SPDT

Single pole double throw switch

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Libraries:
RF Blockset / Circuit Envelope / Junctions

Description

The SPDT block models a single pole double 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 which output port transmits the input signal, In.

• If the control voltage is less than the threshold voltage, then the block transfers the input signal to the first output port, Out1.

• If control voltage is greater than or equal to the threshold voltage, then the block transfers the input signal to the second output port, Out2.

Two different resistors regulate the conduction path for transferring the input signal from the input port to either output port.

Examples

100 Watt TR Module for S-Band Applications

Simulate a 100 Watt transmit and receive (TR) module.

• Open Script

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-3

Port terminations that match the impedance conditions of the SPDT switch, specified as a scalar in ohms or a vector of size 1-by-3 with each element unit in ohms. If the value is a scalar, then all three ( input port and the two output port) impedances are same. If the value is a vector, the first value is the matching required at the inport of the block and the other two values must be identical and represent matching required at the two output ports.

Note

Port terminations is available when you set the SPDT 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

Voltage–Current Relationship

The voltage–current relationship at the terminals depends on the relationship between the control voltage of the input Simulink signal, V_ctl, and the Threshold voltage of the switch, V_threshold.

• If V_ctl < V_threshold:

  $$\begin{array}{l}{I}_{in}=V_{in1}.G_{on}^{}+V_{in2}.G_{off}\\ I_1=-V_{in1}.G_{on}\\ I_2=-V_{in2}.G_{off}+V_2.G_{Z02}\end{array}$$

• If V_ctl ≥ V_threshold:

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

Variable	Definition
Iin, I1, I2	Currents into the input terminal and two output terminals, respectively
Vin1, Vin2	Voltages between the input terminal and the output 1 and output 2 terminals, respectively
V1, V2	Voltages at output port 1 and output port 2, respectively
Gon, Goff	On and off path conductances
GZ01, GZ02	Shunt port conductances

Old content from switch block

The voltage–current relationship for the switch, or controlled resistor:

• If V_ctl < V_thres:

  $$I_{res}.R_{off}=V_{res}$$

• If V_ctl ≥V_thres:

  $$I_{res}.R_{on}=V_{res}$$

Where, R_off is the off resistance, R_on is the on resistance of the switch, V_ctl is the input Simulink signal, and V_thres is the Threshold voltage of the switch.

If R_on is less than R_off , and V_ctl is greater than or equal to V_thres, the switch is on.

If R_on is greater than R_off , and V_ctl is greater than or equal to V_thres, the switch is off.

Version History

Introduced in R2015b