Patent Publication Number: US-6661381-B2

Title: Circuit-board antenna

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to an antenna and, in particular, to a circuit-board antenna. 
     2. Related Art 
     Due to continuous development in communications technology, communication products are very common in daily life. Therefore, the demand for higher mobile communication quality becomes stronger. To obtain high-quality mobile communications, the antenna design in addition to better communication systems is also very important. 
     The conventional dipole antenna design is usually a ½-wavelength (λ) structure (see FIG.  1 ). In FIG. 2, however, the open end  11  of the signal part  10  in the dipole antenna is designed to be (1+¼)λ and the open end  21  of the ground end  20  is designed to be ¼λ. The first radiation section  111  and the third radiation section  113  are radiating in the same direction, whereas the second radiation section  112  is radiating in the opposite direction, canceling with the radiation from the first and third radiation sections  111 ,  113 . This changes the electromagnetic (EM) field shape of the antenna and therefore cannot increase its gain. 
     In this situation, increasing the length of the antenna is unable to effectively increase the gain. Therefore, existing dipole antennas are all designed in a symmetric way and the gain cannot be increased. However, for modern wireless communications, it is of great importance to enhance the antenna gain. How to extend the current antenna designs into those with higher gains has become a significant research field. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an objective of the invention to provide a circuit-board antenna device, which has a higher radiation gain and adjusts to give better radiation orientation. 
     To achieve the above objective, the invention provides a circuit-board antenna, which can radiate and receive EM waves with a particular wavelength and is capable of increasing the radiation gain. The invention includes a circuit board, a signal part with an open end, and an open part with a ground. The circuit board has an upper surface and a lower surface. The signal part is formed on the upper surface of the circuit board. The open end is comprised of a plurality of radiation sections and a plurality of twisty sections. The path length of the open end is (n+¼) times the particular wavelength, where n is a non-negative integer. Each of the twisty section is positioned between two of the radiation sections. The plurality of radiation sections are comprised of some radiation sections with a length of ¼ times the particular wavelength while the rest with a length of ½ times the particular wavelength. The radiation sections are used to radiate and receive EM waves of the particular wavelength. The path length of each of the twisty sections is ½ times the particular wavelength so that the EM waves thus generated cancel with themselves. The open part is formed on the lower surface of the circuit board. The path length of the open part is ¼ times the particular wavelength. Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a schematic view of a conventional ½λ dipole antenna; 
     FIG. 2 is another schematic view of a conventional ½λ dipole antenna; 
     FIG. 3 is a schematic view of the disclosed circuit-board antenna device; 
     FIG. 4 is a schematic view of a (3+½)λ circuit-board antenna of the invention; 
     FIG. 5 shows a first embodiment of the invention; 
     FIG. 6 shows a second embodiment of the invention; and 
     FIGS. 7A and 7B show a third embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In order to increase the antenna gain, the invention makes a second radiation section  112  generate an opposite standing wave with a first radiation section  111  to self-cancel the radiation (see FIG.  2 ), so that the radiation end only has radiation in one direction, thus enhancing the antenna gain. A feature of the invention is to print the antenna on a normal circuit board (using conductive metal as its material). A radiation section with self-radiation cancellation can be manufactured in this way. 
     Please refer to FIG. 3 for an explicit example of making the invention. As the dipole antenna shown in FIG. 2, this antenna includes a signal part  30  and a ground  40 . The second radiation section in FIG. 2 is designed as a twisty section  312  in FIG.  3 . The first radiation section  311 , the third radiation section  313 , and the open end  41  of the ground  40  in this case are exactly the same of those in FIG.  2 . The shape shown in the drawing can be formed using the circuit board fabricating method, so that the radiation from the twisty section  312  can achieve self-cancellation. 
     Since the twisty section  312  in FIG. 3 is made into a twisty shape, the opposite standing wave generated by the second radiation section  112  relative to the first radiation section  111  and the third radiation section  113  in FIG. 2 cancels exactly. Therefore, the first radiation section  311 , the third radiation section  313 , and the open end  41  of the ground  40  in FIG. 3 produce radiation in the same direction. Therefore, the antenna forms an array of two elements. This method can increase the antenna gain and the signal transmission distance. 
     Extending the concept introduced in FIG. 3, the open end  31  of the signal part  30  can be elongated to further enhance the antenna radiation gain. In FIG. 4, the (1+½)λ-long antenna in FIG. 3 is extended into a (3+½)λ-long antenna including the signal part  50  and its open end  51 , and the ground  60  and its open end  61 . In the drawing, the increased 2λ-long antenna is also twisted into a fourth twisty section  514  and a sixth twisty section  516 . The other two sections, i.e. the fifth radiation section  515  and the seventh radiation section  517  form a radiation section radiating in the same direction as the first radiation section  511  and the third radiation section  513 . This can extend the radiation section, producing an array with more elements. Similarly, the embodiment in FIG. 4 is prepared using a circuit board. 
     From FIG. 4, we know that the design of twisty sections can increase the antenna gain without the problem of self-cancellation. Therefore, we can make an antenna with any desired gain. Moreover, such a twisted design can be used in an arrayed antenna. 
     For an explicit example of making antennas, please refer to FIG. 5 where various parts of an antenna are formed on a circuit board. FIG. 6 shows an effective circuit of FIG.  4 . The very same method can be employed to extend the signal part or the open end of the ground to increase the antenna gain. 
     FIG. 7A shows an embodiment of extending both ends of a dipole antenna. The open end  71  of the signal part  70  contains first, third, fifth and seventh radiation sections  711 ,  713 ,  715 ,  717 , and second, fourth and sixth radiation sections  712 ,  714 ,  716 . The open end  81  of the ground  80  contains first, third, fifth and seventh radiation sections  811 ,  813 ,  815 ,  817 , and second, fourth and sixth radiation sections  812 ,  814 ,  816 . The effective circuit made of a circuit board is shown in FIG.  7 B. 
     In practice, one can adjust the number of downward (open end of the ground) or upward (open end of the signal part) extensions to adjust the orientation of the antenna field shape. When the number of upward extending radiation sections is greater than that of the downward extensions (n&gt;m), the radiation direction of the antenna is changed downwards. On the other hand, when the number of upward extending radiation sections is smaller than that of the downward extensions (n&lt;m), the radiation direction of the antenna is changed upwards. 
     Effects of the Invention 
     The disclosed circuit-board antenna device can achieve the goal of increasing the radiation gain and efficiency. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.