Aerospace & Defense Technology - October 2024 - 29

RF & Microwave Technology
* Increased Scanning Speed: Enables
quick scanning of large areas
* Improved Accuracy: Enhances the precision
of target detection and measurement
* Multiple Beams: Supports tracking
multiple targets at the same time
* Adaptability: Allows the radar to quickly
adjust to changing conditions
* Electronic Beam Steering: Provides precise
control over the direction of the radar
beam without mechanical movement
Two types of coaxial cables are typically
used in phased array radar systems:
phase-stable coaxial cables and phasematched
coaxial cables.
Phase Stable Coaxial Cables
In today's increasingly sophisticated
electronic systems, phase-stable cables
are designed for phase consistency
despite environmental factors such as
extreme temperatures. Any inconsistencies
in coaxial cable performance can
directly impact the system's functionality.
Applications requiring extreme phase
stability utilize specialized cables
designed to minimize phase variations.
These cables employ materials with consistent
electrical properties and construction
that resists phase shifts caused by
bending.
Factors that impact phase-stable coaxial
cables include:
* Cable Length: The physical length of
the cable directly impacts its electrical
length and phase shift of the signal.
Shorter cables are less likely to introduce
a large phase shift.
* Bending: The bend of a cable can
potentially create inconsistencies in
phase. Tight bends or kinks can distort
signal transmission.
* Temperature: The dielectric material
can be sensitive to temperature changes,
and due to these changes, the electrical
properties of the dielectric can shift,
causing phase changes in the signal.
* Dielectric Material: Electrical properties
vary between dielectric materials.
For instance, PTFE exhibits a significant
phase shift around room temperature,
which leads to instability.
Other materials like foam fluoropolymer
provide exceptional phase stability
with minimal fluctuations across a
broader temperature spectrum.
* Connectors: Loose or low-quality conAerospace
& Defense Technology, October 2024
PhaseTrack cable assemblies from Times, pictured here, are engineered for applications where precise
phase control is essential and phase change over temperature must be minimized. (Image: Times
Microwave Systems)
nectors or a poorly designed interface
can result in unwanted reflections and
phase changes.
* Frequency: Higher frequencies are generally
more susceptible to phase fluctuations
compared to lower frequencies.
Phase-Matched Coaxial Cables
Phase-matched cables are pairs or
groupings of cables with matched electrical
lengths. Engineered to reduce phase
variations over temperature, phasematched
cables exhibit predictable phase
tracking behavior, or the cable assembly's
ability to preserve a reliable phase
relationship between transmitted and
received signals. These phase variations
are affected by electrical length, operating
temperature, and initial phase
matching tolerances. The challenge to
maintain electrical lengths is mainly
caused by temperature fluctuations; even
with precise initial calibration, coaxial
cables are vulnerable to phase shifts
caused by varying thermal expansion
and contraction rates. These shifts can
result in phase mismatches and lead to
system performance degradation.
For applications requiring phase stability
in varied temperature environments,
accurate phase tracking becomes
mobilityengineeringtech.com
imperative. Since higher frequencies are
used for improved resolution and accuracy,
minimal phase change and consistent
phase tracking are crucial.
Factors Impacting Phase for Coaxial
Cables
Phase is an essential parameter for
many RF systems, ensuring optimal
operation for coaxial cables and connectors.
Since phased array radars are highly
sensitive to variations in phase, the
coaxial cables used in these systems need
to be phase stable to enable the precise
control of phase that make these radars
desirable.
Electrical length is the measurement
of the physical length of a cable divided
by its wavelength. It varies based on
a number of factors and is influenced
by frequency, signal delay, and the
cable's physical properties, including
dielectric material and dimensions.
Dielectrics typically provide stable performance
but environmental factors
like temperature fluctuations and
physical stress can impact electrical
characteristics.
Insertion loss quantifies the reduction
in signal power as it travels through a
coaxial cable. Maintaining low insertion
29

https://mobilityengineeringtech.com

Aerospace & Defense Technology - October 2024

Table of Contents for the Digital Edition of Aerospace & Defense Technology - October 2024