### Where To Find This Example

#### AWR Version 15

#### AWR Version 14

### Design Notes

**BRIDGE-T ATTENUATOR**

This project shows a variable bridge-T attenuator implemented with ideal resistors. It demonstrates how to access a data file which contains a table of resistor values for various attenuation states. This method of using a state table to set element parameters can be used for other variable circuits such as phase shifters.

__Overview__

The "Bridge_T" schematic contains the attenuator design. In it, the two resistors labeled "R1" and "R4" determine the attenuation of the circuit. The values of "R1" and "R4" are specified as a matrix in the data file "Resistor_Values", and are easily varied by changing the variable "state" which corresponds to the attenuation states.

__Referencing the Data File__

The matrix represented by the data file "Resistor_Values" is assigned to variable "dfile" in the schematic "Bridge_T" using the **DataFile() **function:

**dfile = DataFile("Resistor_Values")**

Each row of the "dfile" matrix represents an attenuation state, and can be assigned to another variable "Rvector" using the **row()** function:

**Rvector=row(dfile,state)**

where "state" is an index variable corresponding to the row position in the matrix. The values of "R1" and "R4" correspond to the third and fourth column "dfile", and also correspond to the third and fourth element of "Rvector" for each "state":

**R1 = Rvector[3]**

**R2 = Rvector[4]**

By simply changing the value of "state", the values of "R1" and "R4" are both changed concurrently.

See **Text Data File Format **in the Data Files Chapter of the MWO/AO/VSS User Guide for more information regarding the data file format.

__Simulation__

The attenuation results for "state=5" is plotted on graph "Attenuation". To see results for all attenuation states, enable the SWPVAR element.