Patent Publication Number: US-9899733-B1

Title: Multiband blade antenna

Description:
BACKGROUND OF THE INVENTION 
     Antennas are commonly required in nautical and aeronautical applications for the purposes of communicating with an aircraft or boat. It is often advantageous to have multiband antennas in these applications so that a reduced number of antennas are required for communications on all required frequency bands. U.S. Pat. No. 5,621,420 shows an example of a duplex monopole antenna for use with aircrafts, vehicles and marine vessels. This antenna design however is not aerodynamic and therefore may not be well suited for vehicular, aeronautical, or nautical applications. U.S. Pat. No. 7,746,282 shows an example of a more compact multiband antenna for aircraft applications. 
     Blade antennas, in particular, are commonly used in nautical and aeronautical applications due to their compact and aerodynamic footprint relative to other types of antennas such as monopole, dipole or whip antennas. Blade antennas can also be designed and constructed for receiving and radiating at multiple bands or over a very wide band. Blade antennas further provide the advantage of being more mechanically robust in presence of vibrations experienced during operation on aircrafts compared to many other types of antennas. Blade antennas are typically constructed by providing metal traces on one or both sides of an insulated board, such as an FR-4 circuit board or a fiber glass circuit board. These traces are of dimensions to provide resonance in the particular targeted frequency bands of the antenna. U.S. Pat. No. 7,633,451 shows an example of a blade type multiband antenna for aircraft applications. 
     SUMMARY OF THE INVENTION 
     One embodiment of the invention relates to a compact multiband blade antenna with a slanted design. The compact multiband blade antenna provides all three bands required for general aviation, namely very-high frequency (VHF), ultra-high frequency (UHF) and upper UHF, in a single blade and having a single connection port. Therefore, for aviation applications, only a single antenna is required, rather than multiple antennas. The slanted design provides for greater aerodynamics when mounted, for example, on the outside of an aircraft. The compact multiband blade antenna has an open sleeve element that allows for minimal interaction between the three bands. 
     In another embodiment, a phasing element is provided on a compact multiband blade antenna to further reduce size of the antenna and reduce interactions between the multiple resonant bands of the antenna. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a schematic side view of the exterior housing of a multi-band blade antenna with an open sleeve according to one embodiment of the present invention. 
         FIG. 2  is a schematic front view of the exterior housing of the multi-band blade antenna with an open sleeve of  FIG. 1 . 
         FIG. 3  is a schematic top view of the interior of the multi-band blade antenna with an open sleeve showing a main board of the blade antenna of  FIG. 1 . 
         FIG. 4  is a schematic side view of the main board of the blade antenna of  FIG. 1 . 
         FIG. 5  is an illustration of an equivalent circuit representation of a blade antenna connector board of the blade antenna of  FIG. 1 . 
         FIG. 6  is a schematic side view of the main board of a blade antenna according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is related to a multi-band blade antenna with a compact footprint and targeted for aeronautical and nautical communications applications. In particular, the multi-band blade antenna has three resonant frequency bands with an open sleeve and slanted design. One embodiment includes a phase element to further reduce the size and form factor of the blade antenna. 
     Referring to  FIGS. 1 and 2 , the blade antenna  10  comprises an extended housing  20  extending from a base housing  30 . The extended housing  20  further comprises a sidewall  22  and a base portion  24  that mates with and attaches to the base housing  30 . The extended housing  20  can be slanted and the sidewall  22  can have a bowed profile. Extending from the base housing  30  is a blade antenna main board connector  42  for electrically connecting the blade antenna  10  to downstream or upstream electronics (not shown), such as radios transmitters, radio receivers, or any other electronics that require an antenna. 
     The blade antenna  10  can be mounted on the outer surface of a vehicle, boat, or aircraft and therefore the slanted design of the extended housing  20  can provide for advantageous aerodynamic performance, such as reducing drag resulting from the extension of the blade antenna  10  from an aircraft. The extended housing may be fabricated from sheets of fiber glass cloth reinforced with resin. 
     Referring now to  FIG. 3 , the interior of the blade antenna  10  is seen without the extended housing  20 . The base housing  30  can accommodate mechanical fasteners  36  to attach the blade antenna  10  to a vehicle, aircraft, or boat. A blade antenna main board  50  is attached to the base housing via mechanical fasteners  34 . The blade antenna main board  50  comprises the conductive elements for the reception and transmission of the desired frequency bands, as is discussed in greater detail below in conjunction with  FIGS. 4 and 5 . The blade antenna main board  50  is connected to a base connector board  40 . The base connector board  40  serves the purpose of matching and feeding signals between the blade antenna main board  50  and downstream or upstream electronics (not shown) via the main board connector  42 . 
     Referring now to  FIG. 4 , the antenna main board  50  comprises a circuit board  52  that is slanted in shape to fit within the slanted profile of the extended housing  20  with conductive elements disposed on both sides of the circuit board  52 . The circuit board  52  further has a cut-out region  56  to accommodate the blade antenna main board connector  42  that protrudes from the base connector board  40  in the fully assembled blade antenna  10 . In  FIG. 4 , the conductive elements on only one side of the circuit board  52  are shown, though it is to be noted that the same patterns shown in  FIG. 4  are replicated on the side not shown in the drawing. Furthermore, similar conductive patterns on one side of the circuit board  52  are electrically connected to the corresponding patterns on the other side of the circuit board  52 . The circuit board  52  may be a standard FR-4 type board or any other known type of insulative circuit board. 
     For the purposes of spatial description of elements on the antenna main board  50 , the term “top” shall describe the edge of the circuit board  52  most distal from the base connector board  40  of the fully assembled blade antenna  10 . The term “bottom” shall describe the edge of the circuit board most proximal to the base connector board  40  of the fully assembled blade antenna  10 . The term “forward” shall refer to the direction toward the leading edge shown on the right of  FIG. 4 , and the term “rearward” shall refer to the direction toward the trailing edge shown on the left of  FIG. 4 . It will be understood that in typical applications, the leading edge will be disposed toward the direction of travel of the vehicle to which the antenna is mounted, and the trailing edge will be disposed behind the leading edge and away from the direction of travel. The term “center” refers to a region that is substantially between forward and rearward areas on the blade. 
     A center element  60  is disposed approximately at the center of the circuit board  52  and extends from the top to the bottom of the antenna main board  50 . The center element  60  comprises an upper portion  64 , a lower portion  66 , a transition area  68  between the upper and lower portions, a lower portion tapper  70 , a center element connector  74 , and a connector end  76 . There are open holes  78  disposed in the upper portion  64  that extend through to the other side of the circuit board  52 . The holes  78  are metallized such that the center element  60  on one side of the antenna main board  50  is connected to the center element (not shown) on the other side of the antenna main board  50 . The antenna main board  50  when assembled within the extended housing  20  may contain foam (not shown) to mechanically insulate the antenna main board  50  from the extended housing  20  to prevent damage to the antenna main board  50 . The holes  78  may also have foam passing therethrough to provide improved mechanical reliability of the blade antenna  10 . 
     The upper portion  64  resonates at the very-high frequency (VHF) band, or approximately between 136 and 174 MHz. The slanted design has minimal effects on the performance of the upper portion  64  at the VHF frequency. In other words, little or no modification has to be made to the geometry (length and width) for the upper element  64  regardless of whether the circuit board  52  is slanted or not slanted. In this antenna main board  50  design, the upper element  64  is approximately one quarter (¼) of the targeted wavelength of the VHF band. 
     The lower portion  66  resonates at the lower of the two ultra-high frequency (UHF) bands, or approximately between 380 and 520 MHz. The lower portion  66  is physically connected to the upper portion  64  via the upper portion to lower portion transition  68 . The lower portion  66  is further connected to the center element connector  74  via the lower portion trapper  70 . The center element connector  74  terminates at the connector end  76  at the bottom of the circuit board  52 . The connector end  76  is electrically connected to the blade antenna main board connector  42  and is configured to provide a path for signals for all of the elements on the antenna main board  50  for all three bands of the blade antenna  10 . 
     Still referring to  FIG. 4 , disposed on the circuit board  52  is a forward element  80  and a rearward element  100 . There is a slot  82  between the forward element  80  and the center element  60  and a slot  102  between the rearward element  100  and the center element  60 . The slots  82  and  102  are for blocking the UHF band, or approximately between 380 to 520 MHz. Each of the forward and rearward elements  80  and  100  comprise element extensions  86 ,  88 ,  92 ,  108 , and  110  and ¼ wavelength slots  90  and  112  between the extensions  86 ,  88 ,  92 ,  108 , and  110 . By appropriately sizing and placing the element extensions  86 ,  88 ,  92 ,  108 , and  110  and ¼ wavelength slots  90  and  112 , the upper UHF band, or approximately between 760 and 870 MHz can be blocked for the blade antenna  10 . In the illustrated embodiment of  FIG. 4 , the slant of the antenna main board in the upper UHF band requires the ¼ wavelength slots  90  and  112  to be between the element extensions  86 ,  88 ,  92 ,  108 , and  110 . The forward and rearward elements  80  and  100  also comprise ¼ wave traps  84  and  104  near the top of the circuit board  52  for the purpose of electrically decoupling the upper UHF band from the other two bands. The forward and rearward elements  80  and  100  may also contain holes  78  therethrough, which can provide for an electrical conduit from one side of the circuit board  52  to the other, as well as provide a means to impart greater mechanical stability to the circuit board  52  when packaged within the extended housing  22  with foam for mechanical damping of vibrations. 
     A space  120  is provided for connecting the forward and rearward elements  80 ,  100  to the center element  60  via a discrete electrical part (not shown). The discrete electrical part can be a passive electrical part such as a resistor, inductor, or capacitor of any value, a stripline, or any combination thereof. The discrete part can sit within the space  120  of a fully assembled blade antenna  10 . Alternatively, the forward and rearward elements  80 ,  100  may be connected to the center element by a trace on the circuit board  52 , rather than any discrete electrical parts. 
     The antenna main board  50  further comprises an open sleeve  132  with open sleeve conductive traces  134  and  135  on either side of the center element connector  74  and each open sleeve trace having an open sleeve connector  136  and  138 . The open sleeve  132  is typically electrically grounded in a fully assembled blade antenna  10  via connectors  136  and  138 . When the blade antenna  10  is in use, the open sleeve  132  provides for a low impedance path for the upper UHF band signals via the center element connector  74 . 
     Referring now to  FIG. 5 , the equivalent circuit diagram  150  of the main board connector board  40  with the blade antenna main board  50  connected on the right hand side and the blade antenna main board connector  42  on the left hand side is discussed. The equivalent circuit representation  150  is comprised of resistors R 1  and R 2 , capacitors C 1 , C 2 , C 3 , C 4 , C 5 , C 6 , C 7 , C 8  and C 9 , and inductors L 1 , L 2 , L 3 , and L 4 . By selecting appropriate values of each of the components of the circuit  50 , the blade antenna main board can be electrically matched and coupled to the input impedance and output impedance of the blade antenna main board connector  42  along with upstream or downstream electronics. 
     Referring now to  FIG. 6 , another embodiment of the blade antenna board  250  is discussed. Unlike the blade antenna board  50 , blade antenna board  250  has a phasing element  266  and does not have an open sleeve element. As in circuit board  52 , circuit board  252  of blade antenna board  250  has a cut-out region  256  to accommodate the blade antenna main board connector  42  that protrudes from the base connector board  40  in the fully assembled blade antenna  10 . The conductive elements on only one side of the circuit board  252  is shown, however, it should be noted that the same patterns as the patterns shown are replicated on the side not shown in the drawings. Similar conductive patterns on one side of the circuit board  252  are electrically connected to the corresponding patterns on the other side of the circuit board  252 . 
     A conductive center element  260  disposed on circuit board  252  comprises an upper portion  264 , the phasing element  266 , a lower portion  272 , a connector  274 , and a connector end  276 . The upper portion  264  resonates at the VHF band, and the lower portion  272  resonates at the lower of the two UHF bands. The phasing element  266  comprises a conductive region  268  and a non-conductive region  270 . In other words, the phasing element  266  has metal forming the conductive region  268  disposed on the circuit board  252  surrounding non-metalized areas of the non-conductive region  270 . The phasing element  268  serves to provide a path for the current from the VHF band to center element  260 , rearward element  300 , and forward element  280 , while providing high impedance to currents in the upper UHF band, such that upper UHF currents do not reach the center element  260 , rearward element  300  and forward element  280  and thus do not radiate. The upper portion  264  is connected to the conductive region  268  of the phasing element  266  and the phasing element  266  is further connected to the lower portion  272  and the lower portion is connected to the connector  274 . The center element connector  274  terminates at the connector end  276  at the bottom of the circuit board  252 . The connector end  276  is electrically connected to the blade antenna main board connector  42  and is configured to provide a path for signals for all of the elements on the antenna main board  250  for all three bands of the blade antenna  10 . 
     The antenna board  250  further comprises a forward element  280  and a rearward element  300 , separated from the center element  260  by slots  282 , and  302 , respectively. The forward and rearward elements  280  and  300  comprise lower regions  286  and  308 , respectively, for receiving and radiating the VHF band. The forward and rearward elements  280  and  300 , along with the upper portion  264  of the center element  260  function as ¼ wave traps for the purpose of electrically decoupling the UHF band from the upper parts of the circuit board  252  above the phasing element  266 . 
     A space  320  is provided for connecting the forward and rearward elements  280 ,  300  to the center element  260  via a discrete electrical part (not shown). The discrete electrical part can be a passive electrical part such as a resistor, inductor, or capacitor of any value, a stripline connection, or any combination thereof. The discrete part(s) can sit within the space  320  of a fully assembled blade antenna  10 . Alternatively, the forward and rearward elements  280 ,  300  may be connected to the center element  260  by a trace on the circuit board  252 , rather than any discrete electrical parts. 
     As in the case of antenna main board  50 , for antenna main board  250 , the forward and rearward elements  280 ,  100  and center element  260  may contain holes  278  therethrough. The holes  278  can provide for an electrical conduit from one side of the circuit board  252  to the other, as well as a means to impart greater mechanical stability to the circuit board  252  when packaged within the extended housing  22  with foam for mechanical damping of vibrations. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.