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High Frequency Microwave / RF Interconnect Solutions

GORE™ Microwave Assemblies are small and flexible, and they offer the security of proven reliability. Gore assemblies handle easily, allow a variety of interconnect options, facilitate routing, permit easy servicing, and are extremely robust.

Flexibility

A single Gore assembly can replace several semi-rigid assemblies of equal or shorter lengths. Therefore, fewer designs are required and no costly 3-D drawings or bending machines are needed. Installation time is reduced, and damage risk during installation is virtually eliminated. Fast, risk-free installation makes these cables cost-effective.

Reliability

Gore cable assemblies are manufactured to rigorous quality standards that differentiate all Gore microwave products. They offer proven solutions to in-box, box-to-device, and box-to-box interconnect needs. Their reliability reduces downtime, increases installation efficiency, and reduces troubleshooting requirements due to interconnect failure. A variety of standard cable and connector options are available to satisfy the interconnect needs of most RF applications.

• ATE Systems
• Evaluation test boards
• Antenna arrays
• Backplane interconnects
• Beam-forming networks
• Clock distribution
• General test networks
• LMDS systems
• Module to module
• OC192 standard
• OC768 standard
• DWDM systems

Gore microwave cable assemblies are flexible, and yet durable enough to withstand the rigors of installation. With an inherently flexible cable design, installation time is greatly reduced.

Gore cables are more practical than semi-rigid cables. Semi-rigid cables can be formed, but are not flexible, and manufacturers typically recommend limits on the number of rebends. Semi-rigid cables offer good stability, but their mechanical properties make them impractical and/or difficult to use for many applications. Manufacturers' recommendations are often ignored at installation, resulting in degraded stability and greatly shortened service life. Gore cable can be bent and routed during installation. Fewer designs are required, and no costly 3-D drawings are needed. This makes for cost-effective installation.

Traditionally designed flexible cables require a large bend radius to yield acceptable stability. This large radius and overall cable stiffness make them difficult to use, especially in small or lightweight devices. When the cable is forced into a smaller bend radius, performance degrades appreciably, service life is greatly shortened, and devices may be damaged. Gore cable assemblies provide superior flexibility without sacrificing performance.

Gore pioneered the use of microporous expanded polytetrafluorethylene (ePTFE) as a dielectric for microwave cables. We control the manufacturing process from raw material to finished components; therefore, variability in our ePTFE dielectric is reduced, and our cables provide consistent performance. Our tape-wrapping process and quality control eliminate concentricity concerns and ensure constant impedance through the assembly.

ePTFE's low dielectric constant of 1.4 means:

• Lower relative losses
• Higher velocity of propagation (85 percent speed of light)
• Lower capacitive loading
• Higher cutoff frequencies (DC to 65 GHz)  

Gore assemblies avoid the pitfalls of other traditionally designed assemblies, including RG type, semi-rigid, and solder-dipped, round wire braid constructions. RG-type cables have served the industry as a viable low-cost interconnect option for many years. As modules become smaller and more densely packed and frequencies continue to increase, shielding effectiveness has become more critical. RG constructions rely on round wire braid for their outer conductor. At only 1 GHz, shielding effectiveness of 40 dB can be obtained with a single braid layer. Additional layers add better shielding, but the cable becomes increasingly difficult to terminate and bend, while permitting significant energy leakage at higher frequencies.

Semi-rigid constructions theoretically offer better shielding effectiveness, but their benefits are offset by the difficulties encountered during installation. Pre-bent assemblies often have to be partially unbent to fit in a 3-D setting or to be routed through a panel or deck. Tie-downs are necessary to prevent vibration stress on longer runs, and insulating sleeving may be required to prevent the exposed circuitry from shorting out. High stress may also be placed on the connectors during alignment, resulting in poor mating or damage.

Gore created the use of helically wrapped foil as an outer conductor, and we use this shielding technology in all of our microwave coaxial assemblies. The helically wrapped foil gives when the cable is flexed, thus avoiding the potentially damaging translation of differential stresses as in semi-rigid and solder-dipped, round-wire-braid constructions. This flexibility minimizes the risk of failures at the connector termination point.

Gore cables provide a minimum of 90 dB/ft of shielding effectiveness across the entire microwave frequency range, through 18 GHz and beyond, because there are no openings for leakage in the cable. Assembly shielding effectiveness is limited only by connector selection.

As data rates in sophisticated digital equipment increase, the domains of microwave and digital system designers are beginning to converge. Traditional twisted pair, twin-ax, or tri-axial solutions cannot support the higher data rates, and RF solutions are thus now being pursued.

A simple digital on/off keying, 0-1-0 square wave sequence can be modeled as a series of discrete sinusoidal frequencies. These frequencies are related to pulse width and rise-and-fall times of the digital signal. Hence, there is a relationship between pulses in the time domain and their resulting spectra in the frequency domain. The shortest pulse in a data stream is a bit, which would represent one half of the period of a sine wave when considering the fundamental frequency only. A full period correlates to a half or full clock rate, depending on the system. Therefore, the highest sine wave frequency in gigahertz would be half the data rate in gigabits per second. Lower frequencies represent the longer bits.

Some bandwidth-limited systems operate in this fashion. If greater precision is required, more frequencies are added to the basic sine wave. A rectangular pulse consists of a series of harmonics of the fundamental. These harmonics add definition to the rise and fall times of each pulse beyond the base-half sine wave.

Adding only the third harmonic improves the waveform shape and is generally more than adequate to achieve the desired power or voltage transmission necessary for accurate receiver triggering.

Gore microwave cables are well suited for digital signal transmission. The signal velocity of propagation remains constant over a wide range of frequencies because of the cable dielectric's consistency. The series of harmonics defining the square wave can be transmitted over the cables with minimum distortion.