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 
