Abstract:
A communication circuit and method including communications circuitry having an input and an output and a noise suppressor. The noise suppressor includes an amorphous magnetic core and a bifilar winding around said amorphous magnetic core.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to noise suppression circuitry and methods generally.  
         BACKGROUND OF THE INVENTION  
         [0002]    The following U.S. Patents are believed to represent the current state of the art: Nos. 6,241,920; 6,239,379; 6,183,657; 6,091,025; 6,089,917; 6,069,803; 6,014,071; 6,004,661; 6,002,593; 5,994,992; 5,990,417; 5,978,231; 5,977,853; 5,977,754; 5,966,064; 5,850,336; 5,841,335; 5,831,505; 5,825,272; 5,793,273; 5,635,890; 5,629,661; 5,619,174; 5,611,871; 5,581,224; 5,522,948; 5,506,559; 5,252,148; 5,242,760; 5,225,006; 5,192,375; 5,178,689; 5,067,991; 5,030,933; 5,019,190; 5,012,125; 4,985,088; 4,870,729; 4,859,256; 4,847,575; 4,741,484; 4,637,843; 4,472,693; 4,325,733.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention seeks to provide improved noise suppression circuitry and methods.  
           [0004]    There is thus provided in accordance with a preferred embodiment of the present invention a communication circuit, which includes communications circuitry having an input, an output and a noise suppressor. The noise suppressor includes an amorphous magnetic core and a bifilar winding around said amorphous magnetic core.  
           [0005]    There is also provided in accordance with another preferred embodiment of the present invention a communication noise suppressing method, which includes providing a communications circuitry having an input and an output, providing an amorphous magnetic core, winding a bifilar winding around said amorphous magnetic core and in series with at least one of said communications circuitry input and communications circuitry output and passing a communication signal from said input, through said bifilar winding and to said output for suppressing noise in said communication signal.  
           [0006]    Further in accordance with a preferred embodiment of the present invention the amorphous magnetic core has a toroidal shape. Alternatively, the amorphous magnetic core has a closed E-shape.  
           [0007]    There is also provided in accordance with a preferred embodiment of the present invention a noise suppressor assembly, which includes a multiplicity of noise suppressors. At least one of said multiplicity of noise suppressors includes an amorphous magnetic core and a bifilar winding wound around said amorphous magnetic core.  
           [0008]    There is further provided in accordance with a preferred embodiment of the present invention a noise suppressing method, which includes providing a multiplicity of magnetic cores, at least one of said multiplicity of magnetic cores includes an amorphous magnetic core, winding a bifilar winding around each of said plurality of magnetic cores, connecting said bifilar windings in series and passing a signal through said bifilar windings for suppressing noise in said signal.  
           [0009]    Further in accordance with a preferred embodiment of the present invention the multiplicity of noise suppressors includes at least first and second noise suppressors having cores containing different amorphous magnetic materials.  
           [0010]    There is further provided in accordance with a preferred embodiment of the present invention a noise suppressor assembly, which includes at least one noise suppressor. The noise suppressor includes a core, including ferrite material and an amorphous magnetic material, and a bifilar winding wound around said core.  
           [0011]    There is also provided in accordance with yet a further preferred embodiment of the present invention a noise suppressing method. The method includes providing at least one core including ferrite material and an amorphous magnetic material, winding a bifilar winding around said at least one core and passing a signal through said bifilar winding for suppressing noise in said signal.  
           [0012]    Further in accordance with a preferred embodiment of the present invention the noise suppressor comprises a multiplicity of noise suppressors, which include at least first and second noise suppressors having cores containing different amorphous magnetic materials.  
           [0013]    There is also provided in accordance with a further preferred embodiment of the present invention a wide band noise suppressor, which includes a core assembly comprising a multiplicity of amorphous magnetic cores and a bifilar winding wound around said core assembly.  
           [0014]    There is further provided in accordance with another preferred embodiment of the present invention a wide band noise suppressing method. The method includes providing a core assembly comprising a multiplicity of amorphous magnetic cores, winding a bifilar winding wound around said core assembly and passing a signal through said bifilar winding for suppressing noise in said signal.  
           [0015]    There is further provided in accordance with yet a further preferred embodiment of the present invention a wide band noise suppressor, which includes a core comprising a mixture of a plurality of different amorphous magnetic materials and a bifilar winding wound around said core.  
           [0016]    There is also provided in accordance with a further preferred embodiment of the present invention a wide band noise suppressing method. The method includes providing a core comprising a mixture of a plurality of different amorphous magnetic materials, winding a bifilar winding wound around said core and passing a signal through said bifilar winding for suppressing noise in said signal.  
           [0017]    Further in accordance with a preferred embodiment of the present invention the amorphous magnetic core has a toroidal shape. Alternatively, the amorphous magnetic core has a closed E-shape.  
           [0018]    There is further provided in accordance with yet another preferred embodiment of the present invention a signal to interference enhancer. The enhancer includes at least one passive analog circuit, which operates to decrease radio frequency interference in a received signal and at least one active analog circuit, which operates to decrease radio frequency interference in said received signal. Typically, the passive analog circuit and the active analog circuit are arranged in series for providing radio frequency signal to interference enhancement to said received signal.  
           [0019]    There is further provided in accordance with yet another preferred embodiment of the present invention a signal to interference enhancing method, which includes providing at least one passive analog circuit operative to decrease radio frequency interference in a received signal, providing at least one active analog circuit operative to decrease radio frequency interference in said received signal, arranging the passive analog circuit and the active analog circuit in series and passing a radio frequency signal through said passive analog circuit and said active analog circuit for enhancing said signal to interference therein.  
           [0020]    Further in accordance with a preferred embodiment of the present invention the active analog circuit cancels common mode interference.  
           [0021]    Still further in accordance with a preferred embodiment of the present invention the passive analog circuit reduces the amplitude of common mode interference.  
           [0022]    Additionally in accordance with a preferred embodiment of the present invention the passive analog circuit operates in a frequency range which is at least partially non-overlapping with a frequency range of operation of said at least one active analog circuit.  
           [0023]    Further in accordance with a preferred embodiment of the present invention the passive analog circuit is operative to reduce non-common mode interference due to imperfect balancing of first and second transmission lines by filtering the common mode interference.  
           [0024]    Still further in accordance with a preferred embodiment of the present invention the passive analog circuit employs an EMI filter to attenuate interference at frequencies above a desired frequency pass band and employs a plurality of cascaded common mode chokes connected in series with said EMI filter to attenuate interference at frequencies within said desired frequency pass band.  
           [0025]    Moreover in accordance with a preferred embodiment of the present invention the passive analog circuit includes a low-pass EMI filter operative to attenuate interference at frequencies above a desired frequency pass band and a plurality of cascaded common mode chokes connected in series with said EMI filter. Typically, the common mode chokes operate to attenuate interference at frequencies within said desired frequency pass band.  
           [0026]    Additionally in accordance with a preferred embodiment of the present invention the signal to interference enhancing method also includes employing metallic barriers located at said filter and at said cascaded common mode chokes to reduce parasitic input to output interference coupling.  
           [0027]    Preferably, the core comprises separate core elements made of said metal-based amorphous material and of said ferrite material.  
           [0028]    Still further in accordance with a preferred embodiment of the present invention the signal to interference enhancer also includes metallic barriers located at said filter and at said cascaded common mode chokes in order to reduce parasitic input to output interference coupling.  
           [0029]    Additionally in accordance with a preferred embodiment of the present invention the plurality of cascaded common mode chokes include at least one choke. The choke includes at least one core comprising a metal-based amorphous material and a ferrite material and at least one coil wound about said at least one core.  
           [0030]    Moreover in accordance with a preferred embodiment of the present invention the amorphous material comprises at least one of cobalt and nickel.  
           [0031]    Further in accordance with a preferred embodiment of the present invention the ferrite material comprises silicon steel permalloy.  
           [0032]    Still further in accordance with a preferred embodiment of the present invention the amorphous material has magnetic permeability between 20,000-100,000 and has a saturation current of at least 5 Amperes.  
           [0033]    Additionally in accordance with a preferred embodiment of the present invention the magnetic permeability varies with changes in temperature between −30° C. and 85° C. by less than 5%.  
           [0034]    Further in accordance with a preferred embodiment of the present invention the core comprises separate core elements made of said metal-based amorphous material and of said ferrite material.  
           [0035]    There is also provided in accordance with another preferred embodiment of the present invention a signal to interference enhancer, which includes a low-pass EMI filter operative to attenuate interference at frequencies above a desired frequency pass band and a plurality of cascaded common mode chokes connected in series with said EMI filter. Typically, the common mode chokes operate to attenuate interference at frequencies within said desired frequency pass band.  
           [0036]    There is also provided in accordance with a preferred embodiment of the present invention a signal to interference enhancer embodied in a circuit package, which includes a low-pass EMI filter operative to attenuate interference at frequencies above a desired frequency pass band, a plurality of cascaded common mode chokes connected in series with said EMI filter. Typically, the common mode chokes operate to attenuate interference at frequencies within said desired frequency pass band. The metallic barriers located at said filter and at said cascaded common mode chokes reduce parasitic input to output interference coupling.  
           [0037]    Additionally in accordance with a preferred embodiment of the present invention the plurality of cascaded common mode chokes include at least one choke. The choke includes at least one core comprising a metal-based amorphous material and a ferrite material and at least one coil wound about said at least one core.  
           [0038]    Further in accordance with a preferred embodiment of the present invention the ferrite material comprises silicon steel permalloy.  
           [0039]    Still further in accordance with a preferred embodiment of the present invention the amorphous material has magnetic permeability between 20,000-100,000 and has a saturation current of at least 5 Amperes.  
           [0040]    Additionally in accordance with a preferred embodiment of the present invention the magnetic permeability varies with changes in temperature between −30° C. and 85° C. by less than 5%.  
           [0041]    Further in accordance with a preferred embodiment of the present invention the core comprises separate core elements made of said metal-based amorphous material and of said ferrite material.  
           [0042]    Still further in accordance with a preferred embodiment of the present invention the signal to interference enhancer also includes metallic barriers located at said filter and at said cascaded common mode chokes in order to reduce parasitic input to output interference coupling.  
           [0043]    There is also provided in accordance with yet a further preferred embodiment of the present invention a signal to interference enhancing method, which includes employing a low-pass EMI filter to attenuate interference at frequencies above a desired frequency pass band, employing a plurality of cascaded common mode chokes connected in series with said EMI filter to attenuate interference at frequencies within said desired frequency pass band and employing metallic barriers located at said filter and at said cascaded common mode chokes to reduce parasitic input to output interference coupling.  
           [0044]    There is further provided in accordance with yet another preferred embodiment of the present invention a signal to interference enhancing method, which includes employing a low-pass EMI filter to attenuate interference above a desired frequency pass band, employing a plurality of cascaded common mode chokes connected in series with said EMI filter to attenuate interference at frequencies within said desired frequency pass band and passing a signal through said low-pass EMI filter and said plurality of cascaded common mode chokes for suppressing noise in said signal.  
           [0045]    Further in accordance with a preferred embodiment of the present invention the signal to interference enhancing method also includes metallic barriers located at said filter and at said cascaded common mode chokes in order to reduce parasitic input to output interference coupling.  
           [0046]    Further in accordance with a preferred embodiment of the present invention the amorphous material comprises at least one of cobalt and nickel.  
           [0047]    There is also provided in accordance with yet a further preferred embodiment of the present invention a noise suppressor, which includes an amorphous magnetic core, a bifilar winding wound around said amorphous magnetic core. Typically the amorphous magnetic core has a closed E-shape.  
           [0048]    There is also provided in accordance with yet another preferred embodiment of the present invention a signal to interference enhancer, which includes at least one passive analog circuit operative to decrease radio frequency interference in a received signal and at least one active analog circuit operative to decrease radio frequency interference in said received signal. Typically, the passive analog circuit and the active analog circuit being arranged in series for providing radio frequency signal to interference enhancement to said received signal. Preferably, the active analog circuit operates to interface with a modem.  
           [0049]    There is further provided in accordance with a preferred embodiment of the present invention a signal to interference enhancer, which includes at least one passive analog circuit operative to decrease radio frequency interference in a received signal and at least one active analog circuit operative to decrease radio frequency interference in said received signal. Typically, the passive analog circuit and the one active analog circuit being arranged in series for providing radio frequency signal to interference enhancement to said received signal. Preferably, the active analog circuit operates to interface with an A/D converter.  
           [0050]    There is also provided in accordance with yet another preferred embodiment of the present invention a signal to interference enhancing repeater. The repeater includes a first passive analog circuit operative to decrease radio frequency interference in a received signal, at least one active analog circuit operative to decrease radio frequency interference in said received signal and a second passive analog circuit operative to decrease radio frequency interference in a received signal. Typically, the first passive analog circuit, the active analog circuit and said second passive analog circuit are arranged in series for providing radio frequency signal to interference enhancement to said received signal. Preferably, the one active analog circuit operates as an analog repeater.  
           [0051]    There is further provided in accordance with yet another preferred embodiment of the present invention a signal to interference enhancer, which includes at least one passive analog circuit comprising a differential input and operative to decrease radio frequency interference in a received signal and at least one active analog circuit comprising a single-ended output and operative to decrease radio frequency interference in said received signal. Typically, the passive analog circuit and the active analog circuit being arranged in series for providing radio frequency signal to interference enhancement to said received signal. Preferably, the differential input serves as the input of the cascaded circuit and said single-ended output serves as the output of the cascaded circuits.  
           [0052]    There is also provided in accordance with yet a firer preferred embodiment of the present invention a signal to interference enhancer, which includes at least one passive analog circuit operative to decrease radio frequency interference in a received signal and at least one active analog circuit operative to decrease radio frequency interference in said received signal. Typically, the passive analog circuit and the one active analog circuit being arranged in series for providing radio frequency signal to interference enhancement to said received signal. Preferably, the first said of at least one passive analog circuit includes a differential input and the last of said at least one active analog circuit includes a single-ended output.  
           [0053]    There is also provided in accordance with yet a preferred embodiment of the present invention a signal to interference enhancer, which includes at least one passive analog circuit operative to decrease radio frequency interference in a received signal and at least one active analog circuit operative to decrease radio frequency interference in said received signal. Typically, the passive analog circuit and the active analog circuit being arranged in series for providing radio frequency signal to interference enhancement to said received signal. Typically, the first of said at least one passive analog circuit includes a single-ended input and the last of said at least one active analog circuit includes a single-ended output.  
           [0054]    There is further provided in accordance with yet another preferred embodiment of the present invention a signal to interference enhancer, which includes at least one passive analog circuit operative to decrease radio frequency interference in a received signal and at least one active analog circuit operative to decrease radio frequency interference in said received signal. Typically, the passive analog circuit and the active analog circuit being arranged in series for providing radio frequency signal to interference enhancement to said received signal. Preferably, the first of said at least one passive analog circuit includes a single-ended input and the last of said at least one active analog circuit includes a differential output.  
           [0055]    There is also provided in accordance with yet a further preferred embodiment of the present invention a signal to interference enhancer, which includes at least one passive analog circuit operative to decrease radio frequency interference in a received signal and at least one active analog circuit operative to decrease radio frequency interference in said received signal. Typically, the passive analog circuit and the active analog circuit being arranged in series for providing radio frequency signal to interference enhancement to said received signal. Preferably, the active analog circuit operates to interface with an XDSL modem.  
           [0056]    There is further provided in accordance with yet another preferred embodiment of the present invention a noise suppressing transformer assembly, which includes at least one noise suppressor. The noise suppressor, which includes an amorphous magnetic core and a bifilar winding wound around said amorphous magnetic core, and a transformer. The transformer includes at least one core comprising at least a ferrite material and at least one coil wound about said at least one core. Typically, the noise suppressor and said transformer are arranged in series.  
           [0057]    There is provided in accordance with yet a further preferred embodiment of the present invention a signal to interference enhancer embodied in a circuit package. The enhancer includes a low-pass EMI filter operative to attenuate interference at frequencies above a desired frequency pass band and a plurality of cascaded common mode chokes connected in series with said EMI filter, said common mode chokes being operative to attenuate interference at frequencies within said desired frequency pass band. Typically, each of said low-pass EMI filter and said plurality of cascaded common mode being contained in a separate metallic enclosure.  
           [0058]    There is further provided in accordance with yet a further preferred embodiment of the present invention a signal to interference enhancer embodied in a circuit package, which includes a low-pass EMI filter operative to attenuate interference at frequencies above a desired frequency pass band and a plurality of cascaded common mode chokes connected in series with said EMI filter, said common mode chokes being operative to attenuate interference at frequencies within said desired frequency pass band. Typically, the plurality of cascaded common mode chokes being contained in a metal enclosure and said EMI filter being embodied in a feed-through device inserted in a wall of said enclosure.  
           [0059]    There is also provided in accordance with yet another preferred embodiment of the present invention a transformer, which includes at least one core comprising at least one of metal-based amorphous material and a ferrite material, at least one coil wound about said at least one core and at least one aluminum foil shield wound around at said least one coil.  
           [0060]    There is further provided in accordance with a preferred embodiment of the present invention a noise suppressor embodied in a circuit package, which includes an amorphous magnetic core, a bifilar winding wound around said amorphous magnetic core, said bifilar winding comprising an input portion and an output portion and a metallic barrier located across said amorphous magnetic core and between said input portion and said output portion in order to reduce parasitic input to output interference coupling. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0061]    The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which:  
         [0062]    [0062]FIGS. 1A and 1B are each a simplified illustration of a noise suppressor constructed and operative in accordance with a preferred embodiment of the present invention;  
         [0063]    [0063]FIG. 2 is a simplified illustration of a plurality of noise suppressors of the type shown in FIG. 1A, connected in series;  
         [0064]    [0064]FIG. 3 is a simplified illustration of a noise suppressor of the general type shown in FIG. 1A, having a multilayer core;  
         [0065]    [0065]FIG. 4 is a simplified circuit diagram of a passive magnetic circuit for enhancing signals relative to interference in accordance with a preferred embodiment of the present invention;  
         [0066]    [0066]FIG. 5 is a simplified circuit diagram of a passive/active circuit for enhancing signals relative to interference in accordance with a preferred embodiment of the present invention, which is particularly suitable for incorporation into a hybrid circuit;  
         [0067]    [0067]FIG. 6 is a simplified circuit diagram illustrating incorporation of multiple passive magnetic circuits of the type shown in FIG. 4 in an analog repeater;  
         [0068]    [0068]FIG. 7 is a simplified circuit diagram illustrating incorporation of a passive magnetic circuit of the type shown in FIG. 4 in an active differential input to single-ended output circuit;  
         [0069]    [0069]FIG. 8 is a simplified circuit diagram illustrating incorporation of a passive magnetic circuit of the type shown in FIG. 4 in an active single-ended input to single-ended output circuit;  
         [0070]    [0070]FIG. 9 is a simplified circuit diagram illustrating incorporation of a passive magnetic circuit of the type shown in FIG. 4 in an active single-ended input to differential output circuit;  
         [0071]    [0071]FIG. 10 is a simplified circuit diagram of a circuit for enhancing signals relative to interference in accordance with a preferred embodiment of the present invention, incorporated into an XDSL modem;  
         [0072]    [0072]FIG. 11 is a simplified illustration of a noise suppressing transformer assembly constructed and operative in accordance with a preferred embodiment of the present invention;  
         [0073]    [0073]FIG. 12 is a simplified illustration of a packaged circuit of the type shown in FIG. 4, including metallic enclosures and barriers;  
         [0074]    [0074]FIG. 13 is a simplified illustration of a packaged circuit incorporating a noise suppressor of the type shown in FIG. 1;  
         [0075]    [0075]FIG. 14 is a simplified illustration of an insulating transformer that forms a part of the noise suppressing transformer of FIG. 11; and  
         [0076]    [0076]FIG. 15 is a simplified illustration of a packaged circuit incorporating a noise suppressor of the type shown in FIG. 1 and having a metallic enclosure and barrier. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0077]    Reference is now made to FIGS. 1A and 1B, which are simplified pictorial illustrations of two types of noise suppressors, also known as common mode chokes, constructed and operative in accordance with a preferred embodiment of the present invention. The noise suppressers are preferably used to suppress incoming line noise, such as longitudinal interference, The noise suppressor of FIG. 1A is designated by reference numeral  10  and comprises an amorphous magnetic core  12  and a bifilar winding  14  wound around the amorphous magnetic core  12 . The bifilar winding  14  preferably has a pair of input terminals  16  and a pair of output terminals  18 . Preferably the core  12  has a closed shape such as a toroidal shape and the bifilar winding  14  is wound around the core  12  so that the input terminals  16  and the output terminals  18  are arranged to be located on respective opposite sides of the core  12  in order to minimize electrical interference between the input and the output.  
         [0078]    Core  12  preferably comprises a metal-based amorphous material and a ferrite material. Preferably, the ferrite material comprises silicon steel permalloy. In accordance with a preferred embodiment of the present invention, the amorphous material has a relatively high magnetic permeability, which most preferably is above 20,000. Preferably, the magnetic permeability varies with changes in temperature between −30° C. and 85° C. by less than 5%. In accordance with a preferred embodiment of the present invention, the amorphous material has a saturation current of at least 5 Amperes. The core  12  may include separate core elements made of metal-based amorphous material and of ferrite material, as in the embodiment of FIG. 3. Alternatively, the amorphous material and the ferrite material may be mixed together. As a further alternative, the core need not include ferrite material. The amorphous magnetic material may be, for example, a composite material comprising cobalt or nickel.  
         [0079]    Reference is now made to FIG. 1B, which illustrates another embodiment of a noise suppressor, here designated by reference numeral  20 , which similarly comprises an amorphous magnetic core  22  and a bifilar winding  24  wound around the amorphous magnetic core  22 . The bifilar winding  24  preferably has a pair of input terminals  26  and a pair of output terminals  28 . As distinct from the embodiment of FIG. 1A, the core  22  has an E-shape. The composition of the core of FIG. 1B may be identical to that of FIG. 1A.  
         [0080]    Reference is now made to FIG. 2, which is a simplified pictorial illustration of a passive magnetic assembly  30  comprising three different noise suppressors which are typically of the type designated by reference numeral  10  in FIG. 1A, connected in series. Alternatively, the noise suppressors may be of the type designated by reference numeral  20  in FIG. 1B.  
         [0081]    The noise suppressors of FIG. 2 are specifically designated by numerals  32 ,  34 , and  36 . Each of the noise suppressors  32 ,  34  and  36  has a different type of core, here specifically designated respectively by numerals  37 ,  38  and  39 . Preferably each of the cores  37 ,  38  and  39  provides noise suppression characteristics that are optimal for a different set of requirements. Such requirements may be frequency range characteristics, saturation current characteristics and temperature range characteristics. For example, the noise suppressors  32 ,  34 , and  36  may each be optimal for a different and adjacent frequency band so that the noise suppressor assembly  30  has combined wide band noise suppression characteristics. Alternatively or additionally, the noise suppressors  32 ,  34 , and  36  may have different saturation currents so that the performance of the passive magnetic assembly  30  at different DC currents is better than the performance of each of the noise suppressors  32 ,  34  and  36  when operating independently. It is appreciated that any number of noise suppressors can be assembled to form the passive magnetic assembly  30  in order to achieve desired noise suppression characteristics.  
         [0082]    It is appreciated that placing noise suppressors  32 ,  34  and  36  in various different orders in the passive magnetic assembly  30  may result in different overall noise suppression characteristics.  
         [0083]    Preferably at least one of the noise suppressors  32 ,  34  and  36  comprises a core  12  made of amorphous magnetic material such as composite materials comprising cobalt or nickel.  
         [0084]    Reference is now made to FIG. 3, which is a simplified pictorial illustration of a noise suppressor  40 , which comprises a bifilar winding  42  wound around a core assembly  44  that comprises a plurality of core elements  45 . Core elements  45  are each typically similar to core  12  of FIG. 1A but may be thinner.  
         [0085]    According to a preferred embodiment of the present invention, core assembly  44  comprises three core elements  45 , here specifically designated by numerals  46 ,  48  and  50 , which are of the same shape, such as a toroidal shape, and are made of different materials. The bifilar winding  42  provides a pair of input terminals  52  and a pair of output terminals  54 , preferably arranged on opposite sides of the core assembly  44  in order to minimize electrical interference between the input and the output.  
         [0086]    Preferably each of the core elements  46 ,  48  and  50  provides noise suppression characteristics that are optimal for a different set of requirements. Such requirements may be frequency range characteristics, saturation current characteristics and temperature range characteristics. For example, the core elements  46 ,  48  and  50  may each be optimal for a different and adjacent frequency band so that the noise suppressor  40  has combined wide band noise suppression characteristics.  
         [0087]    Alternatively or additionally, the core elements  46 ,  48  and  50  may have different saturation currents so that the performance of the noise suppressor  40  at different DC currents is better than the performance of each of the cores  46 ,  48  and  50  when operating independently. It is appreciated that any suitable number of core elements  45  can be assembled to form the noise suppressor  40  to achieve desired noise suppression characteristics. Preferably at least one of the core elements  45  is made of an amorphous magnetic material such as composite materials comprising cobalt or nickel.  
         [0088]    Two or more noise suppressors  40  can be connected in series in order to achieve overall noise suppression characteristics that can not be achieved with a single noise suppressor  40 . Preferably the two or more noise suppressors  40  employ different combinations of core elements  45 .  
         [0089]    Reference is now made to FIG. 4, which is a simplified circuit diagram of a passive magnetic circuit  60  for enhancing signals relative to interference in accordance with a preferred embodiment of the present invention, The passive magnetic circuit  60  of FIG. 4 includes an input circuit  62  and a passive magnetic portion  64 .  
         [0090]    The input circuit  62  comprises a pair of low pass EMI filter assemblies  66  and  68 , which are preferably identical. Low pass EMI filter assembly  66  connects between a terminal  70  and a first input terminal  72  of the passive magnetic portion  64 . Low pass EMI filter assembly  68  connects between a terminal  74  and a second input terminal  76  of the passive magnetic portion  64 . Each of low pass EMI filter assemblies  66  and  68  typically comprises a pair of capacitors  77  arranged on either side of an inductor  78  and is operative to attenuate interference at frequencies above a desired frequency pass band and.  
         [0091]    In accordance with a preferred embodiment of the present invention, the passive magnetic portion  64  is preferably identical to the passive magnetic assembly  30  of FIG. 2. Alternatively, the passive magnetic portion  64  may comprise a single noise suppressor, such as noise suppressor  10  shown in FIG. 1A. As a further alternative, the passive magnetic portion  64  may comprise a noise suppressor such as noise suppressor  40  shown in FIG. 3. As yet another alternative, the passive magnetic portion  64  may comprise a plurality of noise suppressors, such as noise suppressors  40 . Irrespective of its specific configuration, the passive magnetic portion  64  defines a pair of terminals  79  and  80 .  
         [0092]    Typically, terminals  70  and  74  are connected to a communication line and terminals  79  and  80  are connected to a modem. Alternatively, terminals  70  and  74  may be connected to a modem and terminals  79  and  80  are connected to a communication line.  
         [0093]    Reference is now made to FIG. 5, which is a simplified circuit diagram of a combined passive and active circuitry for enhancing signals relative to interference in accordance with a preferred embodiment of the present invention. The circuit of FIG. 5, which is particularly suitable for incorporating into a hybrid circuit, includes a passive portion  81 , which is preferably identical to the circuitry of FIG. 4, and an active portion  82  preferably comprising three operational amplifier assemblies  84 ,  86  and  88 .  
         [0094]    Operational amplifier assembly  84  typically comprises three amplifiers  90 ,  92  and  94 , connected as shown in a feedback arrangement, wherein a resistor  96  is connected in series between an output terminal  98  of the passive portion  81  and a junction  99  of an input to amplifier  90 . A feedback connection  102  from an output of amplifier  94  to the input of amplifier  90  is provided and includes a feedback resistor  104  connected between the output of amplifier  94  and the input to amplifier  90 .  
         [0095]    Operational amplifier assembly  86  typically comprises three amplifiers  106 ,  108  and  110  connected as shown in a feedback arrangement, wherein a feedback connection  112  is provided from an output of amplifier  110  to the input of amplifier  106 . A feedback resistor  114  is connected in the feedback connection  112  between the output of the amplifier  110  and the input of amplifier  106 .  
         [0096]    Operational amplifier assembly  88  typically comprises three amplifiers  116 ,  118  and  120  connected as shown in a feedback arrangement, wherein a feedback connection  122  is provided from an output of amplifier  120  to the input of amplifier  116 . A feedback resistor  124  is connected between the output of amplifier  120  and the input of amplifier  116 .  
         [0097]    It is noted that operational amplifier assemblies  86  and  88  may be identical in structure but may have different electrical connections. For example, an output from operational amplifier assembly  84 , may be supplied to a non-inverting input of amplifier  108  of assembly  86 , while an output from operational amplifier  84  may be supplied to an inverting input of amplifier  118  of assembly  88 .  
         [0098]    It is appreciated that although the use of operational amplifier assemblies is preferred, other suitable types of differential amplifier assemblies may be employed.  
         [0099]    It is further appreciated that the gain of operational amplifier assembly  84  is governed by the ratio of the resistance of resistors  104  and  96 .  
         [0100]    The active portion  82  of the circuit of FIG. 5 is preferably characterized by stable gain and by a high common mode rejection ratio over a wide frequency range.  
         [0101]    The functionality of active portion  82  may be summarized as follows:  
         [0102]    1. Provision of impedance matching between the balanced connection  98  and  124  at the output of the passive portion  81  and a balanced connection  126  and  128  at the input to an A/D converter (not shown) or a modem chip-set (not shown).  
         [0103]    2. Provision of gain at least partially sufficient to compensate for signal attenuation in the passive portion  80  and the line leading thereto.  
         [0104]    Operational amplifier assembly  86  typically comprises three amplifiers  106 ,  108  and  110  connected as shown in a feedback arrangement, wherein a feedback connection  112  is provided from an output of amplifier  110  to the input of amplifier  106 . A feedback resistor  14  is connected in the feedback connection  112  between the output of the amplifier  1   10  and the input of amplifier  106 . The output of amplifier  110  is also connected via an impedance matching resistor  115  to terminal  116  of the active portion  82 .  
         [0105]    Operational amplifier assembly  88  typically comprises three amplifiers  117 ,  118  and  120  connected as shown in a feedback arrangement, wherein a feedback connection  122  is provided from an output of amplifier  120  to the input of amplifier  117 . A feedback resistor  124  is connected between the output of amplifier  120  and the input of amplifier  117 . The output of amplifier  120  is also connected via an impedance matching resistor  126  to terminal  128  of the active portion  82 .  
         [0106]    It is appreciated that although the use of operational amplifier assemblies is preferred, other suitable types of differential amplifier assemblies may be employed.  
         [0107]    It is further appreciated that the gain of operational amplifier assembly  84  is governed by the ratio of the resistance of resistors  104  and  96 .  
         [0108]    The active portion  82  of the circuit of FIG. 5 is preferably characterized by stable gain and by a high common mode rejection ratio over a wide frequency range.  
         [0109]    The functionality of active portion  82  may be summarized as follows:  
         [0110]    1. Provision of impedance matching between the balanced connection  98  and  124  at the output of the passive portion  81  and a balanced connection  116  and  128  at the input to an A/D converter (not shown) or a modem chip-set (not shown).  
         [0111]    2. Provision of gain at least partially sufficient to compensate for signal attenuation in the passive portion  80  and the line leading thereto.  
         [0112]    Reference is now made to FIG. 6, which is a simplified circuit diagram illustrating an analog repeater for enhancing signals relative to interference, constructed and operative in accordance with a preferred embodiment of the present invention. The circuit of FIG. 6 includes a first passive magnetic circuit portion  130 , an active circuit portion  132  and a second passive magnetic network circuit portion  134 . The active circuit  132  is connected between the passive magnetic portions  132  and  134 . Each of the two passive portions  130  and  134  is preferably identical to the passive magnetic circuit  60  of FIG. 4.  
         [0113]    The active portion  132  preferably comprises two operational amplifier assemblies  136  and  138 . Inputs of operational amplifier assembly  136  are connected to terminals  140  of the first passive magnetic portion  132  and outputs of operational amplifier assembly  136  are connected to the terminals  142  of the second passive magnetic portion  136 . Inputs of the operational amplifier assembly  138  are connected to terminals  142  of the second passive magnetic portion  136  and outputs of operational amplifier assembly  136  are connected to terminals  140  of the first passive portion  130 .  
         [0114]    Reference is now made to FIG. 7, which is a simplified circuit diagram illustrating incorporation of a passive magnetic circuit of the type shown in FIG. 4 into an active differential input to single-ended output circuit for enhancing signals relative to interference, constructed and operative in accordance with a preferred embodiment of the present invention. The circuit of FIG. 7 includes a passive portion  150  that is preferably identical to the circuitry of FIG. 4, and an active portion  152 , preferably comprising an operational amplifier assembly.  
         [0115]    In a preferred embodiment of the present invention described in FIG. 7, an operational amplifier assembly of the active portion  152  comprises two operational amplifiers  154  and  156 . Inputs of the operational amplifier  154  are connected to output terminals  158  and  160  of the passive portion  150 . The output terminals  158  and  160  of the passive portion  150  are also connected via termination resistors  162  and  164  to a common ground. In a preferred implementation of the present invention the termination resistors  162  and  164  have the same resistance.  
         [0116]    Outputs of the operational amplifier  154  are connected to two corresponding inputs of the operational amplifier  156 . An output of the operational amplifier  156  is connected to output  168  of the circuit of FIG. 7 via a resistor  164  and a ferrite element  166 .  
         [0117]    Reference is now made to FIG. 8, which is a simplified circuit diagram illustrating incorporating a passive magnetic circuit of the type shown in FIG. 4 into an active single-ended input to single-ended output circuit for enhancing signals relative to interference, constructed and operative in accordance with a preferred embodiment of the present invention. The circuit of FIG. 8 includes a passive circuit portion  170  that is preferably identical to the circuitry  60  of FIG. 4, and an active circuit portion  172 , preferably comprising an operational amplifier assembly.  
         [0118]    In a preferred implementation of the current invention, a first output  174  of the passive portion  170  is connected via a ferrite element  176  to a junction  177 . The junction  177  is connected via a termination resistor  178  to a common ground. A second output  180  of the passive portion  170  is connected directly to common ground. Junction  177  is also connected to a non-inverting input of an operational amplifier  182  and to an inverting input of an operational amplifier  184 . The other inputs of the operational amplifiers  182  and  184  are connected to common ground. The outputs of operational amplifiers  182  and  184  are each connected to an input of an operational amplifier  186 . The output of operational amplifier  186  is connected via an impedance matching resistor  188  and a ferrite element  190  to an output  192  of the circuit of FIG. 8.  
         [0119]    Reference is now made to FIG. 9, which is a simplified circuit diagram illustrating incorporation of a passive magnetic circuit of the type shown in FIG. 4 in an active single-ended input to differential output circuit for enhancing signals relative to interference, constructed and operative in accordance with a preferred embodiment of the present invention. The circuit of FIG. 9 includes a passive portion  200  that is preferably identical to the circuit  60  of FIG. 4, and an active portion  202 , preferably comprising an operational amplifier assembly. A single-ended input  204  of the circuit of FIG. 9 is connected to a first input  206  of the passive portion  200  and a shield  208  of the single ended input is connected to a second input  210  of the passive portion  200  and to a common ground. A first output  214  of the passive portion  200  is connected via a ferrite element  216  to a first input  218  of an operational amplifier  220 , preferably the non-inverting input, and a second output  222  of the passive portion  200  is connected to a second inverting input  224  of the operational amplifier  220  and to the common ground. An output of operational amplifier  220  is connected to a non-inverting input of an operational amplifier  226  and to an inverting input of an operational amplifier  228 . An inverting input of operational amplifier  226  and a non-inverting input of operational amplifier  228  are grounded. The outputs of the operational amplifiers  226  and  228  are connected via impedance matching resistors  230  and  232  to respective outputs  234  and  236  of the circuit of FIG. 9.  
         [0120]    Reference is now made to FIG. 10, which is a simplified circuit diagram of a circuit for enhancing signals relative to interference incorporated into an XDSL modem, in accordance with a preferred embodiment of the present invention. The circuit of FIG.  10  includes a line matching portion  240 , an interconnecting portion  242  and an active portion  244  all connected in series.  
         [0121]    Typically, the line matching portion  240  comprises an insulating transformer  246  connected to a passive magnetic circuit  248 . In a preferred embodiment of the present invention, the insulating transformer  246  is typically similar to an insulating transformer described hereinbelow in accordance with FIG. 14 or is identical to a noise suppressing transformer assembly described hereinbelow in accordance with FIG. 11. Passive magnetic circuit  248  is preferably identical to the circuitry of FIG. 4. Line terminals  250  and  252  of the circuit of FIG. 10 are connected via the insulating transformer  246  to terminals  254  and  256  of the passive magnetic circuit  248  and to terminals  258  and  260  of the passive magnetic circuit  248  are connected to the interconnecting portion  242 .  
         [0122]    In a preferred implementation of the present invention, the interconnecting portion  242  comprises a resistor network  261  and the active portion  244  comprises a receiver amplifier  262  and a transmitter amplifier  264 . The terminals  258  and  260  of the passive magnetic circuit  248  are connected via resistors  266  and  268  to a non-inverting input and to an inverting input of the receiver amplifier  262 , respectively. Terminals  258  and  260  of the passive magnetic circuit  248  are also connected via resistors  270  and  272  to an inverting output and a non-inverting output of the transmitter amplifier  264 , respectively.  
         [0123]    One output of the transmitter amplifier  264  is also connected, via a resistor  273 , to a “BRIDGE” input of the receiver amplifier  262  and the other output of the transmitter amplifier  264  is also connected, via a resistor  274  to a “SENSE” input of the receiver amplifier  262 . The output of receiver amplifier  262  is connected via a terminal  276  to the input of a digital portion (not shown) of the XDSL modem and the output of the digital portion of the XDSL modem is connected via a terminal  278  to an input of transmitter amplifier  264 .  
         [0124]    Reference is now made to FIG. 11, which is a simplified illustration of a noise suppressing transformer assembly constructed and operative in accordance with a preferred embodiment of the present invention. Noise suppressing transformer assembly  280  includes a noise suppressor portion  282  and an insulating transformer portion  284 . In a preferred embodiment of the present invention, shown in FIG. 11, the noise suppressor portion  282  comprises the noise suppressor  10  of FIG. 1A, the noise suppressor  20  of FIG. 1B, the passive magnetic assembly  30  of FIG. 2, the noise suppressor  40  of FIG. 3, or the passive magnetic circuit  60  of FIG. 4.  
         [0125]    The insulating transformer portion  284  typically comprises a primary coil  286 , a first shielding aluminum foil  288  wrapped around primary coil  286 , a ferrite core  290 , a secondary coil  292  and a secondary shielding aluminum foil  294  wrapped around the secondary coil  292 .  
         [0126]    In a preferred embodiment of the present invention, shown in FIG. 11, the noise suppressor portion  282  is connected between terminals  296  of the noise suppression transformer assembly  280  and terminals  297  of the primary coil  286  of the insulating transformer portion  284 . Terminals  298  of the secondary coil  292  of the insulating transformer portion  284  constitute another pair of terminals of the noise suppressing transformer assembly  280 . Either terminals  296  or terminals  298  may be used as input terminals, while the other pair of terminals serves as output terminals. Foil  288  is preferably connected to the terminal  297 , while foil  294  is preferably connected to the terminal  298 .  
         [0127]    In an alternative embodiment of the present invention, the noise suppressing transformer assembly  280  includes first noise suppressor portion  282  connected between the terminals  296  of the noise suppressing transformer assembly  280  and the primary coil  286  of the insulating transformer portion  284 . Assembly  280  also includes insulating transformer portion  284  as well as a second noise suppressor portion (not shown), connected between the secondary coil  292  of the insulating transformer  284  and the output terminals  298  of the noise suppressing transformer assembly  280 .  
         [0128]    Reference is now made to FIG. 12, which is a simplified illustration of a packaged circuit  300  including metallic enclosures  302 . In a preferred implementation of the present invention, the packaged circuit  300  embodies the circuit  60  of FIG. 4. In this preferred implementation, each of the low pass EMI filter assemblies  66  and  68  and the noise suppressors  10  shown in FIG. 4 is enclosed in a metallic enclosure  302 . Optionally, metallic barriers  304  may be provided in electrically conductive engagement with enclosures  302  to isolate inputs of circuitry enclosed therein from outputs thereof. It is appreciated that this structure decreases the parasite capacitance between the inputs and the outputs of the circuitry enclosed in each enclosure  302 , thus decreasing the crossover interference therebetween. Preferably enclosures  302  and barriers  304  are connected to a common ground. It is appreciated that any of the circuits described above in FIGS.  4  to  11  and the noise suppressors described above in FIGS. 1A  1 B,  2  and  3  may be packaged in the manner illustrated generally in FIG. 12 and described hereinabove.  
         [0129]    Reference is now made to FIG. 13, which is a simplified illustration of a packaged circuit  310  comprising a noise suppressor  312 , preferably identical to the noise suppressor  10  of FIG. 1A, and two low pass EMI filters  314 , each embodied in a feed-through device. Low pass EMI filters  314  are preferably similar in function to the low pass EMI filter assemblies  66  and  68  of FIG. 4.  
         [0130]    Reference is now made to FIG. 14, which is a simplified illustration of a preferred implementation of the insulating transformer portion  284  of FIG. 11. The insulating transformer of FIG. 14 preferably comprises a core  320  that corresponds to core  290  of FIG. 11; a primary winding connecting terminals  322 , corresponding to terminals  297  of FIG. 11; a secondary winding, connecting terminals  324  corresponding to terminals  298  of FIG. 11; and aluminum foil shields  326  and  328 , corresponding to  288  and  294  of FIG. 11, respectively. Preferably, core  320  is made of ferrite material; of an amorphous magnetic material or of a combination of ferrite and amorphous magnetic materials. The shield  326  is connected to the terminal  322  via a connection  330  and similarly the shield  328  is connected to the terminal  324  via a connection  332 .  
         [0131]    Reference is now made to FIG. 15, which is a simplified illustration of a packaged circuit providing reduced cross-over interference between the input terminals and the output terminals of a noise suppressor, such as noise suppressor  312  of FIG. 13. FIG. 15 shows the packaged circuit  310  of FIG. 13 with the addition of a metallic barrier  330  separating an input portion  334  of the circuit from an output portion  336  thereof. The metallic barrier  330  reduces the parasite capacitance between the input and the output of noise suppressor  312  and thus reduces the cross-over interference.  
         [0132]    It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described herein above. Rather the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove as well as variations and modifications which would occur to persons skilled in the art upon reading the specifications and which are not in the prior art.