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Aerospace & Defense Electronics Supplement
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A&D Test & Measurement
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Stainless Steel Coaxial Cable with Medium Loss at 36 GHz
Fig. 1 Loss per 100 ft. vs. frequency.
Anyone who has tried to use copper cable for high frequency connections in high stress environments knows that it does not hold up very well for long. Attempts to strain relieve it or dampen its vibration in some fashion does not seem to help much. Add the complication of today's millimeter-wave applications and the problem becomes worse.
A new type of 0.145" diameter stainless steel coaxial cable has been developed that offers much improved performance in high stress applications and features medium loss at 36 GHz.
The type 145ML stainless steel cable features enhanced construction over conventional copper cable and 0.141 RG402 cable. The use of a stainless steel outer jacket provides resistance to corrosive atmospheres over standard copper. In addition, the new cable utilizes welded connections as opposed to the common soldered connections used with copper. This provides much greater resistance to metal fatigue, especially in high vibration environments, and increased tensile, torsional and axial load strengths over soldered connections.
The 145ML cable has a characteristic impedance of 50 W and a maximum operating frequency of 36 GHz. It features a Vp of 76 percent and an operating temperature range of -55° to +250°C. The outer conductor is 0.145" diameter 304L stainless steel over copper tube. The inner conductor is 0.0403" diameter solid silver-plated copper and the dielectric is expanded polytetrafluoroethylene (PTFE), type F1.
The cable weighs 35.3 lbs/1000 ft and can handle a safe bend radius of 0.5". Table 1 lists the cable's attenuation and average power vs. frequency. Figure 1 shows loss per 100 ft vs. frequency compared to standard 0.141 copper cable.
*Unity SWR, 40°C ambient, still air
Applications for the 145ML cable include cryogenic test beds requiring direct exposure to liquid nitrogen, high vibration environments and operation in high g-force platforms, as well as any situation involving high tensile, axial or torsional mechanical stress.
The 145ML cable is currently available at 0.145" diameter and 0.093" diameter will soon be available.
SSI Cable Corp., Shelton, WA (360) 426-5719, www.ssicable.com.
Circle No. 302
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