Wearable device

A wearable device includes a nonconductive base, a metal loop, and a matching circuit. The nonconductive base substantially has a hollow structure. The metal loop is disposed on the nonconductive base, and has a feeding point and a grounding point. The metal loop has at least one notch. The grounding point of the metal loop is coupled through the matching circuit to a ground voltage. An antenna structure of the wearable device is formed by the metal loop and the matching circuit.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims priority of Taiwan Patent Application No. 104110186 filed on Mar. 30, 2015, the entirety of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The disclosure generally relates to a wearable device, and more specifically, to a wearable device including an antenna structure.

Description of the Related Art

With the progress of mobile communication technology, mobile devices such as portable computers, mobile phones, tablet computers, multimedia players, and other hybrid functional mobile devices have become common. To satisfy the demand of users, mobile devices can usually perform wireless communication functions. Some functions cover a large wireless communication area; for example, mobile phones using 2G, 3G, and LTE (Long Term Evolution) systems and using frequency bands of 700 MHz, 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, 2100 MHz, 2300 MHz, and 2500 MHz. Some functions cover a small wireless communication area; for example, mobile phones using Wi-Fi and Bluetooth systems and using frequency bands of 2.4 GHz, 5.2 GHz, and 5.8 GHz.

According to some research reports, researchers predict that the next generation of mobile devices will be “wearable devices”. For example, wireless communication may be applied to watches, glasses, and even clothes in the future. However, watches, for example, do not have a large enough space to accommodate antennas for wireless communication. Accordingly, this has become a critical challenge for antenna designers.

BRIEF SUMMARY OF THE INVENTION

In a preferred embodiment, the disclosure is directed to a wearable device including a nonconductive base, a metal loop, and a matching circuit. The nonconductive base substantially has a hollow structure. The metal loop is disposed on the nonconductive base, and has a feeding point and a grounding point. The metal loop has at least one notch. The grounding point of the metal loop is coupled through the matching circuit to a ground voltage. An antenna structure of the wearable device is formed by the metal loop and the matching circuit.

In some embodiments, the wearable device is implemented with a watch.

In some embodiments, the nonconductive base is substantially a box without a lid, and the metal loop is disposed at an open side of the box.

In some embodiments, the wearable device further includes a PCB (Printed Circuit Board). The PCB is disposed in the nonconductive base and includes a ground plane. The ground plane provides the ground voltage.

In some embodiments, the feeding point of the metal loop is close to the first notch.

In some embodiments, the metal loop further has a second notch, and the metal loop is divided into a first portion and a second portion by the first notch and the second notch.

In some embodiments, the grounding point of the metal loop is close to the second notch.

In some embodiments, the matching circuit includes an inductor, a capacitor, or a combination thereof.

In some embodiments, the wearable device further includes a transparent element. The transparent element is surrounded by the metal loop.

In some embodiments, the antenna structure is excited to generate an operation frequency band from about 2400 MHz to about 2484 MHz.

DETAILED DESCRIPTION OF THE INVENTION

In order to illustrate the purposes, features and advantages of the invention, the embodiments and figures of the invention are shown in detail below.

FIG. 1is a partial combined view of a wearable device100according to an embodiment of the invention. In a preferred embodiment, the wearable device100is a wrist-wearable device, such as a smart watch or a smart, sporty bracelet. As shown inFIG. 1, the wearable device100at least includes a nonconductive base110, a metal loop120, and a matching circuit140.

The nonconductive base110may be made of plastic materials. The nonconductive base110substantially has a hollow structure. The shape, pattern, and surface treatment of the nonconductive base110are not limited in the invention. The metal loop120may be made of copper, silver, aluminum, iron, or their alloys. The metal loop120is disposed on the nonconductive base110. The metal loop120has at least a first notch131, and therefore the metal loop120substantially has a C-shape. The metal loop120has a feeding point FP and a grounding point CP. The feeding point FP is close to the first notch131. For example, the space between the feeding point FP and the first notch131may be smaller than 5 mm. The matching circuit140is disposed in the nonconductive base110. The matching circuit140provides a reactance. In some embodiments, the matching circuit140includes one or more capacitors, one or more inductors, or a combination thereof. The capacitors may be chip capacitors, and the inductors may be chip inductors. The grounding point CP of the metal loop120is coupled through the matching circuit140to a ground voltage. In some embodiments, the wearable device100further includes a PCB (Printed Circuit Board)150. The PCB150is disposed in the nonconductive base110, and includes a ground plane. The ground plane provides the aforementioned ground voltage. Other electronic components may be disposed on the PCB150.

An antenna structure of the wearable device100is formed by the metal loop120and the matching circuit140. The feeding point FP of the metal loop120may be coupled to a signal source190, such as an RF (Radio Frequency) module for exciting the antenna structure. The positions of the feeding point FP and the grounding point CP are not limited in the invention. For example, the feeding point FP and the grounding point CP may be positioned at the same side of the metal loop120, or respectively at two opposite sides of the metal loop120, or respectively at two opposite corners of the metal loop120. In some embodiments, the feeding point FP of the metal loop120is coupled through a pogo pin or a metal spring (not shown) to the signal source190on the PCB150, and the grounding point CP of the metal loop120is coupled through another pogo pin or another metal spring (not shown) to the matching circuit140on the PCB150.

In some embodiments, the nonconductive base110is substantially a box without a lid (e.g., a hollow cube without a lid to form a square opening), and the metal loop120is disposed at an open side of the box. The nonconductive base110can accommodate a variety of device components, such as a battery, an hour hand, a minute hand, a second hand, an RF module, a signal processing module, a counter, a processor, a thermometer, and/or a barometer (not shown). In some embodiments, the metal loop120is substantially a square loop, and it may fit a square opening of the nonconductive base110. It should be understood that the wearable device100may further include other components, such as a time adjuster, a connection belt, a waterproof housing, and/or a buckle, although these components are not displayed inFIG. 1.

FIG. 2is a complete combined view of the wearable device100according to an embodiment of the invention. In the embodiment ofFIG. 2, the wearable device100is implemented with a watch. With such a design, the wearable device100further includes a transparent element260and a watchband270. For example, the transparent element260may be a watch surface glass or a transparent plastic board. The transparent element260may be disposed inside the metal loop120, and it may be surrounded by the metal loop120. Other watch components, such as an hour hand, a minute hand, and a second hand, may all be disposed under the transparent element260for the user to observe them. The watchband270may be connected to two opposite sides of the nonconductive base110, so that the user can wear the wearable device100on the wrist using the watchband270.

FIG. 3is a diagram of a matching circuit340according to an embodiment of the invention. The matching circuit340ofFIG. 3may be applied to the wearable device100ofFIG. 1andFIG. 2. In the embodiment ofFIG. 3, the matching circuit340includes an inductor L1. The inductance of the inductor L1may be from about 1 nH to about 10 nH. The inductor L1is configured to adjust the impedance matching of the wearable device100. When the grounding point CP of the metal loop120is coupled through the inductor L1to the ground voltage, the effective resonant length of the antenna structure is increased, and therefore the operation frequency band of the antenna structure is moved toward the lower frequency. In some embodiments, the inductor L1is replaced with a variable inductor. The inductance of the variable inductor is adjustable according to a control signal or a user input signal, and therefore the inductance can correspond to a variety of operation frequencies of the antenna structure.

FIG. 4is a diagram of a matching circuit440according to an embodiment of the invention. The matching circuit440ofFIG. 4may be applied to the wearable device100ofFIG. 1andFIG. 2. In the embodiment ofFIG. 4, the matching circuit440includes a capacitor C1. The capacitance of the capacitor C1may be from about 0.1 pF to about 10 pF. The capacitor C1is configured to adjust the impedance matching of the wearable device100. When the grounding point CP of the metal loop120is coupled through the capacitor C1to the ground voltage, the effective resonant length of the antenna structure is decreased, and therefore the operation frequency band of the antenna structure is moved toward the higher frequency. In some embodiments, the capacitor C1is replaced with a variable capacitor. The capacitance of the variable capacitor is adjustable according to a control signal or a user input signal, and therefore the capacitance can correspond to a variety of operation frequencies of the antenna structure.

It should be understood that the inner structures of the matching circuits330and340ofFIG. 3andFIG. 4are just exemplary, and the invention is not limited thereto. In alternative embodiments, the matching circuit140ofFIG. 1includes one or more capacitors and/or one or more inductors. For example, the matching circuit140may be formed by coupling a capacitor and an inductor in series, or by coupling a capacitor and an inductor in parallel. For example, the matching circuit140may include a short-circuited element or an open-circuited element. By appropriately designing the matching circuit140to adjust the effective resonant length, the designer can make the antenna structure of the wearable device100operate in a variety of frequency bands, without changing the size of the metal loop120. In some embodiments, the length of the metal loop120is reduced to ⅙ wavelength of the desired frequency band or shorter. Since the length of the metal loop120is not required to correspond to ½ or ¼ wavelength as with a conventional design, the wearable device of the invention significantly improves freedom of design for the designer.

FIG. 5is a partial combined view of a wearable device500according to an embodiment of the invention.FIG. 5is basically similar toFIG. 1andFIG. 2. In the embodiment ofFIG. 5, a metal loop520of the wearable device500has a first notch531and a second notch532, such that the metal loop520is divided into a first portion521and a second portion522by the first notch531and the second notch532. A feeding point FP of the metal loop520is close to the first notch531. For example, the space between the feeding point FP and the first notch531may be smaller than 5 mm. A grounding point CP of the metal loop520is close to the second notch532. For example, the space between the grounding point CP and the second notch532may be smaller than 5 mm. The first portion521of the metal loop520has a relatively short length, and substantially has a straight-line shape. The second portion522of the metal loop520has a relatively long length, and substantially has a C-shape. Other features of the wearable device500ofFIG. 5are similar to those of the wearable device100ofFIG. 1andFIG. 2. Therefore, the two embodiments can achieve similar levels of performance.

FIG. 6is a VSWR (Voltage Standing Wave Ratio) of the antenna structure of the wearable device100according to an embodiment of the invention. The horizontal axis represents the operation frequency (MHz), and the vertical axis represents the VSWR. According to the measurement result ofFIG. 6, when the metal loop120of the wearable device100is fed from the signal source190, the antenna structure is excited to generate at least one operation frequency band FB1. In some embodiments, the operation frequency band FB1of the antenna structure is substantially from 2400 MHz to 2484 MHz. As a result, the wearable device100of the invention can support at least the wireless communication of Wi-Fi and Bluetooth frequency bands. Since the metal loop120is implemented with a light, thin metal piece and is used in such a way that it contributes to the overall appearance of the wearable device100, the present invention has the advantages of minimizing the antenna size, keeping the antenna bandwidth, reducing the manufacturing cost, and improving the device's appearance, and it is suitable for application in a variety of small, smart, wearable devices.

Please refer toFIG. 1again and understand the antenna theory and design method of the invention. Due to the shape characteristics of the metal loop120, the antenna structure of the wearable device100has a first resonant path128and a second resonant path129. The first resonant path128is a shorter portion of the path from the feeding point FP to the grounding point CP of the metal loop120. The second resonant path129is a longer portion of the path from the grounding point CP to the first notch131of the metal loop120. A combination of the first resonant path128and the second resonant path129covers a complete metal loop120. As to the antenna theory, the operation band FB1ofFIG. 6is generally excited by the shorter first resonant path128, and then fine-tuned by the matching circuit140. Therefore, the designer can appropriately change the positions of the feeding point FP and the grounding point CP, so as to easily control the operation band FB1of the antenna structure.

In the case ofFIG. 5, as to the antenna theory, the operation band FB1of the antenna structure of the wearable device500is generally excited by the first portion521of the metal loop520(including a first resonant path528from the feeding point FP to the grounding point CP of the metal loop120), and then fine-tuned by the matching circuit140. This antenna theory is similar to that of the antenna structure of the wearable device100ofFIG. 1.

FIG. 7is a partial combined view of a wearable device700according to an embodiment of the invention.FIG. 7is similar toFIG. 1andFIG. 2. In the embodiment ofFIG. 7, a nonconductive base710of the wearable device700is substantially a hollow cylinder without a lid, and has a circular opening. In addition, a metal loop720of the wearable device700is substantially a circular loop, and it may fit the circular opening of the nonconductive base710. In alternative embodiments, adjustments are made such that the nonconductive base710is substantially a hollow elliptical cylinder without a lid, and the metal loop720is substantially an elliptical loop. The metal loop720may have only a first notch731, or it may have both a first notch731and a second notch732. Other features of the wearable device700ofFIG. 7are similar to those of the wearable device100ofFIG. 1andFIG. 2. Therefore, the two embodiments can achieve similar levels of performance.

FIG. 8is a partial combined view of a wearable device800according to an embodiment of the invention.FIG. 8is similar toFIG. 1andFIG. 2. In the embodiment ofFIG. 8, a nonconductive base810of the wearable device800is substantially a hollow trapezoidal cylinder without a lid, and it has a trapezoidal opening. In addition, a metal loop820of the wearable device800is substantially a trapezoidal loop, and it may fit the trapezoidal opening of the nonconductive base810. The metal loop820may have only a first notch831, or it may have both a first notch831and a second notch832. Other features of the wearable device800ofFIG. 8are similar to those of the wearable device100ofFIG. 1andFIG. 2. Therefore, the two embodiments can achieve similar levels of performance.

The invention proposes a novel wearable device, and its antenna structure is integrated with its decorative metal element. Furthermore, a matching circuit and a notch of metal element are incorporated so as to adjust the resonant length, and therefore the invention has both improved functionality and improved appearance.

Note that the element sizes, element shapes, and frequency ranges described above are not limitations of the invention. An antenna designer can adjust these settings or values according to different requirements. It should be understood that the wearable device and the antenna structure of the invention are not limited to the configurations ofFIGS. 1-8. The invention may merely include any one or more features of any one or more embodiments ofFIGS. 1-8. In other words, not all of the features shown in the figures should be implemented in the wearable device and the antenna structure of the invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the invention. It is intended that the standard and examples be considered as exemplary only, with a true scope of the disclosed embodiments being indicated by the following claims and their equivalents.