1. Microwave Passives
Anurag Nigam

2. NatTel Microsystems Pvt. Ltd.
Tutorial 3 E H S I -I E H S
Day1
NatTel Microsystems Pvt. Ltd.

3. NatTel Microsystems Pvt. Ltd.
Lab Objectives
In this lab exercise we will
Modify UMS PH15 Process Substrate to accommodate Air Bridge and Open Substrate at the bottom to simulate distributed ground condition.
Simulate single and two via inductances
Design a small signal tuned gain stage with effect of via inductance included in performance
Design 50Ω and Non 50Ω Planar Lines
Visualize Currents in Planar Lines
NatTel Microsystems Pvt. Ltd.

4. Substrate Definition in ADS
Electrical Properties have been specified in previous presentation
NatTel Microsystems Pvt. Ltd.

5. NatTel Microsystems Pvt. Ltd.
Via For Device Ground
Device Ground Via
Device 60 x 4 um= W
NatTel Microsystems Pvt. Ltd.

6. Via Inductance & Resistance
Performance of Two Via
Performance of Single Via
NatTel Microsystems Pvt. Ltd.

7. Usage of EM Simulated Via in LNA Design
Two Via
Single Via
NatTel Microsystems Pvt. Ltd.

8. NatTel Microsystems Pvt. Ltd.
LNA Gain & Noise Figure
LNA Gain Weakly and Input Match Insertion Loss strongly affects LNA Noise Figure.
Input / Output Match Insertion Loss & Input / Output Mismatch Loss decides LNA Gain
NatTel Microsystems Pvt. Ltd.

9. Source Less, Charge Free Medium & TEM Wave
Maxwell’s Equation In Phasor Form
In Source Free Medium
In Lossless Medium
Implies
Similarly for H
Implies
In Source Free Medium
Implies
Implies
Electric Field is Normal to direction of propagation
propagation constant along
Implies
Magnetic Field is Normal to direction of Electric Field and direction of propagation
NatTel Microsystems Pvt. Ltd.

10. NatTel Microsystems Pvt. Ltd.
Plane of Polarization
Plane in which Electric Field Intensity Vector exists is called Plane of Polarization. Electric Field Intensity vector can be along x-axis and Magnetic Filed Intensity vector can be along y-axis for EM Wave to propagate along positive z-axis. X-axis being vertical, in case shown, the TEM wave is referred to as Vertically Polarized TEM Wave.
Electric Field Intensity vector can be along y-axis and Magnetic Filed Intensity vector can be along negative x-axis for EM Wave to propagate along positive z-axis. Y-axis being vertical, in case shown, the TEM wave is referred to as Horizontally Polarized TEM Wave.
Two Plane Polarized TEM waves- one vertically polarized and other horizontally polarized- with phase difference of 90º between them results in Electrical Field Intensity vector rotating and peak Electric Field Intensity constant. This TEM wave is referred to as Circularly Polarized TEM Wave.
Vertically Polarized TEM Wave
Horizontally Polarized TEM Wave
In case both the plane polarized TEM waves have phase difference other then 90º, the plane of polarization rotates with peak Electrical Field Intensity varying. This TEM wave is referred to as Elliptically Polarized TEM Wave.
Circularly Polarized Wave
Elliptically Polarized Wave
NatTel Microsystems Pvt. Ltd.

11. Wavelength & Propagation Constant
Smallest distance between two equal phase points in space is called Wavelength. This happens when two points are exactly 2π apart in phase
Distance λ
In a lossless charge free medium, wave propagation vector is in same direction as the direction of Propagation, thus their dot product is same as the product of their magnitudes.
Propagation Constant
Propagation Constant is magnitude of Propagation Vector . Propagation Constant refers to angular separation in radians between two points unit distance apart in space along the direction of propagation
1 m = x radian of phase =
Attenuation Constant
Phase Constant
Distance
NatTel Microsystems Pvt. Ltd.

12. Phase Velocity & Characteristic Impedance
Phase Velocity is the velocity with which constant phase point moves in space
Characteristic Impedance of a Medium
Ratio of Electric Field Intensity Magnitude to Magnetic Field Intensity Magnitude at any point in space along the direction of propagation is a constant provided there is no discontinuity along the direction of propagation.
Electric Field Intensity
Magnetic Field Intensity
NatTel Microsystems Pvt. Ltd.

13. Z-directed TEM wave in Lossless Source Free Medium
Maxwell’s Curl Equation1
Maxwell’s Curl Equation2
Using Equation 1 and 2, we can express E and H in xy – plane in terms of E and H along z-direction
Z-directed TEM wave has no z component of E and H. Transverse Components will vanish as well unless relations above are of 0/0 form. This implies
NatTel Microsystems Pvt. Ltd.

14. TEM wave in Lossless Source free Medium along z direction
Propagation Constant
Phase Velocity
Characteristic Impedance
Wavelength
Electric Field Vector
Magnetic Field Vector
NatTel Microsystems Pvt. Ltd.

15. NatTel Microsystems Pvt. Ltd.
Guided Wave
Non-Planar Lines
Two conductors are required for setting up TEM Waves I -I E H S E H S
Twisted Pair Wire
Co-axial Wire
Various Lines supporting TEM Mode of Propagation
Microstrip Line
Coplanar Waveguide
With Ground
Coplanar Waveguide
NatTel Microsystems Pvt. Ltd.

16. Characteristic Impedance of Line & Linecalc
For lossless line, Characteristic Impedance is
where L is series inductance of the line and C is Shunt Capacitance to ground
For any line this relation is true. If ground is moved closer to line, Capacitance to ground increases and Characteristic Impedance of line drops. If line is made narrower, Series Inductance increases and Characteristic Impedance of line increases.
NatTel Microsystems Pvt. Ltd.

17. NatTel Microsystems Pvt. Ltd.
Microstrip Line d T W L
Microstrip Line
Ground Plane
Substrate
Air
Electric & Magnetic Field Configuration H E
Due to finite thickness of line and difference between dielectric constant of substrate & air, Electric Lines of Flux fringe at the edges. This distorts TEM Mode at the edges (Quasi TEM) and increases current density at the edges.
Current Distribution in Microstrip Line
If substrate height is fixed, Capacitance to Ground can not be adequately controlled. Only control that affects Characteristic Impedance of the line is its width. Dimensions of Finite Ground will change characteristic impedance of Microstrip Line due to voltage standing wave pattern set up in Finite Ground Plane.
NatTel Microsystems Pvt. Ltd.

18. NatTel Microsystems Pvt. Ltd.
50 Ω Microstrip Line
Microstrip Line on UMS PH15 Process has slightly different metal stack. Design using Linecalc does consider complex metal stack. We may have to adjust the design.
Microstrip Line Layout in 3D EM Preview
NatTel Microsystems Pvt. Ltd.

19. 50Ω Line Fine Tune & Performance
Microstrip Line Layout
NatTel Microsystems Pvt. Ltd.

20. NatTel Microsystems Pvt. Ltd.
Non- 50Ω Lines
For the substrate used in earlier design, we have to design Microstrip lines with following values of characteristic impedances using Linecalc Program.
DRC Rule EL10 does not allow lines lesser in width than 5 µm on EL Layer. Thus maximum Impedance of a line on this layer is 100Ω.
NatTel Microsystems Pvt. Ltd.

21. NatTel Microsystems Pvt. Ltd.
100Ω Microstrip Line
W=8.2µm, L=842µm
NatTel Microsystems Pvt. Ltd.

22. NatTel Microsystems Pvt. Ltd.
50Ω CPWG Line
DRC Rule EL20a does not allow line spacing lesser than 8 µm for EL Layer.
CPWG Line Layout in 3D EM Preview
NatTel Microsystems Pvt. Ltd.

23. 50Ω Line Fine Tune & Performance
W=7µm, G=8.1µm, L=850µm
NatTel Microsystems Pvt. Ltd.

24. NatTel Microsystems Pvt. Ltd.
Visualizing Currents
Visualization of currents can be used to detect discontinuities visually in the circuit and minimize mismatch losses
NatTel Microsystems Pvt. Ltd.