RADAR
AIR TRAFFIC TECHNOLOGY INTERNATIONAL 2020 63.
domestic and international Air Traffic Control
Radar Systems.
What products and services
does Cobham supply to ATC?
Cobham Advanced Electronic Solutions
supplies a wide variety of components to the
ATC business, including: waveguide and
waveguide products, rotary joints, rotating
sub-systems, pedestals, flat-plate waveguide
antennas, high power microwave cable
assemblies, filters, couplers and a full suite of
ferrite control components such as
circulators, isolators, phase shifters and
switches. Domestically, Cobham is the sole
supplier of multi-channel rotary joints to the
FAA for all Airport Surveillance Radars
(ASR) and Air Route Surveillance Radars
(ARSR) and is the only authorized Depot
Repair facility for rotary joints outside of the
FAA’s own facility in Oklahoma City,
Oklahoma. Cobham is also highly regarded
for its experienced rotary joint engineering
and manufacturing staff and as such,
manufacturers look to us for regular system
improvements, Service Life Extension
Programs (SLEP), and site services for
their customers.
Who exactly are you supplying to?
Cobham Exeter provides ATC products and
services primarily to the Federal Aviation
Authority (FAA) as well as foreign radar
manufacturers and integrators. While the
majority of our ATC business is with aviation
authorities or civilian companies, a good
portion of our business is supplying rotary
joints and other components for military
ATC radars through prime contractors such
as Northrop Grumman Corporation, Boeing,
Raytheon and L-3. Most rotary joint and
other components used in ATC radar
systems are predominantly dual-use items
subject to the US Bureau of Industry and
Security regulatory jurisdiction.
Can you describe the company’s
latest products / services?
One recent advance for Cobham’s ATC
rotary joints is in the area of improved
azimuth position indication. In any
rotational radar system, angular position
information is matched to the radar returns
to accurately determine the azimuth position
of the targets. In older radar systems,
azimuth position generators (APGs) were
integrated directly to the pedestal for this
purpose.
During operation, APGs exhibit a level of
pulse jitter associated with minute variations
in the angular velocity of the APG shaft
caused by the pedestal. As a result, the jitter
directly degrades the accuracy of the azimuth
data and the error increases with increasing
range. Historically, to solve this problem,
APGs have moved from the pedestal to a
point closer to the rotational center of the
radar system, inside the rotary joint for a
more stable environment. Typically, dual
optical encoders are used as APGs inside the
rotary joint with 12- or 14-bit resolution. The
dual APGs are gear driven off the center shaft
of the rotary joint. Even at 14-bit resolution,
accuracy errors between the encoders persist
at maximum range.
To solve this problem, Cobham redesigned
a rotary joint to replace the gear-driven optical
encoders with a shaft-mounted Dual
Inductosyn Assembly (DIA, 16- or 20-bit
resolution). Through this approach,
elimination of the gear-drive on the APGs
restores coherence of the azimuth position
data at maximum range.
What are the main benefits to
users of your product oering?
What separates Cobham Advanced
Electronic Solutions from other rotary joint
manufacturers is our experience, product
diversity and design database. Cobham has
been supplying rotary joints to the ATC
market for more than 37 years. In this
capacity, we have designed, developed,
fielded and refurbished more ATC rotary
joints than any other manufacturer. As
mentioned, Cobham is the sole supplier of
multi-channel rotary joints to the FAA for all
ASR and ARSR radars.
Focusing on this sector of the business,
Cobham has developed the manufacturing
capability and capacity to repair and
refurbish multiple ATC rotary joints
simultaneously as well as the technical
capability of repairing other manufacturers’
rotary joints. Since Cobham has the largest
rotary joint design database of any
manufacturer, we can easily achieve design
changes, upgrades and retrofit operations.
Could you describe a recent
application or case study?
Technological advances in the air traffic
industry are slowly transforming datagathering
technology from radar-based to
satellite-based. The obvious advantage of this
change is to gradually reduce and eventually
eliminate the dependence on ground-based,
high power radar channels. These are the
most expensive sections of the radar to
Above: Cobham is the sole supplier of rotary joints to the FAA for
all of its ASR and ARSR radars
Cobham has been supplying rotary joints to the ATC
market for more than 37 years