Design and Performance of Concealed Enclosures for SATCOM and Telecom

Transcription

1 Design and Performance of Concealed Enclosures for SATCOM and Telecom D. J. Kozakoff 1, J.Fitzhugh 2 and W.Pounds 3 Affiliations: 1. Consultant and Subject Matter Expert, 2. President and CEO of Concealfab Corporation, and 3. Vice President of Engineering of Concealfab Corporation

2 What this presentation is all about For zoning or security reasons it is often desirable to enclose telecom antennas and radios within an RF invisible enclosure to conceal the antenna(s) from public visibility. An RF invisible enclosure, when properly designed, will have negligible effect on the enclosed antenna.

3 What you will learn about in this presentation RF transparent construction materials: parameters that are important. Important antenna parameters to preserve. Mathematical approaches to computing the effect of the enclosure. Unique problems that sometimes arise. Other issues.

4 Small Structures

5 Small Size Structures

6 Medium Size Structure

7 Large Size Structure

8 Small Cell Deployment Poles Environmental Specifications 142 mph continuous wind speed, 3-second gusts of 180 mph (ASCE 7-5/10). TIA-222-G Structural standard for antenna supporting structures and antennas. AASHTO standard specification for structural supports for highway signs, luminaires and traffic signals, 6 th edition.

9 Medium Enclosures Environmental Specifications Medium enclosures are 12 by 12 by 12, or smaller. Structural frame supporting RF transparent materials can also be of an RF transparent material. Structure must conform to the latest version of the International Building Code (IBC). 75 mph basic wind speed with 125 mph gusts. -40 to +125 degrees F ambient rating. Must handle up to 30 pounds per square foot of snow load.

10 Large Enclosures Environmental Specifications Large enclosures are larger than 12 by 12 by 12. Structural frame supporting RF transparent materials must use steel members (non RF transparent). Structure must conform to the latest version of the International Building Code (IBC). 90 mph basic wind speed with 125 mph gusts. -40 to +125 degrees F ambient rating. Must handle up to 30 pounds per square foot of snow load.

11 Some Candidate Thermoplastic Materials Material Dielectric Constant Loss Tangent Acrylic Polypropylene ABS Polycarbonate Polyethylene Teflon Polyvinyl Chloride Nylon Celtek (expanded PVC)

12 Forms of Thermoplastic Materials Candidate structural wall or roofing materials can be flat or corrugated panels. Some candidate materials such as the twin wall polycarbonate roofing material (right) are reduced weight, effective dielectric constant and loss.

13 Some Candidate Thermoset Materials Preferred solid wall materials are a fiber reinforced plastic (FRP) Potential resins include epoxy, polyamide, silicone, cyanate ester Potential reinforcement fibers include fiberglass, quartz, polyester C-sandwich constructions offer ultra broadband performance Candidate skin materials include fiberglass, quartz, polyester or Dyneema (UHMWPE) Most viable core material is a polyethylene core (low cost, low weight

14 Some Candidate C-Sandwich Materials Material Dielectric Constant Loss Tangent Epoxy Fiberglass Epoxy Quartz Cyanate Ester Quartz Dyneema (UHMWPE) Closed Cell Polyethylene Foam Material

15 Dyneema C sandwich siding at 0 deg AOI

16 Dyneema C sandwich siding at 30 deg AOI

17 Corrugated epoxy fiberglass

18 Electromagnetic Considerations The effect of an enclosure on an antenna pattern is determined by comparison of the computed antenna pattern with and without enclosure. Complex transmission coefficient for rays intersecting various portions of an enclosure wall are determined by a boundary value, multilayer dielectric solution.

19 Antenna pattern from A by B size rectangular aperture (no enclosure) E θ, = +A/2 X= A/2 +B/2 Y= B/2 I(X, Y)e i(kxx+kyy) dxdy Where I(X, Y) is the internal aperture distribution and Kx = k Cos θ Cos φ Ky = k Sin θ Sin Ф

20 Antenna pattern from A by B size rectangular aperture (with enclosure) E θ, = +A/2 X= A/2 +B/2 Y= B/2 T(X, Y)I(X, Y)e i(kxx+kyy) dxdy Where T(X,Y)I(X, Y) is the external aperture distribution and Kx = k Cos θ Cos φ Ky = k Sin θ Sin Ф

21 Difference between internal and external antenna aperture

22 Sample Antenna Patterns Satellite Downlink Frequency (Ka Band) Satellite Uplink Frequency (Ka Band)

23 START 3D Radome Program MAIN (EXECUTIVE PROGRAM) INTERNAL APERTURE EXTERNAL APERTURE INTERCEPT COMPUTE PATTERNS WALL END

24 Reduction of Antenna Data For an antenna in a fixed position, comparison of the internal aperture antenna pattern with the external aperture antenna pattern allows quantification of all important structure effects on the antenna performance. For an antenna that is movable or scanned, data can be represented over upper half space for all possible antenna pointing angles.

25 Data Representation for Scanned Antennas Create data contours based on no more than 15 degree computation increments in both AZ and EL. The methodology is somewhat labor intensive.

26 Parameters for Contour Plots Linear Polarized Antennas Principal polarization loss (db) Orthogonal polarization loss (db) Boresight error (MRAD) Registration error (MRAD) Increase in antenna VSWR Increase in antenna noise temperature Circular Polarized Antennas Copol transmission loss (db) Xpol transmission loss (db) Axial ratio (db) Boresight error (MRAD) Registration error (MRAD) Increase in antenna VSWR Increase in antenna noise temperature

27 Thank You for Viewing Our Presentation Have a Nice Day! D. J. Kozakoff dr.kozakoff@yahoo.com J. Fitzhugh jfitzhugh@concealfab.com W. Pounds wpounds@concealfab.com