# spiralInductor

Create spiral inductor in four different shapes

## Description

Use the spiralInductor object to create a spiral inductor in one of four different shapes: square, circle, hexagon, or octagon. The spiral inductor is a two-port planar inductor with a single or multiple dielectric layers. A turn in a spiral inductor is the length of a complete 360-degree revolution. Spiral inductor filaments have uniform spacing and width throughout the structure. Spiral inductors are an integral part of many radio-frequency and microwave circuits, acting as resonant elements or chokes. The inductor feed can be configured in one of the following two ways:

Note

This PCB object supports behavioral modeling. For more information, see Behavioral Models. To analyze the behavioral model for a spiral inductor, set the Behavioral property in the sparameters function to true or 1

• The input and output ports are punched through at the same layer.

• The input port is routed out from the layer below the inductor by a via hole. The output port is extended to the end of the dielectric in the same layer.

## Creation

### Description

example

inductor = spiralInductor creates a square spiral planar inductor. The default properties are for a resonant frequency of 600 MHz.

example

inductor = spiralInductor(Name=Value) sets Properties using one or more name-value arguments. For example, spiralInductor(SpiralShape="Octagon") creates an octagonal spiral inductor. Properties not specified retain their default values.

## Properties

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Shape of the spiral inductor, specified as either "Square", "Circle", "Hexagon", or "Octagon".

Example: inductor = spiralInductor(SpiralShape="Circle")

Data Types: string | char

Inner diameter of the polygon along the edge in meters, specified as a positive scalar.

Example: inductor = spiralInductor(InnerDiameter=8.0000e-04)

Data Types: double

Strip width in meters, specified as a positive scalar.

Example: inductor = spiralInductor(Width=3.8000e-04)

Data Types: double

Distance between the strips in meters, specified as a positive scalar.

Example: inductor = spiralInductor(Spacing=3.8000e-04)

Data Types: double

Number of turns in the spiral inductor, specified as a positive scalar. You can specify a minimum of 1 turn and a maximum of 12 turns. One turn length is the length of a complete 360-degree revolution.

Example: inductor = spiralInductor(NumTurns=6)

Data Types: double

Height from the ground plane to the inductor in meters, specified as a positive scalar.

Example: inductor = spiralInductor(Height=0.0056)

Data Types: double

Length of the ground plane in meters, specified as a positive scalar. This object does not support infinite ground plane length.

Example: inductor = spiralInductor(GroundPlaneLength=0.046)

Example: double

Width of the ground plane in meters, specified as a positive scalar. This object does not support infinite ground plane width.

Example: inductor = spiralInductor(GroundPlaneWidth=0.046)

Example: double

Type of dielectric material used as a substrate, specified as a dielectric object. The default value is a dielectric object with these properties:

• Name{'RTDuroid','RTDuroid','RTDuroid'}

• EpsilonR[3.66,3.66,3.66]

• LossTangent[0.0013,0.0013,0.0013]

• Thickness[0.508e-3,0.508e-3,0.508e-3]

Example: d = dielectric("FR4"); inductor = spiralInductor(Substrate=d)

Data Types: string | char

Type of metal used in the conducting layers, specified as a metal object.

Example: m = metal("PEC"); inductor = spiralInductor(Conductor=m)

Data Types: string | char

## Object Functions

 charge Calculate and plot charge distribution current Calculate and plot current distribution feedCurrent Calculate current at feed port getZ0 Calculate characteristic impedance of transmission line inductance Calculate inductance layout Plot all metal layers and board shape mesh Change and view mesh properties of metal or dielectric in PCB component shapes Extract all metal layer shapes of PCB component show Display PCB component structure or PCB shape sparameters Calculate S-parameters for RF PCB objects

## Examples

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Create and view a default spiral inductor.

inductor = spiralInductor
inductor =
spiralInductor with properties:

SpiralShape: 'Square'
InnerDiameter: 5.0000e-04
Width: 2.5000e-04
Spacing: 2.5000e-04
NumTurns: 4
Height: 0.0010
GroundPlaneLength: 0.0056
GroundPlaneWidth: 0.0056
Substrate: [1x1 dielectric]
Conductor: [1x1 metal]

show(inductor)

Create and view a two-turn octagonal spiral inductor.

inductor = spiralInductor(SpiralShape="Octagon",NumTurns=2);
show(inductor)

Measure the inductance of the inductor.

figure
inductance(inductor,600e6)

ind = inductance(inductor,600e6)
ind = 1.0547e-08

Create a spiral inductor using gold as the conductor.

inductor = spiralInductor;
inductor.Conductor = metal("Gold");
show(inductor)

Compute and plot the behavioral S-parameters of the inductor at 600 MHz.

spar = sparameters(inductor,600e6,Behavioral=true);
rfplot(spar)

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## References

[1] Beeresha, R.S., A.M. Khan, and H.V. Manjunatha Reddy. “The Design and EM-Simulation of Square Spiral Inductor Using Simple Equations.” Materials Today: Proceedings 5, no. 4 (2018): 10875–82. https://doi.org/10.1016/j.matpr.2018.05.074.

[2] Mohan, S.S., M. del Mar Hershenson, S.P. Boyd, and T.H. Lee. “Simple Accurate Expressions for Planar Spiral Inductances.” IEEE Journal of Solid-State Circuits 34, no. 10 (October 1999): 1419–24. https://doi.org/10.1109/4.792620.

## Version History

Introduced in R2021b