Patent Publication Number: US-9905908-B2

Title: Antenna structure with proximity sensor

Description:
FIELD OF THE INVENTION 
     The present invention relates to an antenna structure for use with portable computers or hand-held electronic devices, and more particularly to an antenna structure that has a coupled-fed antenna and a proximity sensor integrated on one circuit substrate. 
     BACKGROUND OF THE INVENTION 
     Normally, to control the amount of radiation emitted from a hand-held electronic device and absorbed by human body, a proximity sensor (i.e. P-sensor) is additionally provided in the hand-held electronic device at a position of a primary antenna for wireless wide-area network (WWAN) for sensing the approach of a human body to the hand-held electronic device and accordingly actuating a power-reduction protection mechanism to lower the amount of radiation emitted from the device. Further, to ensure accurate sensing of approach, usually two proximity sensors are used by most electronic device manufacturers in their device designs to achieve the purpose of radiation protection. 
     Please refer to  FIGS. 1 and 2 . Conventionally, a portable computer or a hand-held electronic device is provided with a primary antenna  10  and two proximity sensors  11 . The primary antenna  10  and the proximity sensors  11  are separate elements and must be spaced from one another by a predetermined distance. As shown in  FIG. 1 , the proximity sensor  11  generally has a substantial size about 10 mm and the primary antenna  10  about 61 mm, and a space of 5 mm between the primary antenna  11  and each proximity sensor  11  is required. Therefore, a total design length as long as 91 mm is required for the primary antenna  10  and the two proximity sensors  11 . However, to meet the progress in the wireless communication transmission technology, the current design size of the antenna needs to be miniaturized. 
     As a result, another type of antenna structure with proximity sensor has been developed. As shown in  FIGS. 3 and 4 , this type of antenna  20  includes a dielectric substrate  21  and a capacitive proximity sensor  22 . The dielectric substrate  21  is provided on two opposite sides with a first patterned conductive layer  23  and a second patterned conductively layer  24 , respectively. The first patterned conductive layer  23  and the second patterned conductive layer  24  are located correspondingly to present patterned traces of an inverted-F antenna, and two capacitors  25 ,  26  are connected to a signal line  27  and a ground line  28 , respectively. Further, the first patterned conductive layer  23  and the second patterned conductive layer  24  are respectively coupled via an inductor  29  to the capacitive proximity sensor  22 . 
     Since this type of antenna structure requires two patterned conductive layers, a plurality of capacitors, and a plurality of inductors to work with the proximity sensor to provide the approach sensing function, it still needs improvement in terms of antenna miniaturization. 
     SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide an improved antenna structure with proximity sensor by integrating a coupled-fed antenna and a proximity sensor on one circuit substrate, so that a part of the antenna is directly used as a capacitor electrode of the proximity sensor. Unlike the conventional antenna structure that has independent antenna and proximity sensors and requires more than one proximity sensor, the antenna structure of the present invention can have reduced volume to effectively save the room and the manufacturing cost needed by it. 
     Another object of the present invention is to provide an antenna structure with proximity sensor, in which a patterned conductive layer connected to the proximity sensor is not in direct contact with a ground signal line and a signal feed line, so that interference to the proximity sensor caused by other parts of the antenna is reduced, enabling the proximity sensor to have effectively increased sensitivity. 
     To achieve the above and other objects, the antenna structure with proximity sensor according to the present invention is electrically connected via a transmission line to at least one transceiver circuit to together form a wireless communication circuit in an electronic device. The transmission line includes a signal feed line and a ground signal line. 
     The antenna structure with proximity sensor according to the present invention includes a patterned conductive layer, a proximity sensor, a capacitor and a dielectric layer. 
     In a first preferred embodiment of the present invention, the patterned conductive layer includes a first conductive layer and a second conductive layer, which together form a coupled-fed antenna. The first conductive layer includes a first feed terminal for electrically connecting to the signal feed line, and the second conductive layer includes a second feed terminal for electrically connecting to the ground signal line. 
     The proximity sensor has a peripheral circuit electrically connected to the second conductive layer and a capacitance to digital circuit electrically connected to the peripheral circuit. The capacitor is located between the second feed terminal and the ground signal line. The dielectric layer has a first side and an opposite second side; and the patterned conductive layer, the proximity sensor and the capacitor all are located on the first side of the dielectric layer. 
     In the first preferred embodiment, the first conductive layer includes a first radiation section and a feeder section that forms the first feed terminal, and the second conductive layer includes a second radiation section that is parallel to the first radiation section and a branch section that forms the second feed terminal. The peripheral circuit of the proximity sensor is electrically connected to the branch section, and the dielectric layer can be a dielectric substrate independently provided in the electronic device or be directly formed of a protective case of the electronic device. 
     In a second preferred embodiment of the present invention, the patterned conductive layer includes a first conductive layer and a second conductive layer, which together form a coupled-fed antenna; and the first conductive layer includes a first feed terminal for electrically connecting to the signal feed line. 
     The proximity sensor has a peripheral circuit electrically connected to the second conductive layer and a capacitance to digital circuit electrically connected to the peripheral circuit. The capacitor is located between the peripheral circuit and the ground signal line. The dielectric layer has a first side and an opposite second side, and the patterned conductive layer, the proximity sensor and the capacitor all being located on the first side of the dielectric layer. 
     In the second embodiment, the first conductive layer includes a first radiation section and a feeder section that forms the first feed terminal, and the second conductive layer includes a second radiation section that is parallel to the first radiation section and a branch section that is electrically connected to the peripheral circuit. Similarly, the dielectric layer can be a dielectric substrate independently provided in the electronic device or be directly formed of a protective case of the electronic device. 
     While the two preferred embodiments are different in their structure, they operate in the same principle. When the antenna structure of the present invention operates at a first frequency, the capacitor has a high impedance value to form an open circuit, so that the second conductive layer is used as the capacitor electrode of the proximity sensor. On the other hand, when the antenna structure operates at a second frequency, the capacitor has a low impedance value to form a short circuit, so that the second conductive layer and the first conductive layer act together to form a radiation conductor of the coupled-fed antenna. Wherein, the first frequency is less than 1 MHz and the second frequency is higher than 700 MHz. 
     The present invention is characterized by integrating the coupled-fed antenna and the proximity sensor on the same one circuit substrate to overcome the problem in the conventional antenna structure as having independently provided antenna and proximity sensors to prevent the antenna structure from having a further reduced volume. Thus, the present invention effectively reduces the room and the manufacturing cost needed by the antenna structure. Moreover, through the design of the capacitor and the coupling patterned conductive layer, the patterned conductive layer connected to the proximity sensor is not in direct contact with the ground signal line and the signal feed line, so that interference to the proximity sensor caused by other parts of the antenna is reduced, enabling the proximity sensor to have effectively increased sensitivity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein 
         FIG. 1  schematically shows the installation of an antenna and two proximity sensors in an electronic device according to a first conventional way; 
         FIG. 2  is a circuit diagram of the antenna and proximity sensors arrangement shown in  FIG. 1 ; 
         FIG. 3  schematically shows the integration of an antenna structure and a proximity sensor in an electronic device according to a second conventional way; 
         FIG. 4  is a perspective view of the antenna structure shown in  FIG. 3 ; 
         FIG. 5  is a block diagram of a wireless communication circuit provided in an electronic device, in which an antenna structure according to the present invention is mounted; 
         FIG. 6  is a schematic view of an antenna structure according to a first preferred embodiment of the present invention; 
         FIG. 7  shows the antenna structure according to the first preferred embodiment of the present invention in a low-frequency state with a capacitor thereof acting like an open circuit; 
         FIG. 8  shows the antenna structure according to the first preferred embodiment of the present invention in a high-frequency state with the capacitor thereof acting like a short circuit; and 
         FIG. 9  is a schematic view of an antenna structure according to a second preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described with some preferred embodiments thereof and with reference to the accompanying drawings. For the purpose of easy to understand, elements that are the same in the preferred embodiments are denoted by the same reference numerals. 
     The present invention provides an antenna structure with proximity sensor, which is also briefly referred to as the antenna structure and generally denoted by reference numeral  30  herein. Please refer to  FIG. 5 . The antenna structure  30  according to the present invention is mounted in an electronic device  40  and is connected via a transmission line  50  to at least one transceiver circuit  60 . The antenna structure  30  and the transceiver circuit  60  work together and thereby form a wireless communication circuit  70  to serve as a transmission means. 
     The electronic device  40  can be a desktop computer, a portable computer, such as a notebook computer or a tablet computer, a game player, a music player, a remote control set, a global positioning system (GPS) device, or a hand-held or wearable device, such as a mobile phone, a watch, a pair of glasses, a headphone and other pendants that are small in size. 
     The transmission line  50  can be a coaxial cable, a microstrip transmission line, or a strip transmission line. Wherein, the transmission line  50  includes a signal feed line  51  and a ground signal line  52 , as can be seen in  FIG. 6 . 
     The transceiver circuit  60  of the wireless communication circuit  70  may include several communication bands for processing multiple radio frequencies, such as WiFi communication 2.4 GHz and 5 GHz bands and Bluetooth communication 2.4 GHz band, or for processing cellular phone communication bands, such as 850 MHz, 900 MHz, 1800 MHz and 1900 MHz GSM bands and 2100 MHz data band. In addition, the transceiver circuit  60  may also include radio circuit and paging circuit for radio signals and television signals. 
     Please refer to  FIG. 6  that is a schematic view of the antenna structure  30  according to a first preferred embodiment of the present invention. As shown, the antenna structure  30  in the first preferred embodiment includes a patterned conductive layer  31 , a proximity sensor  32 , a capacitor  33  and a dielectric layer  34 . The patterned conductive layer  31  includes a first conductive layer  311  and a second conductive layer  312 , which together form a coupled-fed antenna. The first conductive layer  311  includes a first radiation section  313  and a feeder section  314 , and the feeder section  314  forms a first feed terminal  315  for electrically connecting to the signal feed line  51 . The second conductive layer  312  includes a second radiation section  316 , which is parallel to the first radiation section  313 , and a branch section  317 , which forms a second feed terminal  318  for electrically connecting to the ground signal line  52 . 
     The proximity sensor  32  has a peripheral circuit  321  electrically connected to the second conductive layer  312 , and a capacitance to digital circuit  322  electrically connected to the peripheral circuit  321 . As shown in  FIG. 6 , the peripheral circuit  321  of the proximity sensor  32  is directly electrically connected to the branch section  317  of the second conductive layer  312 . 
     The capacitor  33  is located between the second feed terminal  318  and the ground signal line  52 . The dielectric layer  34  has a first side  341  and an opposite second side  342 . The patterned conductive layer  31 , the proximity sensor  32  and the capacitor  33  all are located on the first side  341  of the dielectric layer  34 . In the illustrated first preferred embodiment, the dielectric layer  34  is shown as a dielectric substrate independently provided in the electronic device  40 . 
     Please refer to  FIG. 7 . When the antenna structure  30  of the present invention operates at a first frequency less than 1 MHz, which is a relatively low frequency, the capacitor  33  has a high impedance value equivalent to an open circuit, bringing the proximity sensor  32  to directly use the second conductive layer  312  as a capacitor electrode, as indicated by the area framed by the broken line. At this point, there is no action between the first conductive layer  311  and the second conductive layer  312 . 
     Please refer to  FIG. 8 . When the antenna structure  30  of the present invention operates at a second frequency higher than 700 MHz, which is a relatively high frequency, the capacitor  33  has a low impedance value equivalent to a short circuit, bringing the second conductive layer  312  and the first conductive layer  311  to act together and form a radiation conductor of a coupling antenna. 
     In the present invention, the coupled-fed patterned conductive layer  31  and the proximity sensor  32  are integrated on the same circuit substrate, allowing a part of the antenna structure  30  to be directly used as the capacitor electrode of the proximity sensor  32 . Therefore, changes in the measured capacitance value will reflect and determine whether an external object is located in the proximity of the antenna structure  30 . 
     When the proximity sensor  32  does not detect any external object that is in the proximity of the antenna structure  30 , the power of the transmission radio frequency (RF) signal adopted by the electronic device  40  will not be restricted. However, when the proximity sensor  32  detects there is an external object in the proximity of the antenna structure  30 , the transmission RF signal power will be lowered to reduce the near-field electromagnetic radiation intensity, so that the electronic device  40  being operated by a user at a close distance from the device can have an RF signal power in compliance with the restrictions specified by the current related codes. 
       FIG. 9  is a schematic view of an antenna structure  30  according to a second preferred embodiment of the present invention. The antenna structure  30  in the second embodiment similarly includes a patterned conductive layer  31 , a proximity sensor  32 , a capacitor  33  and a dielectric layer  34 . The patterned conductive layer  31  includes a first conductive layer  311  and a second conductive layer  312 , which together form a coupled-fed antenna. The first conductive layer  311  includes a first radiation section  313  and a feeder section  314 , and the feeder section  314  forms a first feed terminal  315  for electrically connecting to the signal feed line  51 . The second conductive layer  312  includes a second radiation section  316 , which is parallel to the first radiation section  313 , and a branch section  317 . 
     The proximity sensor  32  has a peripheral circuit  321  electrically connected to the second conductive layer  312 , and a capacitance to digital circuit  322  electrically connected to the peripheral circuit  321 . As shown in  FIG. 9 , the peripheral circuit  321  of the proximity sensor  32  is electrically connected to the branch section  317  of the second conductive layer  312  and the ground signal line  52  of the transmission line  50 . 
     The capacitor  33  is located between the peripheral circuit  321  and the ground signal line  52 . The dielectric layer  34  has a first side  341  and an opposite second side  342 . The patterned conductive layer  31 , the proximity sensor  32  and the capacitor  33  all are located on the first side  341  of the dielectric layer  34 . In the illustrated second preferred embodiment, the dielectric layer  34  serves as a part of a protective case of the electronic device  40 . 
     The second preferred embodiment is different from the first preferred embodiment in that, in the second embodiment, the ground signal line  52  is electrically connected to the capacitor  33  and the peripheral circuit  321 . However, the difference in the circuit design between the first and the second preferred embodiment would not have any adverse influence on the operation of the antenna structure  30 . In the second embodiment, when the antenna structure  30  operates at the first frequency less than 1 MHz, the capacitor  33  similarly has a high impedance value equivalent to an open circuit, bringing the proximity sensor  32  to directly use the second conductive layer  312  as a capacitor electrode. On the other hand, when the antenna structure  30  operates at the second frequency higher than 700 MHz, the capacitor  33  similarly has a low impedance value equivalent to a short circuit, bringing the second conductive layer  312  and the first conductive layer  311  to act together and form a radiation conductor of a coupling antenna. 
     The present invention has been described with some preferred embodiments thereof and it is understood that many changes and modifications in the described embodiments can be carried out without departing from the scope and the spirit of the invention that is intended to be limited only by the appended claims.