Attenuator designer
Design a T or π resistor pad, then check its attenuation, match and power dissipation.
E12 / E24 select standard resistor values. Attenuation and match update for those parts; tolerance is set separately in More measurements.
Exact calculated values
- R1 = R3 · series, each
- 16.61 Ω
- R2 · shunt
- 66.93 Ω
- Achieved attenuation
- 6 dB
- Input / output match
- Ideal match · within numerical precision
More measurements
Power & resistor dissipation
Optional. Power the source would deliver to a matched Z₀ load.
- Delivered to the Z₀ load
- 14 dBm
- Delivered load power
- 25.12 mW
- Total pad dissipation
- 74.88 mW
Bars share a 0–100% scale of the available source power. Each row corresponds to the circuit above.
These are nominal dissipations, not recommended resistor ratings or tolerance worst cases. Select ratings with suitable power, voltage, pulse and temperature derating.
Resistor tolerance check
Optional. Use 0–20%; the same limit is applied independently to each resistor.
- Minimum attenuation
- 5.94 dB
- Maximum attenuation
- 6.06 dB
- Worst input return loss
- 48.49 dB
- Worst output return loss
- 48.49 dB
Checks all eight high/low resistor combinations around the selected values, with fixed Z₀ source and load. These bound attenuation and worst port return loss for this positive-resistor model; they do not describe a probability distribution or include parasitics.
Calculated values & numerical check
- Exact R1 = R3
- 16.61 Ω
- Exact R2
- 66.93 Ω
- Attenuation deviation from target
- Within numerical precision
- Input impedance
- 50 Ω
- Output impedance
- 50 Ω
- Calculated input return loss
- Ideal match within numerical precision
- Calculated output return loss
- Ideal match within numerical precision
Opposite port terminated in Z₀; this symmetric pad has the same match at both ports. Raw residuals in the copied calculation check numerical consistency, not hardware performance.
Model & assumptions
The T and π networks attenuate a signal while matching equal real source and load resistances . Convert the positive target attenuation in dB to the matched input-to-output voltage ratio :
The voltage factor uses 20 because power is proportional to voltage squared for equal resistances. Greater attenuation gives a larger .
For a T pad, each of the two series resistors has value and the centre shunt resistor has value . With in ohms, their ideal values in ohms are:
For a π pad, there is one series resistor between two equal shunt resistors . Their ideal values are:
The circuit labels R1–R3 identify the actual positions. After resistor rounding, the tool recalculates reflection and attenuation. Realized attenuation compares delivered load power with available source power, so it includes power reflected as well as dissipated.
Tolerance checks evaluate all eight combinations of the three resistors’ upper and lower endpoints. The nominal dissipation bars use each resistor’s power divided by available source power, on a common 0–100% scale; delivered and reflected power account for the remainder. The resistor shares do not sum to 100%. Each resistor needs its own power rating, with temperature and pulse derating; calculated dissipation is not a rating. Package and layout parasitics and frequency dependence are excluded.
For example, a 6 dB, 50 Ω T pad needs approximately 16.61 Ω in each series arm and 66.93 Ω in the shunt arm. With 100 mW available from the source, the ideal load receives approximately 25.12 mW.
Does a result look wrong? Report a calculation issue
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