Abstract:
A transformer system comprises a transformer star winding to be coupled to an antenna system, and a transformer delta winding disposed with said transformer star winding. The transformer star winding includes a set of star elements and the transformer delta winding includes a set of delta elements each being substantially perpendicularly disposed with a corresponding star element from the set of star elements.

Description:
This application claims the benefit under 35 U.S.C. § 119(e) of Provisional application No. 60/135,098 filed Nov. 9, 1998. 
    
    
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to U.S. patent application No. 08/853,833, entitled “Communications System,” filed May 9, 1997, now U.S. Pat. No. 6,204,810, and U.S. patent application No. 09/064,525 entitled “Communication System,” filed 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. applications filed concurrently: U.S. patent application No. 09/436,236 entitled “Adjustable Balanced Modulator,” pending, U.S. patent application No. 09/436,531 entitled “System For Measuring and Displaying Three-Dimensional Characteristics of Electromagnetic Waves,” now U.S. Pat. No. 6,295,025, U.S. patent application No. 09/436,144 entitled “Cavity-Driven Antenna System,” now U.S. Pat. No. 6,317,097, U.S. patent application No. 09/437,892 entitled “Disc Antenna System,” now U.S. Pat. No. 6,340,950, and U.S. patent application No. 09/436,400 entitled “Two-Dimensional Amplifier,” pending. 
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to transformer systems. More specifically, the present invention relates to a transformer system used in a communication system to perform two dimensional filtering. 
     Known communications systems use, for example, filters to respond differently to signals of different frequencies. Passive filters, for example, are constructed with passive elements such as resistors, inductors and capacitors. Filters can be categorized by type: low pass filters filter out higher frequencies, high pass filters filter out lower frequencies, bandpass filters filter out lower and higher frequencies while passing middle frequencies defined by the pass band, notch filters pass lower and higher frequencies while filtering out middle frequencies defined by the stop (or notch) band. 
     Used in conjunction with a communications receiver system, filters operate on electrical signals detected by the receiver system based on the electromagnetic wave received at the receiver antenna. In the context of a communications transmitter system, filters operate on electrical signals produced by the transmitter system and propagated as an electromagnetic wave via the transmitter antenna. In the communications system context, filters can remove electrical signal components at particular frequencies that are undesirable and can represent, for example, unwanted noise, harmonics, and/or intermodulation products. 
     These known filtering techniques for communications systems, however, suffer several shortcomings. These filtering techniques are “one-dimensional” in the sense that the filtering is performed regardless of the orientation of the electromagnetic wave received and transmitted by the communications system receive antenna and transmit antenna, respectively. 
     In other words, these filtering techniques are of limited use to process signals that are based on information-modulated electromagnetic waves having a particular and varying orientation, for example, to establish a particular information channel. For example, such an electromagnetic wave can have a carrier frequency and an electric field the terminus of which traces a non-linear path at a second frequency between the carrier frequency and zero. Above-mentioned U.S. patent application No. 09/064,525 (“Communication System”) discloses a communications system that utilizes such an electromagnetic wave. 
     In view of the foregoing, a substantial need exists for filtering techniques that account for the orientation of the electromagnetic wave received by a communications receiver and transmitted by a communications transmitter. Such filtering techniques can be referred to as “two-dimensional” filtering. 
     SUMMARY OF THE INVENTION 
     Two-dimensional filtering for a communications system can be performed by a transformer system. The transformer system comprises a transformer star winding to be coupled to an antenna system, and a transformer delta winding disposed with said transformer star winding. The transformer star winding includes a set of star elements and the transformer delta winding includes a set of delta elements each being substantially perpendicularly disposed with a corresponding star element from the set of star elements. 
     In one embodiment, the antenna system includes a set of antenna elements. The transformer star winding includes a set of star elements the number of which are substantially equal to the number of antenna elements in the plurality of antenna elements. The transformer delta winding includes a set of delta elements the number of which are substantially equal to the number of antenna elements in the plurality of antenna elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a block diagram of a communications receiver system using a transformer system according to an embodiment of the present invention. 
     FIG. 2 illustrates a block diagram of a communications transmitter system using a transformer system according to an embodiment of the present invention. 
     FIG. 3 provides an electrical schematic of a transformer system coupled to an antenna system according to an embodiment of the present invention. 
     FIG. 4 illustrates an example of a transformer system with a non-perpendicular arrangement coupled to a phase lock loop, according to another embodiment of the present invention. 
     FIG. 5 illustrates a plan view of a microstrip implementation of a transformer system according to another embodiment of the present invention. 
     FIG. 6 illustrates a cross-sectional view of a microstrip implementation of the transformer system shown in FIG. 5 along line X. 
     FIG. 7 illustrates a cross-sectional view of a microstrip implementation of a transformer system according to an embodiment of the present invention. 
     FIG. 8 illustrates a cross-sectional view of a solid disc antenna system and transformer system combined with the system block component of the two-dimensional amplifier, according to an embodiment of the present invention. 
     FIG. 9 illustrates a plan view of the solid disc antenna system and the transformer system shown in FIG.  8 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a system block diagram of a communications receiver system using a transformer system according to an embodiment of the present invention. Receiver system  100  includes a receive antenna  110  coupled to transformer system  120  which is in turn coupled to nonlinear periodic path demodulator  140 . Nonlinear period path demodulator  140  is coupled to nonlinear period path frequency source  130  and information demodulator  150 . 
     Above-mentioned U.S. patent application No. 09/064,525 (“Communication System”) described a communications receiver system similar to that shown in FIG.  1 . Although the receiver system will be briefly described below, the above-mentioned patent application No. 09/064,525 should be referenced for further details and description for all of the system components except for the transformer system  120  which is discussed herein. 
     Receive antenna  110  can send a signal to transformer  120  based on a received electromagnetic wave. The received electromagnetic wave can include, for example, a number of constituent waves such a linear polarized waves, elliptical polarized waves and waves having a time-varying orientation. For example, these later waves can have a carrier frequency and an electric field vector the terminus of which traces a non-linear path at a second frequency between the carrier frequency and zero. The nonlinear period path of these later waves can, for example, establish a communications channel; these waves can also carry information modulated onto signals generated in the process of transmitting the waves (see the discussion of the transmitter system below). 
     Transformer  120  can filter the received signals so that signals associated with linear and elliptical polarized waves (referred to herein as “linear waves”) are filtered out and signals associated with waves having a time-varying orientation (referred to herein as “nonlinear waves”) are passed to the nonlinear periodic path demodulator  140 . The nonlinear periodic path demodulator  140  also receives a signal from the nonlinear period path frequency source to produce a demodulated signal which is sent to the information demodulator  150 . The information demodulator  150  further demodulates the received demodulated signal based on a carrier frequency to produce the information signal. 
     FIG. 2 illustrates a system block diagram of a communications transmitter system using a transformer system according to an embodiment of the present invention. The embodiment of the transmitter system shown in FIG. 2 can be used in conjunction with the receiver system described above in reference to FIG.  1 . Again, although the transmitter system will be briefly described below, the above-mentioned patent application No. 09/064,525 (“Communication System”) should be referenced for further details and description for all of the system components excepted for the transformer system  240  which is discussed herein. 
     Transmitter system  200  includes an information modulator  110  coupled to nonlinear period path modulator  220  which is also coupled to nonlinear periodic path frequency source  230  and transformer system  240 . Transformer system  240  is also coupled to transmit antenna  250 . 
     Information modulator  210  can modulate a carrier frequency with a received information signal and send this signal to the nonlinear period path modulator  220  which also receives a signal from the nonlinear periodic path frequency source  230 . The nonlinear periodic path modulator  220  modulates the signal received from the information modulator  210  with signal received from the nonlinear periodic path frequency source  230  to produce a signal to transformer system  240 . 
     Transformer system  240  can filter the received signals so that signals once transmitted by transmit antenna  250  that would be associated with linear waves are filtered out and signals that would be associated with nonlinear waves are passed to the transmit antenna  250 . Transmit antenna  250  sends an electromagnetic wave having the carrier frequency and an electric field vector the terminus of which traces a non-linear path at a second frequency between the carrier frequency and zero. 
     FIG. 3 provides an electrical schematic of a transformer system coupled to an antenna system according to an embodiment of the present invention. The transformer system  300  shown in FIG. 3 can be used for the transformer system  120  of the receiver system  100  shown in FIG.  1  and can be used for the transformer system  240  of the transmitter system  200  shown in FIG.  2 . 
     Transformer system  300  includes a transformer star winding  310  and a transformer delta winding  320 . Antenna system  330  is coupled to the transformer star winding  310  and has three monopole antenna elements. Transformer star winding  310  and transformer delta winding  320  each have three legs. 
     Transformer star winding  310  is disposed with transformer delta winding  320  so that the two transformer windings can inductively interact. The term “disposed with” is herein to include, but is not exclusively limited, to the physical arrangement of the transformer star winding  310  in conjunction with the transformer delta winding  320 . The physical arrangement of the two sets of windings can include, for example, the vertical arrangement and/or the angular orientation of the transformer star winding  310  with respect to the transformer delta winding  320 . 
     The particular manner in which transformer star winding  310  is disposed with transformer delta winding  320  will depend on the particular implementation of the transformer system  300 . For example, where the transformer system  300  is implemented in a microstrip as appropriate for a particular transmission frequency(ies) of interest, the transformer star winding  310  can be vertically adjacent to (i.e., on top of) the transformer delta winding  320 . In another implementation, where the transformer system  300  is implemented with an iron core, the windings can be wound together around the arms of the iron core. 
     FIG. 3 illustrates a particular angular orientation between the transformer star winding  310  and the transformer delta winding  320 . In particular, the transformer star winding  310  is arranged with respect to the transformer delta winding  320  so that each leg of the transformer star winding  310  is substantially perpendicular to a corresponding leg of the transformer delta winding  320 . 
     The transformer star winding  310 , however, need not be angularly arranged exactly perpendicular to the transformer delta winding  320 . The term “substantially perpendicular” is used herein to mean perpendicular as well as an range of angles offset from perpendicular, for example, angles plus or minus twenty degrees (±20°) offset from perpendicular. Although other ranges of angles offset from perpendicular may be possible, plus or minus twenty degrees is given as an example because this range of angles is within approximately 94% of the perpendicular case as represented by a cosine function. In embodiments of the transformer system where the transformer star winding is disposed with the transformer delta winding at an angle offset from perpendicular within this range, the transformer system can operate sufficiently without the need for compensation or correction. 
     In some embodiments of the transformer system where the transformer star winding and the transformer delta winding are offset from perpendicular outside an acceptable angular range, a phase lock loop can be used to compensate for the non-perpendicular arrangement. In other words, where he transformer star winding and the transformer delta winding are not disposed substantially perpendicular in the physical sense, the windings can be disposed substantially perpendicular in the electrical sense due to the compensation performed by the phase lock loop. 
     FIG. 4 illustrates an example of a transformer system with a non-perpendicular arrangement coupled to a phase lock loop, according to another embodiment of the present invention. Phase lock loop  340  can receive signals over lines A″, B″ and C″ and then adjust the phase of these signals to compensate for the non-perpendicular arrangement of the transformer star winding  310  and the transformer delta winding  320 . The output of the phase lock loop  340  is coupled to the transformer delta winding  320  over lines A′, B′ and C′. 
     Returning to FIG. 3, each leg of the transformer star winding  310  is coupled to a corresponding antenna element of antenna  330 . As illustrated in FIG. 3, the antenna elements of antenna system  330  have leads labeled A, B and C which are coupled respectively to the legs of the transformer star winding  310  which respectively labeled A, B and C. The transformer delta windings  320  also have three leads labeled in FIG. 3 as A′, B′ and C′; these leads from the transformer delta windings  320  are the output of the transformer system  300 . The outputs of the transformer system  300  are coupled to the nonlinear periodic path modulator or demodulator (for the receiver system or the transmitter system, respectively). Alternatively, the outputs of the transformer system  300  can be coupled to the nonlinear periodic path modulator/demodulator through additional components (not shown in FIG. 3 for simplicity) such as nonlinear amplifiers (NLAs). 
     The transformer system  300  operates to perform two-dimensional filtering due to the physical arrangement of the two transformer windings  310  and  320 . As an electromagnetic wave is received by receive antenna  330 , the electromagnetic wave is converted into a first signal which is sent to the transformer star winding  310  via lines A, B and C. As the first signal is received by the transformer star winding  310 , an electromagnetic field is established based on that first signal. This electromagnetic field can then be inductively coupled into the transformer delta winding  320 . A second signal can then be generated in the individual legs of the transformer delta winding  320 . 
     In embodiments of the transformer system where each leg of the transformer star winding is substantially perpendicular to a corresponding leg of the transformer delta winding, however, components of the second signal based on linear waves (e.g., linear polarized waves and elliptical polarized waves received by the receive antenna system) are not generated. Conversely, components of the second signal based on nonlinear waves (e.g., waves with a time-varying orientation) are generated as the outputs of the transformer system (e.g., via lines A′, B′ and C′ for the embodiment shown in FIG.  4 ). Consequently, the transformer system filters linear waves and passes nonlinear waves. The transformer system can be considered a two-dimensional filter in the sense that received waves having time-varying orientations are passed through to the remaining components of the receiver system (e.g., nonlinear period path demodulator  140  and information demodulator  150  shown in FIG. 1) while linear waves are filtered out and do not pass to the remaining components of the receiver system. The analogous filtering can also performed for a transmitter system. 
     FIG. 5 illustrates a plan view of a microstrip implementation of a transformer system according to another embodiment of the present invention. Transformer system  400  includes transformer star winding  410  disposed with transformer delta winding  420 . Note that the use of the terms “transformer star winding” and “transformer delta winding” are intended to be sufficiently broad to encompass transformer systems that are constructed with actual windings as well as transformer systems that are constructed without actual windings but function similarly. 
     The dimensions of the transformer system  400  can be selected based on the particular frequency of interest. In other words, as is known in the art, the length and width of legs for the transformer star winding  410  and the transformer delta winding  420  can be selected based on the carrier frequency(ies) of the electromagnetic wave received by the receiver system or transmitted by the transmitter system. 
     FIG. 6 illustrates a cross-sectional view of a microstrip implementation of the transformer system shown in FIG. 5 along line X. Transformer delta winding  420  is disposed on a substrate  425 . Transformer star winding  410  is separated by transformer delta winding  420  by an insulator layer  415 . The height of insulator layer  415  (i.e., the distance between the transformer star winding  410  and the transformer delta winding  420 ) can be selected to allow inductive coupling, while preventing conductive coupling, between the transformer layers  410  and  420 . In one embodiment, the insulator layer  415  is as small as possible thereby allowing inductive coupling while still preventing conductive coupling. 
     FIG. 7 illustrates a cross-sectional view of a microstrip implementation of a transformer system according to an embodiment of the present invention. Similar to the arrangement of the transformer windings shown in FIG. 5, the transformer star winding  510  is disposed on a substrate  525  and is separated from the transformer delta winding  520  by insulator layer  515 . Again, the height of insulator layer  515  can be selected to allow inductive coupling, while preventing conductive coupling, between the transformer layers  510  and  520 . 
     Although the embodiments discussed above assume that the antenna system for either the receiver or the transmitter have three monopoles angularly spaced within a plane about a common point, other antenna system configurations are possible; some of these other antenna system configurations are discussed in the above-mentiond U.S. patent application No. 09/064,525 (“Communication System”). The antenna system can have, for example nine angularly spaced monopoles. An embodiment of the transformer system used in conjunction with this nine-monopole antenna system can have, for example, nine legs in the transformer star winding disposed with nine legs in the transformer delta winding. Each antenna monopole can be coupled to a corresponding leg of the transformer star winding. Each leg of the transformer delta winding can be the output of the transformer system. 
     In other embodiments, the transformer system can be used in conjunction with the two-dimensional amplifier and the solid disc antenna system described in above-mentioned U.S. patent application No. 09/436,400 (“Two-Dimensional Amplifier”) and above-mentioned U.S. patent application No. 09/437,892 (“Disc Antenna ”), respectively, the entire contents of which are both hereby incorporated by reference. FIG. 8 illustrates a cross-sectional view of a solid disc antenna system and transformer system combined with the system block component of the two-dimensional amplifier, according to an embodiment of the present invention. FIG. 9 illustrates a plan view of the solid disc antenna system and the transformer system shown in FIG.  8 . 
     Solid disc antenna system  600  is integrally formed with the transformer star winding  610 . The transformer delta winding  611  is connected to the transformer star winding  610  at a point which defines where the transition between the solid disc. antenna  600  and the transformer star winding  610 . The transformer delta winding  611  can be, for example, a loop configuration formed on a printed wiring board as a microstrip. The transformer delta winding  620  is connected to a coupling device  620  which is in turn connected to the two-dimensional amplifier  630 . The specific configurations of the coupling device  620  and the specific manners in which the two-dimensional amplifier  630  can be coupled to the solid disc antenna system  600  is described in further detail in the respective co-pending patent applications described above. 
     It should, of course, be understood that while the present invention has been described in reference to particular component shapes and configurations, other component shapes and configurations should be apparent to those of ordinary skill in the art. For example, although the transformer system configurations discussed above have the number of legs in the transformer star winding and transformer delta winding equal each other and equal to the number of monopoles in the antenna system, other configurations are possible although not necessarily quite as effective. For example, where the antenna system has three monopoles, the transformer star winding can have three legs and the transformer delta winding can have four legs. To the extent that each leg of the transformer star winding is not substantially perpendicular with a corresponding leg of the transformer delta winding, this transformer system will operate less than optimally.