SPST

Single pole single throw switch

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Libraries:
RF Blockset / Circuit Envelope / Junctions

Description

The SPST block models a single pole single throw switch. This block supports both reflective and absorptive switches. The control signal is a Simulink^® signal connected to the Vctl port of the block. The control signal specifies when the output port, Out, transmits the input signal at the input port, In.

Ports

Input

Vctl — Simulink control signal

scalar

Simulink control signal, specified as a scalar.

Data Types: double

Parameters

Threshold voltage — Threshold voltage

0 (default) | positive scalar

Threshold voltage of the switch, specified as a positive scalar in volts.

Characterization — Characterization

Resistance (default) | Insertion loss

Characterization of the switch, specified as Resistance or Insertion loss.

On resistance — On resistance

10 (default) | positive scalar

On resistance value of the switch, specified as a positive scalar in ohms. On resistance is available when you set Characterization to Resistance.

Off resistance — Off resistance

1e-6 (default) | positive scalar

Off resistance value of the switch, specified as a positive scalar in ohms. Off resistance is available when you set Characterization to Resistance.

Insertion loss (dB) — Insertion loss

1 (default) | scalar

Insertion loss value of the switch, specified as a positive scalar in decibels. Insertion loss (dB) is available when you set Characterization to Insertion loss.

Isolation (dB) — Isolation value

70 (default) | scalar

Isolation value of the switch, specified as a scalar in decibels. Isolation (dB) is available when you set Characterization to Insertion loss.

Loading type — Loading type

Reflective (default) | Absorptive

Loading type of the switch, specified as Reflective or Absorptive.

Port terminations (Ohm) — Port terminations

50 (default) | scalar | vector of size 1-by-2

Port terminations that match the impedance conditions of the SPDT switch, specified as a scalar in ohms or a vector of size 1-by-2 with each element unit in ohms. If the value is a scalar, then the input port and the output port impedances are the same. If the value is a vector, the first value is the matching required at the inport of the block and the second values is the matching required at the output port.

Note

Port terminations is available when you set the SPST switch Characterization to Insertion loss or when you set Loading type to Absorptive.

Ground and hide reference terminals — Ground RF circuit terminals

on (default) | off

Select this parameter to internally ground and hide the reference terminals. To expose the reference terminals, clear this parameter. By exposing these terminal, you can connect them to other parts of your model.

More About

Resistance Characterization

• If the control voltage is less than the threshold voltage, then the block attenuates the signal using the resistance value specified in Off resistance. The block places the resistor between the positive input and output terminals.

• If the control voltage is greater than or equal to the threshold voltage, then the block attenuates the signal using the resistance value specified in On resistance.

• When the switch loading type is absorptive, and the control voltage is less than the threshold voltage, the block places internal shunt resistors at the input and output ports. The shunt resistor values provide matching terminations at the input and output ports.

Insertion Loss Characterization

• If the control voltage is less than the threshold voltage, calculate the off resistance value using the Isolation (dB) value.

• If the control voltage is greater than or equal to the threshold voltage, calculate the on resistance value using the Insertion loss (dB) value.

• When the switch loading type is absorptive, and the control voltage is less than the threshold voltage, the block places internal shunt resistors at the input and output ports. The shunt resistor values provide matching terminations at the input and output ports.

Voltage–Current Relationship

The voltage–current relationship at the terminals depends on the relationship between control voltage, V_ctl, and the threshold voltage, V_threshold.

• If V_ctl < V_threshold

  $$\begin{array}{l}{I}_{in}=V_{inout}.G_{off}^{}+V_{in}.G_{Z01}\\ I_{out}=-V_{inout}.G_{off}+V_{out}.G_{Z02}\end{array}$$

• If V_ctl ≥V_threshold

  $$\begin{array}{l}{I}_{in}=V_{in1}{G}_{off}+V_{in2}{G}_{on}\\ I_1=-V_{in1}{G}_{off}+V_1{G}_{Z01}\\ I_2=-V_{in2}{G}_{on}\end{array}$$

• G_on, G_off — On and off path conductances

• G_Z01, G_Z02 — Shunt port conductances

Version History

Introduced in R2015b