WVR workshop, Wettzell, 2006 10 10Miroslav Pantaleev Development of the Dicke-switched WVR prototype...

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


Development of the Dicke-switched prototype for the ALMA WVR

Radiometer design - Double Dicke

Critical components

Lab tests

SMA - tests

Single Dicke prototype


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


Calibration Hot and Cold

Solenoid Vane

Hot load


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


Chopper blade

Dynamically balanced chopper wheel

No holes to avoid turbulences


Chopper support

Bearings – SKF

Lifetime – more than 25 years (depending on the operational rpm)

Flexible coupling to dump vibrations


Chopper protective cover


Chopper blade positioning

Brushless motor3600 step encorder

S/Rinput

Choppercontrolelectronics


Chopper timing

Chopper 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

Chopper

edge

A/D sampling rate

= 0.5 ms


Measured chopper data

Chopper blade jitter


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

GunnIsolator

91,6 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


Mixer


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


DSB - Noise temperature Double Dicke


Sensitivity


Filter bands

0 1000 2000 3000 4000 5000 6000 7000

MHz

-30

-25

-20

-15

-10

-5

-0

dB

WVR Filter bands

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.


Filter and video assembly


Custom designed filters

Bandpass filter B (1.565GHz – 2.315GHz)

Ring resonators bandpass filter

Compact, low insertion-loss, sharp-rejection, and wide-band application


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.


Cooling power


Cooled load mount


Thermal stabilization

Insulation

Frame with Peltier cooler

IF temperature regulation


Single Dicke


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

GunnIsolator

91,6 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


Optics layout - Comparison


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


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


Current status


IF linearity

NoiseDiode

ENR=15.2 dB

Atten.1:stIF

2:ndIF

6 dB

SpectrumAnalyzer

(20 GHz bandpower)

Fixed

3 dB

WVR workshop, Wettzell, 2006 10 10Miroslav Pantaleev Development of the Dicke-switched WVR prototype...

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Transcript of WVR workshop, Wettzell, 2006 10 10Miroslav Pantaleev Development of the Dicke-switched WVR prototype...