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Planar Spiral Inductor Calculator

A Planar Spiral Inductor Calculator based on "Lumped Elements for RF and Microwave Circuits" by Inder Bahl.

Main purpose of this calculator is to compare Inductance, Q and resonant frequency and how they are scaled with inductor parameters. It's not very accurate in absolute sense. From limited 3d EM simulations, the inductance is fairly accurate (within 5-10%). But, inductor Quality factor (Q) is overly optimistic. 3D EM simulation shows Q about half or less of the calculated values. Resonant frequency is typically lower than calculated, by about 10%. The inductor is meant to be driven differentially, and effects of the airbridge and terminals are neglected.

Conditions: W>H/20.

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Distance units: 

Substrate Height, H  
Winding trace Width, W  
Winding trace Thickness, T (1oz=1.4mil)
Inter-winding gap, S  
Outer inductor diameter, Do  
Dielectric Constant, er (FR4: 4.2-4.8)
Metal conductivity s (S/m) (gold:4.10e7, copper:5.96e7)
Number of turns, N  
Test frequency, Freq GHz
Inner inductor diameter, Di  
Low frequency inductance nH
Effective Inductance @ Freq nH
Inductor Quality Factor @ Freq  
Resonance frequency GHz