Radio Telescope Receivers

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1 Radio Telescope Receivers Alex Dunning 25 th September 2017 CSIRO ASTRONOMY AND SPACE SCIENCE

2 A radio receiver is an electronic device that receives radio waves and converts the information carried by them to a usable form Wikipedia 2 Receiver Systems for Radio Astronomy Alex Dunning

3 Ours look more like this Captures the signal reflected from the antenna Determines the beam shape Amplifies the signal Conditions the signal for digitisation Parkes 10/40cm Receiver 3 Receiver Systems for Radio Astronomy Alex Dunning

4 On the outside Feed Horns Vacuum Dewar Control and Monitoring electronics 4 Receiver Systems for Radio Astronomy Alex Dunning

5 On the inside 5 Receiver Systems for Radio Astronomy Alex Dunning

6 Feed Horn 6 Receiver Systems for Radio Astronomy Alex Dunning

7 Detour: Reciprocity Forward VV BB = SS BBBB VV AA A Microwave Network Reverse VV AA = SS AAAA VV BB Reciprocal SS BBBB = SS AAAA B 7 Receiver Systems for Radio Astronomy Alex Dunning

8 8 Receiver Systems for Radio Astronomy Alex Dunning

9 θ α 9 Receiver Systems for Radio Astronomy Alex Dunning

10 10 Receiver Systems for Radio Astronomy Alex Dunning

Corrugated Smooth Walled E-Field At Feed mouth 300 300 250 250 X and Y Feed Patterns Gain 200 150 100 Gain 200 150 100 50 50 0-25

11 Corrugated Smooth Walled E-Field At Feed mouth X and Y Feed Patterns Gain Gain Theta [deg] Theta [deg] 11 Receiver Systems for Radio Astronomy Alex Dunning

12 Feed Coupler Signal Noise source Noise coupled in through small holes 7mm waveguide coupler Noise coupled in through vane 21cm waveguide coupler 12mm noise source 12 Receiver Systems for Radio Astronomy Alex Dunning

13 Signal Feed Coupler Ortho-mode Transducer Pol A Noise source Pol B B output A output Input 13 Receiver Systems for Radio Astronomy Alex Dunning

14 Separating the Polarisations: The OMT 14 Receiver Systems for Radio Astronomy Alex Dunning

15 Signal Feed Coupler Ortho-mode Transducer Pol A LNA Noise source Pol B LNA High Electron Mobility Transistor (HEMT) Low Noise Amplifier 15 Receiver Systems for Radio Astronomy Alex Dunning

16 Noise PP oooooooooooo GGGGGGGG ff Noiseless Termination Low Noise Amplifier Noise PP oooooooooooo = GGGGGGGG ff kk BB TT rrrrrrrrrrrrrrrr Black body Termination Noiseless Amplifier Noise TT eeeeeeeeeeeeeeeeeeee = PP oooooooooooo GGGGGGGG ff kk BB 16 Receiver Systems for Radio Astronomy Alex Dunning

17 T system = T 1 + T2 Gain LNA + T Gain 3 LNA G 2 + Gain LNA T4 G 2 G 3 T 1 T 2 T 3 Feed Signal LNA Second Stage Amplifier Third Stage Amplifier 17 Receiver Systems for Radio Astronomy Alex Dunning

18 10Jy radio source ~1K additional noise Your hand ~300K additional noise Zirconicusso Freepik.com Mobile Phone at 1 km ~ K!! (in primary beam) 18 Receiver Systems for Radio Astronomy Alex Dunning

19 Noise contributions of a typical receiver Part Room Temperature Cryogenic Ratio Sky + CMB (T sky ) 6K 6K 1 Spillover (T spill ) 3K 3K 1 Feed + OMT 10K 2K 5 LNA (T lna ) 35K 5K 7 Rest of the System 1K 1K 1 Total (T sys ) 55K 17K ~3 19 Receiver Systems for Radio Astronomy Alex Dunning

20 15K section 70K section Cold finger Helium Compressor Refrigerator in the Parkes 12mm receiver Helium Refrigerator Helium Lines 20 Receiver Systems for Radio Astronomy Alex Dunning

21 Gap Thermal Isolation waveguide Vacuum Dewar 15K section Helium Refrigerator cold finger Low Noise Amplifiers Copper Radiation Shield 70K 21 Receiver Systems for Radio Astronomy Alex Dunning CSIRO. Receiver Systems for Radio Astronomy

22 The RF System Signal Amplifier Filter Frequency Conversion Level Adjustment To Digitiser Contains: More amplification Band defining filters Frequency conversion Level adjustment Signal detection Band shaping 22 Receiver Systems for Radio Astronomy Alex Dunning

23 Mixer (Multiplier) Signal 1 Signal 1 Signal 2 Signal 2 cos(ω 1 t)cos(ω 2 t)=½[cos((ω 1 +ω 2 )t)+ cos((ω 1 -ω 2 )t)] Power Power Δf Frequency Δf Frequency 23 Receiver Systems for Radio Astronomy Alex Dunning

24 Mixer (Multiplier) Signal 1 Signal 2 Low pass filter cos(ω 1 t)cos(ω 2 t)=½[cos((ω 1 +ω 2 )t)+ cos((ω 1 -ω 2 )t)] Power Power Δf Frequency Δf Frequency 24 Receiver Systems for Radio Astronomy Alex Dunning

25 Mixer (Multiplier) Signal 1 Local Oscillator cos(ω 1 t)cos(ω LO t) ½cos[(ω 1 -ω LO )t] Power f lo Upper Side Band (USB) Power Frequency Frequency Δf Δf 25 Receiver Systems for Radio Astronomy Alex Dunning

26 Mixer (Multiplier) Signal 1 Lower Side Band (LSB) Local Oscillator cos(ω 1 t)cos(ω LO t) ½cos[(ω LO -ω 1 )t] Power f lo Power Δf Frequency Δf Frequency 26 Receiver Systems for Radio Astronomy Alex Dunning

27 Mixer (Multiplier) Signal 1 Band pass filter Local Oscillator Power f lo Power Δf 27 Receiver Systems for Radio Astronomy Alex Dunning Frequency Δf Frequency

28 The modern radio telescope megapixels 28 Receiver Systems for Radio Astronomy Alex Dunning

29 Photo credit: Wheeler Studios 29 Receiver Systems for Radio Astronomy Alex Dunning

30 30 Receiver Systems for Radio Astronomy Alex Dunning

31 31 Receiver Systems for Radio Astronomy Alex Dunning

32 Digital beamformer Weighted (complex) sum of inputs 32 Receiver Systems for Radio Astronomy Alex Dunning

33 33 Receiver Systems for Radio Astronomy Alex Dunning

Thank you CSIRO Astronomy and Space Science Alex Dunning t +61 2 9372 4346

34 Thank you CSIRO Astronomy and Space Science Alex Dunning t e alex.dunning@csiro.au w CSIRO ASTRONOMY AND SPACE SCIENCE

Detector Systems. Graeme Carrad

Detector Systems. Graeme Carrad Detector Systems Graeme Carrad November 2011 The Basic Structure of a typical Radio Telescope Antenna Receiver Conversion Digitiser Signal Processing / Correlator They are much the same CSIRO. Radiotelescope