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Coupler

Model ideal frequency-independent couplers with S-parameters

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  • Coupler block

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

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

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

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Coupler type, specified as:

  • Directional coupler

    The default option is Directional coupler. The S-parameters matrix for the Directional coupler is:

    [rliliscilrlcisiscrlilcisilrl]

    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:

    [0α0jβα0jβ00jβ0αjβ0α0]

    where:

    • |α| ≤ 1 = Power transmission coefficient

    • β = sqrt(1– α*α)

  • Coupler antisymmetrical

    The S-parameters matrix for the Coupler antisymmetrical is:

    [0α0βα0−β00−β0αβ0α0]

    where:

    • |α| ≤ 1 = Power transmission coefficient.

    • β = sqrt (1– α*α)

  • Hybrid quadrature (90deg)

    The S-parameters matrix for the Hybrid quadrature(90deg) is:

    [0-j/20-1/2-j/20-1/200-1/20-j/2-1/20-j/20] 

  • Hybrid rat-race

    The S-parameters matrix for the Hybrid rat-race is:

    [0−j/20−j/2−j/20j/200j/20−j/2−j/20−j/20] 

  • Magic tee

    The S-parameters matrix for the Magic tee is:

    [0011001−111001−100]2

The Divider block uses the ispassive function to test the passivity of the S-parameters matrix.

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.

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.

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.

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.

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 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.

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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