sonnet ports rfic - dr. mühlhaus consulting & software...

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Sonnet Ports for RFIC

Volker Mühlhaus

volker@muehlhaus.com

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Box Wall Ports

• Used for planar feed of the circuitfrom the side

• Analysis box is used as portground

• Optional reference plane shift

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Box Wall Ports

• All feed lines coming from the samebox wall are calibrated together in thesame calibration group

• This means we have 4 calibrationgroups for box wall ports, one for eachbox wall

• When used with reference plane shift,coupling between feed lines in thesame calibration group (= coming fromthe same box wall) is removed

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Auto Grounded Ports

3D Editor View

3D Subsection View with „GLG“ enabled

• Used for ports inside where we haveno access to the box side wall

• A via to the bottom of the analysis boxis created internaly by the solverduring analysis, so that current canflow through the port.

• This ground via is not shown in thexgeom model editor

• The ground via can be seen in the 3Dsubsection view with “GLG“ enabled inthe 3D view options

• Each auto grounded port is calibratedindividually, independent of the rest ofthe model

• Parasitic coupling to other ports or tothe circuit is not removed

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Auto Grounded Ports

• Each auto grounded port is calibratedindividually. Parasitic coupling to otherports or to the circuit is not removed.The longer the ground vias are, andthe closer they are together, the morethis parasitic coupling will show inresults.

• Some circuits are sensitive to thisground via coupling, if ports shouldhave high isolation in certain frequencyrange.

• Calibration of individual vias insteadof coupled vias might remove thewrong amout of ground via inductancefor closely coupled vias, see example

• The amount of error can be easilytested with a simplified simulationmodel that has ports only.

Problem with auto grounded portswith thick substrates

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Co-calibrated Ports

• Co-calibrated ports are calibrated withmultiple vias in the same calibrationgroup, so that parasitic coupling insidethis group is removed from results.

• Group is manually assigned by the user!

• The parasitic coupling between differentgroups can not be removed, only withinthe same calibration group.

• The default ground reference is theSonnet analysis box. Ground vias godown to the bottom of the analysis box,or up to the top of the box.

• The technical requirement is that ports inthe same group must be located “on theboundary of an empty rectangle“. Thiscondition is fulfilled for the ports in theupper left example, and also for the co-linear ports in the lower left example.

Two calibration groups A and BEach group contains two ports.

One calibration group

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Assigning the Port Group

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Co-calibrated Port Groups

• Co-calibrated ports are only co-calibrated(in the original sense of the word) whenthey are in the same calibration group!

• The parasitic coupling between differentgroups can not be removed, only withinthe same calibration group.

A-A = same group

A-B = different group

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Same Group

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Different Group

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Different Group

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Same Group

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Different Group

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Multiple Calibration Groups

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Global (Box) Ground

• In most cases, the Sonnet box is usedas the common port reference (globalground).

• This means that ports have to connectto the box, so that current can flow.

• The results are easy to use and easyto interpret.

Cocal ports with global ground.Vias are created by the solver to get box ground access

Box wall port ground reference = analysis box

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Floating Ground

• If we connect a pure series element,with no shunt path, we can also use alocal ground instead of vias to theanalysis box.

• Be careful with mixing local & globalground: Current can NOT flow fromlocal ground ports directly to the global(box) ground.

• Another way to see it: Currents inports 3 & 4 and not independent!

• We can not interpret the S31 path inthis example because they havedifferent grounds.Complete path through the serieselement at ports 3+4 is required.

Floating ground

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Global vs. Floating Ground

• Global ground is the default choice

• Results are easy to understand and use

• For series elements like the ideal RLC components, a floatingground will give the same results as global ground.

• For RFIC with large distance to box ground, local ground might beuseful to avoid very long vias that might create parasitic coupling.

• Ports with local ground have no connection to the Sonnet box,so there is no shunt path to the global (box) ground.

Global groundLocal ground

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RFIC Inductor Coupling

CoCal Global ground

CoCal Local ground

Box wall• RFIC analysis means thick substrate = long ground vias, so that

we better use box wall ports, for planar feed from the side.

• If box wall ports are not possible, then co-calibrated ports are anoption. Depending on the requirements, these are used with globalor local ground:

– Global ground with long vias will give the proper shunt effectsto the substrate, but might suffer from parasitic coupling of thevias in the port feed structure. Ports within the samecalibration group are properly co-calibrated, but there mightbe coupling between different calibration groups.

– Local ground is useful to avoid the long ground vias.However, this will remove the shunt path to the substrate.

• Example on the left side:

– Box wall ports will provide good inductor models and accuratecoupling results

– Co-cal ports with global ground reference will provide goodinductors model, but might suffer from parasitic coupling

– Co-cal ports with local ground reference will provide accuratecoupling results, but the individual inductor models will missthe shunt path to the substrate

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Application Notes

For more application notes, and todownload this powerpoint presentation,

please visit us at:

www.muehlhaus.com/support