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“Power Amplifier Linearisation for HAP Payload”

Neuchatel, October, 2005

Universitat Politècnica de Catalunya, UPC

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PROBLEM RATIONALE

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64-QAM + single tone separated twice the symbol frequency (intermodulation)

NON-LINEARITY EFFECTS: Out-of Band distortion

Why Linearise ?

32 QAM, = 0,35

Unlinearised PA

NON-LINEARITY EFFECTS: In-band distortion

K1 = 10

K1 = 150

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HAPS: Solar+Battery powered: energy efficient application

Why Linearise ?

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PA

CLASS

THEORETICAL

EFFICIENCY

LINEARITY

A (1) 50 % Good

B (2) 78,5 % Moderate (cross-distortion)

AB (2) < 78,5 % Lower cross-distortion

C (1) > 78,5 % Poor

D (2) ≈ 100 %Poor (main application in audio-frequency as PWM)

E (1) ≈ 100 % Very Poor

F (1) ≈ 100 % Very Poor

G,H (4) ≈ 100 %Poor (application in audio and electrical machinery)

S (1) ≈ 100 % Very poor

Why Linearise ?

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Why Linearise ?

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HARWARE: CURRENT STATUS IN UPC

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Power Amplifier

SAMPLE OF THE PA:

ACORDE,S.A (2.262 EUR): 29.5 to 30.5 GHz

Measured data:

P1dB > 31 dBmPsat > 31.5 dBmGain: 15 dBVSWR: 2:1Power consumption: 1.5 A @ 12 V (0.9 A at low signal level)

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Power Amplifier

28.5 GHz 30.5 GHz

5 dB/

-25 dB

25 dB 28.5 GHz 30.5 GHz

5 dB/

-25 dB

25 dB 28.5 GHz 30.5 GHz

10 dB/

-50 dB

50 dB 28.5 GHz 30.5 GHz

5 dB/

-25 dB

25 dB

CH1

CH2

5 dB/

5 dB/

REF 0 dB

REF 0 dBCH2

CH3

5 dB/

10 dB/

REF 0 dB

REF 0 dBCH3

CH4

10 dB/

5 dB/

REF 0 dB

REF 0 dBCH4 5 dB/ REF 0 dB

CPL

MAG

MAG

dB

dB MAG

MAG

dB

dB S12

S22

MAG

MAG

dB

dB S22 MAGdB

FIL1k 1k FIL1k 1k

CAL

S21

START 28 GHz STOP 31 GHz500 MHz/

S11

1 2 3

3: -10.89 dB

30.4975 GHz

1: -11.12 dB

29.5 GHz

2: -11.31 dB

30.0025 GHz

á 0 dBá 0 dBá 0 dBá 0 dB

Date: 3.DEC.04 12:23:15

S11

S22

S21

28.5 GHz 30.5 GHz

5 dB/

-25 dB

25 dB 28.5 GHz 30.5 GHz

5 dB/

-25 dB

25 dB 28.5 GHz 30.5 GHz

10 dB/

-50 dB

50 dB 28.5 GHz 30.5 GHz

5 dB/

-25 dB

25 dB

CH1

CH2

5 dB/

5 dB/

REF 0 dB

REF 0 dBCH2

CH3

5 dB/

10 dB/

REF 0 dB

REF 0 dBCH3

CH4

10 dB/

5 dB/

REF 0 dB

REF 0 dBCH4 5 dB/ REF 0 dB

CPL

MAG

MAG

dB

dB MAG

MAG

dB

dB S12

S22

MAG

MAG

dB

dB S22 MAGdB

FIL1k 1k FIL1k 1k

CAL

S11

S21

START 28 GHz STOP 31 GHz500 MHz/

S21

1 2 3

3: 16.01 dB

30.4975 GHz

1: 16.61 dB

29.5 GHz

2: 16.48 dB

30.0025 GHz

á 0 dBá 0 dBá 0 dBá 0 dB

Date: 3.DEC.04 12:22:23

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Up&DOWN CONVERSION

Demod.

RF input

To the DSP

In phase

In quadrature

Mod.

RF output

From the DSP

In phase

In quadrature

RF input

To the DSP

RF output

From the DSP

IF output

IF input

PBFPBF PBFPBF AMPLIF.AMPLIF. PBFPBF AMPLIF.AMPLIF.

LO2LO1

1st. IF 2nd. IF

1st. stage 2nd. stage

PBFPBF PBFPBF AMPLIF.AMPLIF. PBFPBF AMPLIF.AMPLIF.

LO2LO1

1st. IF 2nd. IF

1st. stage 2nd. stage

intermodulation distortion, phase noise and PM-AM conversion, spurious generation and other non desired

effects

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Power Amplifier LinearisationTest and measuring equipment

Signal generation:ESG Signal generator: E4433B (modulated signals up to 4 GHz)PSW CW Signal generator E8247C (carriers up to 40 GHz).

Spectrum analysis:ESA Spectrum analyser: E4407 (vector signal analyser, up to 26.5 GHz).ENLARGEMENT OF SPECTRUM ANALYSIS UP TO 40 GHz: E4407BK-AXY (External Mixer) + 11974A (millimetre mixer) 26,5-40 GHz

(Equipment purchased with founds from other projects)

Additional equipment has been ordered, expected delivery time: next November CABLES/CONNECTORS, UP-DOWN CONVERTERS (30 GHz), …

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Balanced Mixer QMB-3028AS

RF: 30 GHz LO: 28 GHz

RF/LO Waveguide: WR-28 2.990,00€/u (x2u)

Phase Locked SourceQPL-280120ES Single frequency,100MHz external

reference Pout: +20dBm

28 GHz 3.190,00€/u

Precision High Directivity CouplerQJR-A03300.

Frequency Range: 26.5-40 GHz Waveguide: WR-28

Coupling Value: 3dB at center freq. Coupling Flatness: ±0.7dB typ

Directivity: 37dB typ Insertion Loss: 0.7dB max

VSWR: 1.1:1 889,00€/u

Termination, low powerQWN-A00000

Frequency: 26.5-40 GHz Waveguide Size: WR-28

VSWR: 1.03:1 Power Handling: 1.0W max

259,00€/u (x 2u)

Waveguide to Coax Adaptor QWA-28S24F

Waveguide: WR-28 Flange: UG-599/U

Coax: 2.4mm female 449,00€/u (x 3u)

12.000 EUR !,

4-6 weeks delivery time

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LINEARISATION STRATEGIES

(BASE BAND)

A: ANALOGUE

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Power Amplifier Linearisation

DISCARDED ALTERNATIVES (already

reported in previous meetings):

• Feedback (and its variants: RF, envelope, cartesian, polar) –

instability-

• Feedforward –quite sensitive to loop mismatches:

milimeter band, 2 Pas

• LINC /CALLUM - 2 PAs, loop balances: milimeter band –

• EE&R (envelope elimination and restoration) - time constants

in the envelope loop (28 MHz bandwidth: risked) -

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PA Linearisation (Analog)

CONSIDERED ALTERNATIVES (already reported

previously):

1.- Hyperstable lineariser (analog)

12 dB

26 dB

Clase A. OBO = 3 dB. Po = 24,8 dBm. IP3= 19 dBm

Only AM/AM distortion

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FROM GENERATOR

Q I

I&Q MODULATOR FROM POWER AMPLIFIER

I&Q MODULATORTO POWER AMPLIFIER

REFERENCE MODEL GAINS (I&Q)

2 MULTIPLIERS OFFSET ADJUST

(I&Q)

1 MULTIPLIERS OFFSET ADJUST (I&Q)

K- GAIN ADJUST(I&Q)

+5 -5 GND

Q

I

Q

I

PA Linearisation (Analog)

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900 MHz class A power

amplifier (Minicircuits)

(NEW RESULT NOT REPORTED IN

M82)

PA Linearisation (Analog)

Carrier + 2 tone test

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LINEARISATION STRATEGIES

(IF-sampling)

B: DIGITAL

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CONSIDERED ALTERNATIVES:

2.- Digital predistortion:

IQ MOD AP

ADAPTATION

LUT

DIGITALPREDISTORTER

IQ DEMOD

( )i t

( )q t

( )y t

ADC

ADC

DACDSP

PAI

Q

MOD

Up-conversion

I

QDEMOD

Carrier

Down-conversion

D/A

D/A

A/D

A/DParameterEstimation

BasebandPredistorter

(·)

Baseband Signal

RF Signal

PA Linearisation (Digital)

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LOW-PASS FILTER

LOW-PASS FILTER

OSCILLATOR

90º PHASE SHIFTER

I COMPONENT

Q COMPONENT

PA Linearisation (Digital)

ANALOG: + cost, + spurious

- Computing time consumption (Nyquist)

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PA Linearisation (Digital)IF

FILTER

DIGITAL I-Q

RECOVERING

LPF

LPF

IF

IF SAMPLING (IQ)

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• Phase noise and frequency stability

• Clock jitter

• In MOS technology, the power consumption of a DSP device is

approximately proportional to the clock frequency

• Frequency distortion introduced by D/A converters

PA Linearisation (Digital)

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PA Linearisation (Digital)

TMS320C6711

(ALREADY REPORTED)

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DSPDSP FPGAFPGAADDR[2…0]

CTRL : rd, wr, cs

IRQIRQ1

FLAGFLAG10

EM

AF

E

DATA[12…0] PA

fo

D/A

A/D

RBW 300 kHzVBW 30 kHzSWT 20 ms

*

*

A

Ref -10 dBm

Center 2.123 GHz Span 30 MHz3 MHz/

Att 10 dB*

*

*1 RMCLRWR

*2 RMVIEW

*

PRN

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

Date: 10.OCT.2005 09:35:43

Motorola MRF21010G = 13.5 dB,

Pin,linear < 25 dBm(WiFi)

ADSP-21065L EZ-KIT Lite, Analog Devices @ 60MHz

►Virtex-II Prototype Plattform,FPGA XC2V250:

24 RAM blocks of 18 Kbit/block (432Kbits), 24 multipliers (18*18)

D/A: Kit AD9765, 2 channels (I/Q),12 bits, fs = 30MHzA/D: Kit AD9238, 2 channels (I/Q) , 12 bits, fs = 30MHz

PA Linearisation (Digital): External collaborations

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Development of the lineariser algorithms.

+

-

y

PredistorterPower

Amplifier

Update

algorithm

sG sAsP

ADAPTACIÓN

LUTs

DSP

ini

( , )i in inf i q

( , )q in inf i qinq

outi

outq

ADAPTATION

PA Linearisation (Digital)

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Issues in the predistorter design (we are working in their evaluation using Matlab and thinking in an efficient TMS320C6711 implementation):

-The size of the LUT: determines the number of points at which the predistortion function is calculated. More point implies a better predistorter quality, but this size is related to the amount of necessary DSP memory.

- Points distribution and LUT address: In some cases it may be desirable to distribute the predistortion function points across the range of the input signal magnitude according different laws:

• linear• square (power distribution)•log

- LUT updated algorithm: The function of the adaptation algorithm is to derive/adjust the values of the predistortion function according to the real-time performance results.

PA Linearisation (Digital)

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.

64-QAM + ISI filter No predistorter LMS Fast Kalman

Digital predistortion: some results (LMS vs. Fast Kalman)

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Digital predistortion: (Models and multi LUT organisation)

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http://cmc.upc.es