Patent Publication Number: US-10333226-B2

Title: Waveguide antenna with cavity

Description:
FIELD OF THE INVENTION 
     Embodiments of the present invention relate generally to antennas. More particularly, embodiments of the invention relate to open waveguide antennas with cavity. 
     BACKGROUND 
     Mobile devices, such as mobile phones, are becoming increasingly popular. Such devices are often provided with wireless communications capabilities. In wireless communications, waveguide antennas are well-known and have been used in various applications. 
     Fifth generation (5G) is the next new standard for mobile communications. For the modern mobile device designs, a thinner phone design is a main stream in the industry. Moreover, a 5G system will adopt antenna array configuration for a good signal to noise ratio. However, a narrow beam width cannot cover a wide range link in the environment and therefore the requirement of multi-polarization can be used for scattering problems. 
     For polarization antennas, the most popular design is the waveguide antenna design. An open wave guide antenna is not appropriate for the design in a thin substrate since the substrate will confine the electric field; furthermore the return loss is bad. A traditional open waveguide antenna needs a wide aperture for power radiation and good return loss. However, the thin board design is not suitable for such waveguide antennas. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements. 
         FIG. 1  shows a perspective view of a waveguide antenna according to one embodiment of the invention. 
         FIG. 2  shows a top view of a waveguide antenna according to one embodiment of the invention. 
         FIG. 3  shows a side view of a waveguide antenna according to one embodiment of the invention. 
         FIG. 4  shows another side view of a waveguide antenna according to one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments and aspects of the inventions will be described with reference to details discussed below, and the accompanying drawings will illustrate the various embodiments. The following description and drawings are illustrative of the invention and are not to be construed as limiting the invention. Numerous specific details are described to provide a thorough understanding of various embodiments of the present invention. However, in certain instances, well-known or conventional details are not described in order to provide a concise discussion of embodiments of the present inventions. 
     Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in conjunction with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification do not necessarily all refer to the same embodiment. 
     According to some embodiments, a waveguide antenna having a cavity for vertical polarization power radiation and a feed point location for good return loss is provided, which can be utilized in a thin package suitable for the 5G design of mobile devices. According one aspect, a waveguide antenna includes a top or first plane made of electrically conductive material (e.g., metal such as copper, silver, platinum), a bottom or second plane made of electrically conductive material, and a first feed member coupled to the top plane and the bottom plane through a first via (also referred to as a through hole). The first feed member can be electrically coupled to a transceiver of an electronic device (e.g., a mobile phone). The waveguide antenna further includes an array of electrical vias disposed surrounding the first via. The array of vias couple the top plane with the bottom plane to form a cavity between the top plane and the bottom plane, leaving an opening of the cavity along or towards the edges of the top plane and the bottom plane. When an electrical signal is provided to the first feed member, the first feed member excites a space within the cavity between the top plane and the bottom plane. Such a structure generates a vertical electrical field between the top plane and the bottom plane. 
     According to another aspect, the waveguide antenna can be embedded within a radio frequency (RF) frontend package or integrated circuit (IC) or chip. The RF frontend chip may include a wireless transceiver, an amplifier, and/or a down-converter or up-converter for converting an RF frequency to a baseband frequency, or vice versa. The RF frontend chip can be utilized by a variety of mobile devices, such as, for example, 5G mobile phones. 
       FIG. 1  shows a perspective view of a waveguide antenna according to one embodiment of the invention. Referring to  FIG. 1 , antenna  100  includes top plane  101 , bottom plane  102 , and a feed member  103  (e.g., a first feed member) coupled to top plane  101  and bottom plane  102  through first via  104 . In this embodiment, the surfaces of top plane  101  and bottom plane  102  are substantially parallel to each other. Similarly, the flat surface of feed member  103  is also substantially in parallel with the surfaces of top plane  101  and bottom plane  102 . In addition antenna  100  further includes an array of vias  105  disposed between top plane  101  and bottom plane  102 , coupling top plane  101  and bottom plane  102 . Vias  105  of the array are arranged in a predetermined pattern, in this example, in a relatively rectangular shape to form cavity  106  between top plane  101  and bottom plane  102 . 
     In electromagnetics and communications engineering, the term waveguide may refer to any linear structure that conveys electromagnetic waves between its endpoints. However, the original and most common meaning is a hollow metal pipe used to carry radio waves. This type of waveguide is used as a transmission line mostly at microwave frequencies, for such purposes as connecting microwave transmitters and receivers to their antennas, in equipment such as microwave ovens, radar sets, satellite communications, and microwave radio links. 
     Referring back to  FIG. 1 , in this example, the vias of the array  105  are arranged in sequence in a U shape to form an opening of cavity  106  along or towards the edges of top plane  101  and bottom plane  102 , while the array of vias  105  operates as part of a wall of cavity  106 , as also shown in  FIG. 2  as a top view of waveguide antenna  100 . Cavity  106  in this example serves as at least a portion of a waveguide for antenna  100 . Note that although arrays  105  are arranged in a relatively rectangular shape, they can also be arranged in other shapes, such as, a circular shape, an oval shape, a triangular shape, or a square shape, etc. 
     In one embodiment, antenna  100  further comprises feed member  107  (e.g., a second feed member) disposed between top plane  101  and bottom plane  102 . The flat surface of feed member  107  is substantially in parallel with the surfaces of top plane  101  and bottom plane  102 . Feed member  107  is coupled to first via  104 , which is in turn coupled to top plane  101 , bottom plane  102 , and feed member  103 . Top plane  101  and bottom plane  102  are coupled to a ground, forming a ground wall. An electrical field is generated vertically between top plane  101  and bottom plane  102  when top plane  101  and bottom plane  102  are excited. 
     In one embodiment, feed member  103  includes elongate section or portion  111  and circular section or portion  112 . Circular section  112  is coupled to a first end of elongate section  111 , while a second end of elongate section  111  can be coupled to transceiver  120 . In this embodiment, the center or origin of circular section  112  is coupled to first via  104 . Feed member  103  is positioned above the top surface of top plane  101 , i.e., the opposite side of bottom plane  102  with respect to top plane  101 . Feed member  103  is coupled to the top plane  101  and bottom plane  102  only through first via  104 , while the rest of feed member  103  is not in contact with top plane  101  or bottom plane  102 . 
     Similarly, feed member  107  includes elongate section or portion  113  and circular section  114 . Circular section  114  is coupled to a first end of elongate section  113 , while a second end of elongate section  113  is a free end without being coupled to anything. Similar to feed member  103 , feed member  107  is coupled to top plane  101  and bottom plane  102  only through first via  104 , while the rest of feed member  107  is not in contact with top plane  101  and bottom plane  102 . In this embodiment, the center or origin of circular section  114  is coupled to first via  104 . With the second feed member, antenna  100  would have a better return loss. The purpose of feed member  107  is to reduce return loss for the desired impedance of the antenna. When feed member  103  receives an electrical signal from transceiver  120 , it excites top plane  101  and bottom plane  102 , which operate as resonating elements or members, to generate a vertical electrical field between top plane  101  and bottom plane  102 . 
     In one embodiment, antenna  100  further includes elongate strip  125  made of electrically conductive material disposed between top plane  101  and bottom plane  102  along the edges of cavity  106 . The surface of elongate strip  125  is substantially in parallel with the surfaces of top plane  101  and bottom plane  102 . Elongate strip  125  is formed and arranged along the distribution pattern of the array of vias  105 , in this example, in a U-shape as shown in  FIG. 2 . Elongate strip  125  is electrically coupled to top plane  101  and bottom plane  102  through the array of vias  105 . That is, each of vias  105  of the array connects top plane  101  with bottom plane  102  through elongate strip  125 . Elongate strip  125  acts as a ground shielding for the antenna. 
     Referring now to  FIGS. 2 and 3 , which shows a top view and a side view of antenna  100 , cavity  106  is formed in a relatively rectangular shape in this embodiment. In one embodiment, width  201  of cavity  106  is approximately lambda (λ)/4.5 and length  202  of cavity  106  is approximately λ/2. The λ represents a wavelength associated with an operating frequency of antenna  100 . In one embodiment, diameter  301  of circular section  112  is approximately λ/5. The width of elongate section  113  is approximately λ/4 and diameter  302  of circular section  114  is approximately λ/4.5. The average distance between two vias of the array of vias  105  is approximately λ/4. 
     According to one embodiment, the free end of elongate section  113  is positioned at the center of cavity  106  (e.g., the center point of cavity&#39;s length  202 ). Distance  203  between the free end of elongate section  113  and the center of circular section  114  is approximately λ/4.5. From the top view, elongate section  111  and elongate section  113  are arranged in a substantially right angle, as the longitudinal axis of elongate section  111  is substantially perpendicular to the longitudinal axis of elongate section  113 . Distance  304  between the surfaces of circular section  112  and top plane  101  is approximately λ/10. Distance  305  between surfaces of elongate strip  125  and bottom plane  102  is approximately λ/10.  FIG. 4  shows another side view of antenna  100 . 
     Embodiments of the present invention are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of embodiments of the invention as described herein. 
     In the foregoing specification, embodiments of the invention have been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the invention as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.