Single pole multiple throw switch
RF Blockset / Circuit Envelope / Junctions
The SPnT block models a single pole multiple throw switch. This block
supports both reflective and absorptive switches. You can specify two to eight output
ports for the switch. The control signal is a Simulink® signal connected to the
Ctl port of the block. The
control signal specifies which output port transmits the input signal. When the input to
Ctl port is between one and the number of output ports, the
Ctl signal value is rounded to the nearest integer. The output
port that corresponds to the integer value transmits the data. If the rounded
Ctl signal value does not correspond to any of the output ports,
then all the output ports are turned off.
Ctl — Simulink control signal
Simulink control signal, specified as a scalar.
Insertion loss (dB) — Insertion loss of switch
1 (default) | scalar
Insertion loss value of switch, specified as a finite scalar in decibels. Specify an insertion loss value greater than zero but less than the isolation value of the switch. For the equation, see Insertion Loss.
Isolation (dB) — Isolation value of switch
70 (default) | scalar
Isolation value of switch, specified as a scalar in decibels. Specify an isolation value greater than the insertion loss value of the switch. For the equation, see Isolation.
Loading type — Switch type
Absorptive (default) |
Switch type, specified as
Number of outputs — Number of outputs for switch
2 (default) | scalar
Number of outputs for the switch, specified as a scalar. The number of outputs must be greater than or equal to two or less than or equal to eight.
Port terminations (Ohm) — Port terminations
50 (default) | scalar
Port terminations representing matching required at all input and output
ports, specified as a scalar in ohms. If you set the Load
Absorptive, the impedance
seen at all disconnected output ports is the value specified in
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 this terminal, you can connect it to other parts of your model.
Reflective and Absorptive SPnT Switches
If there is no internal resistor connected in parallel to the load when the output terminal is turned off, any incident signal at the output side is reflected back to its source. This type of switch is known as reflective switch.
If there is a matching internal resistor connected in parallel to the load when the output terminal is turned off, any incident signal at the output side is absorbed by the switch. This type of switch is known as an absorptive switch.
Insertion loss is given by the equation:
Isolation is given by the equation:
 Razavi, Behzad. RF Microelectronics. Upper Saddle River, NJ: Prentice Hall, 2011.