EMX & PeakView

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LVS check

LVS issue for circuits with customized devices

  • auCdl: Analog and Microwave CDL, is a netlister used for creating CDL netlist for analog circuits

  • auLVS: Analog and Microwave LVS, is used for analog circuit LVS

EMX ports

plain labels

  • pin layer
  • uncheck Cadence pins in Advanced options

rectangle pins

  • drawing layer rectangle pin and specify Access Direction as intended
  • check Cadence pins in Advanced options

The rectangle pins are always selected as driven port while there are only rectangle pin whether Cadence pins checked or not.

check ports used for simulation

use GDS view - EMX

EMX Synthesis Kits

Synthesis is a capability of the EMX Pcell library and uses scalable model data pre-generated by Continuum for a specific process and metal scheme combination.

Synthesis is supported by the Pcells that are suffixed _scalable, and these Pcells have the additional fields and buttons needed for synthesis.

port order (signals)

emxform.ils

type Port order
inductor P1 P2
shield inductor P1 P2 SHIELD
tapped inductor P1 P2 CT
tapped shield inductor P1 P2 CT SHIELD
mom/mim capacitor P1 P2
tcoil P1 P2 TAP
shield tcoil P1 P2 TAP SHIELD
tline P1 P2
differential tline P1 P2 P3 P4

EMX device info

name menu_selection (split with _ ) num_ports modelgen_type generic_model_type plot_fn
Single-ended inductor inductor_no tap_no shield_single-ended 2 inductor inductor EMX_plot_se_ind
Differential inductor inductor_no tap_no shield_differential 2 inductor inductor EMX_plot_diff_ind
Single-ended shield inductor inductor_no tap_with shield_single-ended 3 shield_inductor shield_inductor EMX_plot_se_ind
Differential shield inductor inductor_no tap_with shield_differential 3 shield_inductor shield_inductor EMX_plot_diff_ind
Tapped inductor (diff mode only) inductor_with tap_no shield_differential mode only 3 center_tapped_inductor tapped_inductor EMX_plot_ct_ind
Tapped inductor (common mode too) inductor_with tap_no shield_also fit common mode 3 center_tapped_inductor_common_mode tapped_inductor EMX_plot_ct_ind
Tapped shield inductor (diff only) inductor_with tap_with shield_differential mode only 4 center_tapped_well_inductor_common_mode tapped_shield_inductor EMX_plot_ct_ind
Single-ended cap (symm) capacitor_symmetric single-ended 2 complex_mom_capacitor mom_capacitor EMX_plot_se_cap
Differential cap (symm) capacitor_symmetric differential 2 complex_mom_capacitor mom_capacitor EMX_plot_diff_cap
Single-ended cap (asymm) capacitor_asymmetric single-ended 2 complex_asymmetric_mom_capacitor mom_capacitor EMX_plot_se_cap
Differential cap (asymm) capacitor_asymmetric differential 2 complex_asymmetric_mom_capacitor mom_capacitor EMX_plot_diff_cap
MiM capacitor capacitor_MiM 2 mim_capacitor mim_capacitor EMX_plot_se_cap
Tcoil (simple model) tcoil_simple model 3 tcoil tcoil EMX_plot_tcoil
Tcoil (complex model) tcoil_complex model 3 complex_tcoil complex_tcoil EMX_plot_tcoil
Shield tcoil tcoil_with shield 4 shield_complex_tcoil shield_tcoil EMX_plot_shield_tcoil
Transmission line transmission line_single 2 xline xline EMX_plot_xline
Diff transmission line transmission line_coupled (differential) 4 coupled_xline diff_xline EMX_plot_diff_xline

EMX plot function

EMX's formulation is defined in

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/path/to/EMX/share/emx/virtuoso_ui/emxinterface/emxskill/emxform.ils

EMX import this file at Virtuoso startup, you have to relaunch Virtuoso if you change this file

Single-ended inductor

Both with and without shield apply

  • port-1 impedance when port-2 short

\[ Z_1 = \frac{1}{Y_{11}} \]

  • port-2 impedance when port-1 short

\[ Z_2 = \frac{1}{Y_{22}} \] Then \[\begin{align} L1 &= \frac{Im(Z_1)}{2\pi f} \\ Q1 &= \frac{Im(Z_1)}{Re(Z_1)} \\ L2 &= \frac{Im(Z_2)}{2\pi f} \\ Q2 &= \frac{Im(Z_2)}{Re(Z_2)} \end{align}\]

EMX only plot L1 and Q1

differential impedance

Y parameters to Z parameters

\[\begin{align} |Y| &= Y_{11}*Y_{22} - Y_{12}*Y_{22} \\ \begin{bmatrix} Z_{11} & Z_{12}\\ Z_{21} & Z_{22} \end{bmatrix} &= \begin{bmatrix} \frac{Y_{22}}{|Y|} & \frac{-Y_{12}}{|Y|}\\ \frac{-Y_{21}}{|Y|} & \frac{Y_{11}}{|Y|} \end{bmatrix} \end{align}\]

Then differential impedance is \[ Z_{diff} = Z_{11} - Z_{12} - Z_{21} + Z_{22} \]

image-20220330234833756

similarly, Z parameters to Y parameters \[ \begin{bmatrix} Y_{11} & Y_{12}\\ Y_{21} & Y_{22} \end{bmatrix} = \begin{bmatrix} \frac{Z_{22}}{|Z|} & \frac{-Z_{12}}{|Z|}\\ \frac{-Z_{21}}{|Z|} & \frac{Z_{11}}{|Z|} \end{bmatrix} \] where \[ |Z| = Z_{11}Z_{22} - Z_{12}Z_{21} \]

Differential inductor

Both with and without shield apply

\[\begin{align} L_{diff} &= \frac{Im(Z_{diff})}{2\pi f} \\ Q_{diff} &= \frac{Im(Z_{diff})}{Re(Z_{diff})} \end{align}\]

Center-tapped inductor

\[ Y = \begin{bmatrix} Y_{11} & Y_{12} & Y_{13}\\ Y_{21} & Y_{22} & Y_{23}\\ Y_{31} & Y_{32} & Y_{33} \end{bmatrix} \]

where port order is P1 P2 CT.

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(define (EMX_plot_ct_ind bgui wid what)
  (EMX_plot_aux bgui wid what 3
		'("Differential inductance" "Differential Q")
		'("Henry" "")
		(lambda (ys)
		  (letseq ((z (EMX_differential (nth 0 ys) (nth 1 ys) (nth 3 ys) (nth 4 ys)))
			   (f (xval z))
			   (L (imag z)/(2*3.14159265358979*f))
			   (Q (imag z)/(real z)))
		    `((,L) (,Q))))
		'(("L") ("Q"))))

Assume CT i.e. port 3 in S-parameter is grounded, (z (EMX_differential (nth 0 ys) (nth 1 ys) (nth 3 ys) (nth 4 ys))) obtain differential impedance with \(Y_{11}\), \(Y_{12}\), \(Y_{21}\) and \(Y_{22}\). \[ Y = \begin{bmatrix} Y_{11} & Y_{12}\\ Y_{21} & Y_{22} \end{bmatrix} \] Finally, differential inductance and Q are obtained, shown as below

\[\begin{align} L_{diff} &= \frac{Im(Z_{diff})}{2\pi f} \\ Q_{diff} &= \frac{Im(Z_{diff})}{Re(Z_{diff})} \end{align}\]

image-20220331013735370

Single-ended cap

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(define (EMX_plot_se_cap bgui wid what)
  (EMX_plot_aux bgui wid what 2
		'("Capacitance" "Q" "Capacitance" "Q")
		'("Farad" "" "Farad" "")
		(lambda (ys)
		  (letseq ((z1 1.0/(nth 0 ys))
			   (y12 (nth 1 ys))
			   (z2 1.0/(nth 3 ys))
			   (f (xval z1))
			   (C1 (-1.0/(imag z1))/(2*3.14159265358979*f))
			   (C12 -(imag y12)/(2*3.14159265358979*f))
			   (C2 (-1.0/(imag z2))/(2*3.14159265358979*f))
			   (Q1 -(imag z1)/(real z1))
			   (Q12 (imag y12)/(real y12))
			   (Q2 -(imag z2)/(real z2)))
		    `((,C1) (,Q1) (,C12))))
		'(("Cse") ("Qse") ("C12"))))

We define Port-1 impedance \(Z_1\), Port-2 impedance \(Z_2\)

\[\begin{align} Z_1 &= \frac {1}{Y_{11}}\\ Z_2 &= \frac {1}{Y_{22}} \end{align}\]

Then single-ended cap and Q \[\begin{align} C_1 &= -\frac{1/Im(Z_1)}{2\pi f} \\ Q_1 &= -\frac{Im(Z_1)}{Re(Z_1)} \\ C_2 &= -\frac{1/Im(Z_2)}{2\pi f} \\ Q_2 &= -\frac{Im(Z_2)}{Re(Z_2)} \\ C_{12} &= -\frac{Im(Y_{12})}{2\pi f}\\ Q_{12} &= \frac{Im(Y_{12})}{Re(Y_{12})} \end{align}\]

  • Series equivalent model is used in \(C_1\), \(Q_1\), \(C_2\) and \(Q_2\)
    • \(Z_1 = R + \frac{1}{sC_1}\) and \(Z_2 = R + \frac{1}{sC_2}\)
  • Parallel model is used in \(C_{12}\) and \(Q_{12}\)
    • \(Y_{12} = \frac{1}{R} + sC_{12}\)

EMX plot \(C_{se}\), \(Q_{se}\) and \(C_{12}\), i.e. \(C_1\), \(Q_1\) and \(C_{12}\)

image-20220331020334023

Differential cap

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(define (EMX_plot_diff_cap bgui wid what)
  (EMX_plot_aux bgui wid what 2
		'("Differential capacitance" "Differential Q")
		'("Farad" "")
		(lambda (ys)
		  (letseq ((z (apply EMX_differential ys))
			   (f (xval z))
			   (C (-1.0/(imag z))/(2*3.14159265358979*f))
			   (Q -(imag z)/(real z)))
		    `((,C) (,Q))))
		'(("C") ("Q"))))

First obtain differential impedance, \(Z_{diff}\) then apply series equivalent model \[\begin{align} C_{diff} &= -\frac{1/Im(Z_{diff})}{2\pi f} \\ Q_{diff} &= -\frac{Im(Z_{diff})}{Re(Z_{diff})} \end{align}\]

image-20220331022224865

Tline

Open circuit impedance \(Z_o\), short circuit impedance \(Z_s\) and characteristic impedance \(Z_0\)

\[\begin{align} Z_o &= Z_{11}\\ Z_s &= \frac{1}{Y_{11}}\\ Z_0 &= \sqrt{Z_o*Z_s} \end{align}\]

propagation constant is given as \[\begin{align} \gamma &= \frac{1}{2}\log\left( \frac{Z_0+Z_s}{Z_0-Z_s} \right) \\ &= \alpha + j\beta \end{align}\] where \(\alpha\) is attenuation constant and \(\beta\) is phase constant

The relationship between these parameter and geometry of the transmission line \[\begin{align} Z_0 &= \sqrt{\frac{R+j\omega L}{G+j\omega C}} \\ \gamma &= \sqrt{(G+j\omega C)(R+j\omega L)} \end{align}\] EMX plot the real and imaginary part of \(Z_0\), \(\alpha\) and \(\beta\) of \(\gamma\)

Note EMX plot the absolute value of \(\alpha\) and \(\beta\)

image-20220630215343377image-20220630215418372

image-20220630215630849

Transformer

image-20231015002344332

image-20231015002403566

[IC Prophet GDSII 文件使用和仿真测试说明]

EMX autoplot

using AC simulation, and inductor's parallel model or series model

That is to say: both sp (network parameter) and ac (impedance) can be used to plot inductance, Q value.

usually EMX choose ac method

image-20220501173856442

image-20220501173930035

left 2 figures are used for AC simulation, \(Y_{nn}\) can be obtained conveniently

Foundary model

image-20221217141519947

for single-end capicator \[\begin{align} Q_1 &= -\frac{Im(Z_1)}{Re(Z_1)} \\ &= -\frac{Im(1/Y_{11})}{Re(1/Y_{11})} \\ &= -\frac{Im(Y_{11}^*)/|Y_{11}|^2}{Re(Y_{11}^*)/|Y_{11}|^2} \\ &= \frac{Im(Y_{11})}{Re(Y_{11})} \end{align}\]

So, the EMX model and foundary model is consistent.

Tips

Process file encryption mostly for advanced nodes, like TSMC 16nm Finfet, whose process file is encrypted.

  • Use --key=EMXkey in the EMX Advanced options

GDSviewer has two options

  • EMX: shows the final gds sent to EMX for simulation after it has been processed by EMX
  • Raw: shows the raw gds

If there are port name with the # sign, it means EMX sees a port but it is not in the signal list.

EMX Accuracy

  • Edge mesh: controls layout discretization in the X-Y plane

    • For MoM capacitors, use the edge mesh to be the same as the width of the finger (for example, 0.1um).

  • Thickness: controls layout discretization in the Z dimension

  • 3D metals: skips all 2D assumptions about conductors and their currents and charges

    • If you set 3D metals to * then all metals are treated as 3D
      • For Inductor type structures, only thick metal needs 3D.
      • For MoM, all layers are needed.

Ports entered in Grounds will cause these nets to be grounded; these ports will not show up in the S-parameter result.

Setup Temperature

  • EMX: --temperature=100

ParaView

  • If check ParaView related options when ParaView is not setup properly, EMX simulation stop at Creating mesh... without waring or errors (version 6.2).

Self-Resonant Frequency

image-20240802210109935

\[ f_\text{SRF} = \frac{1}{2\pi \sqrt{LC}} \] The SRF of an inductor is the frequency at which the parasitic capacitance of the inductor resonates with the ideal inductance of the inductor, resulting in an extremely high impedance. The inductance only acts like an inductor below its SRF.

image-20240802205835601

[Understanding RF Inductor Specifications, https://www.ece.uprm.edu/~rafaelr/inel5325/SupportDocuments/doc671_Selecting_RF_Inductors.pdf]

[RFIC-GPT Wiki, https://wiki.icprophet.net/]

reference

Tips on Specifying Ports in EMX [link]

Using 'Cadence pins' as ports with access direction in EMX simulations [[link](Article (20496398) Title: Using 'Cadence pins' as ports with access direction in EMX simulations URL: https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1O3w00000AH2OfEAL)]