTool.
To update the magnitude response while FVTool is running, modify the dialog box parameters and click Apply.
Type of simulation to run. You can set this parameter to:
Code generation
(default)
Simulate model using generated C code. The first time you run
a simulation, Simulink generates C code for the block. The C
code is reused for subsequent simulations, as long as the model does
not change. This option requires additional startup time but provides
faster simulation speed than Interpreted execution
.
Interpreted execution
Simulate model using the MATLAB^{®} interpreter. This
option shortens startup time but has slower simulation speed than Code
generation
.
Data type of the output of the first, second, and third filter stages. You can set this parameter to:
Inherit: Same as input
(default)
— The block inherits the Stage output from
the input signal.
fixdt([],16,0)
— Fixedpoint
data type with binary point scaling. Specify the sign mode of this
data type as []
or true
.
An expression that evaluates to a data type, for example, numerictype([],16,15)
.
Specify the sign mode of this data type as []
or true
.
The block casts the data at the output of each filter stage according to the value you set in this parameter. For the CIC stage, the casting is done after the signal has been scaled by the normalization factor.
Click the Show data type assistant button to display the data type assistant, which helps you set the stage output parameter.
See Specify Data Types Using Data Type Assistant (Simulink) for more information.
Data type of the block output. You can set this parameter to:
Inherit: Same as input
(default)
— The block Inherits the output datatype from the input.
fixdt([],16,0)
— Fixedpoint
data type with binary point scaling. Specify the sign mode of this
data type as []
or true
.
An expression that evaluates to a data type, for example, numerictype([],16,15)
.
Specify the sign mode of this data type as []
or true
.
Click the Show data type assistant button to display the data type assistant, which helps you set the Output parameter.
See Specify Data Types Using Data Type Assistant (Simulink) for more information.
Minimum value of the block output. The default value is []
(unspecified). Simulink software
uses this value to perform:
Simulation range checking (see Signal Ranges (Simulink))
Automatic scaling of fixedpoint data types
Maximum value of the block output. The default value is []
(unspecified). Simulink software
uses this value to perform:
Simulation range checking (see Signal Ranges (Simulink))
Automatic scaling of fixedpoint data types
Select this parameter to prevent the fixedpoint tools from overriding the data types you specify on the block mask.
Port  Supported Data Types 

Input 

Output 

Digital DownConverter  DSP System Toolbox 
dsp.DigitalDownConverter  DSP System Toolbox 
dsp.DigitalUpConverter  DSP System Toolbox 