Transmission-Line Transformers - K5TRA homek5tra.net/tech library/RF...

37
K5TRA Transmission-Line Transformers

Transcript of Transmission-Line Transformers - K5TRA homek5tra.net/tech library/RF...

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K5TRA

Transmission-Line Transformers

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K5TRA

Click to edit Master title style Categories of Transmission-Line Transformers

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• Single l/4 lines and cascades of l/4 lines

• Distributed element approximations of lumped element (LC) designs

• Short, highly coupled unit element structures

- Ruthroff

- Guanella

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K5TRA

Click to edit Master title style ¼ l and Stepped ¼ l Transformers

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222.060 MHz Beacon

STEPPED Z TRANSFORMER

l/4 Z1 l/4 Z2 l/4 Z3

R1 R2

R1 > Z1 > Z2 > Z3 > R2

R1 R2

l/4 Z0 = SQRT(R1*R2)

¼ l Z INVERTER

• Half octave performance from single quarter-wave line transformer

• Nearly 2-octave performance from 3 stepped quarter-wave lines

• Comparison for 50 to 100 transformation (BW also depends on this)

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K5TRA

Click to edit Master title style Stepped ¼ l Transformer Calculation

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DOWNLOAD FROM: http://k5tra.net/

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K5TRA

Click to edit Master title style Transmission-Line Transformer – Elements

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1:1

NO NET

COMMON

MODE

CURRENT

AKA

A

CHOKE

BALUN

=

SHORT (< l/8) LINE

=

1:11:1

CONVENTIONAL TRANSFORMER

TRANSMISSION-LINE TRANSFORMER

SYMBOLIC PHYSICAL

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Click to edit Master title style Ruthroff Transformers

6 T.Apel

1:1R1 R2

• Transmission line ‘unit’ element

• Physically short lines (length < l / 8)

• Analysis based on currents

• R1 / R2 = (I2 / I1)2 = 4

• Ferrite loading extends bandwidth (low end)

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K5TRA

Click to edit Master title style Ruthroff Type 9:1 Transformer

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• Transmission line ‘unit’ elements

• Physically short lines (length < l / 8)

• Analysis based on currents

• R1 / R2 = (I2 / I1)2 = 9

• Ferrite loading extends bandwidth (low end)

1:1R1 R2

1:1

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K5TRA

Click to edit Master title style Various Unbalanced Transformers

8 T.Apel

222.060 MHz Beacon

• Transmission line unit element building blocks

• Parasitic even mode characteristic impedance should be large (k 1)

• Z ratio available as squares of integer ratios

• First order analysis on basis of port current ratio

• Multiple line structures must have at least one shared current path

• DC path is present

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K5TRA

Click to edit Master title style Guanella (4:1) Balanced Transformer

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NO

EVEN-MODE

1:1

1:1

EVEN-MODE

NO

1:1

1:1

CONVENTIONAL 4:1 BALANCED TRANSFORMER

GUANELLA 4:1 SYMBOLIC

NO

EVEN-MODE

GUANELLA 4:1 PHYSICAL

• Two ‘unit’ elements can be used to form a balanced 4:1 transformer

• Analysis based on currents

• R1 / R2 = (I2 / I1)2 = 4

• Ferrite loading extends bandwidth (low end)

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K5TRA

Click to edit Master title style Several Balanced Transformers

10 T.Apel

• Transmission line unit element building blocks

• Parasitic even mode characteristic impedance should be large (k 1)

• Z ratio available as squares of integer ratios

• First order analysis on basis of port current ratio

• Multiple line structures must have at least one shared current path

• DC path is present

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K5TRA

Click to edit Master title style Guanella Transformer and Choke Balun

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• Pushpull PA match example

• Ferrite loaded ‘unit’ elements

• Guanella transformer from coax

• Choke balun (1:1) from coax

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K5TRA

Click to edit Master title style More Guanella Transformers in PA Output

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• Guanella transformer from coax

• ‘Unit’ elements with and without ferrite loading

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Click to edit Master title style Coupled Lines - Symmetric

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DIELECTRIC

METAL

METAL

METAL

• Two transmission-line modes

- Even (or common) mode

- Odd (or differential) mode

• Impedances set coupling level

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K5TRA

Click to edit Master title style Coupling Coefficient

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222.060 MHz Beacon

• Zoo sets the desired Zo • Zoe should be large !

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K5TRA

Click to edit Master title style Coupled Lines - Asymmetric

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DIELECTRIC

METAL

METAL

METAL

• Asymemetric coupled lines

- Two modes: C and p

- Similar to ‘Even’ and ‘Odd’

• Impedances set coupling level

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K5TRA

Click to edit Master title style Coupled Lines - Asymmetric

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DIELECTRIC

METAL

METAL

METAL

• Broadside coupling is better

• Asymmetric: slightly unbalanced

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K5TRA

Click to edit Master title style Coax Over Ground

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DIELECTRIC

COAX

METAL

• Coax coupling is very good

• Asymmetric: slightly unbalanced

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Click to edit Master title style Coupling Coefficient Relationship to Zoe/Zoo

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Click to edit Master title style Coupling Coefficient Relationship to Cm/C

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K5TRA

Click to edit Master title style Ideal Ruthroff Loss vs Length (and Zo)

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• Analysis of original 4:1 Ruthroff transformer (k = 1)

• Normalized port impedances (1 and 4)

• Best BW from Zo=2

• Lowest loss over less BW from Zo=1

Loss

(d

B)

Length (degrees)

4:1 RUTHROFF

MISMATCH LOSS

i 2i

i

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K5TRA

Click to edit Master title style Ruthroff Loss vs Length (and k)

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Zoo = 1

UNCOMPENSATED

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K5TRA

Click to edit Master title style Ruthroff Loss vs Length (and k)

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Zoo = 2

UNCOMPENSATED

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K5TRA

Click to edit Master title style Ruthroff Loss vs Length (and k)

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Zoo = 3

UNCOMPENSATED

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Click to edit Master title style Ruthroff Transformer Frequency Compensation

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• Non-ideal coupling is modeled by leakage and magnetizing inductance

• CS provides DC block and low frequency compensation

• CP1 and CP2 provide high frequency compensation

• If coupling is poor, or Zoo is not optimal, Cp can be used to tune the transformer for the desired frequency band

MODEL FOR (k<1) UNDERCOUPLED LINES

FREQUENCY COMPENSATION

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K5TRA

Click to edit Master title style Ruthroff Loss vs Length (and k)

25 T.Apel

Zoo = 1

COMPENSATED

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K5TRA

Click to edit Master title style Ruthroff Loss vs Length (and k)

26 T.Apel

Zoo = 2

COMPENSATED

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K5TRA

Click to edit Master title style Ruthroff Loss vs Length (and k)

27 T.Apel

Zoo = 3

COMPENSATED

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K5TRA

Click to edit Master title style Ruthroff Transformer Test Laminates

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9:1 TRANSFORMER 4:1 TRANSFORMER

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Click to edit Master title style Flip Chip Multiband PA with Ruthroff 4:1

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RUTHROFF 4:1 TRANSFORMER

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K5TRA

Click to edit Master title style Ruthroff Relationship to Auto Transformers

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RUTHROFF 4:1 UNBALANCED TRANSFORMER

GENERAL N:1 UNBALANCED AUTO

TRANSFORMER

RUTHROFF 4:1 SHOWN AS AUTO TRANSFORMER

• The Ruthroff structure can be redrawn as an auto transformer special case (N=2).

• Transformation can be set by setting the tap (1/N is tapped fraction of total primary)

i 2i

i

2i

i

i

N·i

i

(N-1)·iN:1

TU

RN

S R

AT

IO

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Click to edit Master title style Guanella Relationship to Auto Transformers

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GUANELLA 4:1 BALANCED TRANSFORMER (BALBAL)

VOLTAGE BALANCE

GENERAL N:1 BALANCED AUTO TRANSFORMER

VOLTAGE BALANCE

GUANELLA 4:1 SHOWN AS AUTO TRANSFORMER

• The Guanella balanced structure can be redrawn as an auto transformer special case (N=2). - note couplings –

• A more general auto transformer has secondary coupled to both primary segments

• Transformation can be set by setting the taps (1/N is tapped fraction of total primary)

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Click to edit Master title style Guanella and Auto Transformers

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GUANELLA BALANCED TRANSFORMER (4:1 BALBAL)

MODIFIED GUANELLA BALANCED TRANSFORMER (2.5:1)

AUTO TRANSFORMER (9:1)

TOP VIEW BOTTOM VIEW

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K5TRA

Click to edit Master title style Wideband Flip Chip PA Module

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• 800 MHz – 2 GHz

• WCDMA operation

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K5TRA

Click to edit Master title style Pushpull Multimode PA

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• Laminate contains modified Guanella transformer stacked with choke balun

• Full 824 - 915 MHz operation

• WCDMA, EDGE, and GSM

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K5TRA

Click to edit Master title style Low V Pushpull Multimode PA

35 T.Apel

• Low Vcc operation provided by high ratio transformer

• Three metal layers are used in a 9:1 auto-transformer

• Choke balun

5mm x 4mm PA MODULE

( .20” x .16” )

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K5TRA

Click to edit Master title style GaAs Pushpull PA Circuit Blocks

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ARRAY OF OUTPUT CELLS WITH INTERLEAVED MANIFOLD AND 3RD HARMONIC TUNING

INTERSTAGE GUANELLA TRANSFORMER

INPUT CHOKE BALUN and GUANELLA TRANSFORMER

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K5TRA

Click to edit Master title style Summary

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• Transmission-line transformers – 3 categories

• Coupled lines – Coupling coefficient

– Capacitive compensation

• Unbalanced or balanced forms – Ruthroff : unbalanced

– Guanella: balanced

• Autotransformers

• Some examples