The Design of the SKA Band 5 Receiver
DARA AVN 2019
Jamie Leech, Angela Taylor, Mike Jones, Bob Watkins, Lei Liu, Andre Hector, Amin Aminaei, Tommaso Ghigna.
University of Oxford
Wu Yang, Du Baio
JLRAT / CETC54
Andy Born
UKATC
SKA Science cases
• Extreme tests of general relativity– Was Einstein right with his theory of Gravity (General Relativity)?
– Timing pulsars around black holes
– Looking at the relative timing of pulsars to infer information about gravitational waves
• Galaxies, cosmology, dark matter and dark energy– Observe the 21 cm line
– Build up a 3-D map of large scale structure of the universe, galaxy formation and evolution
• Epoch of re-ionization– “Dark Ages” start 300,000 years after big bang – universe consists of neutral hydrogen gas only
(no start galaxies)
– Around a billion years later, the first starts form. The emit UV and ionise the remaining neutral
hydrogen (“Epoch of Re-ionization”)
– Currently very poorly understood how this happens.
• Cosmic magnetism– Galaxies now have magnetic fields
– We understand how galaxies can become more magnetic if there is some initial field, but where
did the initial field come from.
• “Cradle of Life”– Dusty disks form around a star after the star forms
– These dusty disks become “rocky disks” with peddle or rocks sized particles.
– Eventually these gather together to form planets (some of which may be in the right place to
support extra-terrestrial life)
– How does all of this happen? How commonly do we expect earth like life supporting planets to
form?
Pictures
Pictures
Pictures
Pictures
Pictures
SKA MID frequencies
• Band 1 0.35 - 1.05 GHz.
• Band 2 0.95 - 1.76 GHz.
• Band 3 1.65 - 3.05 GHz.
• Band 4 2.8 - 5.18 GHz.
• Band 5 Originally 4.6 - 13.8 GHz–Now split into 5a (4.6 – 8.5) and 5b (8.3
15.3) GHz.
DISH inauguration Feb 2018
DISH inauguration, China, Feb 2018
SKA DISH Band 5 frontend Rx
• SKA-MID DISH is an offset Gregorian design, using shaped optics to improve
aperture efficiency. Low F-number = 0.5, needs wide beam width horns.
DISH in the Karoo South Africa
Dish Indexer
Dish Indexer
SPF B345 on the Indexer
SPF B345 on the Indexer
Cryostat concept
Cryostat concept
Cryostat concept
Cryostat concept
Thermal Plumbing
Thermal Plumbing
Thermal Plumbing
Thermal Plumbing
Thermal Plumbing
Cryostat body
Cryostat body
Cryostat body
Cryostat body
Cryostat concept
Vacuum windows
Vacuum Windows, Horns, OMTs
Vacuum Windows, Horns, OMTs
Vacuum Windows, Horns, OMTs
Prototype Window (B5a)
Window vacuum tests
Prototype Window (B5a)
Window thermal modelling
Window thermal modelling
Feed Horns
Cryostat concept
Feed horns + windows
Feed horns + windows
GRASP Physical Optics modelling
Aperture Efficiency
Aperture Efficiency
Beam patterns
Beam Patterns
RF Chain
Low Noise Amplifier
Warm Receiver chain
Sensitivity Calculations
Figures of Merit:
• Sensitivity: (A/Tsys) where Tsys =Tspill + Trec
• Single-pointing mapping speed: (A/Tsys)2
Calculate:
• Full optics simulation of feed+telescope
• Aperture efficiency and effective area: aperture efficiency, h, defined as the ratio of the effective collecting area (Aeff = h Ageom = Dl2/4p)
• Coupling to environment: Tspill - calculated by performing overlap integral with the beam and a thermal model of the ground and sky.
• Receiver model: Trec – calculated from a nosie model of Rx
• A/(Tspill + Trec) = Tsys
T_rec (Receiver temperature)Gain (dB) Gain Physical / Noise temp (K) Cumulative Trec Trec from
this component
Primary mirror -0.011 0.998 313 0.837 0.837
Secondary mirror -0.011 0.998 313 1.676 0.839
Cryostat window -0.02 0.995 313 3.207 1.531
Horn -0.045 0.990 70 3.943 0.736
OMT Freq. Dep. Freq. Dep. 15 Freq. Dep. Freq. Dep.
SMA cable Freq. Dep. Freq. Dep. 15 Freq. Dep. Freq. Dep.
LNA 39 7943 Freq. Dep. Freq. Dep. Freq. Dep.
T_rec (Receiver temperature)
Beam Patterns
Sky Brightness Temperature
T_sys = T_rec + T_spill
T_sys = T_rec + T_spill
Future Plans
• Finished building receiver Now to Sept 2019
• Testing / noise measurements in UK Oct, Nov,
2019
• 2020 – Transport receiver to the Karoo Desert attach to the Dish for commissioning
• 2020 – 2021 Procurement.
• 2021 -2023 “Mass” production make 150 units, for 133 Dishes + complete spare units
Thank You