CHEMANDY ELECTRONICS Suppliers of the unusual

Pi Attenuator Calculator

Calculates the resistor values, attenuation, 'impedance', reflection coefficient, VSWR and return loss of a Pi attenuator. This can be built into a FLEXI-BOX and a transmission line PCB is available which easily adapts for this circuit with one simple trimming operation. There is also a selection of suitable RF connectors available.

[pi attenuator formula]

1) Enter the system impedance and required attenuation then then press "Calculate" below to obtain the Ideal resistor values.
System impedance:   Ohms Ideal series resistor:   Ohms
Required attenuation:   dB Ideal shunt resistor:   Ohms

2) Change the calculated resistor values in the amber text boxes below to the nearest Preferred Resistor Values or to those available then press " Calculate" below to get the resulting attenuator parameters.
Preferred series resistor:   Ohms Attenuation:   dB
Preferred shunt resistor:   Ohms Input Impedance:   Ohms
Mismatch Losses:  Included (see note below) Reflection Coefficient: 
Return Loss:   dB

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The calculator uses simple Ohms law calculations, and more comprehensive formulas for Voltage Reflection Coefficient and VSWR which are available at:-

Note: With the Mismatch Losses box ticked the calculator will return an attenuation calculated from the source power in relation to the attenuator output power which is suitable for calculations at RF and Microwave frequencies, particularly if the attenuator is located away from the source at the end of a transmission line. Without the Mismatch Losses box ticked the calculator will return an attenuation calculated from the actual input power to the attenuator in relation to the output power which is more suitable for calculations at audio frequencies. The difference in attenuation with the two methods is only noticeable when there is a significant mismatch.

Mismatch Losses added on 31/12/2012      

This calculator is provided free by Chemandy Electronics in order to promote the FLEXI-BOX

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