Abstract:
A antenna system is provided, including a substantially annular antenna element having an inner perimeter edge. The antenna system also includes a two-dimensional amplifier system coupled to the inner perimeter edge of the antenna element. The two-dimensional amplifier system may comprise a plurality of one-dimensional amplifiers, each one-dimensional amplifier being coupled to the inner perimeter edge of the antenna element at substantially equally spaced angular positions. The two-dimensional amplifier system may also comprise a two-dimensional field effect transistor. The antenna element and two-dimensional amplifier system are configured to either receive or transmit a wave having a carrier frequency and an electric field vector, the terminus of which traces a nonlinear path within a plane transverse to an axis of wave propagation at an angular velocity corresponding to a rotation frequency between the carrier frequency and zero.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application Ser. No. 60/240,949, filed Nov. 9, 1998. The present invention is related to U.S. patent application Ser. No. 08/853,833, entitled “Communications System” and filed on May 9, 1997, now U.S. Pat. No. 6,204,810, and to U.S. patent application Ser. No. 09/064,525, entitled “Communications System” and filed on Apr. 23, 1998, now U.S. Pat. No. 6,271,790, the entire contents of which are hereby incorporated by reference. 
     This application is related to the subject matter of the following U.S. Provisional applications filed concurrently: Ser. No. 60/150,703 entitled “Adjustable Balanced Modulator,” Ser. No. 60/145,571 entitled “System For Measuring and Displaying Three-Dimensional Characteristics of Electromagnetic Waves,” Ser. No. 60/135,098 entitled “A Method and Apparatus For Two Dimensional Filtering In A Communications System Using A Transformer System,” Ser. No. 60/145,744 entitled “Cavity-Driven Antenna System,” and Ser. No. 60/240,949 entitled “Disc Antenna System.” Ser. No. 60/107,660 entitled “Two-Dimensional Amplifier,” Ser. No. 60/107,659 entitled “Phase Shifting Systems,” and Ser. No. 60/107,661 entitled “Omnidirectional Array Antenna System.” 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to antenna systems. More particularly, the present invention relates to a disc antenna system. 
     BACKGROUND OF THE INVENTION 
     U.S. patent application Ser. No. 09/064,525, entitled “Communications System” and filed on Apr. 23, 1998, discloses a receiver system configured to receive a wave having a carrier frequency and an electric field vector, the terminus of which traces a nonlinear path within a plane transverse to an axis of wave propagation at an angular velocity corresponding to a rotation frequency between the carrier frequency and zero. FIG. 2 illustrates the path  99  traced by the extremity of such a rotating vector  96  that propagates along an axis  98 . As shown in FIG. 1, such a wave, referred to herein as a “rotating” wave, can be received using three separate coplanar dipole (or monopole) antennas  10 ,  20 ,  30 . The three dipole antennas may be, for example, separated by 120°. 
     Three taps  15 ,  25 ,  35 —each located on a different one of the one of the dipole antennas  10 ,  20 ,  30 —produce three signals, such as the signals  101 ,  102 ,  103  shown in FIG.  3 . The three signals are then amplified by an amplifier system  40 . Although a single block is used to represent the amplifier system  40  in FIG. 1, three individual amplifiers, such as three Low Noise Amplifiers (LNAs), may be used. Each LNAs is “one-dimensional” in that each amplified signal does not reflect the amplitude and orientation of the received wave. The entire amplifier system  40  (such as the three LNAs taken together), however, is “two-dimensional” because a complete picture of the amplitude and orientation of the received wave is maintained. 
     A nonlinear periodic path demodulator  50  receives the amplified signal (such as the three individual amplified signals), as well as information from a nonlinear period path frequency source  60 . The amplified signal is demodulated with respect to the nonlinear period path and can then be demodulated by an information demodulator  70 . The information signal or signals contained in the received wave can then be reproduced. 
     Although FIG. 1 illustrates a receiver system using three dipole antennas  10 ,  20 ,  30 , a different number of dipoles can be used instead. For example, four dipoles separated by 90° could be used to receive the wave. Moreover, the signal received by each dipole is added coherently while the noise received by each dipole is added incoherently. Thus, increasing the number of dipoles can improve the Signal-to-Noise Ratio (SNR) the receiver system. 
     Although increasing the number of dipoles improves the SNR, such an approach has disadvantages. For example, each dipole will generally require separate electronic components, such as separate LNAs, to process the signal associated with that dipole. That is, the use of 360 dipoles, each separated by 1°, would create a sensitive receiver system but would also require the use of 360 separate LNAs. Such a system would be both difficult and expensive to create. 
     Moreover, the separation between dipoles must be accurately maintained. With a three-dipole system, such as the one shown in FIG. 1, each dipole must be separated by substantially exactly 120°. With different numbers of dipoles and/or different spacing between the dipoles, the physical separation must likewise relate to the phase differences in the modulation envelopes of the received signals. As the number of dipoles increases, maintaining the accuracy of the separation between the dipoles becomes more difficult. 
     Although the above description relates to a receiver antennas and a receiver systems, those skilled in the art will appreciate that similar problems can arise with respect to transmitter antennas and transmitter systems. 
     In view of the foregoing, it can be appreciated that a substantial need exists for an accurate antenna system that solves the problems discussed above. 
     SUMMARY OF THE INVENTION 
     The disadvantages of the art are alleviated to a great extent by an antenna element having an interface portion and a two-dimensional amplifier system coupled to the interface portion of the antenna element. 
     According to one embodiment of the present invention, the antenna element is substantially an annular antenna element and an inner perimeter edge of the antenna element is coupled to the two-dimensional amplifier system. The two-dimensional amplifier system may comprise a plurality of one-dimensional amplifiers, each one-dimensional amplifier being coupled to the inner perimeter edge of the antenna element at substantially equally spaced angular positions. The two-dimensional amplifier system may also comprise a two-dimensional field effect transistor. The antenna element and two-dimensional amplifier system are configured to either receive or transmit a wave having a carrier frequency and an electric field vector, the terminus of which traces a nonlinear path within a plane transverse to an axis of wave propagation at an angular velocity corresponding to a rotation frequency between the carrier frequency and zero. 
     With these and other advantages and features of the invention that will become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims and to the several drawings attached herein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a receiver system configured to receive a rotating wave. 
     FIG. 2 illustrates the path traced by a rotating wave. 
     FIG. 3 illustrates the signals created at the three dipoles shown in FIG. 1 when the wave shown in FIG. 2 is received. 
     FIG. 4 is a block diagram of a receiver system configured to receive a wave using a disc antenna according to an embodiment of the present invention. 
     FIG. 5 is a disc antenna according to an embodiment of the present invention. 
     FIG. 6 is a perspective view of a disc antenna coupled to a two-dimensional amplifier according to an embodiment of the present invention. 
     FIG. 7 is a disc antenna according to another embodiment of the present invention. 
     FIG. 8 is a block diagram of a transmitter system configured to transmit a wave using a disc antenna according to an embodiment of the present invention. 
     FIG. 9 illustrates an antenna system comprising a number of disc antenna elements according to an embodiment of the present invention. 
     FIG. 10 illustrates an antenna system comprising a number of disc antenna elements according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     The present invention is directed to a disc antenna. Referring now in detail to the drawings wherein like parts are designated by like reference numerals throughout, there is illustrated in FIG. 4 a block diagram of a receiver system configured to receive an electromagnetic wave using a disc antenna  100  according to an embodiment of the present invention. 
     As shown in FIG. 4, a passive disc antenna  100  can be used to receive a wave such as the wave shown in FIG.  2 . As used herein, the “disc” antenna  100  may be, for example, a substantially planar annular antenna having an outer perimeter edge and an inner perimeter edge. Three taps  110 ,  120 ,  130  may be placed, for example, on the inner perimeter edge of the disc antenna  100  and the taps  110 ,  120 ,  130  can be separated by 120°. Although the taps are shown attached to the inner perimeter edge of the disc antenna  100 , the taps could instead be attached, for example, away from this inner edge, or in radial slots provided near the center of a solid disc. 
     The three taps  110 ,  120 ,  130  provide three separate signals that can be amplified by an amplifier system  140 . Although a single block is used to represent the amplifier system  140  in FIG. 4, three individual amplifiers, such as three LNAs, can be used. 
     A nonlinear periodic path demodulator  150  receives the amplified signal (such as three separate amplified signals), as well as a signal from a nonlinear period path frequency source  160 , which may provide a Local Oscillator (LO) for demodulation at a given rate. The amplified signal is demodulated with respect to the nonlinear period path signal and can then be demodulated by an information demodulator  170 . The information signal or signals contained in the received wave can then be reproduced. 
     A more detailed explanation of the operation of the disc antenna  100  will now be provided with respect to FIG. 5, which shows the disc antenna  100  according to an embodiment of the present invention. The disc can comprise, for example, solid aluminum or any other material suitable for an antenna. As was the case in FIG. 4, the three taps  110 ,  120 ,  130  can be located on an inner perimeter edge  150  of the disc antenna  100 . Unlike the three dipole antenna system shown in FIG. 1, any number of taps may be placed on the inner perimeter edge  150  of the disc antenna  100 . 
     According to an embodiment of the present invention, the inner perimeter edge  150  is circular and concentric with a circular outer perimeter edge  140 . Moreover, the radius of the disc antenna may be at least ¼ the wavelength of the received wave, if desired, to improve the performance of the antenna. When the antenna element is not a disc, the radius of the antenna may be at least ¼ the wavelength of the received wave at some point between the taps and the outer edge of the antenna element, if desired. 
     The wave shown in FIG. 2 will strike the disc antenna  100  along a line  200  that rotates around the disc, such as in the direction of the arrow  210 . That is, with respect to FIG. 5, an external electric wave propagating into the page and oriented along the rotating line  200  will cause the disc antenna  100  to act much like a dipole antenna along that line  200 . In this way, the disc antenna  100  can act like an infinite number of dipole antennas, each associated with an infinitely small angular separation. Because the signal received by each dipole is added coherently while the noise received by each dipole is added incoherently, the SNR of the receiver system with an apparent infinite number of dipoles is improved over an antenna system with a finite number of dipoles. 
     In addition, the disc antenna  100  acts as a “flywheel” and receives all of the energy from a wave propagating into the page, regardless of the wave&#39;s orientation. This increases the performance of the antenna as compared to the system shown in FIG.  1 . Moreover, configurations that can be created using multiple three dipole antennas, such as an antenna array, can be similarly created using multiple disc antennas  100 . 
     FIG. 6 is a perspective view of the disc antenna  100  coupled to a two-dimensional amplifier  300  according to an embodiment of the present invention. Such a two-dimensional amplifier  300  is disclosed in U.S. Provisional Patent Application Ser. No. 60/107,660 entitled “Two-Dimensional Amplifier” and filed on Nov. 9, 1998. According to this embodiment of the invention, a disc antenna acting as an infinite number of dipoles can interface with a single device acting as an infinite number of LNAs. In this way, the SNR improvement of the disc antenna  100  is not lost during amplification, and the problems of accurately separating the actual dipoles and/or the cost and complexity of a large number of LNAs are eliminated. 
     The two-dimensional amplifier  300  can be, for example, coupled directly to the back of the disc antenna  100 . As described in U.S. Provisional Patent Application Ser. No. 60/107,660 entitled “Two-Dimensional Amplifier” and the disclosure of which is incorporated herein by reference, it is desirable that the impedance of the two-dimensional amplifier  300  be matched as closely as possible with the impedance of the disc antenna  100 , and different devices such as a tube, ring-shaped or cone-shaped coupling device can be used to match these impedances. 
     FIG. 7 is a disc antenna  450  according to another embodiment of the present invention. According to this embodiment, the disc antenna  450  includes a plurality of radial elements  410 ,  420 ,  430  interconnected by at least one circumferential element  450 . In this case, a separate tap  415 ,  425 ,  435  can be placed on each of the radial elements  410 ,  420 ,  430  and the operation of the disc antenna  450  can be similar to the operation of the antenna shown in FIG.  5 . 
     Although FIGS. 4-7 were described with respect to receiving a electromagnetic wave, it will be appreciated by those skilled in the art that a disc antenna may also be used to transmit an electromagnetic wave. FIG. 8 is a block diagram of a transmitter system configured to transmit a wave using a disc antenna  500  according to an embodiment of the present invention. An information signal is modulated by an information modulator  540 . The modulated signal is then modulated by a nonlinear period path modulator  550  based on a signal from a nonlinear periodic path frequency source  560 . The resulting signal is amplified by a two-dimensional amplifier system  570  and transmitted through a disc antenna  500 , such as by driving the disc antenna  500  with three separate signals through three taps  510 ,  520 ,  530 . The three signals may, for example, be similar to those shown in FIG.  3 . Such a system may transmit certain waves, such as the wave shown in FIG. 2, more efficiently as compared to a transmitter system using actual dipoles. 
     Although the antenna systems described herein have comprised a single disc antenna element, it will be appreciated by those skilled in the art that antenna systems can also comprise multiple disc antenna s. FIG. 9 illustrates an antenna system comprising a number of disc antenna elements according to an embodiment of the present invention. In this case, a shorted disc  910  is located behind a driven disc antenna element  900 . The shorted disc  910  may be, for example, slightly larger than the driven disc  900  and act as a reflector. FIG. 10 also illustrates an antenna system comprising a number of disc antenna elements according to an embodiment of the present invention. In this case a shorted disc  920  is placed in front of a driven disc antenna element  900 . The shorted disc  920  may be, for example, slightly smaller than the driven disc  900  and act as a director. 
     Because a disc antenna element relates to a rotating wave in a way similar to the way a dipole antenna relates to a planar wave, known configurations of dipole antenna arrays will have a corresponding disc antenna array designs. Such designs can improve the performance of the antenna system. For example, a plurality of disc antenna elements may form a Yagi-type antenna array of passive elements. Designs related to end-fire and broad-side arrays are also within the scope of the present invention. 
     Although various embodiments are specifically illustrated and described herein, it will be appreciated that modifications and variations of the present invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention. For example, although specific antenna geometries were used to illustrate the present invention, it can be appreciated that other geometries may be used instead. For instance, although the disc antenna was described as a planar annulus, it will be appreciated that the a non-planar (such as a cone) or non-annulus (such as a square) geometry can be used instead. Similarly, although particular types of materials have been described with respect to the construction of disc antennas, other types of materials will also fall within the scope of the invention.