• Beam Handling/Processing

• Optical Beamforming

• Proposed Architecture

• Implementation

• Test and Results

• Technology Comparison

• Further Developments

• Conclusions

PRESENTATION OUTLINE

BEAM HANDLING/PROCESSING

Broadband Telecom Satellites


State-of-the-art

(Europe) French STENTOR

mission

- 48 SSPAs

- 3 beams (Ku-band)

(US) SPACEWAY (Ka-band)

- 3000 SSPAs

- 24 beams (Ku-band)

DirecTV's Spaceway F1 satellite undergoes final

preparations for its launch aboard a Zenit-3SL

vehicle. (Boeing photo)

• Problem to be addressedFUTURE SCENARIOS

Coverage of a wide area by multiple fixed narrow beams

Direct Radiating Array (DRA) scheme

Hundred of antenna elements to be feed

Multibeam capability

„‟Europe + Maghreb‟‟ coverage:

44 spots, =0.8°

Antenna = 256-elements DRA


• Problem to be addressedHigh complexity

High mass and volume of the classical RF implementations

Heavy impact in the digital beamforming approach.

High mass of the feeding cables (hundred of antennas)

Crosstalk and EMI issuesIn the vertical plane, regular beams

arrangement is provided. by a 2nd set of 6

16 Butler matrices, for each of the 48

input ports to feed all R.E

2/ 16 vertical

616 matrices

Optional 18 fast switches

for beam-hopping mode 6

beams independently on

each 8-spot row (would be

implemented on the same

board than input-matrices

1/ 6 horizontal

816 matrices

1+2: 6+16

(6 or 816)

matrices are

necessary

16x16=256

ports to R.E.

16 outputs

per matrix

3dB / 90°

couplers

*2D: in 2

dimensions

Analogue ‘classical’ BFN

(1slide per beam)

Spot-beams

= S inputs

Radiating

Array

(N R.E.)

Nth

beam

j1

-

j2

jm

beam

j1

-

j2

jm

N SSPAN Filters

N CombinersS ->1

S dividers1->N

Fixed or controllable phase shifters

1stb

eam

j1

-

j2

jm

2n

d b

ea

m


• Solution proposedTo use photonic technology for the Beamforming Network

Size reduction

High integration of several functionalities in a single chip

High precision in the phase shifting (SOI technology)

Mass reduction: using optical fiber for the antenna feeding

Huge electrical bandwidth (typically > 40 GHz).

EMI Free technology

Excellent crosstalk

Scalability with low size/mass

OPTICAL BEAMFORMING

Optical Beam Forming

The ESA is assessing the benefits of using optical beam forming networks on Telecom

and EO satellites for steerable pencil or spotlight beams, or for adjusting broadband

multimedia beams.

Different scenarios:

-Wide bandwidth requirements: True Time Delay (TTD) architectures

-Narrow bandwidth: no need of TTD

Broadband Telecom Satellites

•Ka band (30GHz) multimedia satellites

•Large number of beams (200)

•Small Steering Angles (few degrees)

•LC SLMs used for Amplitude and Phase control

(true time delay not required)

•Integrated photonics implementing beamforming

networks as Butler Matrix (true time delay not

required)

Errico Armandillo (ESA), Space Optoelectronic Day, Cork 7 April 2006

OPTICAL BEAMFORMING

E/O

E/O

E/O

… OBM

Subsystem

O/E TIA

O/E TIA

…O/E TIA

SSPA Antenna Element



Up-conv

Up-conv

Up-conv

Optical Beamforming

Network

D1

D2

D44Ort

hogonal B

eam

s

Array Antenna

Optical Fiber

Feeding of antennas

PROPOSED ARCHITECTURE

Butler Matrix: Principle of Operation

Orthogonal beams

Passive structure: couplers and phase shifters

Scalable solution (FFT structure)

Very well known solution


OPTICAL Butler Matrix: Heterodine Generation

fRF

A)

f0 + fRF

B)

DC

Electrical

Spectrum

Optical

Spectrum

f0

E1(t)

E2(t)

C) Optical

Spectrum

f0

E1(t)

f0 + fRF

D) Optical

Spectrum

f0

E2(t)

E1) Optical

Spectrum

f0

E1(t)·ej1

E1) Optical

Spectrum

f0

E1(t)·ej2

S(t)

f0 + fRF

F1) Optical

Spectrum

f0

E2(t) ·ej0

E1(t)·ej1

f0 + fRF

F2) Optical

Spectrum

f0

E2(t) ·ej0

E1(t)·ej2

Out1 = S(t)·ej(1-0)

Out2 = S(t)·ej(2-0)

fRF

A)

f0 + fRF

B)

DC

Electrical

Spectrum

Optical

Spectrum

f0

E1(t)

E2(t)

C) Optical

Spectrum

f0

E1(t)

f0 + fRF

D) Optical

Spectrum

f0

E2(t)

E1) Optical

Spectrum

f0

E1(t)·ej1

E1) Optical

Spectrum

f0

E1(t)·ej2

S(t)

f0 + fRF

F1) Optical

Spectrum

f0

E2(t) ·ej0

E1(t)·ej1

f0 + fRF

F2) Optical

Spectrum

f0

E2(t) ·ej0

E1(t)·ej2

Out1 = S(t)·ej(1-0)

Out2 = S(t)·ej(2-0)

E/O

S(t)Demux

1:2

Optical

Butler

Matrix2x2

+

+

1:2

O/E

O/E

A) B)

C)

D)

E1)

E2)

F1)

F2)

Out1

Out2

OBMS

…


CMOS compatible tech.

Thin silicon (Si) layer on top of an Oxide (SiO2) cladding

Si thickness = 200 nm

SiO2 layer = 3000 nm

Waveguide width = 500 nm

Mode profile highly confined

Effective refraction index @ 1550 nm = 2,36

500 nm

SOI TECHNOLOGY

IMPLEMENTATION

10 cm

0.003 cm

18 GHz 8x8 Butler MatrixTechnical Research and Manufacturing, Inc.

Optica Butler Matrix SOI CHIP

SEM PHOTOGRAPH

MICROSCOPE PHOTOGRAPH

TESTS AND RESULTS

L= 0.5 mm

Lensed

fiber

Ridge waveguide

Objective

Linear Taper

Photonic Wire

Photonic Device

(a)

IR camera

Input

polariser

Lens

Power

Meter

Polarised Lens

Laser signal

Aperture

(x,y,z)-axis traslation stages

Lensed Fiber

Sample

Objective

Microscope

Reference Waveguide (3m wide)

MEASUREMENTS AT CHIP LEVEL

TESTS AND RESULTS

Parameter Specification Obtained

Standard deviation of

phase errors < 10/√2 < 5 - 10º

Standard deviation of

amplitude errorsa < 0.5 dB a < 2 dB

Phase performance in line with the specifications

Amplitude performance worse than specifications

Mainly due to the coupling method (introduce extra attenuations)

Amplitude equalization is expected in future devices.

Chip post-proccesing

Due to the

in-chip test method

TESTS AND RESULTS

• Targeted for high complexity beamforming

networks for array antennas (DRA)

BFN optionEstimated

mass

Estimated

volumeDC consump.

EMI

FREE

Upgradeability in

Nº of antenna

elements

„Pure-RF‟ with

Butler Matrixes100% 100% 100% NO Low/medium

„opto-wave‟ 70% <1% 200% YES High

Comments

Cable vs. Fiber

mass shaving

has not been

considered

Greater for

large

antennas

Including added

amplifiers to

compensate

converion losses

Infinite

isolation

Easy for large number

of antenna elements (in

the Opto-uwave)

Example: 44 beams. 256 antenna elements

TECHNOLOGY COMPARISON

• Improvement of the phase/amplitude

performance

• Extend higher number of I/O ports

• Implementation of the whole heterodine

structure (RF performance)

• Whole system packaged (including the

fiber coupling)

FURTHER DEVELOPMENTS

SBE

SBE

SBE

● ● ● ●

● ● ● ●● ● ● ●

SBE

SBE

SBE

SBE

● ● ● ●

SBE: Side-Band Extraction

Input Ports (#1 to #8)

Output Ports (#1 to #16)

•Basic Unit (BU) for the OBFN design

•Based on 8x8 Butler Matrices and a proprietary

2N beam multiplication solution: simpler than

the truncated 16x16 alternative (especially much

fewer line crossing‟s)

•Heterodine distribution included in the basic

unit:

•Result in a 8x16 Butler matrix “RF-to-RF”

•Different Basic Units can be

interconnected with optical fiber

•Do not requires the integration of optical

switches inside the block.

Optimised OPTICAL Butler Matrix (OBM)

FURTHER DEVELOPMENTS

Conclusions

• Successful fabrication of an SOI integrated 8x8

Optical Butler Matrix

• The performance in terms of phase/amplitude

obtained is comparable with the traditional

electrical solution

• Low mass and size

• Remote feeding by optical fibre: weigh reduction

• EMI free technology

• Promising alternative for the implementation of

Beamforming systems.

CONCLUSIONS

Conclusions

THANK YOU FOR YOUR ATTENTION

photonic beamforming network for multibeam satellite-on

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