Abstract:
A polarized antenna with reduced size includes a substrate, a ground electrode, a radiation electrode and a side-feeding electrode. The substrate is made of dielectric materials, and the ground electrode, the radiation electrode and the side-feeding electrode are made of electrically conductive materials. By forming a plurality of characteristics-setting elements within the radiation electrode, the polarized antenna can have the advantages of wider bandwidth and smaller size. By changing the design of characteristics-setting elements, the circular polarization characteristics of the antenna can be adjusted or a linear polarization antenna can be obtained. The present invention can be implemented to become a through-hole device or an SMD device.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a side-feeding polarized antenna, and more particularly, to an antenna design benefiting from a plurality of characteristic-setting elements formed within a radiation electrode of the antenna that make the antenna wider bandwidth and reduced size. 
         [0003]    2. Description of the Prior Art 
         [0004]    Compared with the other kinds of antennas, a microstrip antenna is smaller, lighter, thinner, and has a lower production cost. Therefore, it has been widely implemented in the military and space industry, and for satellite and commercial purposes.  FIG. 1  shows a diagram of a conventional through-hole microstrip patch antenna. As shown in  FIG. 1 , the microstrip antenna  100  has a substrate  110  used as a body, a ground electrode  120  formed on the bottom surface of the substrate  110 , and a radiation electrode  130  formed on the opposite side to the ground electrode  120 . The substrate  110  is made of dielectric materials, and the ground electrode  120  and the radiation electrode  130  are made of electrically conductive materials. A through hole is formed around the center area of the substrate  110 , and a metal stick  140  is set in the through hole to connect the radiation electrode  130  and an external signal processing device (not shown). This technique only applies to manufactured through-hole devices. The production cost is high. The resonant frequency cannot be pulled down easily. 
         [0005]      FIG. 2  shows a diagram of a conventional surface-mount-device (SMD) microstrip patch antenna. The microstrip antenna  200  has a substrate  210  as a body, a ground electrode  220  formed on the bottom surface of the substrate  210 , and a radiation electrode  230  formed on the opposite side to the ground electrode  220 . One side surface  290  of the microstrip antenna  200  has a feeding electrode  250  that is utilized to replace the metal stick  140  shown in  FIG. 1  to connect the external signal processing device and make the antenna become a surface mount device.  FIG. 3  shows a structure of a circular polarization microstrip antenna disclosed in U.S. Pat. No. 6,140,968. In this structure, in order to adjust the circular polarization characteristics of the microstrip antenna  200 , a second ground electrode  280  needs to be installed on the side surface  290  that the feeding electrode  250  is formed on, or an electrode needs to be disposed on every side surface of the substrate  220 . The manufacturing of the antenna  200  is complex and the production cost is high. Moreover, it is difficult to adjust the circular polarization characteristic of the antenna  200 , and its bandwidth is narrow; its size not easy to be reduced. 
       SUMMARY OF THE INVENTION 
       [0006]    One objective of the present invention is therefore to provide a polarized antenna that can have a low resonant frequency along with a small size. This goal is accomplished by a plurality of characteristic-setting elements formed within the radiation electrode. The polarized antenna can either be an SMD or a through-hole device, depending on the system requirement. By providing the characteristic-setting elements, the polarization characteristic of the antenna can be easily adjusted while having larger bandwidth. 
         [0007]    According to one exemplary embodiment of the present invention, a polarized antenna is disclosed. The polarized antenna comprises a substrate, wherein a ground electrode is disposed on a first surface of the substrate, and a radiation electrode and a feeding end of a side-feeding electrode are disposed on a second surface of the substrate. The substrate is made of dielectric materials, and the ground electrode, the radiation electrode and the side-feeding electrode are made of electrically conductive materials. Within the radiation electrode, a plurality of characteristic-setting elements, such as two symmetrical arc areas, is formed. The characteristic-setting elements can be areas in the radiation electrode that have no electrically conductive materials, or areas in the radiation electrode where the electrically conductive materials have been removed, or areas in the radiation electrode that are formed with non-conductive materials. By modifying the design of the characteristic-setting elements, the polarization characteristic (such as the circular polarization characteristics, elliptical polarization characteristics, or linear polarization characteristics) and the resonant frequency of the polarized antenna can be adjusted to comply with the requirements in implementation. 
         [0008]    Moreover, the feeding electrode of the polarized antenna is disposed outside the radiation electrode. The polarized antenna can therefore become an SMD device with the disposition of a side microstrip line, or become a through-hole device by making a through hole that passes through the substrate and setting an electrically conductive metal pin in the through hole to connect the radiation electrode and a signal processing device. 
         [0009]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  shows a diagram of a conventional through-hole microstrip patch antenna. 
           [0011]      FIG. 2  shows a diagram of a conventional side-feeding microstrip antenna. 
           [0012]      FIG. 3  shows a diagram of a conventional side-feeding circular polarization microstrip antenna. 
           [0013]      FIG. 4  shows a diagram of a microstrip antenna according to one exemplary embodiment of the present invention. 
           [0014]      FIG. 5  shows a diagram of signal marching routes of the microstrip antenna in  FIG. 4 . 
           [0015]      FIG. 6  shows a diagram of a microstrip antenna according to another exemplary embodiment of the present invention. 
           [0016]      FIG. 7  shows a diagram of a microstrip antenna according to another exemplary embodiment of the present invention. 
           [0017]      FIG. 8  shows a diagram of a microstrip antenna according to another exemplary embodiment of the present invention. 
           [0018]      FIG. 9  shows a diagram of a microstrip antenna according to another exemplary embodiment of the present invention. 
           [0019]      FIG. 10  shows a diagram of a through-hole-feeding microstrip antenna according to another exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”. 
         [0021]    Please refer to  FIG. 4 , which shows a diagram of a polarized antenna according to one exemplary embodiment of the present invention. The polarized antenna  300  comprises a substrate  310  made of dielectric materials; for example, ceramics materials, magnetic materials, high polymer materials such as Teflon, or compound materials comprising the ceramics materials, magnetic materials or high polymer materials. The substrate  310  has a first surface and a second surface corresponding to the first surface. An electrically-conductive ground electrode  320  is formed on the first surface of the substrate  310 , while an electrically-conductive radiation electrode  330  and an electrically-conductive side-feeding electrode  350  are formed on the second surface of the substrate  310 . Within the radiation electrode  330 , two symmetric arc characteristic-setting elements  340  are formed, wherein the characteristic-setting elements  340  can be gaps that have no electrically conductive materials in the radiation electrode  330  or bad electrically conductive areas in the radiation electrode  330 . Please note that although the arc characteristic-setting elements  340  shown in  FIG. 4  are in the shape of a half-ring, this is not a limitation of the present invention. 
         [0022]    The side-feeding electrode  350  extends from the second surface to the first surface via a side surface of the substrate  310 . An isolation area  370  having no electrically conductive layer is formed between the side-feeding electrode  350  and the ground electrode  320 . A concave isolation area  360  having no electrically conductive layer is formed between the side-feeding electrode  350  and the radiation electrode  330 . 
         [0023]    When a high-frequency signal couples from the side-feeding electrode  350  to the radiation electrode  330 , the marching routes of the signal are shown in  FIG. 5 . Compared to the conventional polarized antenna designs, the signal marching routes of the polarized antenna  300  increase due to the characteristic-setting elements (the two arc characteristic-setting elements  340  in this embodiment) within the radiation electrode  330 . Therefore the bandwidth at the resonance point of the polarized antenna  300  is widened, resulting in the increase of the receiving frequency range of the antenna  300 . 
         [0024]    Furthermore, by properly modifying the length of the arc characteristic-setting elements  340  (for example, modifying the diameter of the half-ring in this embodiment) and modifying the locations where the passages  410  and  420  between the characteristic-setting elements  340  are set, a 90° phase difference can be generated between the X-axis electric field and Y-axis electric field, which makes the polarized antenna  300  have a circular polarization characteristic. If the location of the characteristic-setting elements  340  are modified so that the passages  410  and  420  are in a straight line with the side-feeding electrode  350 , as shown in  FIG. 6 , the polarized antenna  300  becomes a linear polarized antenna. The relative direction of the passages  410 ,  420  and the side-feeding electrode  350  determines the direction of circular polarization: in the embodiment shown in  FIG. 4  and  FIG. 5 , the polarized antenna  300  is provided with the right hand circular polarization (RHCP) characteristic; however, when the characteristic-setting elements  340  are disposed as shown in  FIG. 7 , the polarized antenna  300  is provided with the left hand circular polarization (LHCP) characteristic. 
         [0025]    Please note that the arc characteristic-setting elements  340  are an embodiment rather than a limitation of the present invention. Other shapes that differ slightly from an arc can also achieve similar effects. For example, the characteristic-setting elements  340  can be a combination of an eyebrow shape, a semicircular shape, an ‘S’ shape or line segments, or a shape having some slight concave and convex features added to the above-mentioned shapes. These modifications all belong to the scope of the present invention. Moreover, ‘symmetry’ is not a necessary limitation of the present invention for achieving the above-mentioned functionalities. For example, the asymmetric patterns shown in  FIG. 8  can also have substantially the same effects. 
         [0026]    Please refer to  FIG. 4  again. The side-feeding electrode  350  is disposed on the second surface (i.e. the surface that the radiation electrode  330  is formed on) of the substrate  310 , and extends to the first surface (i.e. the surface that the ground electrode  320  is formed on) via the side surface of the substrate  310 . In this embodiment, a nonconductive isolation area  370  is formed between the ground electrode  320  and the side-feeding electrode  350 , and a nonconductive concave isolation area  360  is formed between the radiation electrode  330  and the side-feeding electrode  350 . In another embodiment, as shown in  FIG. 9 , the side-feeding electrode  350  connects directly to the radiation electrode  330 . These different structures can all enable the polarized antenna  300  to be used as a surface mount device. 
         [0027]      FIG. 10  shows another embodiment of the present invention. As shown in  FIG. 10 , at the location outside the radiation electrode  300  where the side-feeding electrode is originally disposed, a through hole passing through the substrate  310  is formed. A conductor  951  such as a metal stick is disposed inside the through hole, and is used as a feeding electrode to feed in signals. In this way, the polarized antenna  300  can still have the polarization characteristics disclosed in the above embodiments where the feeding electrode extends through the side surface of the substrate  310 , but the polarized antenna  300  is suitable for conventional through-hole fabrication techniques. Please note that the above-mentioned modifications and designs are applicable to this embodiment; for example, the feeding electrode  951  can connect directly to the radiation electrode  330 , or a nonconductive concave isolation area can be formed between the feeding electrode  951  and the radiation electrode  330 . In another embodiment, the shape of the radiation electrode  330  corresponding to the feeding electrode  951  can be a concave or a line. The feeding electrode  951  can be located close to a side of the substrate  310 , or on a corner of the substrate  310 . A person having ordinary skill in the art can appreciate how to apply the above modifications to this embodiment, and therefore detailed description is omitted here for brevity. The polarized antenna  300  shown in  FIG. 10  is suitable to be a through-hole device. Compared to the conventional microstrip antenna  100 , the through hole and the feeding electrode  951  of the polarized antenna  300  are not located in the center area of the radiation electrode  330 , thereby a low resonant frequency of the polarized antenna  300  and a reduced size can be achieved. 
         [0028]    Please note that the above embodiments and the disclosed figures are for illustrative purposes only. The present invention does not limit the sizes and shapes of the substrate  310 , the ground electrode  320 , the radiation electrode  330 , the characteristic-setting elements  340  and the feeding electrode  350  ( 951 ). For example, the substrate  310  can be rough and not flat, or have a multi-layer structure composed of a stack of radiation conductive layers and nonconductive layers. Furthermore, a nonconductive layer can be formed on the radiation electrode  330  to isolate air from oxidizing the radiation electrode  330  and to increase the dielectric coefficient and lower the resonant frequency. These designs that are derived from the spirit of the present invention all fall within the scope of the present invention. 
         [0029]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.