The Design of the SKA Band 5 Receiver DARA AVN...

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

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

Cryostat concept

Thermal Plumbing

Cryostat body

Cryostat concept

Vacuum windows

Vacuum Windows, Horns, OMTs

Prototype Window (B5a)

Window vacuum tests

Prototype Window (B5a)

Window thermal modelling

Feed Horns

Cryostat concept

Feed horns + windows

GRASP Physical Optics modelling

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

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

The Design of the SKA Band 5 Receiver DARA AVN...

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