Millimeterwave radar has been around for quite a while, as
evidenced by this article in the April 1967 edition of Electronics
World. We don't read much about Q-band systems nowadays, but
Q-band is used in some familiar contemporary applications like
satellite communications, terrestrial microwave communications,
automotive radar, and radio astronomy. For radar purposes, the
8-mm (about 1/3 inch) wavelength allows for very fine feature
resolution. Stability of the radar platform is the limiting
factor in this case.
New Q-Band Marine Radar
By Richard Humphrey
Radar operating at 8-mm wavelength (about 35,000 MHz) is
now being used on crowded European waterways. It provides better
resolution, will pick up smaller targets and show their shapes.
In talking with many users of radar - Coast Guard, commercial,
and military - the author found that the emphasis in marine
navigational radar is on close capability and performance. In
many cases, existing equipment (operating mainly in the 9000-MHz
range) sometimes is just not good enough in this regard.
Transmitter-receiver unit and double antenna
of Q-band radar.
A distance potential of 200 miles or more is necessary in
search radar or that used by the U.S. Weather Bureau (the radar
used by the Bureau's New York office has a range of 250 miles),
but a cargo vessel steaming at 15 to 17 knots on the open sea
or 3 to 7 knots in inland waters has little interest in a radar
contact on the extreme range of its instrument unless the course
and speed of the target vessel can be seen as constituting a
converging course with its own. Even then, if the speeds involved
are not too great, another bearing and range check will not
usually be made for some time.
What the captain or pilot of a freighter or tanker is interested
in are the near targets, the ones that he might hit or that
might hit him. Here, minimum-range capability, high bearing
resolution, and high range resolution are essential.
Indicator unit of the Philips marine radar
uses a 12-in CRT.
These three factors become more and more important as the
ship progresses from port area to port proper and are vital
when the vessel enters certain inland waters where channel width
and congestion are considerations.
There is increasing need for radar which will have better
range and bearing resolution, pick up smaller targets, have
faster picture recovery, and actually present the shape of the
target on the viewing screen as well as be capable of much closer
work than heretofore possible.
Radar display produced on equipment installed
in vessel traveling along the Rhine. The vessel's position is
at the dot at the center of the inner range ring. These rings
are about 1000 feet apart. The river banks, which are about
500 feet from the vessel, as well as other ships can be clearly
Same display taken about 6 minutes later.
All these requirements are said to be found in the new 8-millimeter
wavelength radar (approximately 35,000 MHz) now coming into
use on narrow, crowded European rivers such as the Rhine where
traffic sometimes reaches a count of 35 vessels per kilometer.
This 8-millimeter or Q-band radar, in its upward excursion
in frequency, has gained many advantages for navigational radar.
[Actually, there are two frequency bands involved in millimeter-band
radar. One of these, 34,500 to 35,200 MHz (nominally 8 mm ),
is in use in Europe, and the other, 31,800 to 33,400 MHz (nominally
9 mm) is not permitted in Europe].
First, Q-band radar has increased small-target recovery,
higher frequency waves are more readily reflected by smaller
Second, since high bearing discrimination or resolution is
a function of antenna beam width, and beam width in turn is
a function of antenna size, it becomes possible for small antennas
to have very narrow beam widths at these frequencies.
This physically smaller antenna, also being lighter, can
be given a higher rate of rotation (typically 40 rpm in Q-band
use) which leads naturally to better close-range capability
and faster picture recovery.
Unfortunately, there was a bad side effect resulting from
small-target advantage gained by using higher frequencies. Since
smaller targets are reflected much better at 8- and 9-millimeter
wavelengths, the interference from rain and drizzle is also
increased. This was a major problem with Q-band radar. A radar
which is inoperative during drizzle and rain cannot be
classified as a useful navigational instrument.
This rain- and sea-clutter interference problem, according
to one maker (Phillips), is now solved by a refinement of the
basic r.f. sensitivity time-control circuit used in radar equipment
for suppression of clutter.
With marine commerce becoming ever more sensitive to "man-hour"
figures, the need to keep cargo vessels (especially in port
and inland water use) moving in all sorts of weather is assuming
vital importance. The ability of a radar to allow the master
or pilot of a ship to thread a narrow, constricted, and usually
well-traveled waterway is probably the most important factor
in judging a radar's usefulness. This capability seems to be
quite high with Q-band radar.
Possibly the most significant contribution to marine navigation
offered by Q-band radar is in very quick determination of any
change of course of the target vessel. With optical observation,
the changing silhouette of the ship will immediately tell the
captain that the vessel is altering course. On centimeter radar,
the target ship must progress a certain distance along the new
course before the radar operator can detect that such a change
has in actuality been made.
In some cases, 8-millimeter radar will make a course change
apparent even before it is possible by visual observation because
the actual outline of the ship is presented on the display screen.
The swing of the target vessel is seen in an instant, and for
this reason 8-millimeter radar is often used in clear-weather
Among captains and pilots of commercial craft on inland waters
and harbors, the true yardstick of a radar's performance is
its minimum-range capability. With millimeter radar's ability
to "see" as closely as 35 to 40 feet, with its better delineation
of small targets, and with its high range and bearing discrimination,
close-in navigation in sticky situations is no longer the nerve-wracking
job it once was. The only factor preventing quick acceptance
in America is its price, and the fact that the only major manufacturer
(to come to the author's attention) is a European concern.
The Philips 8GR260 marine radar shown in the photos is transistorized
(with the exception of the magnetron, video output tube, klystron,
and CRT). It has a peak power output of 20,000 watts on 35,000
MHz, with a pulse length of only 0.04 µsec.
This unit uses the "double-cheese" type of antenna (0.6°
horizontal beam width by 17° vertical) since a duplexer and
T/R units for the frequencies involved are too expensive and
prone to failure. This small antenna has solved one difficulty
associated with harbor-monitor radar which is mounted in many
instances on lighthouses. The larger cross-section presented
to the wind of centimeter radar often sets up a vibration in
the optical system of the light and makes it impossible to maintain
focus. The small cross-section of a millimeter radar antenna
makes it especially well adapted to this service.
Another view of the airport but taken at
somewhat reduced range. Above and to left of the bright dot,
you can see a large plane near maintenance hangar.
Radar display shows small portion of an airport.
Runways are clearly visible and, if you look to the left of
the bright dot near the center of the display, you can see a
small aircraft moving along the ground.
April 1967 Electronics World
of Contents] People old and young enjoy waxing nostalgic about
and learning some of the history of early electronics. Electronics World
was published from May 1959 through December 1971. All copyrights are hereby acknowledged.
Electronics World articles.