baluns, balance, and differential signaling

Baluns, Balance, and Differential SignalingDoug Jorgesen|April 2, 2020

For Signal CancellationEliminate unwanted signals without filtering.

Why Balance?

Marki Microwave Inc. 3

Balanced MixersIsolate ports and suppress even order spurious products

Differential SignalingEliminate common mode noise

Differential CircuitsEliminate even harmonic products and IP2

Eliminate Reflections

Quadrature Phase

• Increases linearity or power handling

• Improves Return Losses

Eliminates Input Signal for Harmonics

Mixed Phase

• Useful for gathering converted signals

Used in mixers, doublers, quadruplers, etc.

Maximize PowerIn Phase

• Increases power handling, linearity, or power generation

• Usually lowest loss for broadband applications

Eliminates Noise and Harmonics

Out of Phase

• Increases linearity and power handling

• Eliminates common mode and even harmonics

Power Combining

Marki Microwave Inc.

F 2F

F 2F

4

A Balun Creates Equal and Opposite Signals

What does a balun do?


Balance

Amplitude and phase balance quantify how close to ideal a real balunis.

Positive/0°/Non-inverted

Negative /180°/Inverted

Unbalanced/Single Ended/ Common

Balanced/Differential Isolation

Digital Data

Vunbalanced

Vbalanced

Vbalanced

Amplitude Balance

PhaseBalance

Zunbalanced

Zbalanced

Vunbalanced

Single Frequency

Single FrequencyDigital Data

Single FrequencyDigital Data

Mode Converter

A passive balun converts bidirectionally between differential and single ended signals.

Balun Transformer

Transforms between single ended and differential impedance according to the impedance ratio.

Isolation

High insertion loss between differential ports improves signal integrity.

Common Mode Rejection• Quantifies how much of a signal in

the ‘common mode’ of a differential line will be rejected

Common Mode Rejection


Phase BalanceGood baluns provide 15-20°Marki baluns provide 5-10°

Amplitude BalanceGood baluns provide ±2 dBMarki baluns provide ±1 dB

-3

-2

-1

0

1

2

3

0 1 2 3 4 5 6 7 8 9

Am

plit

ud

e B

alan

ce (

dB

)

Frequency (GHz)

150

160

170

180

190

200

210

0 1 2 3 4 5 6 7 8 9

Ph

ase

Bal

ance

(d

egr

ee

)

Frequency (GHz)

-50

-40

-30

-20

-10

0

0 1 2 3 4 5 6 7 8 9

Co

mm

on

Mo

de

Re

ject

ion

(d

B)

Frequency (GHz)

Mixed Mode S-Parameters


S-Parameters

Three ports with one mode each

Better for isolation and output impedance matching

Single Ended

Mode s

Differential Mode d

+

-

Common Mode c

++

2 1

3

Mixed Mode S-Parameters

Two ports, differential port has two modes

Better for differential return loss, common mode rejection, and mode

conversion loss

-25

-20

-15

-10

-5

0

0 1 2 3 4 5 6 7 8 9

Re

turn

Lo

ss (

dB

)

Frequency (GHz)

Common

Output 1

Output 2

-15

-12

-9

-6

-3

0

0 1 2 3 4 5 6 7 8 9

Inse

rtio

n L

oss

\Is

ola

tio

n (

dB

)

Frequency (GHz)

Insertion Loss (Output 1)

Insertion Loss (Output 2)

Isolation

Importance of Isolation


With IsolationSignal integrity improved in Differential to Single ended conversion

Two Port VNA with Post-Processing

VNA

In0°

180° Out0°180°

Isolated Baluns Allow Complete Measurements

Without IsolationLack of isolation causes poor differential return loss

Four Port Dual Source VNA

Linear S-ParametersStep Response Impulse ResponsePower CompressionHarmonic GenerationTwo Tone IntermodulationMultitone SpuriousEye DiagramsBit Error RatioError Vector MagnitudeTotal Harmonic DistortionSpectral Regrowth

LinearNonlinearSignal Integrity

Marki Isolation Baluns

Length Matching1• Any differential trace mismatch produces a linear phase walk

• Traces, cables, connectors, and other interconnects

Trace Isolation2• Neighboring channels can appear as aggressors

• Far away channels will be more ‘common mode’ than nearby

Lack of Isolation3• Low differential port isolation = high differential mode RL

• Bad for differential to single ended conversions

Top Three Mistakes

Marki Microwave Inc.

Frequency

Ph

aseΔΦ

9

Poll Questions

10

Balun Types: Transformer Based


Flux Coupled BalunTransformer

All coupling provided by magnetic field

Provides ground/DC isolation

Massive bandwidth ratio

Limited to low frequencies

Transmission Line Balun

Float the ground to create differential output

Has problematic half wave resonance

Transmission Line Transformer Balun

Combines transmission line balunwith magnetic material to eliminate resonance and extend low end

Massive bandwidth ratio

High frequency extends >10 GHz

Typically lossy (>2 dB excess insertion loss)

Magnetic Core

Unbalanced Input

Balanced Output

Magnetic Coupling

Unbalanced Input Balanced

OutputCapacitive Coupling

Bifilar

Balanced Output

Unbalanced Input

Capacitive and Magnetic Coupling

New 10 MHz-12 GHz smaller form factor SMT Balun

Balun Types: Coupler Based


Coupled Lines Based BalunsCoupled line structures with open/short ports can be designed as baluns

These baluns can be integrated and made in a planar structure

Hundreds of circuit structure options

Low frequency is limited to 1-2 GHz

Tapered Balun

Tapered Balun Marchand Balun

Spiral Balun

New 2 GHz-20 GHz MMIC balun SMT

MBAL-0220SM

Balun Types: Power Divider-Phase Shift


Power Divider – Phase ShiftDifferential signaling can be realized by separating the signal first and then applying a phase shift

Can provide extended high frequency, extended low frequency, and high isolation

Power Divider – Inverter Balun Planar Coupler Baluns

Balun Types: Magic Tee/Hybrid Coupler


Rat Race CouplerEasy to Design and Fabricate

Sub-octave bandwidth

Power Divider – Inverter Balun Planar Coupler Baluns

Asymmetric Tandem CouplerDifficult to Design and Fabricate

Can be very broadband

Possible but not practical

Waveguide Magic TeeThe original high isolation, low loss

Limited bandwidth

180° Couplers Can be Used as Baluns, but also Have an Isolation/Sum Port.

Marki Balun Catalog

Marki Microwave Inc. © 15

Empower our customers to design faster, simplify production, eliminate complexity, and shatter performance barriers

Marki Mission Statement

Surface Mount and Bare Die BalunsAnalog to Digital InterfacesDigital to Analog InterfacesClock Driver InputsBalanced CircuitsAntenna Feeds

Test and Measurement BalunsComponent MeasurementsLaboratory ExperimentsADC/DAC InterfacingHigh Speed Data

For More InformationBalun PrimerTech [email protected]

Amplifier Biasing Made EasyJacob Trevithick and Rob Maurer | April 16, 2020

Register for our next webinars via links in upcoming email.

A Brief Guide to Mixer SpursHarley Berman and Christopher Marki | April 30, 2020

16

baluns, balance, and differential signaling

Documents