Satellite Communications/Feed Membrane C Band

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Question
Hi,

I'm looking for a substance that is tougher to be penetrate by animal, i.e. monkeys/birds for the C-band feed membrane. We are currently using Teflon sheet recommended by the antenna manufacturer.

Would appreciate the advice.

Regards,
HoonLeong

Answer
Dear Hoon Leong:

Material science is not my specialty, but your question intrigued me because I have not previously encountered a requirement that something be monkey proof.

I did a Google search on the term “materials for radomes at 4 – 8 GHz.”

The Microwave Product Digest featured an article entitled “A Fundamental and Technical Review of Radomes.” (http://www.mpdigest.com/issue/articles/2008/may/mfg/default.asp) It indicates “Modern ground-based and ship-based radomes are manufactured using composite materials such as fiberglass, quartz, and aramid fibers held together with polyester, epoxy, and other resins [1], such as the one shown in Figure 1. [You will have to go to the website to see Figure 1.]Foam and honeycomb cores are often added between inner and outer “skins” of the radome to function as a low-dielectric-constant spacer material providing structural strength and rigidity.”

“Avionic Radome Materials” is a NATO report that was published in 1974. It is extremely comprehensive including a wide range of materials, both inorganic and organic. The report is available at http://www.dtic.mil/dtic/tr/fulltext/u2/a007956.pdf.

Section 2 provides data on 15 inorganic materials and numerous categories of organic materials including fiberglass; resin composites; polyester resins and composites; epoxy resins and composites; polyimide and P.B.I. resins and composites; silicon resins and composites; phenolic resins and composites; and diallyl phthalate composite. For each of the many materials, the report provided its electrical, mechanical, thermal, and environmental properties.

The report notes that “Inorganic materials come into their own particularly when organic materials fail due to loss of strength at higher temperatures.” This generally applies to radomes on high performance aircraft or missiles.

Fused silica (SiO2) is suitable for most shaped radomes (p. 39). I assume that a flat membrane would be suitable for your application. Because fused silica and quartz are readily available, you might consider them. I suspect that membranes from either of these materials would be cost effective and less susceptible to the types of penetration that you describe.

“The majority of the requirements of the wall materials of civil and military airborne radomes have been satisfied by the use of resins laminated with reinforcements, such as glass fibers. Polyester and epoxy resins have been the more commonly used and occasionally silicone or phenolic. In extreme cases, which are growing more common, the application of the high temperature resin polyimide is becoming more noticeable.” (page 138)

The report then describes the various type of glass fiber and the pros and cons.

I am not able to go through the entire report to summarize it.

Recommendation:

You might try a piece if quartz or fused silica… I think that both are reasonably inexpensive. The insertion loss will depend upon the thickness of the material. You would like it to be ˝, 1˝, 2˝… wavelengths thick.

I hope that assists you in selecting an alternate material that is monkey proof.

Sincerely,

Thomas E. Burke, PhD, PMP

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Thomas E. Burke

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Experience

Forty years of experience with satellite communications. Have held roles as system engineer on JPL Mariner 9 program and a program manager for a number of classified communication satellite programs. Served as head of TRW / Defense Communications Division / Engineering Development Operation, a 1,400-person organization responsible for all aspects of classified communication satellite design and development.

Education/Credentials
Ph.D. Chemistry, California Institute of Technology (1969) B.A. magna cum laude Chemistry, University of Minnesota (1962)

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