detailed presentation on momentum - part 2 of...
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Momentum Seminar momentum_01_03 Page 1
Details of Momentum
•Solution process
•Select Mode
•Substrate definition
•Port Setup
•Mesh Generation
•Planar Solve
•Display Results
Momentum Seminar momentum_01_03 Page 2
Defining Mesh ParametersMesh Setup Control
Global mesh is the default.But you have choices.
In general, smallpatterns are moreaccurate but takemore time to solve.
Momentum Seminar momentum_01_03 Page 3
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.
Momentum Seminar momentum_01_03 Page 4
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...
Momentum Seminar momentum_01_03 Page 5
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)
Momentum Seminar momentum_01_03 Page 6
Edge Mesh Accuracy
Momentum Seminar momentum_01_03 Page 7
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
Momentum Seminar momentum_01_03 Page 8
Using Momentum
•Solution process
•Select Mode
•Substrate definition
•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
Momentum Seminar momentum_01_03 Page 9
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.
Momentum Seminar momentum_01_03 Page 10
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)
Momentum Seminar momentum_01_03 Page 11
Using Momentum
•Solution process
•Select Mode
•Substrate definition
•Port Setup
•Mesh Generation
•Planar Solve
•Display Results
More on this in the next section…
Momentum Seminar momentum_01_03 Page 12
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 Seminar momentum_01_03 Page 13
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)
Momentum Seminar momentum_01_03 Page 14
RFIC/MMIC Applications
Momentum
Mesh: 20 cells/wavelength, 5 GHz Frequencies: 7
Matrix size : 274 Process size : 10.29 MB User time : 11m 09s
Momentum RF Mesh: 20 cells/wavelength, 5 GHz Frequencies: 7
Matrix size : 35 Process size : 3.33 MB User time : 1m 39s
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)
Momentum Seminar momentum_01_03 Page 15
RFIC / MMIC Applications
Momentum Momentum RF Measurements
Momentum
Mesh: 20 cells/wavelength, 50 GHz Frequencies: 12
Matrix size : 221 Process size : 6.32 MB User time : 2 m 03 s
Momentum RF Mesh: 20 cells/wavelength, 50 GHz Frequencies: 10
Matrix size : 203 Process size : 4.50 MB User time : 0 m 26 s
[1] 100 um GaAs
GND
AIR
0.76mm
1.65mm
Rule of thumb: freq < 83.3 GHzPC-NT Pentium II workstation (330 MHz)
Momentum Seminar momentum_01_03 Page 16
Microwave Lowpass Filter (Stripline)
Momentum
Mesh: 20 cells/wavelength, 15 GHz Frequencies: 20
Process size : 18.07 MB User time : 36 m 07 s
Momentum RF
Mesh: 20 cells/wavelength, 15 GHz Frequencies: 15
Process size : 12.29 MB User time : 2 m 21 s
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)
Momentum Seminar momentum_01_03 Page 17
RF Board Power/Ground
Momentum Momentum RF Measurements
[1] 59 mil
AIR
GND
FR4
50.8mm
76.2mm
P1 P2
50.8mm
76.2mm
P1 P2
Rule of thumb: freq < 1.63 GHz
Momentum RF
Process size : 15.0 MB User time : 4 m 41 s
Momentum RF
Process size : 17.0 MB User time : 5 m 33 s
Momentum
Process size : 20.2 MB User time : 50 m 29 s
Momentum
Process size : 20.8 MB User time : 30 m 42 s
PC-NT Pentium II workstation (330 MHz)
Momentum Seminar momentum_01_03 Page 18
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
Matrix size : 733 Process size : 59.35 MB User time : 48m 24s
Speed & Capacitymemory: 3 xspeed: 14 x
35.60 mm
43.67 mm
[1] 30 mil
AIR
GND
FR4
PC-NT Pentium II workstation (330 MHz)
FYI
Momentum Seminar momentum_01_03 Page 19
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
Rule of thumb: freq < 13.8 GHz
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
PC-NT Pentium II workstation (330 MHz)
FYI
Momentum Seminar momentum_01_03 Page 20
Microwave Applications
Momentum
Mesh: 10 cells/wavelength, 20 GHz Frequencies: 18
Matrix size : 181 Process size : 2.92 MB User time : 1 m 02 s
Momentum Momentum RF
Momentum RF
Mesh: 10 cells/wavelength, 20 GHz Frequencies: 14
Matrix size : 122 Process size : 2.13 MB User time : 0 m 09 s
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
Momentum Seminar momentum_01_03 Page 21
Microwave Applications
Momentum
Mesh: 20 cells/wavelength, 7 GHz Frequencies: 27
Process size : 8.26 MB User time : 7 m 53 s
Momentum RF
Mesh: 20 cells/wavelength, 7 GHz Frequencies: 25
Process size : 4.75 MB User time : 0 m 29 s
5.21mm
24.82 mm
Momentum Momentum RF
mag(S21)
mag(S11)
Rule of thumb: freq < 5.9 GHz
[1] 25 mil Alumina
GND
[2] 185 mil AIR
PC-NT Pentium II workstation (330 MHz)
FYI
Momentum Seminar momentum_01_03 Page 22
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
Momentum Seminar momentum_01_03 Page 23
Digital Application
isolated trace
port 1
port 2
0.4 GHz
output
S(1,1)
isolated trace
S(1,2)
isolated trace
FYI
Momentum Seminar momentum_01_03 Page 24
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
Momentum Seminar momentum_01_03 Page 25
Digital Application
harmonic signal 2.33 GHz
harmonic signal is coupled to neighboring traces and spread around the board
FYI
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