Abstract:
An antenna for radiating and/or receiving signals. The antenna includes (i) a first hollow and helical pipe, (ii) a second hollow and helical pipe, (iii) a first transmission wire, (iv) a second transmission wire, and (v) a dielectric connector. The dielectric connector physically couples to the first hollow and helical pipe and the second hollow and helical pipe. The first hollow and helical pipe and the second hollow and helical pipe comprise an electrically conductive material. The first transmission wire comprises a first portion and a second portion. The second transmission wire comprises a third portion and a fourth portion. The first portion of the first transmission wire and the third portion of the second transmission wire are inside the first hollow and helical pipe.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to antennas, and more particularly to shortened antennas which are substantially balanced in their emission and reception fields. 
   BACKGROUND OF THE INVENTION 
   A typical antenna is used to generate signals to the surrounding space and/or receive signals from the surrounding space. There is often a need to make the antenna physically shortened, and with as balanced or symmetrical a radio-frequency field as possible. When end-fed ( FIG. 1 ) this balancing efficiency improves coupling to the free-space environment, and reduces non-wanted coupling into local conductive or dielectric objects. When center fed ( FIG. 2 ) there is the additional advantage of reduced coupling from interfering noise sources. 
   SUMMARY OF THE INVENTION 
   The present invention provides a structure, comprising a first hollow and helical pipe; a second hollow and helical pipe; a first transmission wire; a second transmission wire; and a dielectric connector physically coupled to the first hollow and helical pipe and the second hollow and helical pipe, wherein the first hollow and helical pipe and the second hollow and helical pipe comprise an electrically conductive material, wherein the first transmission wire comprises a first portion and a second portion, wherein the second transmission wire comprises a third portion and a fourth portion, and wherein the first portion of the first transmission wire and the third portion of the second transmission wire are inside the first hollow and helical pipe. 
   The present invention provides an antenna that is balanced and shorter than that of the prior art. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a side-view of a dipole antenna and a signal source electrically coupled to the dipole antenna, in accordance with embodiments of the present invention. 
       FIG. 2  shows a side-view of a folded dipole antenna and a signal source electrically coupled to the folded dipole antenna, in accordance with embodiments of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a side-view of a dipole antenna  100  and a signal source  130  electrically coupled to the dipole antenna  100 , in accordance with embodiments of the present invention. More specifically, with reference to  FIG. 1 , the dipole antenna  100  comprises hollow helix radiating elements  110   a  and  110   b  and transmission wires  120   a  and  120   b . The hollow helix radiating elements  110   a  and  110   b  can be hollow and helical pipes. The hollow helix radiating elements  110   a  and  110   b  can be formed by winding two straight hollow pipes into helical shape. Alternatively, it can be formed by a coaxial cable manufactured with two center conductors. In one embodiment, the helical axis  110   a ′ of the hollow helix radiating element  110   a  and the helical axis  110   b ′ of the hollow helix radiating element  110   b  are on the same straight line. 
   Each of the hollow helix radiating elements  110   a  and  110   b  can be right-handed or left-handed. With the line of sight being helical axis, if clockwise movement of the helix corresponds to axial movement away from the observer, then it is a right-handed helix. If counter-clockwise movement corresponds to axial movement away from the observer, then it is a left-handed helix. It should be noted that the hollow helix radiating elements  110   a  and  110   b  shown in  FIG. 1  are left-handed. If both the hollow helix radiating elements  110   a  and  110   b  are left-handed or if both the hollow helix radiating elements  110   a  and  110   b  are right-handed, it is said that the hollow helix radiating elements  110   a  and  110   b  are wound in the same direction. In an alternative embodiment, one of the hollow helix radiating elements  110   a  and  110   b  is left-handed whereas the other is right-handed. 
   In one embodiment, the hollow helix radiating element  110   a  comprises a left end  110   a L and a right end  110   a R. The hollow helix radiating element  110   b  comprises a left end  110   b L and a right end  110   b R. The hollow helix radiating elements  110   a  and  110   b  can comprise an electrically conductive material. In one embodiment, the hollow helix radiating elements  110   a  and  110   b  are electrically insulated from each other. A dielectric connector  160  can be used to physically couple the hollow helix radiating elements  110   a  and  110   b  together so as to keep the hollow helix radiating elements  110   a  and  110   b  in place. 
   Let La and Lb represent axial lengths of the hollow helix radiating elements  110   a  and  110   b , respectively. Let Da and Db represent diameters of the hollow helix radiating elements  110   a  and  110   b , respectively. Let Lta and Ltb (not shown) represent the physical lengths of the hollow helix radiating elements  110   a  and  110   b , respectively. The physical length of the hollow helix radiating element  110   a  is a length measured from the left end  110   a L to the right end  110   a R along the solid body of the hollow helix radiating element  110   a . Similarly, the physical length of the hollow helix radiating element  110   b  is a length measured from the left end  110   b L to the right end  110   b R along the solid body of the hollow helix radiating element  110   b . This is shorter than the physical length, while still being balanced. In one embodiment, Lta=Ltb=λ/4 (allowing plus and minus 10% tolerance), wherein λ is the wavelength of the signal generated by the signal source  130 . In other words, the dipole antenna  100  is essentially a half-wave dipole antenna. For example, at a signal frequency of 46 MHz (λ˜6.2 m), Lta=Ltb=1.550 m. With plus and minus 10% tolerance, each of Lta and Ltb can be in the range of 1.395 m to 1.705 m. The physical lengths (i.e., La and Lb) can be shorter. 
   In one embodiment, the transmission wires  120   a  and  120   b  are electrically conductive wires. A portion of the transmission wire  120   a  and a portion of the transmission wire  120   b  are inside the hollow helix radiating element  110   a  and electrically insulated from each other. In one embodiment, the transmission wires  120   a  and  120   b  are shielded (covered) by a dielectric material such that the transmission wires  120   a  and  120   b  are electrically insulated from each other and electrically insulated from the hollow helix radiating element  110   a.    
   In one embodiment, one end of the transmission wire  120   a  is electrically connected to the signal source  130 , whereas the other end of the transmission wire  120   a  is electrically connected to the right end  110   a R of the hollow helix radiating element  110   a . The connection point  140   a R represents electrical connection of the transmission wire  120   a  and the right end  110   a R. In one embodiment, the transmission wire  120   a  is electrically connected to the hollow helix radiating element  110   a  via an electric path that goes through the right end  110   a R such that there is no electric path between the transmission wire  120   a  and the hollow helix radiating element  110   a  that does not go through the right end  110   a R. It should be noted that the transmission wire  120   a  is not electrically connected to the hollow helix radiating element  110   b.    
   In one embodiment, one end of the transmission wire  120   b  is electrically connected to the signal source  130 , whereas the other end of the transmission wire  120   b  is electrically connected to the left end  110   b L of the hollow helix radiating element  110   b . The connection point  140   b L represents electrical connection of the transmission wire  120   b  and the left end  110   b L. In one embodiment, the transmission wire  120   b  is electrically connected to the hollow helix radiating element  110   b  via an electric path that goes through the left end  110   b L such that there is no electric path between the transmission wire  120   b  and the hollow helix radiating element  110   b  that does not go through the left end  110   b L. It should be noted that the transmission wire  120   b  is not electrically connected to the hollow helix radiating element  110   a . The dipole antenna  100  receives signal from the signal source  130  via the transmission wires  120   a  and  120   b  and radiates the received signal to the surrounding space using the hollow helix radiating elements  110   a  and  110   b.    
   In one embodiment, two IBM TwinAx™ cable segments can be used to create the hollow helix radiating elements  110   a  and  110   b  and the transmission wires  120   a  and  120   b . More specifically, the first IBM TwinAx™ cable segment is used as the hollow helix radiating element  110   a  and the transmission wires  120   a  and  120   b . The second IBM TwinAx™ cable is used as the hollow helix radiating element  110   b , wherein the two transmission wires of the second IBM TwinAx™ cable segment are not used (i.e., not electrically connected to anything). 
   It should be noted that the hollow helix radiating elements  110   a  and  110   b  are in shape of helix. Therefore, the axial lengths La and Lb of the hollow helix radiating elements  110   a  and  110   b , respectively, are much shorter than their physical lengths Lta and Ltb. In the example above in which the physical lengths Lta and Ltb are equal to 1.55 m, the axial lengths La and Lb can be a few centimeters. 
   In one embodiment, the electromagnetic fields generated by transmitted signals on the portions of the transmission wires  120   a  and  120   b  inside the hollow helix radiating element  110   a  exists only in the space within the hollow helix radiating element  110   a . As a result, the electromagnetic fields generated by transmitted signals on the portions of the transmission wires  120   a  and  120   b  inside the hollow helix radiating element  110   a  does not affect the radio wave generated by the hollow helix radiating elements  110   a  and  110   b , as well as the radio wave transmitted to the hollow helix radiating elements  110   a  and  110   b  via the surrounding space (if any). 
   In one embodiment, the portions of the transmission wires  120   a  and  120   b  outside the hollow helix radiating element  110   a  are arranged in proximity such that the electromagnetic fields generated by transmitted signals on these portions essentially cancel each other out. 
   It should be noted that the current flowing into the hollow helix radiating element  110   a  is equal to the current flowing into the hollow helix radiating element  110   b.    
   It should be noted that, with reference to  FIG. 1 , the dipole antenna  100  is an end-fed antenna. More specifically, the signal generated by the signal source  130  is fed at one end (the left end  110   a L) of the dipole antenna  100 . It should be noted that the dipole antenna  100  has two ends: the left end  110   a L and the right end  110   b R. The dipole antenna  100  can be used for operation in HF (high frequency) bandwidth, VHF (very high frequency) bandwidth, and UHF (ultra-high frequency) bandwidth. 
   In summary, with the two transmission wires  120   a  and  120   b  running inside the hollow helix radiating element  110   a , the dipole antenna  100  is end-fed, balanced, and shortened (La and Lb are much shorter than Lta and Ltb). 
     FIG. 2  shows a side-view of a folded dipole antenna  200  and the signal source  130  electrically coupled to the folded dipole antenna  200 , in accordance with embodiments of the present invention. More specifically, with reference to  FIG. 2 , the folded dipole antenna  200  comprises the hollow helix radiating elements  110   a  and  110   b , transmission wires  220   a  and  220   b , and a connection wire  250 . In one embodiment, the helical axis  110   a ′ of the hollow helix radiating element  110   a  and the helical axis  110   b ′ of the hollow helix radiating element  110   b  are on the same straight line. In one embodiment, the hollow helix radiating elements  110   a  and  110   b  are electrically connected to each other via an electric path that goes through the right end  110   a R and the left end  110   b L such that there is no electric path between the hollow helix radiating elements  110   a  and  110   b  that does not go through right end  110   a R and the left end  110   b L. More specifically, the hollow helix radiating elements  110   a  and  110   b  are electrically connected to each other via only the connection wire  250  at connection points  240   a R and  240   b L, as shown in  FIG. 2 . 
   In one embodiment, the transmission wires  220   a  and  220   b  are electrically conductive wires. A portion of the transmission wire  220   a  is inside the hollow helix radiating element  110   a , whereas a portion of the transmission wire  220   b  is inside the hollow helix radiating element  110   b . In one embodiment, the transmission wires  220   a  and  220   b  are shielded (covered) by a dielectric material such that the transmission wires  220   a  and  220   b  are electrically insulated from the hollow helix radiating elements  110   a  and  110   b , respectively, and such that the transmission wires  220   a  and  220   b  are electrically insulated from each other. The advantage of  FIG. 2  is that the antenna picks up less electrical noise, and is effectively shielded from non-resonant interference. 
   In one embodiment, one end of the transmission wire  220   a  is electrically connected to the signal source  130 , whereas the other end of the transmission wire  220   a  is electrically connected to the left end  110   a L of the hollow helix radiating element  110   a  at the connection point  240   a L. The connection point  240   a L represents electrical connection of the transmission wire  220   a  and the left end  110   a L. In one embodiment, the transmission wire  220   a  is electrically connected to the hollow helix radiating element  110   a  via an electric path that goes through the left end  110   a L such that there is no electric path between the transmission wire  220   a  and the hollow helix radiating element  110   a  that does not go through the left end  110   a L. 
   Similarly, one end of the transmission wire  220   b  is electrically connected to the signal source  130 , whereas the other end of the transmission wire  220   b  is electrically connected to the right end  110   b R of the hollow helix radiating element  110   b  at the connection point  240   b R. The connection point  240   b R represents electrical connection of the transmission wire  220   b  and the right end  110   b R. In one embodiment, the transmission wire  220   b  is electrically connected to the hollow helix radiating element  110   b  via an electric path that goes through the right end  110   b R such that there is no electric path between the transmission wire  220   b  and the hollow helix radiating element  110   b  that does not go through the right end  110   b R. The folded dipole antenna  200  receives signal from the signal source  130  via the transmission wires  220   a  and  220   b  and radiates the received signal to the surrounding space using the hollow helix radiating elements  110   a  and  110   b.    
   In one embodiment, two IBM TwinAx™ cable segments are used to create the hollow helix radiating elements  110   a  and  110   b  and the transmission wires  120   a  and  120   b  of  FIG. 2 . More specifically, the first IBM TwinAx™ cable segment is used as the hollow helix radiating element  110   a  and the transmission wire  220   a . The other transmission wire of the first IBM TwinAx™ cable segment is not used (i.e., not electrically connected to anything). The second IBM TwinAx™ cable is used as the hollow helix radiating element  110   b  and the transmission wire  220   b . The other transmission wire of the second IBM TwinAx™ cable segment is not used (i.e., not electrically connected to anything). Alternatively, each of the hollow helix radiating elements  110   a  and  110   b  of  FIG. 2  can be formed using a regular coax cable with one center conductor or can be formed by winding a hollow tube with an inner conductor into a helix. 
   It should be noted that the hollow helix radiating elements  110   a  and  110   b  are in shape of helix. Therefore, the axial lengths La and Lb of the hollow helix radiating elements  110   a  and  110   b , respectively, are much shorter than their physical lengths Lta and Ltb. In the example above in which the physical lengths Lta and Ltb are equal to 1.55 m, the axial lengths La and Lb can be a few centimeters. 
   It should be noted that the electromagnetic fields generated by transmitted signals on the portions of the transmission wires  220   a  and  220   b  inside the hollow helix radiating elements  110   a  and  110   b  exists only in the space within the hollow helix radiating elements  110   a  and  110   b . As a result, the electromagnetic fields generated by transmitted signals on the portions of the transmission wires  220   a  and  220   b  inside the hollow helix radiating elements  110   a  and  110   b  does not affect the radio wave generated by the hollow helix radiating elements  110   a  and  110   b , as well as the radio wave transmitted to the hollow helix radiating elements  110   a  and  110   b  via the surrounding space (if any). 
   In one embodiment, the portions of the transmission wires  220   a  and  220   b  outside the hollow helix radiating elements  110   a  and  110   b , respectively, are arranged in proximity such that the electromagnetic fields generated by transmitted signals on these portions essentially cancel each other out. 
   It should be noted that the current flowing into the hollow helix radiating element  110   a  is equal to the current flowing into the hollow helix radiating element  110   b , Therefore, the dipole antenna  110  is a balanced antenna. 
   It should be noted that, with reference to  FIG. 2 , the folded dipole antenna  200  is a center-fed antenna. More specifically, the signal generated by the signal source  130  is fed at exact center of the folded dipole antenna  100 . The folded dipole antenna  200  can be used for operation in HF (high frequency) bandwidth, VHF (very high frequency) bandwidth, and UHF (ultra-high frequency) bandwidth. 
   In the embodiments described above, the hollow helix radiating elements  110   a  and  110   b  are electrically connected to each other by the connection wire  250 . In an alternative embodiment, the hollow helix radiating elements  110   a  and  110   b  are bonded together such that the connection points  240   a R and  240   b L are in direct physical contact with each other. In other words, the right end  110   b L of the hollow helix radiating element  110   a  and the left end  110   b L of the hollow helix radiating element  110   b  are in direct physical contact with each other. 
   In summary, with the two transmission wires  220   a  and  220   b  running inside the hollow helix radiating elements  110   a  and  110   b , respectively, the folded dipole antenna  200  is end-fed, balanced, and shortened (La and Lb are much shorter than Lta and Ltb). 
   In the embodiments described above, the dipole antenna  100  of  FIG. 1  and the folded dipole antenna  200  of  FIG. 2  receive signals from the signal source  130 . Alternatively, the dipole antenna  100  and the folded dipole antenna  200  are used to receive signals from the surrounding space. 
   While particular embodiments of the present invention have been described herein for purposes of illustration, many modifications and changes will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications and changes as fall within the true spirit and scope of this invention.