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Millitech is certified to
AS9100 Rev C, ISO 9001:2008,
ISO 14001:2004 and OHSAS 18001:2007

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Cassegrain Antenna

Features:

  • Highly efficient, low VSWR
  • Wide rand of sizes available
  • Available for use from 18 to 325 GHz
  • Polarization options offered

Applications:

  • Communication systems
  • Radars and radiometers
  • EW/ELINT

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Download the CRA specsheet (.pdf)

Description

Millitech offers a wide range of parabolic reflector antennas with Cassegrain feeds. Series CRA antennas are available for operation over 18 to 325 GHz with standard reflector diameters ranging from 6”/15.24 cm to 48"/121.92 cm, depending on the frequency. The main reflector has a highly accurate metalized surface and is constructed of either carbon fiber skin with honeycomb core or machined aluminum. The sub-reflector is a machined aluminum hyperboloid which is rigidly supported by struts. These struts are designed to have minimal cross-section with reduced aperture blockage, and hence, produce low sidelobe levels (typically 18 dB).

The feeds are designed to obtain the best performance over the widest bandwidth possible. The gain of the antenna depends upon its diameter, illumination, and frequency of operation.

The sidelobes are determined by the edge illumination taper as well as by the sub-reflector blockage. Typical match into the antenna feed input is 1.44:1 with a net efficiency of 50%. For boresighting the antenna, an optional boresighted telescopic sight can be provided. Reflector diameters of 6 to 12 inches are available for frequencies from 18 to 325 GHz. 24 to 48 inch models are available for 18 to 110 GHz.

Millitech also offers fixed polarizers (series POL) and series OMT orthomode transducers.

Radomes are available for select frequency bands, contact Millitech for more details.

Electrical Specifications:

Performance Parameter Range Remarks
Frequency Range (GHz) 18 to 325 Practical range for waveguide feeds.
Standard Reflector Diameters (in)* 6, 10, 12, 18, 24, 36, 48 Other diameters available as custom products.
Beamwidth (degrees) (nom) 0.1 to 3.0 Beamwidth depends on frequency and diameter selected.
Gain (dBi) (nom) 35 to 60 Depending on the frequency and diameter selected.
Sidelobes (dB) (typ) 18 Typical value for standard product. Blockage by subreflector determines sidelobe level.
VSWR (typ) 1.5:1

* Larger, non-standard reflector diameters are available. Please consult Millitech for details.

Outline Drawings:

CRA Outline Drawing

Mechanical Specifications

A Reflector Diameter (in/mm) 6.0/152 10.0/254 12.0/305 18.0/457 24.0/610 36.0/914 48.0/1219
B Housing Diameter (in/mm) 6.0/152 10.0/254 12.0/305 18.8/478 24.8/630 36.8/935 49.2/1250
C (in/mm) 4.0/102 7.0/178 10.0/254 10.0/254 16.5/419 24.0/610 36.0/914
D (in/mm) 3.6/91 5.1/130 5.4/137 6.9/175 7.8/198 9.5/241 14/356
E (in/mm) .190-24UNC. .375-16UNC. .375-16UNC. .375-16UNC. .375-16UNC. .375-16UNC. .500-13UNC.

Circular Waveguide Sizes

Rectangular Waveguide Band Circular Diameter Size Frequency Range (GHz)* Circular Waveguide Diameter (in/mm) Specify When Ordering
K Large 17.5-20.5 0.455/11.56 455
Medium 20.0-24.5 0.396/10.06 396
Small 24.0-26.5 0.328/8.33 328
Ka Large 26.5-33.0 0.315/8.00 315
Medium 33.0-38.5 0.250/6.35 250
Small 38.5-40.0 0.219/5.56 219
Q Large 33.0-38.5 0.250/6.35 250
Medium 38.5-43.0 0.219/5.56 219
Small 43.0-50.0 0.188/4.78 188
U Large 40.0-43.0 0.210/5.33 210
Medium 43.0-50.0 0.188/4.78 188
Small 50.0-60.0 0.165/4.19 165
V Large 50.0-58.0 0.165/4.19 165
Medium 58.0-68.0 0.141/3.58 141
Small 68.0-75.0 0.125/3.18 125
E Large 60.0-66.0 0.136/3.45 136
Medium 66.0-82.0 0.125/3.18 125
Small 82.0-90.0 0.094/2.39 094
W Large 75.0-88.0 0.112/2.84 112
Small 88.0-110.0 0.094/2.39 094
F Large 90.0-115.0 0.089/2.26 089
Small 115.0-140.0 0.075/1.91 075
D Large 110.0-140.0 0.073/1.85 073
Small 140.0-160.0 0.059/1.50 059
G Large 140.0-180.0 0.058/1.47 058
Small 180.0-220.0 0.045/1.14 045
--- --- 170.0-260.0 0.049/1.25 049
--- --- 220.0-325.0 0.039/0.99 039

* If the required frequencies fall within two waveguide diameter sizes, the larger one should be selected.

How To Order

Specify Model Number
CRA-XX-ABBBCCD
XX = Waveguide Band
  • WR – number

A = Flange Type
  • R – round (WR-28 through WR-03 only)
  • S – square (WR-42 and WR-28 only)
  • A – Precision Flange per Millitech IS000131, flat option (WR-08 through WR-05 only)
BBB = Circular Waveguide Diameter (in inches
  • See Waveguide Sizes Table (previous table)
  • Specify ØØØ for rectangular waveguide
CC = Reflector Diameter (in/cm)
  • 06 – 6/15.24
  • 10 – 10/25.4
  • 12 – 12/30.48
  • 13 – 13/33.02
  • 15 – 15/38.10
  • 18 – 18/45.72
  • 24 – 24/60.96
  • 36 – 36/91.44
  • 48 – 48/121.92
  • D = Material Options
  • C – carbon fiber skin with honeycomb core
  • A – machined aluminum (6” and 12” diameters only)