Almost unknown PAR radars

While reading older book about naval radars (by Norman Friedman) found highly interesting few almost unknown early PAR radars.

navalised version of AWG-9

On a larger scale, we are beginning to see systems designed specifically to defeat saturation missile attacks on carrier task forces: Aegis and Phoenix, supported by an improved AEW/flying CIC airplane, the E-2C. Future development will probably be in the direction of smaller and cheaper electronic scanning systems analogous to the Aegis SPY-1, as missiles proliferate and as saturation attacks on less valuable targets become increasingly practical. In 1981 attention is concentrated on the radar suit to be fitted to the new-design destroyer, tentatively designated DDGX. This radar and its associated combat system may well drive up the size, and thus to some extent the cost, of the DDGX. One possibility is a modified SPY-1, redesigned to take advantage of new technology and thus considerably lighter and less expensive. There are two competitors: Sperry and Hughes, the latter with a FLEXAR (Flexible Adaptive Array Radar) derived from the AWG-9 which controls the Phoenix missile in the F-14 fighter. It recalls a 1974 proposal for a destroyer armed with a shipborne version of Phoenix, a weapon proposal revived from time to time for carrier self-defence. Electronic scanning is also being proposed for smaller ships. For example, at the end of 1980 Congress authorized a study of a Perry class upgrade incorporating a fixed-array replacement for the present Mk 92 fire control system.

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more on navalised AWG-9 plus info on A. Burke class radar suit contenders…

DDGX radar
In 1981 the major US Navy surface combatant program is the DDGX missile destroyer, with up to fifty units envisaged for construction from the FY85 program onwards. The goal is a combat system simpler than that of Aegis, but more capable than the one- or two-channel Tartar/Standard type of earlier ships. In principal it is to have a Multi-Function Array Radar for target acquisition and tracking, plus a Terminal Engagement Radar for terminal mis- sile control; the weapon will presumably be some version of the Standard missile, fired from a vertical launcher. Details have not yet been settled, even to the extent of whether the TER will be slaved to the MFAR, as in Aegis. An alternative possibility is the use of interrupted CW Illumination (ICW) so that a single illuminator can be time-shared among several defensive missiles even during the 10-20 seconds of missile flight. Such a system would be a phased array illuminator which would allow multiple illumination; alternatively it might be a multifrequency radar.

In 1981, ICW is still in the laboratory stage, and the 1985 construction date is quite possibly too close for the first DDGXs to be fitted with it. Candidate engagement radars include the Sperry X-band system proposed for the FFG-7 upgrade and a Hughes FLEXAR radar loosely based on the AWG-9 of the Phoenix/F-14 airborne system.

As currently envisaged, FLEXAR (Flexible Adaptive Radar) employs a rotating single-face electronically scanning radar and searches both a zenith cone and the horizon. Over most of the hemisphere, which is covered by a conventional two-dimensional radar, it tracks and engages designated targets only. Its computer system is to provide TWS and multiple tracking, and the single antenna rotates rapidly. Pulse-doppler wave-forms reduce clutter.

For the primary MFAR radar there are several contenders. RCA has proposed a lightweight derivative of its SPY-1, which has the great advantage of already being in production, with software in place. Gilfillan proposes a dual-frequency S/L-band system. Sperry has proposed a C-band system, which it considers superior to S-band because the lower wavelength makes for narrower beams and hence for better resistance to ECM. In theory a C-band radar cannot reach S-band range, Sperry’s view being that clear range is not nearly so important as is range in the presence of severe jamming. C-band also makes for greater accuracy in tracking, and may therefore eliminate the need for trackers and illuminators entirely. In that case possibilities include commanding a missile into an acquisition ‘basket’ so small that a K-band active seeker will suffice.

proposed OHP class upgrade (see some resemblance with ASMD ugrade program on ANZAC class frigates…)

FFG-7 Upgrade

This is a Sperry private venture which received $20 million of Congressional Appropriation as a line item in the FY81 budget. Sperry’s view was that the Perry class frigates would have to face the entire spectrum of Soviet weapons, including steeply diving air-launched missiles. In that case, in a severe jamming environment, conventional two-dimensional air search radars might well be unable to detect these weapons before their dive, and the lack of a zenith search or target acquisition capability might prove fatal. It was necessary to provide some system which could see at angles above 30°.

The Sperry proposal was to supplement the existing Mk 92 CAS system, which was designed specifically against the ‘pop-up’ threat with a 1-second data rate, with a phased array. X-band was chosen in view of space and weight constraints, and alternatives considered included back-to-back rotating radars, the new dome radar and a single face type. Ultimately a four-face system was chosen for the data rate required. Sperry proposed one break-in modification kit and six production kits for frigate refits, as well as an uplink permitting the system to fire the SM-2 (Aegis) missile. The Navy rejected the latter on the grounds that the uplink software would be too complex, but Congress appropriated the $20 million for research and engineering as part of a 3-year effort which Sperry estimated would cost $65-70 million.

and last abortive SPG-59 for Typhon AD system

SPG-59

The main radar of the abortive Typhon system, employing a Luneberg lens for electronic beam-steering. Primary requirements included large bandwidth and frequency independence in steering the beam, to avoid several types of countermeasure. The cylindrical Luneberg lens focussed a beam projected onto it from any point on its surface. In the complete system, a lens deep in the ship was used, in effect, as a computer to generate signals with the appropriate phase relationships, for transmission from a sphere atop the cylindrical housing of the radar. It proved necessary to amplify these signals to overcome losses, and 356 travelling-wave tube amplifiers (TWTs), originally not part of the design, had to be interposed between the lens and the radiating sphere. Three more spheres were used for reception.

One problem in system design was that the spheres had a very small effective radiating aperture, less than 4ft, which had to be balanced by high radiated power. Altogether, 1800 medium-power amplifiers and associated waveguides were required for the ‘small ship’ system, with proportionately more for the 10,000-element ‘large ship’ system. It was tested aboard Norton Sound after the cancellation of the system proper. As installed aboard the test ship, it had a maximum peak power of 8.7 MW (pulselengths of 2 microseconds for search, 0.1 microsecond for tracking, with jittered PRFs of, respectively, 200,000 and 400,000 on average burst) in C-band. Average power was 200MW, and pulse doppler operation provided high velocity resolution (100 fs in search, 9 fs in track). Range resolution was 20ft in search and 2ft in track, and acquisition range was stated as 165nm on a 1m2 target. In principle the system could handle up to ten targets at a 0.1-second data rate for high-precision (3.5-mil) tracking, and could control up to 30 defensive missiles at the same time. At a lower data rate (4 seconds) it could maintain track on up to 120 targets (TWS).

SPG-59 was designated to carry out a high-power hemispherical search, with acquisition on 1m2 targets (with a 6-14 second data rate, and a detection probability of 0.5) at 165nm (horizon to 5.1°), 155nm (to 8.5°) or 105nm (to 80°) and a low-power horizon search (37nm on a 0.5m2 target with a detection probability of 0.9 at a 1-second data rate). Like the current Aegis, Typhon envisaged command control of defensive missiles.

Anybody got more info on these systems?