development of the dicke-switched wvr prototype for alma · development of the dicke-switched wvr...
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![Page 1: Development of the Dicke-switched WVR prototype for ALMA · Development of the Dicke-switched WVR prototype for ALMA Magne Hagström, Lars Pettersson and Leif Helldner ... 91.6 GHz](https://reader034.vdocuments.us/reader034/viewer/2022042205/5ea7824877eec60f0755d82a/html5/thumbnails/1.jpg)
WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Development of the Dicke-switched WVR prototype for ALMA
Magne Hagström, Lars Pettersson and Leif Helldner
Collaboration with
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
![Page 3: Development of the Dicke-switched WVR prototype for ALMA · Development of the Dicke-switched WVR prototype for ALMA Magne Hagström, Lars Pettersson and Leif Helldner ... 91.6 GHz](https://reader034.vdocuments.us/reader034/viewer/2022042205/5ea7824877eec60f0755d82a/html5/thumbnails/3.jpg)
WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Development of the Dicke-switched prototype for the ALMA WVR
• Radiometer design - Double Dicke
• Critical components
• Lab tests
• SMA - tests
• Single Dicke prototype
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Optics layout - Double Dicke
M5
M5
C2
M4
C1
M3
• Chopper wheel to select between sky - calibration
• Measure all the time
• Cryo cooler as cold load
• Warm mixers and LNA
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Calibration Hot and Cold
Solenoid Vane
Hot load
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Chopper wheel function and design goals
• Reliable > 10 years of continuous running
• Small blade diameter – cut a small beam waist
• Phase locked to external square wave
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Chopper blade
• Dynamically balanced chopper wheel
• No holes to avoid turbulences
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Chopper support
• Bearings – SKF
• Lifetime – more than 25 years (depending on the operational rpm)
• Flexible coupling to dump vibrations
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Chopper protective cover
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Chopper blade positioning
Brushless motor3600 step encorder
S/Rinput
Choppercontrolelectronics
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Chopper timingChopper speed = 10.42 Hz
48 ms
-36 dBbeam
Blanking = 3.2 ms 6.7 %
± Blade Jitter 0.2 ms
-.9 ms
89 A/D samples
Dicke radiometer Sampling rate and Chopper timing
Chopperedge
A/D sampling rate= 0.5 ms
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Measured chopper data
Phase locked to external square wave. Switching rate 5-32 Hz (31 - 200 ms) Blanking time (-35 dB taper) 4.5 % (6.7 %) Blade jitter <0.5 ms Lock-in time 6-10 s Allowed external TTL jitter without affecting the blade jitter <0.5 ms
Chopper blade jitter
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Block diagram Double Dicke
6 dB
LP 960 MHz
LP 2315 MHz
LP 3800 MHz
BP 3,95-6,45
BP 2,55-3,80
BP 1,56-2,32
BP 800-960
GunnIsolator91,6 GHz
Coupler
-3dB
-3dB
Harm.
Diplexer
6 dB
Ch 1
Ch 2
Phase lock6 dB
6 dB
6 dB
Mixer
G=47 dBG=32 dB
Powersupply
IF= .5 - 8 GHz
WVR Dicke version
0.048 dB/C 0.070 dB/C
LO power0.026 dB/C
0.017 dB/C -0.004 dB/C
Fixed Atten.
4 way P/S
Power Splitter
Phase Lock
Copper control
Calibration control
Temp. control
Micro- processor
-0.9 dBm / 10 GHz(1 dB Comp.= +14 dBm)
-23 dBm / ∆ B
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Mixer
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
3 dB, 91.6 GHz power divider
• Waveguide branch type couplers – many section required to cover wide bandwidth
• Double probe structure is coupled to the E-field in a waveguideBy courtesy of V.Vassilev
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
DSB - Noise temperature Double Dicke
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Sensitivity
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Filter bands
0 1000 2000 3000 4000 5000 6000 7000
MHz
-30
-25
-20
-15
-10
-5
-0
dB
• The LO frequency is kept very close to line frequency.
• Mixers are double sideband.
• Four IF channels with larger bandwidth away from the centre of the line.
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Filter and video assembly
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Custom designed filters
• Bandpass filter B (1.565GHz – 2.315GHz)
•Ring resonators bandpass filter
• Compact, low insertion-loss, sharp-rejection, and wide-band application
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Calibration reference loads
• Two reference temperatures with a ∆T ≈ 150 K,
one of them close to sky the temperature
• Peltier element - not possible to get below – 50 ºC
• Noise diode - only ≈ 4 dB ENR
Sterling cooler• Cool a microwave absorber to below 150 K.
• Stabilize the temperature of the absorber to < 0.05 K
• Absorber reflectivity > 30 dB at 183 GHz.
• Maintenance free time ≈ 10 years.
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Cooling power
80 90 100 110 120 130 140 150 160
Cooled load in °K
200
300
400
500
600
700
800
mW
Airglass + PPA30
Polyurethane + PPA30
Hymatic cooling power
Hymatic cooling power vs.conductivity loss
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Cooled load mount
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Thermal stabilization
Insulation
Frame with Peltier cooler
IF temperature regulation
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Single Dicke
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Block diagram Single Dicke
6 dB
LP 960 MHz
LP 2315 MHz
LP 3800 MHz
BP 3,95-6,45
BP 2,55-3,80
BP 1,56-2,32
BP 800-960
GunnIsolator91,6 GHz
Coupler
-3dB
-3dB
Harm.
Diplexer
6 dB
Ch 1
Ch 2
Phase lock6 dB
6 dB
6 dB
Mixer
G=47 dBG=32 dB
Powersupply
IF= .5 - 8 GHz
WVR Dicke version
0.048 dB/C 0.070 dB/C
LO power0.026 dB/C
0.017 dB/C -0.004 dB/C
Fixed Atten.
4 way P/S
Power Splitter
Phase Lock
Copper control
Calibration control
Temp. control
Micro- processor
-0.9 dBm / 10 GHz(1 dB Comp.= +14 dBm)
-23 dBm / ∆ B
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Optics layout - Comparison
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Physical size comparison: Double -Single Dicke
Cost saving pre-production design work
• Single Dicke Receiver
• Replacement of the Hymatic Sterling cooler with a Peltier cooler
• Replacement of the cold load with a cool/hot load combination
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Cold load
• Single Dicke Receiver
• Replacement of the Hymatic Sterling cooler with a Peltier cooler
• Replacement of the cold load with a cool/hot load combination
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
Current status
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WVR workshop, Wettzell, 2006 10 10 Miroslav Pantaleev
IF linearity
NoiseDiode
ENR=15.2 dB
Atten. 1:stIF
2:ndIF6 dB
SpectrumAnalyzer
(20 GHz bandpower)
Fixed
3 dB