Elastomeric Absorbers

C-RAM FLX is a series of flexible microwave absorber sheet material which absorbs approximately 99% of incident RF energy at design frequencies in the range of 1 to 35 GHz. The material is weatherproof and will withstand a wide temperature range. It will conform to complex shapes and is readily bonded to metal surfaces. C-RAM FLX is intended for attachment to aircraft structures, nose cones, ship masts, instrument housings, and other surfaces for the reduction of specular radar reflections.

C-RAM FLX-800 is a magnetically lossy silicone microwave absorber rubber sheet material. When backed with an electrically conductive surface, it will act as a reflectivity reduction layer, resonant at around 850 MHz (see graph).

Because of its large ferromagnetic loss in the UHF region, it can be used to line one or more walls of a cavity to attenuate modal resonances. This is useful for enclosed devices, as well as for small chambers used to test device emissions.

C-RAM FLX-800 can be custom designed for reflectivity reduction resonances at other UHF frequencies. For applications having limited clearance, or having weight restrictions, C-RAM FDSS and FDSU should be considered. These are flexible sheet materials made of the same silicone or urethane rubber, having the same magnetically lossy loading. These materials are available in thicknesses of 0.8 -6.4 mm (.030 – .250 in.), and provide some resonance damping ability traded off against reduced weight.

For applications not exceeding temperatures of 120 oC (250 oF), C-RAM FLX-U-800, an equivalent urethane rubber material, can be used.

C-RAM GDSS is a thin, magnetically filled, silicone rubber microwave absorber sheet stock which has high loss at microwave frequencies. It is applied to metal surfaces to attenuate RF surface currents. It can be used to modify antenna patterns, lower the Q of a cavity, act as a transmission line attenuator, and modify the radar cross section of targets.

C-RAM GDSS is a thin elastomer sheet, so it will conform to curvatures of the substrate. It is not electrically conductive, and has high dielectric strength. It is a soft material and is readily die-cut or cut with a razor. Since it is made of silicone, it will withstand wide temperature ranges, and survive outdoor exposure.

C-RAM GDSS has a high magnetic loss tangent from about 4 GHz to 35 GHz. It will perform well in the 900 MHz cellular frequencies. Generally, thicker grades are required to attenuate lower frequencies to the same degree as a thinner grade at higher frequency. In the VHF and lower UHF frequencies, C-RAM FDSS will attenuate RF energy better; it has a different magnetic filler, which exhibits high loss tangents at lower frequencies.

C-RAM FDSS is a thin, magnetically filled, silicone rubber microwave absorber sheet stock, which has high loss at UHF frequencies. It is similar to C-RAM GDSS, except that it has higher magnetic loss at lower frequencies. It is applied to metal surfaces to attenuate RF surface currents. It can be used to modify antenna patterns, lower the Q of a cavity, act as a transmission line attenuator, and modify the radar cross section of targets.

C-RAM FDSS is a thin elastomer sheet, so it will conform to curvatures of the substrate. It is not electrically conductive, and has high dielectric strength. It is a soft material and is readily die-cut or cut with a razor. Since it is a silicone rubber, it will withstand wide temperature ranges, and survive outdoor exposure.

C-RAM FDSS has a high magnetic loss tangent from about 300 MHz to 3 GHz. It will perform well in the 900 MHz cellular frequencies. Generally, thicker grades are required to attenuate lower frequencies to the same degree as a thinner grade at higher frequency.

C-RAM FFS-125 is a flexible microwave absorber sheet material, which absorbs approximately 10 dB of incident RF energy across a frequency range of 2 to 12 GHz, over a wide range of incidence angles. The material is weatherproof and will withstand a wide temperature range. It will conform to complex shapes and is readily bonded to metal surfaces. C-RAM FFS-125 is intended for attachment to aircraft structures, nose cones, ship masts, instrument housings, and other surfaces for the reduction of specular radar reflections.

C-RAM FF-2 is a thin, ferrite filled, silicone microwave absorber rubber sheet stock which has high magnetic loss at UHF and microwave frequencies up to X-band. It is applied to metal surfaces to attenuate RF surface currents. It can be used to modify antenna patterns, lower the Q of a cavity, act as a transmission line attenuator, and modify the radar cross section of targets.

C-RAM FF-2 is thin and elastomeric, so it will conform to curvatures of the substrate. It is not electrically conductive and has high dielectric strength. It is a soft material and is readily die-cut or cut with a razor. Being based on a silicone rubber, it will withstand wide temperature ranges, and survive outdoor exposure.

C-RAM FF-2 has a high magnetic loss tangent from about 500 MHz to 10GHz. It will perform well in the 900 MHz cellular frequencies. In the UHF range, C-RAM FDSS will perform in an equal fashion; it has different magnetic filler which exhibits high loss tangents at UHF frequencies, but C-RAM FF-2 should be used if absorption above 2 GHz is also desired.

C-RAM FGMM is a flexible sheet material, which absorbs on average -10 dB of incident RF energy across a frequency range of 4 to 10 GHz, over a wide range of incidence angles. The material is weatherproof and will withstand a wide temperature range. It will conform to complex shapes and is readily bonded to metal surfaces. C-RAM FGMM is intended for attachment to structures, nose cones, ship masts, instrument housings, and other surfaces for the reduction of specular radar reflections.

C-RAM GDX is a thin, magnetically filled microwave absorber rubber sheet stock which has high loss at microwave frequencies from 1 to 18 GHz. It is applied to metal surfaces to attenuate RF surface currents. It can be used to modify antenna patterns, lower the Q of a cavity, act as a transmission line attenuator, and modify the radar cross section of targets.

C-RAM GDX is thin and elastomeric, so it will conform to curvatures of the substrate. It is not electrically conductive, and has high dielectric strength. It is a soft material and is readily die-cut or cut with a razor. Being based on a silicone rubber, it will withstand wide temperature ranges, and survive outdoor exposure.

C-RAM GDX has a high magnetic loss tangent from 1 GHz to 18 GHz. Thicker grades are required to attenuate at lower frequencies to obtain the same performance as a thinner grade at higher frequencies.

C-RAM GDX is available in silicone or urethane elastomers. Please refer to Technical Bulletin No. 310-1 for properties and benefits of each type of elastomer.

C-RAM RGD-S is a filled silicone rubber microwave absorber sheet material with a high magnetic loss. It is available in three grades: -117, -124 and -192. The -192 grade has higher loading and higher losses.C-RAM RGD-S is used for terminations, loads, and attenuators in waveguides, coaxial lines, and microstrip circuits. It can also be used for lowering the Q of cavities and eliminating unwanted resonances.C-RAM RGD-S is cut readily with a sharp knife, and can be sawed, die cut, waterjet cut, or otherwise machined to complex shapes. Since it is ferromagnetic, it is easily held in place during machining with magnetic chucks. It is flexible and can be bonded to contoured surfaces.Because it is flexible, C-RAM RGD-S can withstand temperature cycling when bonded to metals. The material has good thermal conductivity and can be used to dissipate heat, including that generated by its own magnetic loss mechanism.

Smart phone and tablet PCs claim huge data bandwidths and wireless network operators must ensure subscribers’ data demand is sufficiently satisfied. Research conducted by CISCO in 2011 found that compared to a regular mobile phone, smart phones require twenty-four times the data bandwidth. Tablets have an even higher demand: they require 122 times the data bandwidth of standard mobile phones. Wireless network operators are upgrading their networks to LTE in order to satisfy the massive data hunger.

Passive Inter Modulation (PIM) has existed since two or more frequencies were combined in one RF path. PIM is an unwanted effect caused by passive components. Since they are passive, one would expect a perfectly linear behavior. In reality, every single passive component comes with a certain degree of non-linearity.

Indeed, any component generates PIM.

This is of little concern if only one frequency at a time is transmitted; as soon as two or more frequencies share the same RF path, PIM avoidance becomes very critical, and PIM can be caused by the fences, metal flashing, and other objects located on the rooftops where cell sites are often installed in urban settings.

Designing low PIM into modern wireless high speed data networks is paramount for bandwidth optimization and maximum quality of service. Cuming Microwave offers PIM reduction materials for both isolation between antennas and reflectivity from metal surfaces:

Cuming Microwave manufactures a complete line of flat sheet absorbers.

LF is used as a free space absorber in most applications. LF is useful to reduce specular reflections in anechoic chambers, modify antenna patterns, or wherever a broadband absorber is needed. This material system can also be ordered weather wrapped or sprayed with a weatherproof coating. Flame retardant versions of LF are also available and meet UL94 HBF flame spread requirements.