DeltaGapFeed

R2026b

Create delta gap feed

Since R2026b

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    Description

    Use the DeltaGapFeed object to specify the FeedDefinitions property in a parent pcbStack object.

    The DeltaGapFeed object applies an idealized lumped excitation across an infinitesimally small gap between the two conductors.

    Creation

    Syntax

    f1 = DeltaGapFeed
    f1 = DeltaGapFeed(PropertyName=Value)

    Description

    f1 = DeltaGapFeed creates a default DeltaGapFeed object.

    f1 = DeltaGapFeed(PropertyName=Value) sets object properties using one or more name-value arguments. PropertyName is the property name, and Value is the corresponding value. You can specify several name-value arguments in any order as PropertyName1=Value1,...,PropertyNameN=ValueN. Properties that you do not specify retain their default values.

    example

    Properties

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    Center location of the delta-gap feed, specified as a 1-by-2 vector in meters. The location must lie within the chosen metal layer. The first and second elements are the x- and y-coordinates, respectively. The location must lie within the chosen metal layer.

    Example: [0.01,0.01]

    Data Types: double

    Layer index for the excitation site, specified as a positive integer scalar. SignalLayers is the layer index into the pcbStack layer stack.

    Example: 2

    Data Types: double

    Width of the delta-gap feed, specified as a positive scalar in meters. Typically, the width must be large enough for the feed to reach the metal edges nearest the feed site. Reaching these edges divides the metal layer into two isolated regions, preventing a short-circuit current path that can readily wrap around the feed.

    Example: 0.002

    Data Types: double

    Direction of the current produced by the delta-gap feed, specified as a 1-by-2 unit vector or "auto". The first and second elements contain the x and y values, respectively, of the unit vector. When you specify "auto", the delta-gap feed orients automatically based on its width and the nearest metal layer edges.

    Example: [0.6,0.8]

    Data Types: double | string

    Examples

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    Open Live Script

    Define the dipole length, the conductor width, and the spacing between the two arms.

    L  = 0.15;
Wc = 2e-3;
sp = 6e-3;

    Create the folded dipole from four rectangles using the antenna.Rectangle object: two parallel arms and two shorting bars that join them at each end. Keep both arms continuous. The DeltaGapFeed forms the feed gap in the lower arm. Combine the rectangles to create a single conductor region.

    topArm = antenna.Rectangle(Length=L, Width=Wc, Center=[0,  sp/2]);
botArm = antenna.Rectangle(Length=L, Width=Wc, Center=[0, -sp/2]);
endL = antenna.Rectangle(Length=Wc, Width=sp, Center=[-(L/2 - Wc/2), 0]);
endR = antenna.Rectangle(Length=Wc, Width=sp, Center=[ (L/2 - Wc/2), 0]);
dipole = topArm + botArm + endL + endR;

    Define a Rogers RO4725JXR laminate from the dielectric catalog and set its thickness. This low-loss material is well suited to printed antennas.

    d = dielectric("RO4725JXR");
d.Thickness = 1.6e-3;

    Create the pcbStack object with a board outline larger than the dipole. Assign the conductor and the dielectric as a two-layer stack with no ground plane beneath.

    p = pcbStack;
p.BoardShape = antenna.Rectangle(Length=L*1.2, Width=sp*3);
p.BoardThickness = d.Thickness;
p.Layers = {dipole, d};

    To enable the FeedDefinitions property, set the FeedFormat property to FeedDefinitions.

     p.FeedFormat = 'FeedDefinitions';

    Create the DeltaGapFeed object and orient it at the center of the lower arm. Use the SignalLocations property to set the feed position. Use the SignalWidths property to set the conductor width, and SignalLayers property to place the feed on the conductor layer.

     f = DeltaGapFeed(SignalLocations=[0 -sp/2], ...
     SignalWidths=Wc, SignalLayers=1);
 p.FeedDefinitions = f;

    Display the structure to confirm the folded geometry, the substrate, and the feed location.

    figure
show(p)
title("Printed Folded Dipole Antenna with Delta-Gap Feed")

    Figure contains an axes object. The axes object with title Printed Folded Dipole Antenna with Delta-Gap Feed, xlabel x (mm), ylabel y (mm) contains 4 objects of type patch, surface. These objects represent PEC, feed, RO4725JXR.

    Compute the reflection coefficient. Because a folded dipole presents a high input impedance, reference the S-parameters to 200 Ω rather than the default 50 Ω. On the RO4725JXR substrate, the antenna resonates near 850 MHz.

    s = sparameters(p, linspace(0.6e9, 1.4e9, 71), 200);
figure
rfplot(s)

    Figure contains an axes object. The axes object with xlabel Frequency (GHz), ylabel Magnitude (dB) contains an object of type line. This object represents dB(S_{11}).

    Version History

    Introduced in R2026b

    See Also

    Objects