Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57.
Reduction in antenna efficiency for internal antennas coupled to ground planes can occur when single or dual resonance antennas are coupled to ground planes formed by the ground layer of, for example, a host printed circuit board (PCB) of a device integrating an antenna. For frequencies below 1000 MHz, the efficiency of the internal antenna may be reduced when the ground plane length is less than 100 mm. When a ground plane is too short for efficient antenna operation, a technique that is used to compensate for the loss in efficiency is to place a parasitic element at an end of the ground plane opposite the location of the antenna. This technique provides a narrow band effect, but requires fabrication and installation of a second component to the PCB.
Certain antenna systems described herein include an antenna configurable to operate in a range of 600 MHz to 1000 MHz having an efficiency greater than 70% in operation; and a ground plane having a length from an attachment location of the antenna to a farthest edge of the ground plane less than 100 mm, wherein the antenna is electrically connected to the ground plane. Additionally, in some configurations, the ground plane can include an LC circuit. A plurality of slots can be provided which are positioned on the ground plane. In some configurations, a capacitor is added to an inductor such that the LC circuit is at least one of a series LC circuit or a parallel LC circuit and further wherein the LC circuit is positioned across a slot of the plurality of slots. Additionally, at least one of a capacitor and a resistor can be provided on the ground plane. The LC circuit can include an L-shaped slot and an inductor. Two or more inductors can be provided wherein the two or more inductors are attached across an L-shaped slot at two or more locations along the length of the L-shaped slot. The L-shaped slot is also configurable in some configurations to disconnect a first portion of the ground plane from a second portion of the ground plane. The antenna can also be connected to a transmission line. The transmission line can have a length of from 2 mm to about 60 mm. The ground plane can have a first dimension of about 35 mm or less and a second dimension of about 80 mm or less. The antenna can have a low frequency resonance and a high frequency resonance. An LC circuit that is provided can further comprises a plurality of slots positioned on the ground plane and/or an L-shaped slot and an inductor.
Another aspect of the disclosure is directed to a ground plane for use with an antenna including a ground plane having an exterior length less than 120 mm; a first slot in the ground plane extending from a first location of the ground plane and a second slot adjacent a portion of the first slot extending from a second location of the ground plane. The ground plane can have a first dimension of from about 35 mm and a second dimension of less than about 80 mm. The ground plane can have a shape selected from square, rectangular, hexagonal, pentagonal, circular, and oval. The ground plane can also have an irregular shape, including for example a shape having more than 5 sides.
Still another aspect of the disclosure is directed to a ground plane for use with an antenna comprising: a ground plane having an exterior length less than 100 mm; and a first slot in the ground plane extending from a first location of the ground plane and a second slot extending from a second location perpendicular the first location of the ground plane. In some configurations, a first slot is linear and a second slot is I-shaped. The first slot can also electromagnetically couple with the second slot. The ground plane can have a first dimension of from about 35 mm and a second dimension of less than 80 mm.
Yet another aspect of the disclosure is directed to a ground plane for use with an antenna comprising: a ground plane having a length and a width, a first edge, a second edge, a third edge, and a fourth edge, wherein the length is less than 120 mm; and an LC circuit comprising a slot and an inductor. The ground plane can have a first dimension of from about 35 mm and a second dimension of less than about 80 mm.
Another aspect of the disclosure is directed to a method of optimizing a ground plane for use with an antenna comprising: selecting a shape of the ground plane; identifying an antenna position on the ground plane wherein the antenna position is near an edge of the ground plane; determining an electrical length of the ground plane from the antenna position to a location on the ground plane farthest from the antenna position; and positioning one or more slots on the ground plane between the antenna position and the location on the ground plane farthest from the antenna position. Additionally, the method can include positioning an LC circuit on the ground plane and, in some aspects, selecting a bandwidth for the LC circuit wherein the bandwidth is selected to optimize a low band frequency for the antenna without decreasing efficiency of a high band frequency.
The features of the various embodiments described herein are set forth with particularity in the appended claims. A better understanding of the features and advantages of such embodiments will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the various embodiments are utilized, and the accompanying drawings.
Described herein are antenna configurations, systems and methods having a ground plane which can be deployed in small spaces without negatively impacting performance of the antenna. Techniques are also described to reduce a decrease in antenna efficiency of an internal antenna coupled to a ground plane that typically occurs when the ground plane length is reduced. The related methods disclosed below have been developed and both bring benefits to the performance of the antenna being addressed.
The efficiency of an antenna placed next to a ground plane that is shortened in length is improved by adding a slot geometry to the ground plane which increases an electrical length of the ground plane. Adding a slot geometry allows for optimized antenna performance without an increase in the ground plane length or the addition of a parasitic element. The increase in efficiency of the antenna results in a more reliable communication link and higher data rates for the system.
Certain embodiments described herein described with respect to NB-IoT antennas. However, as will be appreciated by those skilled in the art, the disclosed modifications of electrical length can be applied to any antenna where a small installation environment is necessary or desirable. These include, but are not limited to, machine-to-machine (M2M), IoT, cellphones and wearable devices. The NB-IoT is a low power wide area networked radio technology that enables a wide range of cellular devices and services. Advantages of NB-IoT include low power consumption and better range than standards using an unlicensed band. As will be appreciated by those skilled in the art, disclosure of the ground plane and antennas with reference to planes and direction is provided for illustrating relative orientations illustrated and actual planes and directions can vary during implementation without departing from the scope of the disclosure. For purposes of illustration, the planes and axis are the u-axis (e.g., which is depicted from right to left across the page in the view of
Turning to
By using one or more non-bisecting slots, such as the two slots illustrated in
By controlling the slot lengths, the distance between the slots, and the length of overlap region between the slots, a resonance condition is formed such that the ground plane across a specific frequency bandwidth has a larger electrical length. The resonance of the LC section formed by the slots should then coincide with the frequency of the antenna to be optimized. As will be appreciated by those skilled in the art, the two slots can vary in length but should not be so long as to cut completely thru the ground plane (i.e., bisect the ground plane). Additionally, three or more slots can be used to extend the electrical length of the ground plane. As more slots are added the RF currents are forced to meander back and forth around the slot sections as current flows from the antenna to the opposite end of the ground plane. In some configurations, the slots can be angled with respect to the sides of the ground plane, so that they are positioned such that the slot is not perpendicular to one side of the ground plane or parallel to a side of the ground plane. Thus, slots can be, for example, angled slots, non-parallel slots, curved slots, and slots that are not linear, such as “L” shaped slots. The ground plane can be flexible.
The first u-axis slot 452 and the second u-axis slot 454 are separated by a portion of the ground plane between the slots 456. The first u-axis slot 452 does not extend all the way from the right side of the ground plane to the left side of the ground plane, and thus does not bisect the ground plane. Similarly, the second u-axis slot 454 does not extend all the way from the left side of the ground plane to the right side of the plane. The resulting illustrated ground plane has an area of 2800 mm2, but has a perimeter length greater than 230 mm. In some configurations, the perimeter length is greater than 300 mm. In still other configurations, the perimeter length is greater than 350 mm. An elongated transmission line 420 is provided that has a front section 422 and a rear section 424 the elongated transmission line 420 is electrically connected to the antenna. A gap 426 is positioned between the elongated transmission line 420 and first horizontal slot 452 in the ground plane 450. The width of the gap 426 is determined by the impedance of the transmission line 420 which can be etched into the ground plane. Where the transmission line is 50 ohms, the gap width would be, for example, 0.5 mm to 1.0 mm in width.
The combination of the first u-axis slot 452 and the second u-axis slot 454 represent an LC circuit which results in an increased electrical length of the ground plane, which in turn results in a higher efficiency of the antenna. Turning to
Turning to
As will be appreciated by those skilled in the art, the antenna is well matched at 855 MHz with a return loss 760 shown in
In use, single or multiple slot configurations can be used which are grouped close to an antenna. The use of the slot configurations disclosed makes integration of an antenna into a device easier. The use of desired slot geometry and placement of the inductor in the ground plane facilitates the use of antennas in a wider variety of applications. By slightly increasing the area assigned to the antenna, antenna efficiency is improved when the PCB would not otherwise be long enough for good efficiency performance.
Turning to
In use, a ground plane can be optimized for use with an antenna and an installation location by selecting a shape of the ground plane, and a flexibility of the ground plane; identifying an antenna position on the ground plane wherein the antenna position is near an edge of the ground plane; determining an electrical length of the ground plane from the antenna position to a location on the ground plane farthest from the antenna position; and positioning one or more slots on the ground plane between the antenna position and the location on the ground plane farthest from the antenna position. Additionally, an LC circuit can be positioned either in parallel or in series on the ground plane.
A Q value, i.e., quality factor, or bandwidth of the LC circuit provided with the antenna(s) and ground plane configurations is selected to increase the electrical length of the ground plane at the low frequency band by a specific fraction of a wavelength and to increase the electrical length of the ground plane by a different specific fraction of a wavelength at the high frequency band.
The methods and configurations disclosed allow an LC value to be chosen that optimizes a low band frequency performance without decreasing the efficiency of the antenna at high band frequencies. As will be appreciated by referring back to
The use of the ground plane configurations disclosed allows for optimization of both the low band frequency and the high band frequency of a dual band antenna by proper selection of LC characteristics, i.e., slot length, overlap region between slots, value selected for inductor. For dual frequency band antennas different electrical lengths would be used at the low band frequency and the high band frequency.
The ground plane layout can be provided as part of a kit which includes an antenna.
While certain embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.
Number | Date | Country | |
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62701809 | Jul 2018 | US |