Patent Publication Number: US-9837063-B1

Title: Pickup coil sensors and methods for adjusting frequency response characteristics of pickup coil sensors

Description:
BACKGROUND ART 
     The frequency response of a pickup coil sensor in an electromagnetic pickup (also known as an induction coil sensor, induction sensor, search coil sensor, pickup coil sensor, or magnetic loop sensor), especially its resonance frequency, is an important determinant of the timbre of amplified sound transferred from vibrating ferromagnetic strings. The resonance frequency is largely a function of the internal resistance, inductance, and self-capacitance of the coil. These properties depend upon the geometry of the coil, the number and density of turns in the winding, and gauge of wire. Heretofore, electromagnetic pickups for stringed musical instruments have comprised one or more coils, each of which is wound with a single strand of wire (referred to as a single-winding coil). The resonance frequency of an electromagnetic guitar pickup, for example, typically lies within the range of 4,000 to greater than 20,000 Hertz. However, the fundamental frequencies of notes on the guitar fret board range from ˜80 Hertz (open sixth string E) to ˜1318 Hertz (first string E at the 24 th  fret), and the frequencies of the corresponding musically important overtones are mostly less than 4,000 Hertz. 
     Electromagnetic pickups referred to commonly as ‘single coil’ as disclosed in U.S. Pat. No. 2,087,106 (HART) Jun. 13, 1937 and U.S. Pat. No. 2,089,171 (BEAUCHAMP) Aug. 10, 1937 comprise a single-winding coil (as shown schematically in  FIG. 1  and depicted in cross-sectional views in  FIG. 10A-10B ) in which the winding is disposed about one or more ferromagnetic or permanent magnet pole pieces. Electromagnetic pickups comprising two or more coils (as disclosed in U.S. Pat. No. 2,892,371 (BUTTS) Jun. 30, 1959 and U.S. Pat. No. 2,896,491 (LOVER) Jul. 28, 1959) employ several single-winding coils disposed side-by-side and electrically connected in series or in parallel, often with their magnetic field vectors arranged anti-parallel in order to provide at least partial cancellation of unwanted signal due to external electromagnetic transmissions and main power alternating current. Variations of the two-coil electromagnetic pickup in which one of the single-winding coils is wound with a different gauge of wire (as disclosed in U.S. Pat. No. 4,501,185 (BLUCHER) Feb. 26, 1985) or wound with significantly more turns of wire (commonly referred to as ‘unbalanced’ or ‘ mismatched’ coils) provide for altered timbre of amplified sound due to the coils having different resonance frequencies. Other embodiments of two-coil electromagnetic pickups comprise several single-winding coils that are stacked one atop another (as disclosed in U.S. Pat. No. 3,657,461 (FREEMAN) Apr. 18, 1972) or nested within each other (as disclosed in U.S. Pat. No. 3,711,619 (JONES) Jan. 16, 1973). 
     Present embodiments provide for the construction of pickup coil sensors comprising a plurality of concurrently wound and fully or partially interpenetrating windings for which the resonance frequency can be varied over a broad range and can be adjusted to emphasize certain frequency regimes. I have found that 1) such coils, whether each winding is used individually or they are connected in series or in parallel, have resonance frequencies that are appreciably different from single-winding pickup coil sensors with the same or similar geometry and similar total number of turns in the winding, and 2) that the frequency response characteristics of such coils can be adjusted by altering the number of turns in each winding, the degree of interpenetration of the windings, and the region within the coil where the interpenetration occurs. In  FIG. 17  the frequency response profile for an example of this type of pickup coil sensor is shown for the case in which primary and secondary windings each of ˜2,500 turns of 42 AWG wire are concurrently wound and fully interpenetrating (as shown schematically in  FIG. 2  and depicted in cross-sectional views in  FIG. 11A-11B ) and electrically connected in series  1703  or in parallel  1704 . When the primary and secondary windings are connected in parallel a resonance frequency at ˜19,322 Hertz is observed. When the primary and secondary windings are connected in series a resonance frequency at ˜1,363 Hertz is observed. The frequency response profiles for two single-winding pickup coil sensors (as shown schematically in  FIG. 1  and depicted in cross-sectional views in  FIG. 10A-10B )  1701  with ˜2,500 turns of 42 AWG wire (resonance frequency at ˜17,804 Hertz) and  1702  with ˜5,000 turns of 42 AWG wire (resonance frequency at ˜9,907 Hertz) are also shown in  FIG. 17 . A pickup coil sensor with concurrently wound and interpenetrating windings can be combined with another such pickup coil sensor or with a single-winding pickup coil sensor to form a two-coil combination with a distinct frequency response profile. In  FIG. 18  the frequency response profile for this type of two-coil combination  1803  is shown in which a pickup coil sensor (as shown schematically in  FIG. 2  and depicted in cross-sectional views in  FIG. 11A-11B ) comprising primary and secondary windings each of ˜2,500 turns of 42 AWG wire and in which said windings are connected in series is in turn connected in series with a single-winding pickup coil sensor (as shown schematically in  FIG. 1  and depicted in cross-sectional views in  FIG. 10A-10B ) with ˜5,000 turns of 42 AWG wire. The frequency response profiles for the single-winding pickup coil sensor  1801  and the two wire concurrently wound and interpenetrating pickup coil sensor  1802  comprised by the two-coil combination are also shown in  FIG. 18 . 
     The embodiments comprise:
     1. A plurality of wires   2. of the same or different gauge   3. that are wound concurrently (in right-handed or left-handed fashion),   4. with or without one or more ferromagnetic pole pieces, magnets, or other material in the core region,   5. with the same or different number of turns,   6. to form fully or partially interpenetrating windings   7. that can be connected in series,   8. in parallel,   9. in phase or out of phase, or   10. connected independently in a circuit or circuits, or   11. not connected in a circuit.   

     The following is a tabulation of some prior art that presently appears relevant: 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Relevant Prior Art 
               
            
           
           
               
               
               
               
            
               
                   
                 Pat. No. 
                 Issue Date 
                 Patentee 
               
               
                   
                   
               
               
                   
                 8,519,251 
                 August 2013 
                 Lingel 
               
               
                   
                 7,288,713 
                 October 2007 
                 Krozack, et al. 
               
               
                   
                 7,189,916 
                 March 2007 
                 Kinman 
               
               
                   
                 7,022,909 
                 April 2007 
                 Kinman 
               
               
                   
                 6,846,981 
                 January 2005 
                 Devers 
               
               
                   
                 4,545,278 
                 October 2005 
                 Gagon, et al. 
               
               
                   
                 4,501,185 
                 Feburary 1985 
                 Blucher 
               
               
                   
                 3,983,778 
                 October 1976 
                 Bartolini 
               
               
                   
                 3,715,446 
                 Feburary 1973 
                 Kosinski 
               
               
                   
                 3,711,619 
                 January 1973 
                 Jones, et al. 
               
               
                   
                 3,657,461 
                 April 1972 
                 Freeman 
               
               
                   
                 3,629,483 
                 December 1971 
                 Welch 
               
               
                   
                 3,588,311 
                 June 1971 
                 Zoller 
               
               
                   
                 3,571,483 
                 March 1971 
                 Davidson 
               
               
                   
                 3,541,219 
                 November 1970 
                 Abair 
               
               
                   
                 3,535,968 
                 October 1970 
                 Rickard 
               
               
                   
                 3,483,303 
                 December 1969 
                 Warner 
               
               
                   
                 3,249,677 
                 May 1966 
                 Burns, et al. 
               
               
                   
                 3,236,930 
                 Feburary 1966 
                 Fender 
               
               
                   
                 3,177,283 
                 April 1965 
                 Fender 
               
               
                   
                 3,147,332 
                 September 1964 
                 Fender 
               
               
                   
                 3,066,567 
                 December 1962 
                 Kelley 
               
               
                   
                 2,911,871 
                 November 1959 
                 Schultz 
               
               
                   
                 2,909,092 
                 October 1959 
                 De Armond, et al. 
               
               
                   
                 2,896,491 
                 July 1959 
                 Lover 
               
               
                   
                 2,892,371 
                 June 1959 
                 Butts 
               
               
                   
                 2,683,388 
                 July 1954 
                 Keller 
               
               
                   
                 2,612,072 
                 September 1952 
                 De Armond 
               
               
                   
                 2,557,754 
                 June 1951 
                 Morrison 
               
               
                   
                 2,294,861 
                 September 1942 
                 Fuller 
               
               
                   
                 2,293,372 
                 August 1942 
                 Vasilach 
               
               
                   
                 2,262,335 
                 November 1941 
                 Russell 
               
               
                   
                 2,089,171 
                 August 1937 
                 Beauchamp 
               
               
                   
                 2,087,106 
                 July 1937 
                 Hart 
               
               
                   
                   
               
            
           
         
       
     
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, features, and advantages will become apparent from the following description of present embodiments in conjunction with the accompanying drawings, of which there are four sheets, in which: 
         FIG. 1  is a schematic diagram of a single-winding pickup coil sensor comprising a core  101  and a winding  102 . 
         FIG. 2  is a schematic diagram of a pickup coil sensor comprising a core  101 , a primary winding  202 , and a secondary winding  203  in which the primary and secondary windings are concurrently wound and fully interpenetrating. 
         FIG. 3  is a schematic diagram of a pickup coil sensor comprising a core  101 , a primary winding  302 , and a secondary winding  303  in which the primary and secondary windings are concurrently wound and partially interpenetrating and in which the region of interpenetration begins at the start of the windings and ends in the midst of the primary winding  302 . 
         FIG. 4  is a schematic diagram of a pickup coil sensor comprising a core  101 , a primary winding  402 , and a secondary winding  403  in which the primary and secondary windings are concurrently wound and partially interpenetrating and in which the region of interpenetration begins in the midst of the primary winding  402  and continues to the end of the windings. 
         FIG. 5  is a schematic diagram of a pickup coil sensor comprising a core  101 , a primary winding  502 , and a secondary winding  503  in which the primary and secondary windings are concurrently wound and partially interpenetrating and in which the region of interpenetration begins and ends in the midst of the primary winding  502 . 
         FIG. 6  is a schematic diagram of a pickup coil sensor comprising a core  101 , a primary winding  602 , and a secondary winding  603  in which the primary and secondary windings are concurrently wound and partially interpenetrating and in which the region of interpenetration begins in the midst of the primary winding  602  and ends in the midst of the secondary winding  603 . 
         FIG. 7  is a perspective view of a general form of a pickup coil bobbin  106  comprising a core  101 , an upper flange  104  and a lower flange  105 . A partial winding  102  is depicted, with arrows  103  showing the counter-clockwise direction of winding when viewed from the top. Clockwise winding is also equally applicable to pickup coil sensors. 
         FIG. 8  is a perspective view of a general form of a pickup coil sensor comprising a bobbin  106  and a coil  107 . 
         FIG. 9  shows the depiction used for the primary winding  901 , the depiction used for the secondary winding  902 , and the depiction used for the region of interpenetration of the primary and secondary windings  903  that are used in  FIGS. 10-15 . 
         FIG. 10A  is a cross-sectional view of a single-winding pickup coil sensor as depicted in  FIG. 1  taken along the section  1 - 1  of  FIG. 8 . Refer to  FIG. 9  for conventions regarding the depiction of the windings. 
         FIG. 10B  is a cross-sectional view of a single-winding pickup coil sensor as depicted in  FIG. 1  taken along the section  2 - 2  of  FIG. 8 . Refer to  FIG. 9  for conventions regarding the depiction of the windings. 
         FIG. 11A  is a cross-sectional view of a two-winding pickup coil sensor as depicted in  FIG. 2  taken along the section  1 - 1  of  FIG. 8 . Refer to  FIG. 9  for conventions regarding the depiction of the windings. 
         FIG. 11B  is a cross-sectional view of a two-winding pickup coil sensor as depicted in  FIG. 2  taken along the section  2 - 2  of  FIG. 8 . Refer to  FIG. 9  for conventions regarding the depiction of the windings. 
         FIG. 12A  is a cross-sectional view of a two-winding pickup coil sensor as depicted in  FIG. 3  taken along the section  1 - 1  of  FIG. 8 . Refer to  FIG. 9  for conventions regarding the depiction of the windings. 
         FIG. 12B  is a cross-sectional view of a two-winding pickup coil sensor as depicted in  FIG. 3  taken along the section  2 - 2  of  FIG. 8 . Refer to  FIG. 9  for conventions regarding the depiction of the windings. 
         FIG. 13A  is a cross-sectional view of a two-winding pickup coil sensor as depicted in  FIG. 4  taken along the section  1 - 1  of  FIG. 8 . Refer to  FIG. 9  for conventions regarding the depiction of the windings. 
         FIG. 13B  is a cross-sectional view of a two-winding pickup coil sensor as depicted in  FIG. 4  taken along the section  2 - 2  of  FIG. 8 . Refer to  FIG. 9  for conventions regarding the depiction of the windings. 
         FIG. 14A  is a cross-sectional view of a two-winding pickup coil sensor as depicted in  FIG. 5  taken along the section  1 - 1  of  FIG. 8 . Refer to  FIG. 9  for conventions regarding the depiction of the windings. 
         FIG. 14B  is a cross-sectional view of a two-winding pickup coil sensor as depicted in  FIG. 5  taken along the section  2 - 2  of  FIG. 8 . Refer to  FIG. 9  for conventions regarding the depiction of the windings. 
         FIG. 15A  is a cross-sectional view of a two-winding pickup coil sensor as depicted in  FIG. 6  taken along the section  1 - 1  of  FIG. 8 . Refer to  FIG. 9  for conventions regarding the depiction of the windings. 
         FIG. 15B  is a cross-sectional view of a two-winding pickup coil sensor as depicted in  FIG. 6  taken along the section  2 - 2  of  FIG. 8 . Refer to  FIG. 9  for conventions regarding the depiction of the windings. 
         FIG. 16  is a perspective view of a general form of a two-coil pickup coil sensor comprising two bobbins ( 106   a  and  106   b ), and two coils ( 107   a  and  107   b ). 
         FIG. 17  is an overlay of frequency response profiles for pickup coil sensors as depicted in  FIG. 10A-10B  comprising windings of ˜2,500 turns  1701  and ˜5,000 turns  1702  of 42 AWG enameled copper wire and a pickup coil sensor as depicted in  FIG. 11A-11B  comprising primary and secondary windings each of ˜2,500 turns of 42 AWG enameled copper wire in which said windings are connected in series  1703  or in parallel  1704 . 
         FIG. 18  is an overlay of frequency response profiles for a pickup sensor coil as depicted in  FIG. 10A-10B  comprising a winding of ˜5,000 turns  1801  of 42 AWG enameled copper wire, a pickup sensor coil as depicted in  FIG. 11A-11B  comprising primary and secondary windings each of ˜2,500 turns of 42 AWG enameled copper wire in which the windings are connected in series  1802 , and a two-coil pickup coil sensor as depicted in  FIG. 16  comprising the pickup sensor coils represented by frequency response curves  1801  and  1802  in which the pickup coil sensors are connected in series  1803 . 
     
    
    
     MODE(S) FOR CARRYING OUT THE INVENTION 
     A first embodiment is shown schematically in  FIG. 2  and depicted in cross-sectional views in  FIG. 11A-11B . This embodiment comprises a primary winding  202  and a secondary winding  203  in which said primary and secondary windings are concurrently wound and fully interpenetrating and in which said primary and secondary windings are of the same or different gauge, with or without one or more ferromagnetic pole pieces, magnets, or other material in the core region. 
     A second embodiment is shown schematically in  FIG. 3  and depicted in cross-sectional views in  FIG. 12A-12B . This embodiment comprises a primary winding  302  and a secondary winding  303  in which said primary and secondary windings are concurrently wound and partially interpenetrating and in which the region of interpenetration begins at the start of the windings and ends in the midst of the primary winding  302  and in which said primary and secondary windings are of the same or different gauge, with or without one or more ferromagnetic pole pieces, magnets, or other material in the core region. 
     A third embodiment is shown schematically in  FIG. 4  and depicted in cross-sectional views in  FIG. 13A-13B . This embodiment comprises a primary winding  402  and a secondary winding  403  in which said primary and secondary windings are concurrently wound and partially interpenetrating and in which the region of interpenetration begins in the midst of the primary winding  402  and continues to the end of the windings and in which said primary and secondary windings are of the same or different gauge, with or without one or more ferromagnetic pole pieces, magnets, or other material in the core region. 
     A fourth embodiment is shown schematically in  FIG. 5  and depicted in cross-sectional views in  FIG. 14A-14B . This embodiment comprises a primary winding  502  and a secondary winding  503  in which said primary and secondary windings are concurrently wound and partially interpenetrating and in which the region of interpenetration begins and ends in the midst of the primary winding  502  and in which said primary and secondary windings are of the same or different gauge, with or without one or more ferromagnetic pole pieces, magnets, or other material in the core region. 
     A fifth embodiment is shown schematically in  FIG. 6  and depicted in cross-sectional views in  FIG. 15A-15B . This embodiment comprises a primary winding  602  and a secondary winding  603  in which said primary and secondary windings are concurrently wound and partially interpenetrating and in which the region of interpenetration begins in the midst of the primary winding  602  and ends in the midst of the secondary winding  603  and in which said primary and secondary windings are of the same or different gauge, with or without one or more ferromagnetic pole pieces, magnets, or other material in the core region. 
     An additional set of five embodiments is illustrated by combination of one single-winding pickup coil sensor (as shown schematically in  FIG. 1  and depicted in cross-sectional views in  FIG. 10A-10B ) and another coil of the type of one of the first to fifth embodiments described hereinabove to form a two-coil electromagnetic pickup of either a side-by-side or stacked configuration. 
     An additional set of twenty-five embodiments is illustrated by the various possible combinations of one coil of the type of one of the first to fifth embodiments described hereinabove and another coil of the type of one of the first to fifth embodiments described hereinabove to form a two-coil electromagnetic pickup of either a side-by-side or stacked configuration. 
     Embodiments described herein above comprise concurrently wound and interpenetrating coils employing two windings. However, it is apparent that concurrently wound coils comprising three or more interpenetrating windings will have additional utility in creating desirable frequency response characteristics. 
     Embodiments described herein above comprise one or two coils. However, the usefulness of embodiments in the form of pickup coil sensors with three or more coils variously connected (or not connected) in the manners described herein above is apparent. 
     It is generally known that a coil that serves as a sensor can be employed as a transmitter. Thus coils comprising a plurality of concurrently wound and fully or partially interpenetrating windings as described herein with their attendant characteristics have equally useful embodiments as transmitting coils. Such coils are suitable for transmission and reception of wireless signals for digital signals (such as wireless internet connections and communication between peripheral devices such as printers and cameras) and analogue signals (such as sound for wireless speakers, radio, or cochlear implants), field generation or sensing for magnetic resonance imaging, and for power transmission (such as in transformers or wireless chargers for cellular telephones and other rechargeable devices). 
     It is understood that variations and modifications can be effected within the scope and spirit of the embodiments described hereinabove and as defined in the appended claims and their legal equivalents. 
     REFERENCES 
     
         
         Slawomir Tumanski, “Induction Coil sensors—a review,” Measurement Science and Technology 18 (2007) R31-R46 
         Christophe Coillot and Paul Leroy (2012). Induction Magnetometers Principle, Modeling and Ways of Improvement, Magnetic Sensors—Principles and Applications, Dr Kevin Kuang (Ed.), ISBN: 978-953-51-0232-8