detailed presentation on momentum - part 2 of...

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Detailed Presentation on Momentum - Part 2 of 3

Momentum Seminar momentum_01_03 Page 1

Details of Momentum

•Solution process

•Select Mode

•Substrate definition

•Port Setup

•Mesh Generation

•Planar Solve

•Display Results


Defining Mesh ParametersMesh Setup Control

Global mesh is the default.But you have choices.

In general, smallpatterns are moreaccurate but takemore time to solve.


Defining Mesh ParametersGlobal Mesh example with Edge Mesh

1 - Port

2 - Calibration Line

3 - Mesh

4 - Edge Mesh

1

43

2

NOTE: You can view the mesh, ports, and reference linebefore simulating and make adjustments if desired.

Here, the cell size is the same forall parts of the geometry, except forthe edges around each primitive.

The calibration lineis automaticallydrawn when theport is defined -more on this later.


Defining Mesh ParametersPrimitive Mesh example

The center primitive of this geometry has adifferent mesh (50 cells/wavelength) than the twooutside geometries (20 cells/wavelength).

12

You can combine primitive mesh,layer mesh, and global mesh.

Next, let’s discuss ports...


Discretion Error - Longitudinal

• Number of cells/wavelengthdetermines samples used forapproximation of true currents

• Typical cells/wavelength is 20

• 30 or more is fine, but will slow downthe simulation

• Minimum required to retain high-frequency accuracy is 10

• Can retain accuracy AND speed with10 cells/wavelength AND edge mesh

• Remember, can also have layer-specificmeshes (or even object-specificmeshes) which allows finer mesheswhere needed and coarser mesheswhere current density is not as high(such as a finite ground plane)


Edge Mesh Accuracy


Mesh: Momentum versus MomentumRFMomentum RF & Polygon Mesh

•Meshing complex geometries with POLYGONAL cells•Eliminates “slivery” triangles•Eliminates redundant R,L,C elements•Uncompromised accuracy for RF frequencies•Strongly reduced computer memory•Strongly reduced computation time

mesh topology

reduction

reduction 1cell

4cells

10cells


Using Momentum

•Solution process

•Select Mode


•Port Setup

•Mesh Generation

•Planar Solve

•Display Results

B1(r) B2(r) B3(r)

I1

I2

I3

I1 I2 I3

C11

C22

C12

L11

L23

L22

L13L12

L33R22

≤λ/10

Method of Moments

Maxwell’s Equations

Matrix Equation

Equivalent Circuit

[Z].[I]=[V]

[Z] = [R] + jω[L] + 1/jω [C]-1


The Low-frequency Breakdown Problem

• This problem is essentially one of mathematical aspect ratios. When rooftop basisfunctions are used, the interaction matrix contains all of the reactances in a singlematrix. As frequency approaches zero, the inductive reactances approach zero while thecapacitive reactances approach infinity. This results in an ill-conditioned matrix.

• Any tool that uses rooftop functions as the sub-sectional basis functions will have thisproblem.

• Momentum (not Momentum RF) experiences this low-frequency limitation. To helpaccount for this, interpolation is used for three frequencies (in addition to the selectedsweeps): DC, f0, and 2f0. The low-frequency limit (f0, typically in kHz), which isselected in an empirical way and is a function of cell edge lengths and substrate height,increases as cell sizes decrease (resulting in shorter edges).

• Momentum RF alleviates this problem by breaking the rooftop functions intostar and loop basis functions.


MomentumRF & Star-Loop Basis Functions

star basis functionloop basis function

Loop basis functions are solenoidalStar basis functions are irrotational Rooftop basis functions

Star-loop basis functions

db(S11) db(S21)

db(S11) db(S21)

1

2

- give well-conditioned interaction matrix at low frequencies - eliminate LF breakdown of numerical solution - give stable, accurate solutions

down to DC (both magnitude andphase)


Using Momentum

•Solution process

•Select Mode


•Port Setup

•Mesh Generation

•Planar Solve

•Display Results

More on this in the next section…


Momentum Accuracy: A couple of absolutes

• Directly simulated frequency points have –60 dB accuracy. (This noise floor wascharacterized on through-lines. In other words, the observed numerical noise onthose structures is ~ -60 dB. This does not mean that valid results of < -60 dBcan not be obtained for designs with an isolation or other figure of merit that is <-60 dB.)

• For an AFS sweep, the simulated frequency points have –60 dB accuracy while theAFS calculated frequency points have ~ –50 to –60 dB accuracy

• The rest depends on how accurately you can define your problem.

• Here are a few benchmarks…


Momentum

Mesh: 20 cells/wavelength, 3 GHz Frequencies: 14

Matrix size : 218 Process size : 14.13 MB User time : 5 m 14 s

Momentum RF Mesh: 20 cells/wavelength, 3 GHz Frequencies: 10

Matrix size : 56 Process size : 7.59 MB User time : 45 s

(*) Example from National Semiconductor

LTCC Filter Design Momentum Momentum RF Measurements

7.29mm

[1] 25.2 mil LTCC

GND

AIR

[2] 3.6 mil[3] 7.2 mil

dB(S21)

phase(S21)


RFIC/MMIC Applications

Momentum


Matrix size : 274 Process size : 10.29 MB User time : 11m 09s



Momentum Momentum RF Measurements

0.30mm 0.80

mm

[1] 600 um Silicon σ=12.5

GND

AIR

[2] 1.7 um[3] 1.55 um

εr=3.9εr=3.9

Rule of thumb: freq < 176 GHzPC-NT Pentium II workstation (330 MHz)

dB(S11)

dB(S21)


RFIC / MMIC Applications


Momentum





[1] 100 um GaAs

GND

AIR

0.76mm

1.65mm

Rule of thumb: freq < 83.3 GHzPC-NT Pentium II workstation (330 MHz)


Microwave Lowpass Filter (Stripline)

Momentum


Process size : 18.07 MB User time : 36 m 07 s

Momentum RF



mag(S21)

mag(S11)

6.0 mm

25.4mm

Rule of thumb: freq < 5.76 GHz

[1] 31 mil Duroid

GND

[2] 31 mil Duroid

GND Momentum Momentum RF Measurements

PC-NT Pentium II workstation (330 MHz)


RF Board Power/Ground


[1] 59 mil

AIR

GND

FR4

50.8mm

76.2mm

P1 P2

50.8mm

76.2mm

P1 P2


Momentum RF


Momentum RF


Momentum


Momentum




RF Board Application

Momentum

Mesh: 20 cells/wavelength, 1 GHz Ports: 60 Frequencies: 6

Matrix size : 3428 Process size : 152.48 MB User time : 11h 04m 51s

reduced polygonal mesh

rectangular & triangular mesh

Momentum RF Mesh: 20 cells/wavelength, 1 GHz Ports: 60 Frequencies: 6


Speed & Capacitymemory: 3 xspeed: 14 x

35.60 mm

43.67 mm

[1] 30 mil

AIR

GND

FR4


FYI


Packaging Application

S(1,3)

S(1,1)

Momentum

Mesh: 20 cells/wavelength, 5 GHz

Matrix size : 8244 Process size : > 1 GB User time : > 2 days

Momentum RF Mesh: 20 cells/wavelength, 5 GHz

Matrix size : 1354 Process size : 106.57 MB User time : 5h 17m 53s


port 1

port 2

port 3

7.6 mm

7.6 mm

port 4

ref 3

ref 4

S(1,2)

S(1,4)

1 2

4 3

ref 3ref 4

GNDVboard

Vchip

epoxi

FR4


FYI


Microwave Applications

Momentum



Momentum Momentum RF

Momentum RF



radiatedpower

mag(S21)

mag(S11)[1] 25 mil Alumina

GND

AIR

6.65mm

9.90mm

Rule of thumb: freq < 12.5 GHzPC-NT Pentium II workstation (330 MHz)

FYI


Microwave Applications

Momentum



Momentum RF



5.21mm

24.82 mm

Momentum Momentum RF

mag(S21)

mag(S11)


[1] 25 mil Alumina

GND

[2] 185 mil AIR


FYI


Digital Application

full boardisolated trace

port 1

port 2

port 1

port 2

S(1,1)

isolated trace

S(1,2)

isolated trace

MomentumMomentum RF

S(1,1)

full board

S(1,2)

full board

FYI


Digital Application

isolated trace

port 1

port 2

0.4 GHz

output

S(1,1)

isolated trace

S(1,2)

isolated trace

FYI


Digital Application

isolated trace

port 1

port 2

harmonic signal 2.33 GHz

resonanceblocks the signal

no output

S(1,1)

isolated trace

S(1,2)

isolated trace

FYI


Digital Application

harmonic signal 2.33 GHz

harmonic signal is coupled to neighboring traces and spread around the board

FYI

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Printed in USA, May 19, 2003 5989-9598EN

detailed presentation on momentum - part 2 of...

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