Documentation |
Connection block from RF physical blocks to Simulink environment
The Output Port block produces the baseband-equivalent time-domain response of an input signal traveling through a series of RF physical components. The Output Port block
Partitions the RF physical components into linear and nonlinear subsystems.
Extracts the complex impulse response of the linear subsystem for baseband-equivalent modeling of the RF linear system.
Extracts the nonlinear AMAM/AMPM modeling for RF nonlinearity.
The Output Port block also serves as a connecting port from an RF physical part of the model to the Simulink^{®}, or mathematical, part of the model. For more information about how the Output Port block converts the physical modeling environment signals to mathematical Simulink signals, see Convert to and from Simulink Signals.
Note: Some RF blocks require the sample time to perform baseband modeling calculations. To ensure the accuracy of these calculations, the Input Port block, as well as the mathematical RF blocks, compare the input sample time to the sample time you provide in the mask. If they do not match, or if the input sample time is missing because the blocks are not connected, an error message appears. |
For the linear subsystem, the Output Port block uses the Input Port block parameters and the interpolated S-parameters calculated by each of the cascaded physical blocks to calculate the baseband-equivalent impulse response. Specifically, it
Determines the modeling frequencies f as an N-element vector. The modeling frequencies are a function of the center frequency f_{c}, the sample time t_{s}, and the finite impulse response filter length N, all of which you specify in the Input Port block dialog box.
The nth element of f, f_{n}, is given by
$$\begin{array}{cc}{f}_{n}={f}_{\mathrm{min}}+\frac{n-1}{{t}_{s}N}& n=1,\mathrm{...},N\end{array}$$
where
$${f}_{\mathrm{min}}={f}_{c}-\frac{1}{2{t}_{s}}$$
Calculates the passband transfer function for the frequency range as
$$H(f)=\frac{{V}_{L}(f)}{{V}_{S}(f)}$$
where V_{S} and V_{L} are the source and load voltages, and f represents the modeling frequencies. More specifically,
$$H(f)=\frac{{S}_{21}\left(1+{\Gamma}_{l}\right)\left(1-{\Gamma}_{s}\right)}{2\left(1-{S}_{22}{\Gamma}_{l}\right)\left(1-{\Gamma}_{in}{\Gamma}_{s}\right)}$$
where
$$\begin{array}{l}{\Gamma}_{l}=\frac{{Z}_{l}-{Z}_{o}}{{Z}_{l}+{Z}_{o}}\\ {\Gamma}_{s}=\frac{{Z}_{s}-{Z}_{o}}{{Z}_{s}+{Z}_{o}}\\ {\Gamma}_{in}={S}_{11}+\left({S}_{12}{S}_{21}\frac{{\Gamma}_{l}}{\left(1-{S}_{22}{\Gamma}_{l}\right)}\right)\end{array}$$
and
Z_{S} is the source impedance.
Z_{L} is the load impedance.
S_{ij} are the S-parameters of a two-port network.
The blockset derives the passband transfer function from the Input Port block parameters as shown in the following figure:
Translates the passband transfer function to baseband as H(f – f_{c}), where f_{c} is the specified center frequency.
The baseband transfer function is shown in the following figure.
Obtains the baseband-equivalent impulse response by calculating the inverse FFT of the baseband transfer function. For faster simulation, the block calculates the IFFT using the next power of 2 greater than the specified finite impulse response filter length. Then, it truncates the impulse response to a length equal to the filter length specified.
For the linear subsystem, the Output Port block uses the calculated impulse response as input to the DSP System Toolbox™ Digital Filter Design block to determine the output.
The nonlinear subsystem is implemented by AM/AM and AM/PM nonlinear models, as shown in the following figure.
The nonlinearities of AM/AM and AM/PM conversions are extracted from the power data of an amplifier or mixer by the equations
$$\begin{array}{c}A{M}_{out}=\sqrt{{R}_{l}{P}_{out}}\\ P{M}_{out}=\phi \\ A{M}_{in}=\sqrt{{R}_{s}{P}_{in}}\end{array}$$
where AM_{in} is the AM of the input voltage, AM_{out} and PM_{out} are the AM and PM of the output voltage, R_{s} is the source resistance (50 ohms), R_{l} is the load resistance (50 ohms), P_{in} is the input power, P_{out} is the output power, andϕ is the phase shift between the input and output voltage.
Note: You can provide power data via a .amp file. See AMP File Format in the RF Toolbox™ documentation for information about this format. |
The following figure shows the original power data of an amplifier.
This figure shows the extracted AM/AM nonlinear conversion.
Load impedance of the RF network described in the physical model to which it connects.
This tab shows parameters for creating plots if you display the Output Port mask after you perform one or more of the following actions:
Run a model with two or more blocks between the Input Port block and the Output Port block.
Click the Update Diagram button to initialize a model with two or more blocks between the Input Port block and the Output Port block.
For information about plotting, see Create Plots.