12
P. Maat, L. Goudbeek, R.H. Witvers, J. Idserda Low cost, long distance RF over fiber link technology for radio telescope systems
P. Maat, L. Goudbeek, R.H. Witvers, J. Idserda
Low cost, long distance RF over fiber link technologyfor radio telescope systems
Antennas
Antennas
Antennas
CentralProcessor
Photonic Technology for TelescopesAntennas
SKA / Low Frequency Aperture Array: RFoF based signal transport130000 antennas, each requiring two RFoF links to a Central Processor Frequency band: 50 – 350 MHzTransmission distance up to 10 kmCost level of less than 50 Euro per linkLow power consumptionEasy assembly
ASTRON/URSI GA 2017 p1
RFoF: Design
Design of the RFoF modulePluggable moduleNo fibre pigtail. Instead: patch position for fibre-optic cable connectorLow cost TOSA / ROSA package with DFB laserUSB-A connector interface: RF, DC bias and controlLayout:
(a) Body(b) Laser and PCB (RF amplifier / impedance matching)(c) Cover
ASTRON/URSI GA 2017 p2
LaserInGaAP/InP, single mode DFB Laser DiodeOutput Power to 2 mWWide Operation Temperature 0~70C without Active CoolingBandwidth up to 2 GHzBuilt-in 1 Stage Optical Isolator
PhotodetectorInGaAP/InP PIN PhotodiodeSaturation Power > 1.5 mWResponsivity @ 1310 nm of 0.85 A/WWavelength from 1100 nm to 1600 nmBandwidth beyond 2 GHz
RFoF: Design
1300 1310 1320Wavelength (nm)
-10°C 20°C 50°C
-60
-30
0
dB
ASTRON/URSI GA 2017 p3
Electronic designIntensity ModulationPower Supply: +3.3 V
Supply Current Tx: 23 mA Supply Current Rx: 11 mA
Bandwidth 50 – 350 MHzBlock Diagram:
RFFilter
RF Amplifier
Signal in
Laser
RFFilter
RF Amplifier
Signal out
Fibre-optic cable
Detector
RFoF: Design
0 15 30Current (mA)
0
1
2
Opt
ical
Pow
er (m
W)
ASTRON/URSI GA 2017 p4
S11
S22
S21
S12
RFoF: Performance
-30
-15
0
(dB
)
0 500 1000Frequency (MHz)
0
10
20
(dB
)
0 500 1000Frequency (MHz)
-80
-40
0
(dB
)
0 500 1000Frequency (MHz)
-30
-15
0
(dB
)
0 500 1000Frequency (MHz)
-10°C 20°C 50°C
ASTRON/URSI GA 2017 p5
Noise Figure
Distortion LevelsIIP2: -1.26 dBm at 20°C and 144 MHzIIP3: -1.74 dBm at 20°C and 144 MHz
RFoF: Performance
-10°C20°C
50°C
0
10
20
(dB
)
0 500 1000Frequency (MHz)
ASTRON/URSI GA 2017 p6
Modulation window
-10°C20°C
50°C
RFoF: Performance
-10°C50°C
15
20
25
RF
out (
dB)
-30 -15 0RF in (dB)
0
1
2
Opt
ical
Pow
er (m
W)
0 15 30Current (mA)
-1 dB Compression
Distortion & Compression at T> 50°C Low power operation => bias point close to threshold
ASTRON/URSI GA 2017 p7
RFoF: Cost
Nor
mal
ised
Cos
t Lev
el
Quantity
0
0.2
0.4
0.6
0.8
1
1.2
1 10 100 1000 10000 100000
Body Cover ROSA TOSA PCB total
Component Cost per Link
ASTRON/URSI GA 2017 p8
Transmitter Module
Performance distribution
RFoF: Performance
0
30
60
Qua
ntity
-10 -6 -2Link Gain (dB)
0
40
80
Qua
ntity
14 18 22Link Gain (dB)
Receiver Module
10
30
50
Qua
ntity
14 18 22Link Gain (dB)
RFoF Link (Tx + Rx)
ASTRON/URSI GA 2017 p10
ASTRON/URSI GA 2017 p9
Accelerated ageing at 80°C
RFoF: Reliability
12
16
20
Link
Gai
n (d
B)
Dec 2015 Jul 2017
P. Maat, L. Goudbeek, R.H. Witvers, J. Idserda
RF over Fiber Tx and Rx modulesLow cost designLow cost productionReliable operation
