Coupler
Model ideal frequency-independent couplers with S-parameters
Libraries:
RF Blockset /
Circuit Envelope /
Junctions
Description
The Coupler block models four port directional
couplers in a circuit envelope environment as an ideal S-parameter
model. The four ports of the coupler are Input port
(Port
1), Through port
(Port 2), Isolated port
(Port
3), Coupled port
(Port 4).
Directional couplers are used to sample forward and reflected waves propagating along a transmission line. Directional couplers find uses in many RF design applications such as line power sensors and transmitter automatic level controls.
Hybrid couplers are used to split or combine signals with specific phase relations.
Examples
Modeling RF Front End in Radar System Simulation
In a radar system, the RF front end often plays an important role in defining the system performance. For example, because the RF front end is the first section in the receiver chain, the design of its low noise amplifier is critical to achieving the desired signal to noise ratio (SNR). This example shows how to incorporate RF front end behavior into an existing radar system design.
(Phased Array System Toolbox)
Digital Predistortion to Compensate for Power Amplifier Nonlinearities
Use digital predistortion in a transmitter to offset the effects of nonlinearities in a power amplifier.
Parameters
Select component — Coupler type
Directional coupler
(default) | Coupler symmetrical
| Coupler antisymmetrical
| Hybrid quadrature (90 deg)
| Hybrid rat-race
| Magic tee
Coupler type, specified as:
Directional coupler
The default option is
Directional coupler
. The S-parameters matrix for theDirectional coupler
is:where:
rl = 10(-ReturnLoss/20)
il = j10(-InsertionLoss/20)
is = j10(-(Coupling+Directivity)/20)
c = 10(-Coupling/20)
Note
In release 2019a, the S-parameters representation of the Directional Coupler block is altered to permit a valid implementation for all specified mask values. This implementation adds a 90 degree phase shift to s12, s13, s21, s24, s31, s34, s42, and s43 terms. In addition, a -180 phase shift is added to the s14, s23, s32 and s41 terms.
Use this option to model coupler parameters from data sheets.
Coupler symmetrical
The S-parameters matrix for the
Coupler symmetrical
is:where:
|α| ≤ 1 = Power transmission coefficient
β = sqrt(1– α*α)
Coupler antisymmetrical
The S-parameters matrix for the
Coupler antisymmetrical
is:where:
|α| ≤ 1 = Power transmission coefficient.
β = sqrt (1– α*α)
Hybrid quadrature (90deg)
The S-parameters matrix for the
Hybrid quadrature(90deg)
is:Hybrid rat-race
The S-parameters matrix for the
Hybrid rat-race
is:Magic tee
The S-parameters matrix for the
Magic tee
is:
The Divider block uses the ispassive
function to test the passivity of the S-parameters
matrix.
Coupling (dB) — Fraction of input signal power coupled to output port
0 (default) | nonnegative and real scalar
Fraction of input signal power coupled to output port of the Directional
coupler
, specified as a nonnegative and real scalar. The
default value is 0
dB.
Dependencies
To enable this parameter, select Directional coupler
in Select
component tab.
Directivity (dB) — Ratio of power at coupled port to power at isolated port
inf
(default) | nonnegative and real scalar
Ratio of power at coupled port to power at isolated port of
the Directional coupler
, specified as a nonnegative
and real scalar. The default value is inf
.
Dependencies
To enable this parameter, select Directional coupler
in Select
component tab.
Insertion loss (dB) — Loss of signal power between input and output ports
inf
(default) | nonnegative and real scalar
Loss of signal power between input and output ports of the Directional
coupler
, specified as a nonnegative and real scalar. The
default value is inf
.
Dependencies
To enable this parameter, select Directional coupler
in Select
component tab.
Return loss (dB) — Loss of signal power due to impedance mismatch
inf
(default) | nonnegative and real scalar
Loss of signal power due to impedance mismatch of the Directional
coupler
, specified as a nonnegative, and real scalar. The
default value is inf
.
Dependencies
To enable this parameter, select Directional coupler
in Select
component tab.
Power transmission coefficient — Transmitted signal power
0 (default) | real scalar
Transmitted signal power of the Directional coupler
,
specified as a real scalar. The default value is 0.
Dependencies
To enable this parameter, select Coupler
symmetrical
or Coupler
antisymmetrical
in Select
component tab.
Reference impedances (Ohm) — Reference impedance of coupler
50
(default) | positive scalar | positive three-tuple vector
Reference impedance of coupler, specified as a scalar or positive three-tuple vector.
Note
When the reference impedances of all the ports are not equal, the model inside the Coupler block is normalized to 50 ohms.
Ground and hide negative terminals — Ground RF circuit terminals
on
(default) | off
Select this parameter to ground and hide the negative terminals. To expose the negative terminals, clear this parameter. By exposing these terminals, you can connect them to other parts of your model.
By default, this option is selected.
Version History
Introduced in R2014a
See Also
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