WE4E-2

Transmission-Line Broadband GaN FET Class-E Power Amplifier

Ramon A. Beltran, PhD

Skyworks Solutions

Newbury Park CA.

Outline

• Introduction; Transmission-line Class-E Amplifier

• Transmission-line Transforms

• Transformation Sequence

• Breadboard Technique

• Performance and Closing Remarks

Introduction Transmission line class-E

amplifier design

Ideal

LC class-E

T-lines class-E

Design Example

Polyfet GP2001

Coss=4pF

• Driving signal and loading network

• High-frequency approximation

• Reactance compensation

Richard’s transforms

All wire-lines and UE are 45o of length at f0

Other transforms can be found in the literature;

You can design your own transforms using network theory

Transmission-line transforms

Pout =20-W

20-V

• Simple design @ 1 GHz

• Ideal RFC

• Ideal DC-block

• Design equations in paper

Matching section

• Wire-lines

• Matching to 30-Ohms

• Series OC wire-lines

• Series SC wire-lines

Transforms for matching to 50-Ohms

Broadband Matching to 50-Ohms

By transformer N1

L-left to L right Transform

To ZTL3 and ZTL5

Transformers N1 and N2 vanish

Matched to 50-Ohms

Transformers N2 and N1 elimination

Transforms for network topology

Introducing a Unit Element 1 and applying a

Richard’s transforms

Apply a Richard’s transform

Apply a Richard’s transform

Shift capacitor C2 to the right side

Of the transformer and Introducing a

Unit Element 5

Transforms for network topology

Applying a Richard’s transform to UE5 and C3

Final schematic with all shunt wire-lines

New network topology

Applying a Richard’s transform to UE6 and TL9

Transforms for network topology

Transforms for transformer elimination

Split TL1 into TL13 and TL12

Apply and L-right to L-left to TL12

and UE4. Introduce N5. Eliminate

TL11

Shift transformer N5 to the right and

merge with transformer N3

Shift transformer N4 to the left passing

UE6 and C4

Final network

Transformer N6 and N4 Vanish

Network with all shunt transmission-lines

No transformers

And broadband matched to 50-Ohms

Microstrip realization

Amplifier schematic

• Synthesized network

– No PCB substrate: Dielectric constant Er=1

– Conductor thickness: 30 mil

– Distance from ground to conductors: 10 mil

– Brass-bars for transmission-lines

Breadboard

Brass-bars transmission-line cuts

Transmission-lines

and

ground plane

Breadboard

Amplifier assembly

Breadboard

Output

Output

Input

Input

Vgs VDD

SC Stub

OC Stub

Plastic support

Side

views

FET

Performance

Measured output power and drain efficiency; fixed input power

80% efficiency

BW=300-MHz

60% efficiency

BW=500-MHz

Closing remarks

• Transmission-line class-E PA design can be simple

• Practical implementation can be improved by applying transforms

• Knowing how and when to apply a transmission line transform could yield to

a better practical realizability of a PA loading network

• Broadband efficiency can be achieved at UHF frequencies

• The presented bread-boarding technique allows multiple tuning knobs.

WE4E-2

Transmission-Line Broadband GaN FET Class-E Power Amplifier

Thank you

Clear skies and

High Efficiency