PCB Feeds

R2026b

Since R2026b

This topic discusses PCB feed basics and the specific ways to set up feeds in a PCB stack.

Basic Feed Concepts

Feeds provide signal input and output interfaces to printed circuit boards (PCB). Feed ports on the PCB may be placed along a board edge, or within the interior of the board (away from any edge). Feeds can be implemented on single layer and multi-layer PCBs. From the feed port the signal will be routed internally within a PCB layer. In a multi-layer board the signal may also be routed between various layers through conductive vias.

There are two fundamental types of signal feeds, whether serving as an input or output port:

Single-ended (also called unbalanced) feed.
A single-ended feed consists of one signal line and a ground return. In a single-ended configuration the signal is measured between the signal trace and the ground return. The most common type of single-ended PCB feed is a microstrip line, that consists of a signal trace, usually on the top board layer, and a ground plane on a layer directly below the top layer.
Differential (also called balanced) feed.
A differential feed consists of two coplanar signal lines. An optional ground plane is included to control impedance and provide shielding. The signal is measured across the two signal lines, that are 180 degrees out of phase. A common differential configuration feed implementation is an edge-coupled differential stripline where two parallel lines share identical electrical and physical characteristics.
Differential feeds provide excellent immunity to external ingress of electromagnetic signals, including noise, because coupled external signals result in a common mode signal across the pair of lines that cancel out when measured across the pair. Differential feeds reduce unintentional radiation of internally generated signals because the external electromagnetic fields from the pair of lines cancel each other, resulting in EMI reduction, and improved signal integrity within the PCB.

Location-Defined Feeds

By default, feeds in a pcbStack object only show locations of signal feed ports. The type of feed at a port is automatically set up by the software based on the geometry of the object. The feed details are not revealed. The advantage of using location-based feeds is that you do not have to select the appropriate feed type, and manually create the feed geometry. When using location-defined feeds, any analysis of a PCB, such as S-parameters, employs the automatically created feed. To use a default feed set the FeedFormat property to "FeedLocations" in the pcbStack object.

Note

When starting with an antenna catalog object you must first convert the object to a PCB stack object by entering pcb = pcbStack(ant) in the command line, where "ant" is the name of the catalog object.

User-Defined Feeds

The other way to work with feeds is to manually create feeds using available feed definition objects within the pcbStack object .The advantage of this method is that you can manually select the feed type and control its detailed geometry. Experience with PCB feed applications and geometry is recommended to efficiently use this method.

To create user-defined feeds:

The FeedFormat property must be set to "FeedDefinition" in the pcbStack object.
Use the FeedDefinitions property to set the feed type in the pcbStack object. There is a choice of six feed types that can be configured. The choice of which feed type to use depends on the application of the PCB antenna.
Configure the chosen feed type from within the individual feed-type object.

For further details on creating user-defined PCB feeds, refer to individual feed-type reference pages.

This table shows typical applications for feed definitions supported in the pcbStack object.

Feed Type and Applications

Feed Type	Description	Applications
`ArbitraryFiniteGapFeed`	Defines a lumped feed across arbitrarily shaped finite gaps between multiple metal regions, enabling the specification of potential relationships among the conductors	Coplanar-Waveguide (CPW)-fed monopole and slot antennas Multi-ground antenna feeds Differential MIMO antenna feeds Complex multi-port PCB antenna structures with multiple signal and ground conductors
`ProbeFeed`	Models a vertical conductive pin or via that excites the PCB by connecting a signal layer to a reference ground	Probe-fed microstrip patch antennas, stacked patch antennas, planar Inverted-F antenna (PIFA) structures Antennas where the feed is brought from the ground plane through a via to the radiator
`EdgeFeed`	Excites the structure from the edge of the PCB, typically representing a microstrip or stripline launch	Inset-fed microstrip patch antennas, edge-fed rectangular and circular patch antennas PCB trace antennas fed directly from a microstrip line Vivaldi and tapered-slot antennas where excitation originates at the PCB edge
`DeltaGapFeed`	Applies an idealized lumped excitation across an infinitesimally small gap between two conductors	Dipole PCB antennas Bow-tie antennas Folded dipoles Slot antennas excited across a narrow feed gap General balanced PCB radiator structures
`CoaxialFeed`	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)	High-fidelity modeling of probe-fed patch antennas SMA-fed patch antennas Via-fed PCB antennas requiring accurate feed parasitics Correlation of simulation with measured coax-fed prototypes
`FiniteGapFeed`	Represents a lumped excitation across a physically finite gap between conductors for improved realism over delta‑gap feeds	Slot antennas with finite-width excitation Aperture-coupled patch antennas (feed aperture region) Internal antenna ports in PCB antenna structures Differentially excited PCB radiators requiring physical feed width representation

Arbitrary Finite Gap Feed

The ArbitraryFiniteGapFeed is a type of contact feed used for complex configurations that include multiple signals and multiple grounds. The figure shows an exploded view of an arbitrary finite gap feed. The captions correspond to the properties that you can set.

Probe Feed

The ProbeFeed is a type of contact feed used for patch antennas, or where a vertical PCB feed configuration is required. Feed point is placed anywhere in the antenna element, which facilitates impedance matching. Figures show probe placement, and feed properties.

Edge Feed

The EdgeFeed is a type of contact feed used when an edge connection to a PCB layer is required. An edge feed is used with either microstrip elements, or stripline elements with two grounds.

The figure shows an exploded view of an edge feed to a stripline element with two grounds. Captions in the figure correspond to the feed properties that you can set.

Delta Gap Feed

The DeltaGapFeed is a type of contact feed used for balanced structures, dipole antennas and lumped loads.

Captions in the figure show the properties that you can set.

Coaxial Feed

The CoaxialFeed is a type of direct contact feed. It is similar to the probe feed, but provides higher resolution. The figure shows an exploded view of a coaxial feed. Signal is fed to the element layer using a via, which runs from the center conductor of a coaxial cable to the via's pad. The via's antipad isolates the signal from ground. Coaxial ground runs to the ground layer. Captions in the figure correspond to feed properties that you can set.

The figure provides a detailed coaxial feed view.

Finite Gap Feed

The FiniteGapFeed is a type of contact feed used for coplanar feed applications. The figure shows a single-gap configuration. The captions correspond to the properties that you can set.