
Helically-wrapped foil is used as an outer conductor on all GORE™
Microwave Coaxial Assemblies and provides consistent shielding
effectiveness even when exed. The helically-wrapped foil “gives”
when the cable is exed, thus avoiding the potentially damaging
translation of differential stresses that occur in semi-rigid and
solder-dipped round wire braid constructions. This exibility
minimizes the risk of failure at the connector termination point.
shielding Effectiveness
Test method MIL-STD-1344, Method 3008
The graph shows the typical shielding performance for four dierent coax
cable types. Each type diers only in the construction of the cable’s outer
shield. As shown, a GORE™ Microwave Cable provides signicantly better
shielding than braiding or aluminized mylar approaches because of the
helically-wrapped foil outer shield.
GORE™ Microwave Cables provide a minimum of 90 dB/ft of
shielding effectiveness across the entire microwave frequency
range through 18 GHz and beyond; by eliminating any openings
for leakage in the cable, assembly shielding effectiveness is
limited only by connector selection and not by the cable.
Digital vs. Microwave
As data rates in sophisticated digital equipment increase, the
worlds of microwave and digital system designers are coming
together. Traditional twisted pair, twin-ax, or tri-axial solutions
cannot support the higher data rates so designers are turning to
RF solutions.
A simple digital on-off keying, a 0-1-0 square wave sequence, can
be modeled as a series of discrete sinusoidal frequencies. These
frequencies are related to pulsewidth and rise and fall times of
the digital signal. Consequently, there is a relationship between
the pulses in the time domain and their resulting spectra in
frequency domain.
The shortest pulse in a data stream is a bit, which represents
one-half of the period of a sine wave when only considering the
fundamental frequency. A full period correlates to half a clock rate
or a full clock rate, depending on the system. From this it can be
stated that the highest sine wave frequency in gigahertz equals
half the data rate in gigabits per second. Lower frequencies will
exist representing the longer bits.
Some bandwidth-limited systems operate in just this fashion. If
greater precision is required, more frequencies are added to the
basic sine wave. A rectangular pulse can be shown to consist of
a series of harmonics of the fundamental. These harmonics add
denition to the rise and fall times of each pulse beyond the
base half-sine wave. Adding just 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’s velocity of propagation remains
constant over a wide range of frequencies because of the
consistency of the cable dielectric. The series of harmonics
dening the square wave can be transmitted over the cable with
minimum distortion.
GORE™ Microwave Cables offer:
Lower relative loss for cleaner eye patterns •
Low VSWR minimizing reections •
Consistent response with frequency for lower group delay •
Capabilities
Gore offers standard, reliable assembly solutions from DC through
65 GHz. Various standard push-on/blindmate and threaded
connector options are available to mate with virtually any system.
As the necessity for increased frequency and bandwidth drive
your application needs, Gore’s interconnects provide solutions.
In addition to standard interconnects, Gore offers precision test
assemblies and adapters to meet all of your high data rate digital
and microwave needs.
If you need other congurations, please contact Gore to discuss
your requirements.