Passive Technology Presentation

8/8/2019 Passive Technology Presentation

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www.BesserAssociates.com

Besser Associates, Inc.

Passive Component

Technology

Bob Froelich, Besser Associates

Sponsored byRes-net Microwave, Inc.

Wavetronix Corp.


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In business for over 25 years

Leading supplier of passive components

to 26.5 GHz

Custom & standard parts available

ISO 9001:2000 certified

www.res-netmicrowave.com

Res-net Microwave, Inc.At a Glance

Thinking at a Higher Frequency


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Microwave Resistors & Terminations

DC to 26.5 GHz

Coaxial, Flange, & Rod

Available in AlN & BeO


Res-net Microwave, Inc.


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Microwave Attenuators

DC to 26.5 GHz up to 2,000 watts

Coaxial & Flange

Available in AlN & BeO


Res-net Microwave, Inc.


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MIL-C-17U

Low loss cable

0.034 to .250 diameters

Custom assemblies available

Typical VSRW 1.2:1 @ 18GHz

Wavetronix Corp

www.wavetronix-eti.com


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Passive Component

Technology

Dr. Bob Froelich

Senior Principal Engineer

Cobham


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The Ideal Elements

Element Principle Relation Impedance

Ohms

Law

V = IR R

Faradays

LawV = L dI/dt jL

Gauss Law I = C dV/dt 1/jC


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Real Elements

Are never ideal

Can often be modeled as a simpleequivalent circuit of ideal elements

Come in many physical forms, dependingon Cost

Frequency Power Levels

Etc.


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Some Surface Mount Sizes

W

L

Metric LxW(mm)

US LxW(mils)

0603

(= 0.6 x 0.3)

0201

(= 24 x 12)1005

(= 1 x 0.5)

0402

(= 40 x 20)

1608 0603

2012 0805

3216 1206


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Models and Parasitic Elements

An ideal element of the type desired is usuallythe main feature of the model network.

The other elements in the model are often called

parasitic elements. How parasitics arise Energy loss (as heat) => resistance

Physical area => capacitance

Physical length => inductance All elements in the model can vary with

frequency and temperature.


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Lumped vs. Distributed

Lumped element:

Small compared to the wavelength of the highestfrequency which is significant.

Can be treated (electrically) as having zero size. Distributed element:

Not small compared to wavelength. (>~ / 10)

Voltage or current phase differs from one side to the

other due to distance.

Model must include transmission line or manyincremental lumped elements.


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Inductors

In HF/RF/Microwave circuits, inductors aremainly used for RF blocking element to feed DC power or

connect DC ground. (RF chokes) Impedance matching.

Manufacturers often furnish equivalentcircuit model or S-parameters.

Many forms, but all include a conductingspiral that couples to a magnetic field.


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Some RF/Microwave Inductors

Wire on ceramic

Laminated Spiral

Wire onFerrite Toroid

Conical


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Primary Inductor Properties

Inductance: Primary function of the part

Self Resonance: As some frequency thereis a parallel resonance between the

inductor the parasitic capacitor. Quality factor (Q): characterizes the loss

Defined as Im(Z) / Re(Z)

Differs from the Q definition used forresonators:

2(peak stored energy)/(energy loss in 1 cycle)


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Modeled Inductor Reactance and Q

0.2 0.4 0.6 0.8 1.0 1.2 1.40.0 1.6

-2000

0

2000

-4000

4000

5

10

15

0

20

freq, GHz

Reactance

,Ohms

Q


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Some Inductor Types

Different cores Air: lowest loss and lowest C Ceramic: close to air, better structure Ferrite: more L in a small space. Can be lossy and

frequency-dependent. Different windings

Wire: low loss Printed/laminated windings: low cost / low Q

Planar Spiral Used in RFICs Usually have poor performance: low Q and high C.


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82 uH Multilayer Inductor

Black: Simplemodel with 1.4pFparallel

capacitance

Blue: Measuredresponse

0 1.0

1.0

-1.0

10.0

10.0

-10.0

5.0

-5.0

2.0

2.0

-2.

0

3.0

-3.

0

4.0

-4.0

0.2

0.2

-0.2

0.4

0.

4

-0

.4

0.6

0.

6

-0

.6

0.8

0.

8

-0

.8

Reflection CoefficientSwp Max

3000MHz

Swp Min

0.1MHz

814 MHzr=0.644

x=-3.1e-3

Measured

Modeled

5.0

x=-1003.

0

4.0

r=12.115 MHz

5.0

x=-1003.

0

4.0

r=12.13.0

4.0

r=12.115 MHz


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Using Inductors

RF choke Goal is high reactance with low resistance

OK to use an inductor at self-resonance

Impedance matching

Goal is accurate reactance and (usually) low resistance Usually must stay well below self-resonance

Some things to look for Tolerance and SRF

Q

Current handling

Try to use the lowest L that can do the job.


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Capacitors

In HF/RF/Microwave circuits, capacitors aremainly used for

DC blocking to isolate bias or create an RF ground

(RF bypass) Impedance matching

Manufacturers often furnish a circuit model or S-parameters

Possibly the most complicated passive due toeffects of structure, temperature, materials, etc.


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Multilayer Capacitor Structure


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www.BesserAssociates.comBesser Associates, Inc.

Example of Capacitor Model

Model approximates thereal capacitor from DCto above first self-resonance.

Parasitic elements are Loss: Contact and plate

resistance, plus loss indielectric

Inductance: Current flowsets up magnetic field

0.3nH 0.07

36k

27pF

27pF, 0402 SMT Capacitor


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Primary Capacitor Properties

Capacitance: Primary function of the part

Self-resonance: At some frequency there is aseries resonance between the capacitor and the

parasitic inductance. Quality factor Defined the same as for an inductor

RF/Microwave capacitors often have higher Q than

inductors. Other

Breakdown voltage


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Modeled Capacitor Susceptance

and Q

0.5 1.0 1.5 2.00.0 2.5

0

-1

1

Susceptan

ce,mhos

0.5 1.0 1.5 2.00.0 2.5

-5

0

5

-10

10

100

200

300

0

400

freq, GHz

Susceptance,mhos

Q


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Some Capacitor Types

Plate Configuration

Multi-layer is an encapsulated stack of metal plates.

Single-layer is just two plates; used with chip-and-

wire Dielectric (Insulator) Material

Ceramic: many kinds

Oxide (i.e. MOS capacitor): primarily single-layer

Electrolytic and tantalum capacitors are seldomused at high frequencies.


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Dielectric Materials

Ceramics Most common material

Ceramics with high dielectric constant () deliver morecapacitance in a small package.

High- ceramics are temperature- and voltage-dependent, andthey are often more lossy than low- materials.

Oxide Very temperature stable

Producible in thin layers for high capacitance

Thin layers result in low breakdown voltage Used mainly in single-layer capacitors.

Categories for ceramics have been defined by theElectronic Industries Alliance


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Other Dielectric Properties

Materialtype

r at roomtemperature, typ.

Dissipation factor, % ofenergy converted to heat

(low frequency), typ.

Change withvoltage (0V to rated

voltage), typ.

SiO2 3.9 < 0.1 ~ 0

NPO 60 0.1 ~ 0

X7R 3500 3.5 -50%

Y5V >16000 9 -90%


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Using Capacitors

DC block or RF bypass: Requires high susceptance OK to use a capacitor near self-resonance

Impedance matching Requires accurate susceptance Usually must be well below self-resonance

Watch out for Temperature sensitivity

Tolerance and SRF Breakdown voltage

Try to use the lowest C than can do the job.


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Resistors

In HF/RF/Microwave circuits, resistors are

used mainly for

Attenuators

Terminations

Feedback

Manufacturers sometimes furnish model or

S-parameters.


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Example of Resistor Model

Model approximatesthe real resistor fromdc to about 6GHz.

Parasitic elementsare

Inductance: due tolength

Capacitance: due tocontact area

50 0.17nH

0.08pF0.08pF

50 0603 SMT Resistor


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Modeled Resistor Impedance

2 3 4 5 6 71 8

51

52

53

54

55

50

56

1

2

3

4

5

6

0

7

freq, GHz

Resistance,

Ohms

Reactance,Ohms


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Other Resistive Forms for

RF/Microwave

Attenuator (coaxial orsurface mount)

Fixed

Temperature-dependent

Termination

High power (with heat

sink) Small/high frequency


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Watch Out For

Leaded resistors (or capacitors, inductors)

Leads add series inductance and/or length

Wire-wound, carbon film and MELFcylindrical resistors

Resistive element is often in the form of aspiral. At RF it becomes a lossy inductor.

1/F noise: Some resistor types generatemore than others.


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www BesserAssociates com

Passive Component

TechnologyBob Froelich, Besser Associates

Sponsored byRes-net Microwave, Inc., www.res-netmicrowave.com

Wavetronix Corp., www.wavetronix-eti.com

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Passive Technology Presentation