1. DVAC PROGRESS OFFSET GREGORIAN DISH (DVAC-1) 郑元鹏 (Yuanpeng Zheng ) Joint Lab. for Radio Astronomy and Technology MAY 29, 2012

2. 1.DVAC-1 Concept Design 2.DVAC-1 Main Specification Budget Outline DVAC-1 DVAC-2

3. Antenna TypeOffset-Gregorian Antenna, Diameter 15m Mount Type EL over AZ (AZ ： Gear ， EL: Screw) Frequency Band0.3GHz ~ 10GHz Frequency Band Switch MannerSwitching Feeds within 30s Surface Accuracy of Main Reflector  0.6 mm RMS ( T  3°C,  9.8 m/s) Pointing Accuracy  10 arcsec RMS Antenna Aperture Efficiency (%)  62% 1. DVAC-1 Concept Design Main Specifications for DVAC-1

4. PolarizationDual-LP/Dual-CP Travel Range AZ ：  270°, EL ： 15°  85° Slew Rates (Max) AZ ： 3°/s, El ： 1°/s Acceleration (Max) AZ ： 3°/s 2, El ： 1°/s 2 Wind Velocity Drive to stow :70 km/h Survival: 160 km/h Design Lifetime  30 years 1. DVAC-1 Concept Design Main Specifications for DVAC-1

5. 1. DVAC-1 Concept Design Concept design progress 2010 2011 2012

6. (1) Microwave Optical Design (2) Structure Design (3) Servo Control Design 1. DVAC-1 Concept Design

7.  Feed Design Operating frequency: 0.3GHz~10GHz (33 octaves) 1. Concept Design (1) Microwave Optical Design two wide-band feeds (WBF) WBF advantages:  Bandwidth of several octaves;  Dual linear or circular polarization  Constant phase centre  Equal E- and H-plane beamwidth

8. 1. Concept Design (1) Microwave Optical Design  Feed Design Feed 1(0.3GHz ~ 1.5GHz ) and Feed 2(1.5GHz ~ 10GHz ) Eleven Feed Simulation Model Frequency (GHz) Length×Width×Height (mm) Weight (kg) 0.3~1.51040×1040×35020 1.5~10250×250×1208

9. Optimum Design  Main and Sub Reflector Curve Design 55°Opening Angle -13dB Feed Edge Taper 1. Concept Design (1) Microwave Optical Design

10.  Reflector Design  Mount Design  Structural Mechanics Analysis 1. Concept Design (2) Structure Design

11.  Reflector Design  Main reflector  Back structure  Subreflector  Feed switch mechanism 1. Concept Design (2) Structure Design

12.  Reflector Design — Main reflector 1. Concept Design (2) Structure Design One-piece composite foam sandwich structure with metalizing surface Carbon fibre skins and sandwich polyurethane foam Back ribs Surface accuracyσ≤0.5mm rms

13.  Reflector Design — Back structure 1. Concept Design (2) Structure Design

14.  Reflector Design — Subreflector One-piece composite foam sandwich structure with metalizing surface. Surface accuracy σ≤0.2mm rms 1. Concept Design (2) Structure Design Accuracyσ≤0.3mm

15. Elevation Part Azimuth Part Pedestal  Mount Design 1. Concept Design (2) Structure Design

16.  Mount Design — Azimuth part  Dual-motor anti-backlash drive  External gear bearing, easy to maintain  Seal cover is used to exclude dust and sand 1. Concept Design (2) Structure Design

17.  Mount Design — Elevation part A planetary reducer with a ball screw drive is used for the elevation part. 1. Concept Design (2) Structure Design

18.  Mount Design  A flexible-axis drive technique is adopted for Az and EI encoder mechanism.  A double-layer ring structure is used for AZ cable wrap.  A modular design for all rotating parts.  A Line-Replaceable Unit (LRU) design is applied to reducer, motor, encoder and limit device, azimuth cable wrap, and elevation lock device. Not only for ease of replacement and maintenance, but also suitable for batch production. 1. Concept Design (2) Structure Design

19.  Structural Mechanics Analysis  Finite Element Model 1. Concept Design (2) Structure Design

20.  Reflector Surface Deformation by Gravity  Structural Mechanics Analysis Best Fit Surface Error by Gravity 1. Concept Design (2) Structure Design EL=15°EL=45°EL=90°

21.  Structural Mechanics Analysis 1. Concept Design (2) Structure Design  Reflector Surface Deformation by Gravity, Wind, and Temperature Total Surface Accuracy: Less than 0.62 mm from 15 to 90 degree

22.  Antenna control unit (ACU)  Feed Control  Antenna drivers  Motors  Power distribution devices  Encoders  Local control pendant  Limit and safety protection device 1. Concept Design (3) Servo Control Design

23.  Mature Product  State-of-the-art components  Fully digital control system  Very high reliability  Modular design, easy for maintenance  Brushless motors, no maintenance  Spare part available Main features of control system 1. Concept Design (3) Servo Control Design

24.  STANDBY Power-on default operation mode or return-on-fault mode  PRESET Moving to predefined position  RATE Moving at user-defined constant velocity  PROGRAM TRACK Tracking of an object along a pre-defined path  STOW Automatically rotating to preset stow position and locking stow pin 1. Concept Design (3) Servo Control Design

25. 2. Main Specification Budget (1) Antenna Aperture Efficiency Frequency （ GHz ） η 1 η 2 η3η3 η4η4 η5η5 η( % ) 0.30.7110.950.9866 0.90.7610.950.9871 1.5(feed 1)0.7810.950.9872 1.5(feed 2)0.7710.950.9871 60.810.930.950.9871 100.810.820.950.9862

26. 2. Main Specification Budget (2) Pointing accuracy Error source (r.m.s.)Error (arcsec) Residual error (arcsec) Modification method Verticality of the azimuth axis103Pointing model Azimuth-Elevation non- orthogonality 33- Azimuth bearing run-out44- Adjust error of sub-reflector and feed 33- Gravity deformation112Lookup table Thermal deformation<1 Wind deformation-- Servo error55 Uncertain error33 Total error (RMS)8.7 arcsec (at night and windless)

27. Thank You END