CoaxialFeed

R2026b

Create a coaxial feed

Since R2024b

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    Description

    Use the CoaxialFeed object to specify the FeedDefinitions property in a parent pcbComponent object.

    The CoaxialFeed object models a coaxial-style feed as a signal via excited across an annular antipad gap in a ground metal layer (higher-fidelity version of a probe feed).

    Creation

    Syntax

    f1 = CoaxialFeed
    f1 = CoaxialFeed(PropertyName=Value)

    Description

    f1 = CoaxialFeed creates a default CoaxialFeed object.

    f1 = CoaxialFeed(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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    Cross-sectional shape of the feed's via pad, specified as an antenna.Circle object. The pad forms the signal via of the coaxial feed. This shape must correspond exactly to a feature on the pcbComponent metal layer specified by GroundLayers.

    PadShape and AntipadShape must have the same number of edges, and corresponding edges on each shape must be parallel.

    Example: c=antenna.Circle(Radius=0.002);PadShape=c

    Data Types: double

    Cross-sectional shape of the feed's via antipad, specified as an antenna.Circle object. The antipad is the outer ring removed from the metal layer specified by GroundLayers, and it typically surrounds the associated PadShape.

    AntipadShape and PadShape must have the same number of edges, and corresponding edges on each shape must be parallel.

    Note

    The size of the AntipadShape must be greater than the size of its associated PadShape.

    Example: c=antenna.Circle(Radius=0.004);

    Data Types: double

    Layer index for positive excitation site, specified as a positive integer scalar. SignalLayers is the layer index into the pcbComponent layer stack identifying the layer that the feed via reaches from the GroundLayer layer. Only the via terminus lies on this layer, while the pad, antipad, and cross-gap excited edges lie on the GroundLayer layer.

    Example: 2

    Data Types: double

    Layer index for negative excitation site, specified as a positive integer scalar. GroundLayer is the layer index into the pcbComponent layer stack. The entire feed structure consisting the AntipadShape, the PadShape, and the cross-gap excited edges must lie on this layer. Extrude a via from this layer up to the layer specified by the SignalLayers property.

    Example: 4

    Data Types: double

    Examples

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    Open Live Script

    This example shows how to configure a CoaxialFeed object to model a probe feed with an antipad gap for a pcbComponent.

    Create a microstrip patch antenna using a pcbComponent object.

    r1 = traceRectangular('Length', 0.075, 'Width', 0.0357);
r2 = traceRectangular('Length', 0.150, 'Width', 0.0750);
d = dielectric('Air');
p = pcbComponent;
p.BoardShape = r2;
p.BoardThickness = d.Thickness;
p.Layers = {r1, d, r2};

    To expose the FeedDefinitions property set the FeedLocations property to FeedDefinitions.

    p.FeedFormat = 'FeedDefinitions';

    Create two circles: one to define a via shape at the feed site, and the other to define the via's antipad shape at the feed site.

    cPad = antenna.Circle('Center', [-0.0187 0], 'Radius', 0.5e-3, 'NumPoints', 16);
cAntipad = antenna.Circle('Center', [-0.0187 0], 'Radius', 1.5e-3, 'NumPoints', 16);

    Punch out the antipad shape on the ground plane, and add back in the pad shape.

    p.Layers{3} = p.Layers{3} - cAntipad + cPad;

    Instantiate the CoaxialFeed object using cPad and cAntipad as the shapes for the PadShape and AntipadShape properties.

    f = CoaxialFeed('PadShape', cPad, 'AntipadShape', cAntipad, 'SignalLayers', 1, 'GroundLayers', 3);
p.FeedDefinitions = f;

    Show the structure, then calculate and plot its S-parameters over a frequency band.

    figure; show(p);

    Figure contains an axes object. The axes object with title pcbComponent element, xlabel x (mm), ylabel y (mm) contains 7 objects of type patch, surface. These objects represent PEC, feed.

    s = sparameters(p, linspace(1e9, 5e9, 51));
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 R2024b

    See Also

    Objects

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