This calculator allows you to determine the values of the resistors R1 and R2 of a T-shaped attenuator according to the desired attenuation (in dB) and the characteristic impedance of the system. It simplifies the design of balanced attenuators for RF, audio and microwave circuits.
Ideal for RF engineers, technicians and circuit designers looking to adjust signal levels while maintaining precise impedance matching.
Formulas
R1 (Ω) = Z0 × ( (10^(dB/20) – 1) / (10^(dB/20) + 1) )
R2 (Ω) = 2 × Z0 × ( 10^(dB/20) / (10^(dB/10) – 1) )
Explanation of formulas
- Z0 is the characteristic impedance of the system, typically 50 or 75 Ω.
- R1 represents the series resistors placed on either side of the T.
- R2 is the shunt resistor connected between the two branches of the T.
- The equations use logarithmic dB → voltage ratio conversion for accurate sizing.
Calculating the 10 dB T-Attenuator at 50 ohms
Input : Attenuation = 10 dB, Z0 = 50 Ω
Exit :
- R1 = 13.36 Ω
- R2 = 284.1 Ω
Benefits and uses
- Rapid design of symmetrical attenuators for RF signals.
- Maintains perfect impedance matching across the entire bandwidth.
- Useful for reducing signal strength or balancing transmission lines.
- Practical for prototype design and laboratory test benches.