Abstract:
A flexible printed antenna comprises a flexible substrate, a radiation conductor, a flexible feeder cable and a grounding member. The radiation conductor includes a primary conductor and at least one secondary conductor. The flexible substrate is interposed between the primary conductor and the secondary conductor. One end of the feeder cable connects with the primary conductor, and another end extends far away from the primary conductor and connects with the signal source. The present invention is characterized in adopting a flexible substrate made of a FPCB material and forming a radiation conductor and a flexible feeder cable on different surface of the flexible substrate. Thereby, the antenna module of the present invention has better flexibility and applies to various non-planar structures of various communication products. Further, the present invention can be fabricated into a multi-layer antenna structure to greatly reduce the thickness of the antenna.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a flexible printed antenna, particularly to a flexible multi-layer antenna structure. 
         [0003]    2. Description of the Related Art 
         [0004]    The wireless communication technology is developing rapidly, and the tendency of antenna design is to meet the miniaturization and multiband requirements of the communication devices. Thus, different types of antennae are integrated into a single antenna module to satisfy the strict design standard of antennae. 
         [0005]    Refer to  FIG. 1  a diagram schematically a conventional integrated antenna for a dual-network communication device. The integrated antenna comprises a grounding plane  13 , a first antenna  14 , a second antenna  15 , a first coaxial feeder cable  16  and a second coaxial feeder cable  17 . The rectangular grounding plane  13  has a first grounding point  132  and a second grounding point  133 . The first antenna  14  is arranged near the top edge  131  of the grounding plane  13  to implement the operation of a first wireless network. The second antenna  15  is also arranged near the top edge  131  of the grounding plane  13  to implement the operation of a second wireless network. The abovementioned antenna design can realize the dual-network function of a mobile phone system or a WLAN (Wireless Local Area Network) system. 
         [0006]    The first and second coaxial feeder cables  16  and  17  have to be embedded in the system to respectively implement the operations of the first and second antennae  14  and  15 . When signals are simultaneously transmitted in the feeder cables, they are likely to interfere with each other. Further, the feeder cables are very long, which increases the difficulties in embedding and wiring the feeder cables and prolongs the fabrication time of the antenna. 
       SUMMARY OF THE INVENTION 
       [0007]    One objective of the present invention is to provide a flexible printed antenna, wherein a flexible substrate of the antenna adopts a FPCB (Flexible Printed Circuit Board) material, and wherein a radiation conductor and a feeder cable are directly formed on the surface of the flexible substrate, whereby the antenna module has a better flexibility and applies to the curved structures of various communication products. 
         [0008]    Another objective of the present invention is to provide a flexible printed antenna, wherein a flexible printed circuit board, a printed radiation conductor and a printed flexible feeder cable are integrated into a thin antenna module, whereby is formed a multi-layer antenna structure, greatly reduced the thickness of the antenna, and increased the convenience of assembling the antenna module. 
         [0009]    A further objective of the present invention is to provide a flexible printed antenna, wherein the feeder cable is integrated with the antenna, whereby the feeder cable does not occupy additional space, and whereby the radiation area of the antenna is greatly increased, and whereby the performance and radiation efficiency of the antenna is greatly promoted. 
         [0010]    A further another objective of the present invention is to provide a flexible printed antenna, wherein the flexible feeder cable is directly printed on a flexible substrate without soldering and wiring, whereby the antenna module is easy to bend, and whereby the fabrication time and cost is effectively reduced. 
         [0011]    To achieve the abovementioned objectives, the present invention proposes a flexible printed antenna, which comprises a flexible substrate, a radiation conductor, a flexible feeder cable, and a grounding member. The radiation conductor includes a primary conductor and at least one secondary conductor. The flexible substrate adopts a FPCB material. The primary conductor and the secondary conductor are respectively formed on different surfaces of the flexible substrate, and the flexible substrate is interposed between the primary conductor and the secondary conductor. The flexible feeder cable is printed on the surface where the primary conductor is formed. One end of the flexible feeder cable is connected to the primary conductor, and another end of the flexible feeder cable is connected to a signal source. 
         [0012]    In a first embodiment of the present invention, the flexible substrate adopts a FPCB material and cooperates with the primary conductor, secondary conductor and flexible feeder cable to form a super-thin antenna module, wherein the flexible feeder cable is integrated with the antenna structure, whereby is greatly reduced the whole thickness of the antenna, and whereby are increased the radiation area, performance and radiation efficiency of the antenna, wherefore is expanded the application field of the antenna. As the elements of the antenna module are all made of flexible materials, the entire antenna module has superior flexibility. Thus, the present invention applies to the non-planar structures of various communication products. Besides, the flexible feeder cable is directly printed on the surface of the flexible substrate without the wiring and soldering processes that are required in the conventional technology. Therefore, the present invention can effectively reduce the time and cost of fabrication. 
         [0013]    A third embodiment and a fourth embodiment are basically similar to the first embodiment in that one end of the flexible feeder cable is connected to the primary conductor but different from the first embodiment in that a capacitor unit and an inductor unit extend from another end of the flexible feeder cable. The inductor unit and the capacitor unit may be connected in parallel or in series. The inductor unit is designed to have a serpentine form. The capacitor unit is formed of a first coupling unit and a second coupling unit, which are arranged opposite to each other. 
         [0014]    Below, the embodiments are described in detail to make easily understood the technical contents of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a diagram schematically a conventional integrated antenna for a dual-network communication device; 
           [0016]      FIG. 2  is a perspective assembly drawing of a flexible printed antenna according to a first embodiment of the present invention; 
           [0017]      FIG. 3  is a perspective exploded view schematically showing a flexible printed circuit according to a second embodiment of the present invention; 
           [0018]      FIG. 4  is a top view of the flexible printed antenna according to the second embodiment of the present invention; 
           [0019]      FIG. 5  is a sectional view of the flexible printed antenna along Line A-A in  FIG. 4 ; 
           [0020]      FIG. 6  is a perspective exploded view schematically showing a flexible printed circuit according to a third embodiment of the present invention; and 
           [0021]      FIG. 7  is a perspective exploded view schematically showing a flexible printed circuit according to a fourth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    Refer to  FIG. 2  a perspective assembly drawing of a flexible printed antenna according to a first embodiment of the present invention. The antenna module  2  of the present invention comprises a radiation conductor  21 , a flexible substrate  22 , a flexible feeder cable  23  and a grounding member  24 . The radiation conductor  21  includes a primary conductor  211  and a secondary conductor  212 . The grounding member  24  has a plurality of through-holes  241  reaching the secondary conductor  212  and used to conduct the electrical signals between the secondary conductor  212  and the grounding member  24 . 
         [0023]    The flexible substrate  22  adopts a FPCB material. The primary conductor  211  and the secondary conductor  212  are respectively printed on the upper surface  221  and the lower surface  222  (not shown in the drawing) with the flexible substrate  33  interposed between the primary conductor  211  and the secondary conductor  212  to form the main structure of the radiation conductor of the antenna. The flexible feeder cable  23  is printed on the upper surface  221  where the primary conductor  211  is printed. One end of the feeder cable  23  is connected to the primary conductor  211 , and another end of the feeder cable  23  extends far away from the primary conductor  211  to connect with the feed-in signal source of the antenna. The grounding member  24  is also formed on the upper surface  221  where the primary conductor  211  is printed. The grounding member  24  is arranged on the upper surface  221  where the primary conductor  211  is printed and near the feeder cable  23  and the feed-in signal source. The signal source feeds the positive signal of the antenna to the flexible feeder cable  23 , and the feed-in signal is then transmitted through the flexible feeder cable  23  to the primary conductor  211 . The negative signal is transmitted from the signal source through the grounding member  24  and the through-holes  241  to the secondary conductor  212 . The flexible cable  23  and the secondary conductor  212  jointly form the feeding-transmitting interface of the high-frequency signal of the antenna, whereby the antenna signal is transceived. 
         [0024]    The primary conductor  211  has a trapezoid-like shape with a top base of about 24 mm, a bottom base of about 0.5 mm, a height of about 11 mm and two legs each of about 16 mm. The secondary conductor  212  has a length of about 40 mm, a width of about 10 mm and a thickness of about 0.1 mm. The flexible substrate  22  may be roughly divided into two rectangles. The rectangle supporting the primary conductor  211  has a length of about 32 mm, a width of about 12 mm and a thickness of about 0.3 mm. The rectangle supporting the secondary conductor  212  has a length of about 40 mm, a width of about 10 mm and a thickness of about 0.3 mm. The flexible feeder cable  23  has a length of about 37 mm and a width of about 0.33 mm. The grounding member  24  has a length of about 10 mm and a width of about 0.1 mm. 
         [0025]    Refer to  FIG. 3  a perspective exploded view schematically showing a flexible printed circuit according to a second embodiment of the present invention. The second embodiment is basically similar to the first embodiment except two sides of the flexible feeder cable  23  have conduction holes  223  reaching the secondary conductor  212  in the second embodiment. In the second embodiment, a first flexible substrate  25  is arranged on the upper surface  221  of the flexible substrate  22 , and a first secondary conductor  26  is arranged on the upper surface of the first flexible substrate  25 . The first flexible substrate  25  also has conduction holes  223  reaching the first secondary conductor  26  and corresponding to the conduction holes  223  on two sides of the flexible feeder cable  23 . The first flexible substrate  25  and the first secondary conductor  26  contract from the signal source toward the primary conductor  211  lest the feeding of the positive signal of the antenna be retarded. The signal source feeds the positive signal of the antenna to the flexible feeder cable  23 , and the feed-in signal is then transmitted through the flexible feeder cable  23  to the primary conductor  211 . The negative signal is transmitted from the signal source through the grounding member  24  and the through-holes  241  to the secondary conductor  212 . The negative signal is further transmitted through the conduction holes  223  of the flexible substrate  22  to the first secondary conductor  26 . Thereby is transceived the antenna signal. 
         [0026]    Refer to  FIG. 4  and  FIG. 5  a top view and a sectional view of the flexible printed antenna according to the second embodiment of the present invention. In the second embodiment, the first flexible substrate  25  and the first secondary conductor  26  contract from the signal source toward the primary conductor  211  to prevent from retarding the transmission of the feed-in signal of the feeder cable. In the second embodiment, the radiation conductor  21 , flexible substrate  22 , flexible feeder cable  23 , first flexible substrate  25  and first secondary conductor  26  jointly form a thin laminated antenna structure, which has improvements over the conventional hard multi-layer PCB (Printed Circuit Board) antenna structure. 
         [0027]    Refer to  FIG. 6  a perspective exploded view schematically showing a flexible printed circuit according to a third embodiment of the present invention. In the third embodiment, the flexible printed antenna comprises a radiation conductor  61 , a first flexible substrate  62 , a flexible feeder cable  63 , a grounding member  64 , a second flexible substrate  65  and a third flexible  66 . 
         [0028]    The third embodiment is basically similar to the first embodiment in that one end of the flexible feeder cable  63  is connected to a primary conductor  611  but different from the first embodiment in that an inductor unit  631  and a capacitor unit  632  are arranged in another end of the flexible feeder cable  63 . The capacitor unit  632  is formed of a first coupling member  632   a  and a second coupling member  632   b . In the present invention, the inductor unit  631  and the capacitor unit  632  may be connected in parallel or in series. In the third embodiment, the inductor unit  631  and the capacitor unit  632  are connected in parallel. Further, the inductor unit  631  is fabricated to have a serpentine form, and the first coupling member  632   a  and the second coupling member  632   b  of the capacitor unit  632  are arranged oppositely. 
         [0029]    In assembling the antenna, a second secondary conductor  613  is arranged on a first surface  651  of the second flexible substrate  65 , which is the top surface of the second flexible substrate  65 . First sides of the primary conductor  611 , the inductor unit  631  and the first coupling member  632   a  of the flexible feeder cable  63  are stuck on to the lower surface (not shown in the drawing) of the second flexible substrate  65 . Second sides of the primary conductor  611  and the inductor unit  631  are stuck onto a second surface  661  of the third flexible substrate  66 , which is the top surface of the third flexible  66 . One terminal of the inductor unit  631  is connected to the flexible feeder cable  63 . The other terminal of the inductor unit  631  extends serpentinely far away from the flexible feeder cable  63  toward one lateral of the third flexible substrate  66  and then reaches a second conduction hole  622 , whereby the signal transmitted by the inductor unit  631  goes through the second conduction hole  622  to the first flexible substrate  62 , the second flexible substrate  65  and the third flexible substrate  66 . The serpentine inductor unit  631  has a better performance, and thus the inductive impedance of the antenna system is increased. The lower surface (not shown in the drawing) of the third flexible substrate  66  is arranged on a third surface  623 , which is the top surface of the first flexible substrate  62 . The third flexible substrate  66  contracts from the signal source toward the primary conductor  611  lest the third flexible substrate  66  cover the second coupling member  632   b , which is stuck onto the first flexible substrate  62 . Thus, the first coupling member  632   a  and the second coupling member  632   b  are located oppositely and have a gap therebetween to generate a capacitive coupling effect and enhance the performance of the capacitive coupling of the antenna. Thereby, the antenna has better capacitive impedance. Besides, the first secondary conductor  612  is arranged on the lower surface (not shown in the drawing) of the first flexible substrate  62 . 
         [0030]    In transmitting signals, the signal source feeds the positive signal of the antenna into the feeder cable  63 . Next, the feed-in signal is transmitted to the second coupling member  632   b , and then transmitted to the first coupling member  632   a  in a capacitive coupling way. Next, the signal is transmitted to the inductor unit  631  and then the primary conductor  611 . Via the second conduction holes  622 , the inductor unit  631  further transmits the signal to the first, second and third flexible substrates  62 ,  65  and  66 . The negative signal of the antenna is transmitted to the grounding member  64  and then to the first secondary conductor  612  via through-holes  641 . Further, the negative signal is transmitted to the second secondary conductor  613  via first conduction holes  621 . Thereby is transceived the antenna signal. 
         [0031]    Refer to  FIG. 7  a perspective exploded view schematically showing a flexible printed circuit according to a fourth embodiment of the present invention. The fourth embodiment is basically similar to the third embodiment except the inductor unit  631  is connected with the capacitor unit  632  in series. The signal transmission path in the fourth embodiment is similar to that in the third embodiment. In the fourth embodiment, the signal source feeds the positive signal of the antenna into the feeder cable  63 . Next, the feed-in signal is transmitted to the second coupling member  632   b , and then transmitted to the first coupling member  632   a  in a capacitive coupling way. Next, the signal is transmitted to the inductor unit  631  and then the primary conductor  611 . Via the second conduction holes  622 , the inductor unit  631  further transmits the signal to the first, second and third flexible substrates  62 ,  65  and  66 . The negative signal of the antenna is transmitted to the grounding member  64  and then to the first secondary conductor  612  via through-holes  641 . Further, the negative signal is transmitted to the second secondary conductor  613  via first conduction holes  621 . Thereby is transceived the antenna signal. 
         [0032]    The present invention possesses utility, novelty and non-obviousness and meets the condition for a patent. Thus, the Inventor files the application for a patent. The embodiments described above are only to exemplify the present invention but not to limit the scope of the present invention. Any equivalent modification or variation according to the spirit of the present invention is to be also included within the scope of the present invention.