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Tee Attenuator Calculator

A 10 dB tee attenuator for 50 Ω uses R1 = 25.97 Ω (series) and R2 = 35.14 Ω (shunt).

By Jasper · Updated

Calculator

PASS10.00 dBE96 10.06 dB

K = 10^(A/20). Matched both ports to Z0. E96 nearest preferred values are re-driven with 20·log10(|Vin/Vout|). A above 60 dB: parasitics dominate; values are theoretical.

Z0 presets:

K
3.162
R shunt
35.14 Ω
R series
25.97 Ω
Zin
50 Ω
Ideal att
10.00 dB
R shunt E96
34.8 Ω
R series E96
26.1 Ω
E96 Zin
49.98 Ω
E96 att
10.06 dB
Return loss
∞
E96 return loss
73.93 dB
  • Pass K: K = 10^(A/20) = 3.16228
  • Pass Input impedance: Zin = 50.0000 Ω

Formula

Voltage ratio

K=10A/20 K = 10^(A/20)

High attenuation

A>60dB A above 60 dB: parasitics dominate; values are theoretical

Preferred values

RE96=nearestE96(R) E96 nearest preferred values

Tee Attenuator Calculator

Rse=Z0K-1K+1,Rsh=2Z0KK2-1 Rse = Z0 (K−1)/(K+1); Rsh = 2 Z0 K/(K²−1)

Variables

Symbol Meaning Unit Typical range Precision Default
A Attenuation dB ≥ 0 dB A must be > 0 4 sig 10 dB
Z0 Characteristic impedance Ω ≥ 0 mΩ 4 sig 50 Ω
Pin Input power (optional) W ≥ 0 µW 4 sig
K Voltage ratio — — 4 sig —
Zin Input impedance Ω — 4 sig —
AdB Ideal attenuation dB — 4 sig —
AE96 E96 attenuation dB — 4 sig —
RL Return loss dB — 4 sig —
Rse Series resistor Ω — 4 sig —
Rsh Shunt resistor Ω — 4 sig —
RseE96 Series E96 Ω — 4 sig —
RshE96 Shunt E96 Ω — 4 sig —
PseIn Input series dissipation W — 4 sig —
Psh Shunt dissipation W — 4 sig —
PseOut Output series dissipation W — 4 sig —
Pload Load power W — 4 sig —

Worked example

10 dB / 50 Ω

Input Value
A · Attenuation 10 dB
Z0 · Characteristic impedance 50 Ω
Output Value
K · Voltage ratio 3.162
AdB · Ideal attenuation 10 dB
AE96 · E96 attenuation 10.06 dB
Zin · Input impedance 50 Ω
Rse · Series resistor 25.97 Ω
Rsh · Shunt resistor 35.14 Ω

6 dB / 50 Ω

Input Value
A · Attenuation 6 dB
Z0 · Characteristic impedance 50 Ω
Output Value
AdB · Ideal attenuation 6 dB
K · Voltage ratio 1.995

How it works

A T-pad is two series resistors and one shunt. The algebra is the dual of the π-pad. Ideal values, nearest E96, and the voltage-ratio back-calc are all on the page. A above 60 dB still prints, with a parasitics warning.

Pitfalls

  • Trusting A above 60 dB on a lumped pad. Parasitics dominate; the numbers are theoretical.
  • Swapping series and shunt relative to a π-pad.
  • Omitting the load when you check attenuation on the bench.

FAQ

What resistors make a 10 dB, 50 Ω T-pad?

About 26.0 Ω series and 35.1 Ω shunt.

Why does A = 0 fail?

K = 1 and the shunt formula divides by K²−1.

When should I use T instead of π?

When you want series elements at the ports, or to reuse a layout that already has a shunt to ground in the middle.

What does E96 attenuation mean?

20·log10(|Vin/Vout|) of the loaded E96 network.

Related

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