Communications: radio wave antennas – Antennas – Wave guide type
Reexamination Certificate
2000-04-28
2001-06-26
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Wave guide type
C343S7810CA, C343S756000, C343S909000
Reexamination Certificate
active
06252559
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a multiple frequency band and/or multiple polarization mode antenna system having multiple antenna subsystems for radar, remote sensing, communications or a combination of various applications, where each antenna subsystem (each band or mode) shares a common aperture and boresight, More particularly, the present invention relates to multi-band/dual-polarization radar antenna system for a radar seeker that employs properties of frequency selective surfaces to allow several antenna subsystems to use a common aperture and boresight.
2. Discussion of the Related Art
Many applications exist for the transmission and reception of signals for both radar and communications purposes. Radar systems are known to provide target tracking and acquisition. Various antenna configurations known in the art provide dual-band and dual-polarization functions for the radar systems. U.S. Pat. No. 5,451,969 issued to Toth et al. entitled “Dual Polarized Dual Band Antenna” discloses an antenna configuration for such an application.
Modern, advanced tactical missiles are typically equipped with a radar seeker to provide target acquisition and tracking functions, and also are outfitted with electronic-counter-counter-measure (ECCM) devices to mitigate known electronic-counter-measures (ECM), such as cross-eye, cross-polarization, towed decoy and terrain bouncing jamming, to achieve a desirable “hit-to-kill” ratio. To counter these existing and potential future threats, radar sensors with enhanced capabilities which can successfully function in an advanced ECM threat environment are needed for the next-generation advanced tactical missiles. To achieve this goal, an advanced multi-band and polarization-diversified radar antenna architecture is necessary.
Advanced multi-band/polarization-diversified radar antenna architectures possess many advantages over conventional antenna architectures. These advantages include providing up to four separate antennas sharing a single common aperture and operating at four different frequency bands with full aperture RF performance; providing any selected polarization for each antenna; providing a co-boresight for all four antenna beams; providing a compact volume/size for missile applications; providing enhanced anti-jamming capability in general; providing additional ECCM enhancements; and providing precision profiling of targets by high band channels with higher resolution during the terminal homing phase.
To make a multi-band/dual-polarization radar system, it is necessary to provide a multi-band/polarization-diversified antenna system which shares a given aperture with minimum antenna performance degradations in the presence of each different antenna. The use of frequency selective surfaces (FSS) offers a practical technique for integrating different frequencies and/or polarization modes in a multi-band/polarization-diversified antenna system. Properly designed FSS devices are able to pass signals at one frequency band and reflect or block signals at another frequency band, and are non-discriminative to various polarization modes, both linear and circular types, to both designed frequency bands. Antenna systems employing these types of FSS have been identified in the art, and are shown, for example, in U.S. Pat. Nos. 5,949,387 entitled “Frequency Selective Surface (FSS) Filter For An Antenna”; 5,497,169 entitled “Wide Angle, Single Screen, Gridded Square-Loop Frequency Selective Surface For Diplexing Two Closely Separated Frequency Bands” and 5,373,302 entitled “Double-Loop Frequency Selective Surface For Multi Frequency Division Multiplexing in A Dual Reflector Antenna”.
SUMMARY OF THE INVENTION
In accordance with the teachings of the present invention, an antenna system architecture is disclosed that accommodates a plurality of independent and separate antennas that share a common aperture and boresight. In one embodiment, for radar applications, the antenna system includes two low-frequency antennas operating at frequencies F
1
and F
2
using the same or orthogonal polarization modes, and two high-frequency antennas operating at frequencies F
3
and F
4
using the same or orthogonal polarization modes. The low-frequency antennas, in general, are array antennas and the high-frequency antennas, most suitably, are dual reflector antennas such as Cassigrian or Gregorian reflector antennas. The dual reflector antenna includes a main reflector, a sub-reflector, a feed subsystem and a sub-reflector support structure, which can either be struts or a cone structure.
In the most practical configuration, the high-frequency reflector antenna is packaged immediately in front of the low-frequency antenna. For the transmitting case, the high-band feed subsystem is positioned at the focal point of the dual reflector antenna. Signals transmitted from the high-band feed subsystem are directed towards the sub-reflector, and are reflected therefrom towards the main reflector. The signals are then reflected from the main reflector in a collimated format and pass through the support structure towards free space. The low band signals from the low-frequency antenna, located behind the high-frequency reflector antenna, pass through the main reflector, the sub-reflector and the support structure towards free space. For the receiving case, the signals from free space are reflected by the main reflector and directed to the subreflector, then reflected by the subreflector to be collected by the feed subsystem. The main reflector, the sub-reflector and the support structure are suitable frequency selective surfaces so that the main reflector and the sub-reflector reflect the high band signals and are transparent to the low band signals. The support structure, however, requires being transparent to both the high-band and low-band signals. The use of an FSS cone surface as the subreflector support structure provides an additional ECCM enhancement by making the entire multi-band and polarization diversified antenna system a low observable target to any out-of-band hostile ECM system due to its FSS design and its conical shape.
Additional objects, features and advantages of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 3209355 (1965-09-01), Livingston
patent: 4257047 (1981-03-01), Lipsky
patent: 4264907 (1981-04-01), Durand, Jr. et al.
patent: 4791427 (1988-12-01), Raber et al.
patent: 5061930 (1991-10-01), Nathanson et al.
patent: 5130718 (1992-07-01), wu et al.
patent: 5307077 (1994-04-01), Branigan et al.
patent: 5373302 (1994-12-01), Wu
patent: 5384575 (1995-01-01), Wu
patent: 5673056 (1997-09-01), ramanujam et al.
patent: 5717405 (1998-02-01), Quan
patent: 5751254 (1998-05-01), Bird et al.
patent: 5764192 (1998-06-01), Fowler et al.
patent: 5793332 (1998-08-01), Fowler et al.
patent: 5872543 (1999-02-01), Smith
patent: 5949387 (1999-09-01), Wu et al.
Harness & Dickey & Pierce P.L.C.
Le Hoang-anh
The Boeing Company
LandOfFree
Multi-band and polarization-diversified antenna system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multi-band and polarization-diversified antenna system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-band and polarization-diversified antenna system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2489113