Basic of Load Pull Measurements Active and Passive load pull & Harmonic load pull testbench

(1)

Prof. Ernesto LimitiProf. Ernesto Limiti

Basic of Load Pull Measurements

Active and Passive load pull &

Harmonic load pull

testbench

credits to Prof. Andrea

(2)

Basics of load

-

pull

• Load-pull

– Controlling the loading condition at the output port

• Source-pull

– Controlling the loading condition at the input port

• Fundamental load-pull

– Controlling the loading/source condition at the fundamental

frequency

• Harmonic load-pull

– Controlling the loading condition at one or more harmonic

frequencies

(3)

Basics of load

-

pull

Example of load-pull data

Output power [dBm]

(4)

Basics of load

-

pull

• Power meter or scalar analyzer-based

– only scalar information on DUT performances

– economic

• Vector receiver (ANA, 6-port)

– vectorial and more complete informations on DUT

performances

– high accuracy, thanks to vector calibration

– expensive

• Time Domain Receiver (MTA)

– Waveform capabilities

– Complexity, high cost

(5)

Passive load

-

pull systems

• Passive loads

– Mechanical tuners

– Electronic tuners (PIN diode-based)

and power sensors

Power

Meter

Power Sensor Power Sensor

Passive tuners

Γ

S

Γ

L

(6)

Passive load

-

pull

Features

Single or double slug tuners

High repeatability of tuner positions

Pre-characterization with a network analyzer

High power handling

Drawback

Load reflection coefficient limited in magnitude

by tuner and test-set losses

This is true especially for harmonic tuning

higher frequency

(7)

Passive load

-

pull

• Pre-matching

– To reach higher gamma while characterizing highly

mismatched transistors

• Pre-matching networks

• Pre-matched tuners

Γ

_L

LOSS

Γ

L

Features

Highest gamma attainable

Difficult pre-calibration (5D space!!)

Harmonic Loading uncontrolled

Γ

_L

(8)

Passive load

-

pull

Passive Harmonic system

• A Tuner for each harmonic

– Complex

– Easy to change frequency

– More control of the harmonic load

• Harmonic Resonators

– Difficult to change frequency

– Only Phase control of the load

Γ

_f0

Γ

_2f0

Fundamental

(9)

Real Time load

-

pull

SWITCHING NETWORK

PORT 2

Vector network analyzer-based system

NETWORK ANALYZER

DUT

4CHANNEL RECEIVER

IF BUS

Input

Load

Output

Load

VECTOR INFO

NORMAL VNA CAL

(10)

SWITCHING NETWORK

Test Signal

Time domain load

-

pull

Transition Analyzer based system

MTA TD WAVEFORMS

DUT

Input

Load

Output

Load

VECTOR

AND TD INFO

TD CAL REQUIRED

ACTIVE LOADS

Ref Signal

(11)

Active Load

(12)

Active load

(13)

Active load

-

pull

• Two signal path

– No risk of oscillations

– Difficulty to keep constant the load while

• sweeping the input power

• the DUT heats up

• Active loop

– High load stability, once the loop oscillation problem is

solved

– Simple and safe operation

(14)

Harmonic active load

-

pull

(15)

Harmonic active load

-

pull

Extending the active loop technique

(16)

Load

-

pull Accuracy

• Reference plane definitions

VNA-based system: calibration

Γ

t

Thru

Line

Short

Load

Open

PwrMeter

DUT

1 Γ

in

2 Γ

_L

3 SWITCHING NETWORK

HP8510C NETWORK ANALYZER

Probe Tip

(17)

Main Contributions to Power Wave

Calibration Residual Uncertainty

• NVA

measurement repeatability

(0.1 %)

• Uncertainty on power calibration

coefficient

(input TWTA during

calibration: 2%, no TWTA 0.5%)

• On-wafer probe

position repeatability

(0.2%)

Uncertainty Evaluation

(18)

Prof. Ernesto LimitiProf. Ernesto Limiti uP crout () (%)

P

_out

uncertainty vs. |Γ

_L

|

( )

₂ L 4 L r out r c

1

1 pw

u

2 P

u

Γ

−

+

⋅

=

TWTA : ~2 %

no TWTA: ~0.55 %

0.41

0.79

1.1

1.5

1.8

2 dBm

Example

(19)

Passive LP System

• tuner

position repeatability

• S-parameter measurement uncertainty:

– residual

NVA calibration uncertainty

– NVA repeatability

• measured power uncertainty

(

PWM

)

(20)

Absolute standard

uncertainty (tuner

repeatability) on

|S

₁₁

|, |S

₂₁

| for

each tuner position

from 0 to 100

Tuner Repeatability

(21)

S

_ij

: tuner S-parameters (pre-characterization)

PWM

out

P

S

P

₂

_{_}

21

2

11 |

|

1 −

=

PWM

in

av

in

P

S

P

₂

_{_}

22

2

21 _

|

1 |

|

−

=

av

in

out

T

P

G

_

=

DUT input power, output power and gain:

POWER

METER

POWER SENSOR POWER SENSOR

P

_{in_av}

P

_{in_PWM}

P

_out

P

_{out_PWM}

Uncertainties combinations

(22)

Comparison Passive vs. Active

Output Power Standard Uncertainty

0.086

0.17

0.25

0.34

0.4

0.5 dBm

• passive LP: red line

(23)

• Classical PA design Information

like:

– Power Sweep

– Optimum Loads

• MAP based design

• Additional info with Active Real Time System

– GammaIn

– AM/PM conversion

• Harmonic Load condition

Load Pull and PA Design

(24)

Load Pull and PA Design

(25)

Power Sweep and more

Power Sweep @ Best Load for Pout

-70.00 -60.00 -50.00 -40.00 -30.00 -20.00 -10.00 0.00 10.00 20.00 30.00 27.55 26.75 25.44 23.60 21.60 19.58 17.71 15.96 14.31 12.74 Pav (dBm) dB / dB m 40.00 42.00 44.00 46.00 48.00 50.00 52.00 54.00 56.00 58.00 60.00 Pout Gain IM3L IM3R AM/PM Eff GammaL= 0.41 , 167 Frequency= 18 GHz 1dB Compression 1dB compression Point Pout=26.29dBm Gain= 9.72dB IM3R= -18.34 dBc IM3L=-18.50dBc Eff=48.07 %