Abstract:
A method and system is disclosed for a microstrip antenna module having an antenna structure with one or more radiating elements and an integral feed structure enclosing at least one transmission line, wherein the antenna structure and the feed structure share a ground plane.

Description:
The present application claims the benefits of U.S. Patent Provisional Application No. 60/707,469, entitled “Microstrip Antenna With Integral Feed and Antenna Structures”, which was filed on Aug. 10, 2005. 
    
    
     BACKGROUND 
     The invention is related to a design of microstrip antenna and particularly related to a microstrip antenna having an integral feed structure and multiple radiating elements. 
     In the field of wireless communication technology, an antenna is a component to receive and transmit electromagnetic wave. A good antenna can increase the efficiency, sensitivity and reliability of a wireless communication system. Hence, a good design of an antenna having high performance is an important part of the wireless communication system. 
     With the advancement of integrated circuit technology, the wireless products such as the mobile terminals become smaller in size. As they get small-sized and high-graded, newer antennas are desired. Microstrip antennas have been presented as one special research and product development area in the telecommunication field. 
     The concept of microstrip antennas was proposed in early 1950s, and became commercially viable in 1970s. A microstrip antenna is light, small and easy to be manufactured. Microstrip antennas can be easily attached to an object moving at a high speed. Because of these characteristics, microstrip antennas are widely applied on the fields of satellite communication, global positioning system, and low-power personal communication. 
     Typically, the microstrip antenna has a better efficiency when a dielectric constant becomes lower, and a substrate becomes thicker. Also, since the microstrip antenna has a high efficiency when using a high frequency, it can be considered as the very good choice for satisfying the miniaturization requirement for portable communication tool such as cell phones. 
     A microstrip antenna has several advantages. The first advantage is that the radiation of electromagnetic wave emits from a single side of the antenna so as to reduce the impact of electromagnetic wave on human body. Another advantage is that a microstrip antenna has a simple structure which is easy to construct. Another advantage is that the microstrip antenna can be designed on a circuit board together with solid-state modules such as an oscillator, amplifying circuit, variable attenuator, switch, modulator, mixer, or phase shifter. The microstrip antenna can also be manufactured at a low cost with a small size and a light weight, and thus it is suitable to mass production. 
     SUMMARY 
     The present invention provides a microstrip antenna that includes a non-conductive substrate, a conductive ground plane attaching to a first surface of the substrate, an integral feed structure mounted on the conductive ground plane enclosing at least one transmission line and isolating it from the ground plane, and a plurality of radiating elements mounted on a second surface of the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a cross-section diagram of a microstrip antenna according to one embodiment of the present invention. 
     
    
    
     DESCRIPTION 
     The present invention provides a microstrip antenna with an integral feed structure and multiple radiating elements. The integral feed structure is constructed on a conductive ground plane and is separated from the radiating elements. 
     Referring to  FIG. 1 , a microstrip antenna structure  200  is built on a substrate  100  composed of a dielectric material. For example, the substrate  100  can be a foam circuit board. It can also be a Teflon impregnated fiberglass weave microwave substrate material. A conductive ground plane  110  is placed on a first surface of the substrate  100  and an integral feed structure  116  is mounted on the substrate  100 . The integral feed structure  116  has three components that enclose a space  130  between the substrate and itself. The integral feed structure  116  includes a supporting substrate  118 , two sidewalls  120 , and a transmission line  140 . The supporting substrate  118  is non-conductive, as well as the two side walls  120 , which can be made of dielectric materials such as the Teflon impregnated substrate material. It is understood that the supporting substrate and the two sidewalls can be fabricated as a single piece, but it can be three separate pieces attached to each other. For example, when Teflon materials are used, as they are not designed to be materials that are easily adhere to each other, some adhesion mechanism such as adhesive tapes are used to bound them. Furthermore, the transmission line  140  of the integral feed structure is mounted on the down surface or the interior surface of the supporting substrate  118 , but not in contact with the substrate  100  or the ground plane  110 . The air filled space  130  also serves as an isolating mechanism of the microstrip antenna  200  that separates the supporting substrate and the transmission line  140  from the conductive ground plane  110 . It is understood that the space  130  can be filled with a predetermined dielectric material that is RF friendly so that it also provides the isolation function. For example some RF friendly foam may be used to fill this space. 
     One or more radiating elements  150  are mounted on the other surface of the substrate  100  and share the conductive ground plane  110  with the integral feed structure  116 . The non-conductive substrate  100  separates the radiating elements  150  from the integral feed structure  116 . There is an ohmic connection  160  such as a small via or connecting line that is placed between the radiating elements  150  and the transmission line  140  to connect them. The connection  160  can be placed through an aperture in the ground plane and the substrate. The location of the aperture or the connection  160  is specifically determined to avoid any significant interference to the function of the ground plane. It is understood that since the microwave current only occupies a very thin layer of the ground plane  110 , the ground plane  110  can provide two such thin layers on two sides of it, one for the transmission line  140  and the other for the radiating element  150 . The substrate  100  and the radiating elements  150  can be collectively referred to as an antenna structure. The integral feed structure  116  is placed in a predetermined location with respect to the conductive ground plane  110  and the radiating elements  150 . The microwave signal is passed between radiating elements of the antenna structure and the transmission line of the feed structure. In one example, the radiating element is about 1.25 inches wide, the conductive ground plane  110  is about 0.4 inch wide, and the transmission line is about 0.18 inch wide. 
     The preferred embodiment of the present invention is a novel composition of a microstrip antenna, as stand alone or part of a linear antenna array, where each antenna structure is comprised of multiple radiating elements and a supporting substrate with a shared conductive ground plane. 
     The above illustration provides embodiments for implementing different features of the invention. Specific embodiments of components and processes are described to help clarify the invention. These are, of course, merely embodiments and are not intended to limit the invention from that described in the claims. 
     Although the invention is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention, as set forth in the following claims.