Preamp decoupling network calculator

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Source (coil) impedance, Zcoil:
+ j Ω

Output impedance, Zout:
+ j Ω

Amplifier input impedance, Zamp:
+ j Ω

Optional 4th element:

Frequency: Hz

Number of decimals:

Noise matching of any impedance to any impedance. Fill in the fields above, select the type of impedance and press calculate.

Calculate for :


Input impedance, Zin =

T-network, Solution #1:


Skeleton first first first first

T-network, Solution #2:


Skeleton first second third fourth

Π-network, Solution #1:


Skeleton first first first first

Π-network, Solution #2:


Skeleton first first first first

Explanation:

The designed here network transforms the source (coil) impedance, Zcoil, to the optimal noise impedance of the amplifier Zn,opt=Zout and, at the same time, it transforms the amplifier input impedance, Zamp, to the optimal decoupling impedance Zin (high or low), presented to the terminals of the source (coil).

"High impedance" option will design network with highest possible Zin providing maximum decoupling for conventional wire loop coils and series resonance ciols (Rin>Rcoil).

"Low impedance" option will design network with lowest possible Zin providing decoupling for parallel resonance ciols, such as coaxial coils, shielded coils, high impedance coils (Rcoil>Rin).

Skeleton
Designed matching network
Zamp
Zcoil
Zin
Zout

Calculations are based on the equations from the publication below. If you use this calculator, credit must be given by referencing rftoolbox.dtu.dk and the journal paper:

Wenjun Wang, Vitaliy Zhurbenko, Juan Diego Sánchez-Heredia, Jan. H. Ardenkjær-Larsen, “Trade-off between preamplifier noise figure and decoupling in MRI detectors,” Magnetic Resonance in Medicine, Volume 89, Issue 2, October 2022, pp. 859-871.