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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.

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 the directional coupler is:
$[\begin{matrix} r_{l} & i_{l} & i_{s} & c \\ i_{l} & r_{l} & c & i_{s} \\ i_{s} & c & r_{l} & i_{l} \\ c & i_{s} & i_{l} & r_{l} \end{matrix}]$
where:
- r_l = 10^{(-returnloss/20)}
- i_l = j10^{(-insertionloss/20)}
- i_s = 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:
$[\begin{matrix} 0 & α & 0 & j β \\ α & 0 & j β & 0 \\ 0 & j β & 0 & α \\ j β & 0 & α & 0 \end{matrix}]$
where:
- |α| ≤ 1 = power transmission coefficient
- β = sqrt(1– α*α)
coupler antisymmetrical
the s-parameters matrix for the coupler antisymmetrical is:
$[\begin{matrix} 0 & α & 0 & β \\ α & 0 & - β & 0 \\ 0 & - β & 0 & α \\ β & 0 & α & 0 \end{matrix}]$
where:
- |α| ≤ 1 = power transmission coefficient.
- β = sqrt (1– α*α)
hybrid quadrature (90deg)
the s-parameters matrix for the hybrid quadrature(90deg) is:
$[\begin{matrix} 0 & - j / \sqrt{2} & 0 & - 1 / \sqrt{2} \\ - j / \sqrt{2} & 0 & - 1 / \sqrt{2} & 0 \\ 0 & - 1 / \sqrt{2} & 0 & - j / \sqrt{2} \\ - 1 / \sqrt{2} & 0 & - j / \sqrt{2} & 0 \end{matrix}]$
hybrid rat-race
the s-parameters matrix for the hybrid rat-race is:
$[\begin{matrix} 0 & - j / \sqrt{2} & 0 & - j / \sqrt{2} \\ - j / \sqrt{2} & 0 & j / \sqrt{2} & 0 \\ 0 & j / \sqrt{2} & 0 & - j / \sqrt{2} \\ - j / \sqrt{2} & 0 & - j / \sqrt{2} & 0 \end{matrix}]$
magic tee
the s-parameters matrix for the magic tee is:
$\frac{[\begin{matrix} 0 & 0 & 1 & 1 \\ 0 & 0 & 1 & - 1 \\ 1 & 1 & 0 & 0 \\ 1 & - 1 & 0 & 0 \end{matrix}]}{\sqrt{2}}$

the divider block uses the 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 | three-tuple

reference impedance of coupler, specified as a scalar or three-tuple. the default value is 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

model ideal frequency-凯发k8网页登录

description

examples

modeling rf front end in radar system simulation

parameters

select component — coupler type directional coupler (default) | coupler symmetrical | coupler antisymmetrical | hybrid quadrature (90 deg) | hybrid rat-race | magic tee

coupling (db) — fraction of input signal power coupled to output port 0 (default) | nonnegative and real scalar

dependencies

directivity (db) — ratio of power at coupled port to power at isolated port inf (default) | nonnegative and real scalar

dependencies

insertion loss (db) — loss of signal power between input and output ports inf (default) | nonnegative and real scalar

dependencies

return loss (db) — loss of signal power due to impedance mismatch inf (default) | nonnegative and real scalar

dependencies

power transmission coefficient — transmitted signal power 0 (default) | real scalar

dependencies

reference impedances (ohm) — reference impedance of coupler 50 (default) | positive scalar | three-tuple

ground and hide negative terminals — ground rf circuit terminals on (default) | off

version history

see also

wechat

select component — coupler type
`directional coupler` (default) | `coupler symmetrical` | `coupler antisymmetrical` | `hybrid quadrature (90 deg)` | `hybrid rat-race` | `magic tee`

coupling (db) — fraction of input signal power coupled to output port
0 (default) | nonnegative and real scalar

directivity (db) — ratio of power at coupled port to power at isolated port
`inf` (default) | nonnegative and real scalar

insertion loss (db) — loss of signal power between input and output ports
`inf` (default) | nonnegative and real scalar

return loss (db) — loss of signal power due to impedance mismatch
`inf` (default) | nonnegative and real scalar

power transmission coefficient — transmitted signal power
0 (default) | real scalar

reference impedances (ohm) — reference impedance of coupler
`50` (default) | positive scalar | three-tuple

ground and hide negative terminals — ground rf circuit terminals
`on` (default) | `off`