Receiver Architecture for Radio over Glass, Analog or ......Receiver Architecture for "Radio over Glass, Analog or Digital? Progress from Australia" NGVLA WORKSHOP#2 9 DEC 2015 Ron

Receiver Architecture for "Radio over Glass, Analog or Digital? Progress from Australia"

NGVLA WORKSHOP#2 9 DEC 2015

Ron Beresford [ Photonic/RF Systems Engineer]

CSIRO Astronomy and Space Science

• ASKAP BETA Digital over Fiber

• ASKAP ADE RF over Fiber

• Update on Digitizer design

• High DNR RFoF

• Interference Issues (low level)

Agenda

NRAO 9 Dec 2015 ngVLA_Workshop#2 | CSIRO| CASS | Ron Beresford 2 |

Phased Array Feed

Gain Signal

Transport 7km

Filter Banks

Beamformer

Co

rrelato

r

ADC

Clock

Phased Array Feed

Gain Superhet

Local Oscillators

ADC

Clock

Beamformer Signal

Transport 7km

Co

rrelato

r Antenna

Central Shielded Building

ASKAP MK I BETA

ASKAP MK II ADE

Filter Banks

3 | NRAO 9 Dec 2015 ngVLA_Workshop#2 | CSIRO| CASS | Ron Beresford

2Tbps

RFoF

Direct Sampled @ RF [Software Radio]

700-1800MHz

8b

12b

BETA antenna fit-out


3kW

electronics

Dry Air Compressor Transients


EMC

MIL461F RE102


• Bigger FPGA’s Xilinx V7 (more logic/watt/$)

• Low cost ADC 12bit, RF 3GHz, sample rate 1600MHz

• Low cost Board interconnects 120Gbps Multi-mode parallel optics.

(Avago Minipods)

• Low cost Board interconnects Passive Optical Cross-connects

• Low cost DFB lasers Uncooled, linear, usable slope

efficiency RF over Fiber

MKII Technology Enablers

DSP board to board interconnects


Parallel Optics Modules • Low cost short spans with multi-

mode ribbon fibre and parallel optical VCSEL modules Avago Minipod, ~$3/Gbps, 50mW per channel


Why change the 2008 MK1 design?

• Simpler antenna – cheaper

• No high speed digital near receptors ( no self RFI or clocks)

• Less power at antenna

• Less cooling required

• Galvanic isolation – lightning isolation

• Less electronics hence reduced maintenance at antenna

A Simpler system


+6vdc 50A (RF)

-6vdc 15A (RF)

+6vdc 5A Controller

20vdc 30A (TEC)

415vac (TEC blower)

194 SMF’s

MKII Backend is Shielded >160dB and RFoF fed.


75dB

Gr

E

O

E O

RFoF G > -20dB

SMF

19dB

AD

C

DSP DFB’s XCOR

ANTENNA PAF CENTRAL BUILDING

Ga

Phase

Switching

Remote Western Australia = low RFI

Sydney

Pop. 4 million

Narrabri (ATCA)

Pop. 6,000

Murchison Shire

Pop. 120 (and dropping)


RFI at the Western Australia Site.



RFI modelling Parkes Site.

RFoF The Distributed Feedback Laser


PAF Low Cost Direct Modulation RFoF Direct Detection Intensity Modulation Intrinsic Link


Vee

Z RFin

Bias/APC

Vcc

1310nm SSMF

max 6km x 0.35dB/km

6mW >1mW Lf ~ 3dB

RFout

G= k. SL2.Rd

2

SL Rd

NF ~ 1

G (RIN limited)

Op

tica

l P

ow

er

mW

Laser IF mA

SL dPo

dIF

= Slope Efficiency

Linear

SL

Rd

=0.3 mW/mA

=0.85 mA/mW

Typical DNR Performance


1000 10000

Pushing RFoF Span


RFoF stable RF subsystem


Measured LNA/Filter/RFoF Tx Stability

19 | NRAO 9 Dec 2015 ngVLA_Workshop#2 | CSIRO| CASS | Ron Beresford

188 Channel PAF Digitized 600 x 1MHz CFB


Longterm Stability


Unwanted PAF to PAF coupling


case emission

d > 22.4m

PAF1

Ant#2

0dBi

reflection

3.8fW 35mK

0.5mJy

Phase switching option will help this!

Unwanted Correlations

• All analogue signals come into a single shielded room in ADE • A 30μ Jy source is at -75dB relative to Tsys

• Hard to guarantee all noise and cross talk is below this level


Antenna

1

Antenna

2

RFoF RX

RFoF RX +

+

Common Noise Correlator

Digitiser

Digitiser

Central site Shielded Room

RF

on

Fibre

Simplified system description

Digitizer Developments


NRAO 9 Dec 2015 ngVLA_Workshop#2 | CSIRO| CASS | Ron Beresford

Observatory Timeframe.

25 |

BETA conversion and ADC Timimg/LO


4-way

BAT

156/159MHz

768MHz

LO1

LO2

10 MHz

1-w

ay

1-w

ay

4-w

ay

4-w

ay

4-w

ay

Synthesizer

Control

BAT Receiver

and decoder

USB/SPI

Slave

8 MHz

Receiver

and

Cleanup

3-way

split

USB/SPI BAT

optical

8MHz

Optical

carier

Ph

as

e

Mo

n

LO

2

4.4

3G

Hz

1-w

ay

15

6/1

59M

Hz

8 M

Hz

LO

2

BA

T

76

8M

Hz

10

MH

z LO

1

5.8

5-

6.6

5G

Hz

Joint Electron Devices Engineering Council (JEDEC) JESD204B standard


SERDES all done!

ADC12J4000

12-Bit, 4.0 GSPS RF sampling ADC with JESD204B interface


5GHz RF input

Deterministic Latentcy


Proof of concept JESD204B Digitizer


Credit:Paul Roberts

QSP+ Interface 64Gbps Decoder


Xilinx LogiCORE™ IP JESD204 core

Jitter specification critical With RFoF could be centralized Hi-Spec Synthesizer


Ultralow Noise and Spurious 0.37GHz to

6.39GHz Integer-N Synthesizer with

Integrated VCO

ENOB vs Jitter Specification


RF over Fiber with External Modulation

(can modulate to 100GHz)


The Pie Town to VLA RF over Fiber Link


MZ

Modulator

T201 1

325M

Hz....1675M

Hz

CW Laser 50mW Class III 1550nm

104km SSMF Lf = 23dB

PD

V:A

Ba

cke

nd

An

t#2

2

G = Lf Po

k

p V

2

NF ~ 1

G

High Performance, but expensive ($2k in large qty)

Direct Detection Intensity Modulation

using External Modulation

DNR Performance for External Modulation


100GHz generally higher Vp


Credit: Keith Williams NRL

Good quality laser required.


What is possible at HF/VHF


Vp Vdc

V

V

V

V

+Vb

-Vb

50W

V

V

V

V

-VDFB

CW APC

1550nm 158mW (22dBm) +14dBm +15dBm

V

V

Balanced High Power RFoF Link 130dBHz1/2 120dBHz2/3

Dual Output Mach-Zehnder Modulator LiNbO3 EOspace USA, Photline UK

Discovery DSC710 InGaAs 30dB CMRR

6dB more Gain

20dB more DNR thru RIN cancellation

Phase matching fiber required

RFoF Options

• MZM modulation

• Direct Modulation

• ElectroAbsorption Modulation

• Direct Frequency Modulation

• Phase Modulation

• Polarization Modulation

• SSB Modulation

• Linearization, Predistortion, Feedforward

• Photonic Sampling

• Optical Amplification


• Location of ADC is major architectural decision

• RFoF is undersold in a digital world.

• RFoF is an option for inner core spans.

• Prototype RFoF circuit blocks early and be ready to argue application.

• Look at risky solutions with potential

Thoughts


ngVLA will have lots of fiber (4 ADE B’ends)


End


Receiver Architecture for Radio over Glass, Analog or ......Receiver Architecture for "Radio over Glass, Analog or Digital? Progress from Australia" NGVLA WORKSHOP#2 9 DEC 2015 Ron

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