Integrated antenna and electrostatic discharge protection

A mobile communications device having an antenna partly formed from an electrostatic discharge shield covering a microphone. The antenna includes a radiator arm extending from the electrostatic discharge shield and includes a feed element connecting the electrostatic discharge shield to a signal trace. To the extent the microphone employs an acoustic tube to form an acoustic pathway between the device casing and the microphone, the radiator arm of the antenna may be arranged over the acoustic tube.

FIELD

The present application generally relates to an antenna and, in particular, to an antenna integrated with an electrostatic discharge protection shield and devices that include an antenna integrated with an electrostatic discharge protection shield.

BACKGROUND

As consumer electronics devices become more compact and achieve greater functionality, it has become increasingly difficult to arrange the interior components to realize higher density. This is especially so with wireless communications devices, including handheld devices, personal digital assistants, mobile smartphones, etc., where the devices are increasingly compact, yet include a greater number of components and features than ever before. Many such devices now include keyboards, cameras, trackballs, display screens (ordinary or touchscreen), memory cards, speakers, microphones, I/O jacks, and multiple antennas, for cellular, IEEE 802.11, Bluetooth®, GPS, and other radio frequency communications. This has made the configuration of the components challenging and puts circuit board space at a premium.

It would be advantageous to provide for an electronic device having a new configuration of components that permits greater density.

DESCRIPTION OF EXAMPLE EMBODIMENTS

The present application describes an antenna partly formed from the electrostatic discharge shield covering a microphone in an electronic device. By exploiting the presence of the electrostatic discharge shield and using it as the shorting element in the antenna, space is saved. Moreover, to the extent the microphone employs an acoustic tube to form an acoustic pathway between the device casing and the microphone, the radiator arm of the antenna integrally formed with the electrostatic discharge shield may be arranged over the acoustic tube, which results in an efficient arrangement of elements.

In one aspect, the present application describes a handheld electronic device. The device includes a substrate having a ground plane and an antenna signal trace; a microphone mounted to the substrate; a metallic shield disposed over the microphone and being connected to the ground plane; and a radio frequency antenna formed in part from the metallic shield and having at least one radiator arm connected to the metallic shield. The antenna includes a feed point connected to the antenna signal trace.

In another aspect, the present application describes a mobile communications device. The device includes a device casing having an acoustic microphone opening; a substrate within the device casing, the substrate having an electrical ground and a signal trace; a microphone mounted to the substrate; an electrostatic discharge shield disposed over the microphone and connected to the electrical ground, the electrostatic discharge shield defining an acoustic port; and an antenna having a radiator arm and a feed element both connected to the electrostatic discharge shield, and wherein the feed element is further connected to the signal trace.

Many electronics devices include an antenna for radio frequency communications, including mobile devices, laptop computers, desktop computers, smartphones, personal digital assistants, and many other such devices. Many of these devices also include a microphone that functions to receive audio input and convert the audio to electrical signals that are processed by the device. In many cases, the microphone serves to permit voice communications, such as in a mobile telephone and other devices configured for wireless communications.

Microphones are transducers that require exposure to the environment in order to receive acoustic signals. The environment can also have a detrimental impact on microphones, as they become exposed to environmental hazards such as human liquids or oils. Accordingly, in some cases microphones are encased in a sealed rubber covering, except for an opening (i.e. a port or hole) through which acoustic waves are to be received. A gasket or “rubber boots” may be used to seal the port or hole to the exterior casing of the electronic device.

Microphones and their associated coder/decoder (CODEC) integrated circuits (ICs) are also vulnerable to electrostatic discharge (ESD). Techniques that have been developed for protecting microphones from electrostatic discharge include covering the microphone (except the acoustic opening/port) with a grounded casing or shield. Alternatively or additionally, transient voltage suppressor (TVS) diodes may be added to the microphone circuit to absorb ESD events. Adding TVS diodes can be costly and may negatively impact the performance of the audio circuits.

Reference is now made toFIG. 1, which shows a side view of one embodiment of an antenna10integrated with ESD protection. The antenna10is formed partly with an ESD shield (generally14) over a microphone12. The microphone12is illustrated in phantom lines. The microphone12is mounted or connected to a printed circuit board16or other substrate. In this application, the term “substrate” is intended to encompass printed circuit boards and any other such substrate on which electrical components may be assembled and interconnected to form an electronic device. The printed circuit board16includes a ground connection or plane (not illustrated). The microphone12is connected to suitable audio circuitry and a CODEC IC for receiving and processing signals from the microphone12. In one embodiment, the microphone12is an Electret Condenser Microphone (ECM), however in other embodiments other types of microphones may be used.

A top plan view of the antenna10is shown inFIG. 2.FIG. 3shows a front view of the antenna10, andFIG. 4shows a perspective view.

The microphone12is protected from ESD events by the ESD shield14. The ESD shield14is a metal covering or casing connected to a ground plane or trace on the circuit board16. InFIGS. 1-4the microphone12is shown as a cylindrical element for ease of illustration. Those skilled in the art will appreciate that the microphone12is not necessarily cylindrical and is not necessarily arranged on the circuit board16in the manner illustrated inFIGS. 1-4.

The ESD shield14generally covers the microphone12, and, in the illustrated embodiment, has a top section20, and side sections22,24. At the front of the ESD shield14, the side sections22,24are separated to define an acoustic opening or port26through which the microphone12may receive acoustic waves. The interior of the ESD shield14creates an acoustic cavity. At least one of the side sections22,24is connected to electrical ground. For example, one or both of the side sections22,24may be directly connected to a ground plane on or within the printed circuit board16or substrate to which the microphone12is mounted. Because the ESD shield14is grounded, it protects the microphone12from spurious ESD events and from electromagnetic interference. In many embodiments, this may eliminate the need for TVS diode protection, which may reduce the cost associated with the microphone12.

Reference is now made toFIG. 5, which shows a perspective view of an example embodiment of an acoustic shield30for use with the microphone12. The acoustic shield30is intended to shield the microphone12from unwanted acoustic interference and/or reflections but permit desired voice range acoustic waves to be received through the acoustic port26.

The acoustic shield30includes a non-metal acoustic tube32for connecting the acoustic port26to the casing of the electronic device (not shown). The acoustic tube32is formed from rubber or other suitable material. The acoustic tube32provides a pathway34for acoustic waves to travel from a port or opening in the exterior casing of the device to the acoustic port26in the ESD shield14. Although the tube32is straight in many embodiments, in some embodiments it may be possible for the tube32to have bends or curves provided that its interior dimensions and angles permit a reasonably efficient transfer of sound in the voice range down the pathway34of the tube32. The end of the tube32at the casing may be sealed to the casing.

In some embodiments the acoustic shield30includes a cavity portion36sized to fit within the ESD shield14and substantially surround the microphone12. It will be appreciated that the cavity portion36does not pass underneath the microphone12where the microphone12is attached to the circuit board16, but rather fits on top of the microphone12. The interior of the cavity portion36is dimensioned so that the tube resonance is above the audio band used in telephony.

The interior of the cavity portion36is in sealed communication with the pathway34of the tube32to permit sound transfer down the pathway34to the interior of the cavity portion36and, thus, the microphone12. The cavity portion36may otherwise have a sidewall38and top wall40that substantially surrounds the microphone12.

Those ordinarily skilled in the art will appreciate the range of suitable materials that may be employed to create the acoustic shield30.

Referring still toFIGS. 1 to 5, the antenna10includes a radiator arm50and a feed element52. The radiator arm50is, in this embodiment, a metal planar element. The radiator arm50may, in some embodiments, be formed integrally with the ESD shield14. In this particular embodiment, the radiator arm50lies in the same plane as the top section20of the ESD shield14. The feed element52is a metal element connected to approximately the opposite side of the top section20from the radiator arm50. The feed element52extends down to the circuit board16or other substrate where it connects to a signal trace or other circuit element through which it may electrically conduct received or transmitted signals. In the embodiment shown inFIGS. 1-4, the feed element52extends downwards at an acute angle; however, in other embodiments it may extend downwards perpendicular to the top section20.

The radiator arm50may be arranged to extend partly or wholly above the acoustic tube32(FIG. 5). In some embodiments the radiator arm50may be wider, thinner or the same width as the acoustic tube32. In some embodiments the radiator arm50is the same or shorter than the length of the acoustic tube32. The length and width of the radiator arm50are selected in conjunction with the dimensions of the top section20and the feed element52to give the antenna10the desired RF properties. The length and width of the radiator arm50may be selected so as to frequency tune the antenna10.

The radiator arm50, ESD shield14, and feed element52are, in one embodiment, formed from a metal stamping process.

Reference is now also made toFIG. 6, which shows a block diagram of the antenna10. The antenna10is formed from the radiator arm50, the grounded ESD shield14, and feed element52. The ESD shield14, in particular the top section20, serves as a shorted element of the antenna10. Either one of the sides22,24of the ESD shield14or both sides22,24may be connected to ground. The feed element52is connected to a signal trace or circuit element connected to a matching block60. The matching circuit60is configured to impedance match with the antenna10, as will be understood by those skilled in the art. The matching circuit60may, in some embodiments, be implemented using integrated passive devices (IPDs).

The feed element52is coupled to a signal source62through the matching circuit60. The signal source62is configured to drive the antenna10at one or more frequencies to which the antenna10is tuned. Those ordinarily skilled in the art will appreciate the range of circuit elements and variations on configuration for using an RF antenna such as the antenna10for sending or receiving RF signals.

It will be appreciated that the antenna10shown inFIG. 6and inFIGS. 1-4is configured as an Inverted-F antenna. In other embodiments other microstrip antennas may be implemented. It will be understood that the antenna10discussed herein is an example only. Other embodiments of antennas integrated with the ESD shield of a microphone may include multiple feed points, multiple shorting elements, slots, or parasitic elements. It will also be understood that the radiator arm50may, in some embodiments, be folded and/or non-planar. For example, the radiator arm50may be arranged as a folded three-dimensional structure. In one embodiment, the radiator arm50may have elements arranged along one or more of the sides of the acoustic tube32.

Reference will now be made toFIGS. 7 through 11, which illustrate other example embodiments of the antenna10.

FIG. 7shows a perspective view of an embodiment of the antenna10with a non-cylindrical ESD shield114. In this embodiment, the ESD shield114is rectangular. In other embodiments, the ESD shield114may be arranged in other shapes.

FIG. 8shows a perspective view of an embodiment of the antenna10with an ESD shield314having the same width as the radiator arm50. In this embodiment, the top section320of the ESD shield314has the same width as the radiator arm and is generally rectangular in shape. The sides322,324of the ESD shield314extend downwards from the top section320and the acoustic opening or port326occupies the entire front of the ESD shield314.

FIG. 9shows a right front perspective view of yet another embodiment of the antenna10. In this embodiment, the ESD shield14is cylindrical, like inFIGS. 1-4; however, the feed element152in this embodiment extends perpendicular to the top portion20. Gaps154,156between the feed element152and the sides of the ESD shield14prevent the feed element152from being shorted out in this embodiment.

FIG. 10illustrates an embodiment of the antenna10ofFIGS. 1-4arranged together with the acoustic tube32ofFIG. 5. The acoustic tube32is shown in dashed lines for ease of illustration. In this embodiment, the radiator arm52substantially covers the top of the acoustic tube32and has nearly the same length as the acoustic tube32.

FIG. 11shows another embodiment of the antenna10together with the acoustic tube32. In this embodiment, the radiator arm150is formed as a folded three-dimensional structure. The radiator arm50features portions on the top of the acoustic tube32and interconnecting portions on one or more of the sides of the acoustic tube32, so as to form a winding or switchback pattern in three-dimensions.

In the foregoing embodiments, the radiator arm50is shown lying in the same plane as the top section20of the ESD shield14. In other embodiments, the radiator arm50may extend in a different plane from the top section20. As noted in connection withFIG. 11, the radiator arm50may have a three-dimensional shape. In addition, although the top section20is illustrated as being planar in many of the embodiments, in some embodiments the top section20may not be planar.

Those ordinarily skilled in the art will appreciated that the foregoing embodiments are examples only and that many other configurations or shapes may be used to form the ESD shield, radiator arm, and/or feed element of the antenna, depending on the application desired.

Reference is now made toFIG. 12, which shows an example embodiment of a mobile communication device201which may incorporate the antenna10described herein. The mobile communication device201is a two-way communication device having voice and possibly data communication capabilities; for example, the capability to communicate with other computer systems, e.g., via the Internet. Depending on the functionality provided by the mobile communication device201, in various embodiments the device may be a multiple-mode communication device configured for both data and voice communication, a smartphone, a mobile telephone or a PDA (personal digital assistant) enabled for wireless communication, or a computer system with a wireless modem.

The mobile communication device201includes a controller comprising at least one processor240such as a microprocessor which controls the overall operation of the mobile communication device201, and a wireless communication subsystem211for exchanging radio frequency signals with the wireless network101. The processor240interacts with the communication subsystem211which performs communication functions. The processor240interacts with additional device subsystems. In some embodiments, the device201may include a touchscreen display210which includes a display (screen)204, such as a liquid crystal display (LCD) screen, with a touch-sensitive input surface or overlay206connected to an electronic controller208. The touch-sensitive overlay206and the electronic controller208provide a touch-sensitive input device and the processor240interacts with the touch-sensitive overlay206via the electronic controller208. In other embodiments, the display204may not be a touchscreen display. Instead, the device201may simply include a non-touch display and one or more input mechanisms, such as, for example, a depressible scroll wheel.

The processor240interacts with additional device subsystems including flash memory244, random access memory (RAM)246, read only memory (ROM)248, auxiliary input/output (I/O) subsystems250, data port252such as serial data port, such as a Universal Serial Bus (USB) data port, speaker256, microphone258, input mechanism260, switch261, short-range communication subsystem272, and other device subsystems generally designated as274. Some of the subsystems shown inFIG. 12perform communication-related functions, whereas other subsystems may provide “resident” or on-device functions.

The communication subsystem211may include a receiver, a transmitter, and associated components, such as one or more antenna elements10, local oscillators (LOs), and a processing module such as a digital signal processor (DSP). The antenna10may be embedded or internal to the mobile communication device201and a single antenna may be shared by both receiver and transmitter, as is known in the art. As will be apparent to those skilled in the field of communication, the particular design of the communication subsystem211depends on the wireless network101in which the mobile communication device201is intended to operate. As described above, the antenna10may be formed integral with the microphone258ESD protection.

The mobile communication device201may communicate with any one of a plurality of fixed transceiver base stations of a wireless network101within its geographic coverage area. The mobile communication device201may send and receive communication signals over the wireless network101after a network registration or activation procedures have been completed. Signals received by the antenna10through the wireless network101are input to the receiver, which may perform such common receiver functions as signal amplification, frequency down conversion, filtering, channel selection, etc., as well as analog-to-digital (A/D) conversion. A/D conversion of a received signal allows more complex communication functions such as demodulation and decoding to be performed in the DSP. In a similar manner, signals to be transmitted are processed, including modulation and encoding, for example, by the DSP. These DSP-processed signals are input to the transmitter for digital-to-analog (D/A) conversion, frequency up conversion, filtering, amplification, and transmission to the wireless network101via the antenna10.

The processor240operates under stored program control and executes software modules220stored in memory such as persistent memory, for example, in the flash memory244. As illustrated inFIG. 12, the software modules220comprise operating system software222and software applications224.

Those skilled in the art will appreciate that the software modules220or parts thereof may be temporarily loaded into volatile memory such as the RAM246. The RAM246is used for storing runtime data variables and other types of data or information, as will be apparent to those skilled in the art. Although specific functions are described for various types of memory, this is merely one example, and those skilled in the art will appreciate that a different assignment of functions to types of memory could also be used.

The software applications224may include a range of other applications, including, for example, a messaging application, a calendar application, and/or a notepad application. In some embodiments, the software applications224include an email message application, a push content viewing application, a voice communication (i.e. telephony) application, a map application, and a media player application. Each of the software applications224may include layout information defining the placement of particular fields and graphic elements (e.g. text fields, input fields, icons, etc.) in the user interface (i.e. the display device204) according to the application.

In some embodiments, the auxiliary input/output (I/O) subsystems250may comprise an external communication link or interface, for example, an Ethernet connection. The mobile communication device201may comprise other wireless communication interfaces for communicating with other types of wireless networks, for example, a wireless network such as an orthogonal frequency division multiplexed (OFDM) network or a GPS transceiver for communicating with a GPS satellite network (not shown). The auxiliary I/O subsystems250may comprise a vibrator for providing vibratory notifications in response to various events on the mobile communication device201such as receipt of an electronic communication or incoming phone call, or for other purposes such as haptic feedback (touch feedback).

In some embodiments, the mobile communication device201also includes a removable memory card230(typically comprising flash memory) and a memory card interface232. Network access may be associated with a subscriber or user of the mobile communication device201via the memory card230, which may be a Subscriber Identity Module (SIM) card for use in a GSM network or other type of memory card for use in the relevant wireless network type. The memory card230is inserted in or connected to the memory card interface232of the mobile communication device201in order to operate in conjunction with the wireless network101.

The mobile communication device201stores data240in an erasable persistent memory, which in one example embodiment is the flash memory244. In various embodiments, the data240includes service data comprising information required by the mobile communication device201to establish and maintain communication with the wireless network101. The data240may also include user application data such as email messages, address book and contact information, calendar and schedule information, notepad documents, image files, and other commonly stored user information stored on the mobile communication device201by its user, and other data. The data240stored in the persistent memory (e.g. flash memory244) of the mobile communication device201may be organized, at least partially, into a number of databases each containing data items of the same data type or associated with the same application.

The serial data port252may be used for synchronization with a user's host computer system (not shown). The serial data port252enables a user to set preferences through an external device or software application and extends the capabilities of the mobile communication device201by providing for information or software downloads to the mobile communication device201other than through the wireless network101. The alternate download path may, for example, be used to load an encryption key onto the mobile communication device201through a direct, reliable and trusted connection to thereby provide secure device communication.

In some embodiments, the mobile communication device201is provided with a service routing application programming interface (API) which provides an application with the ability to route traffic through a serial data (i.e., USB) or Bluetooth® (Bluetooth® is a registered trademark of Bluetooth SIG, Inc.) connection to the host computer system using standard connectivity protocols. When a user connects their mobile communication device201to the host computer system via a USB cable or Bluetooth® connection, traffic that was destined for the wireless network101is automatically routed to the mobile communication device201using the USB cable or Bluetooth® connection. Similarly, any traffic destined for the wireless network101is automatically sent over the USB cable Bluetooth® connection to the host computer system for processing.

The mobile communication device201also includes a battery238as a power source, which is typically one or more rechargeable batteries that may be charged, for example, through charging circuitry coupled to a battery interface such as the serial data port252. The battery238provides electrical power to at least some of the electrical circuitry in the mobile communication device201, and the battery interface236provides a mechanical and electrical connection for the battery238. The battery interface236is coupled to a regulator (not shown) which provides power V+ to the circuitry of the mobile communication device201.

The short-range communication subsystem272is an additional optional component which provides for communication between the mobile communication device201and different systems or devices, which need not necessarily be similar devices. For example, the subsystem272may include an infrared device and associated circuits and components, or a wireless bus protocol compliant communication mechanism such as a Bluetooth® communication module to provide for communication with similarly-enabled systems and devices.

A predetermined set of applications that control basic device operations, including data and possibly voice communication applications will normally be installed on the mobile communication device201during or after manufacture. Additional applications and/or upgrades to the operating system221or software applications224may also be loaded onto the mobile communication device201through the wireless network101, the auxiliary I/O subsystem250, the serial port252, the short-range communication subsystem272, or other suitable subsystem274other wireless communication interfaces. The downloaded programs or code modules may be permanently installed, for example, written into the program memory (i.e. the flash memory244), or written into and executed from the RAM246for execution by the processor240at runtime. Such flexibility in application installation increases the functionality of the mobile communication device201and may provide enhanced on-device functions, communication-related functions, or both. For example, secure communication applications may enable electronic commerce functions and other such financial transactions to be performed using the mobile communication device201.

Although in this embodiment, it is the communication subsystem211that employs the antenna10integrated with the microphone258ESD protection, in other embodiments a different communication system within the mobile device201may use an antenna integrated with the microphone258ESD protection, such as a GPS system, or the short-range communication subsystem272.

The wireless network101may comprise one or more of a Wireless Wide Area Network (WWAN) and a Wireless Local Area Network (WLAN) or other suitable network arrangements. In some embodiments, the mobile communication device201is configured to communicate over both the WWAN and WLAN, and to roam between these networks. In some embodiments, the wireless network101may comprise multiple WWANs and WLANs. In some embodiments, the mobile device201includes the communication subsystem211for WWAN communications and a separate communication subsystem for WLAN communications. In most embodiments, communications with the WLAN employ a different antenna than communications with the WWAN. Accordingly, the antenna10may be configured for WWAN communications or WLAN communications depending on the embodiment and desired application.

In some embodiments, the WWAN conforms to one or more of the following wireless network types: Mobitex Radio Network, DataTAC, GSM (Global System for Mobile Communication), GPRS (General Packet Radio System), TDMA (Time Division Multiple Access), CDMA (Code Division Multiple Access), CDPD (Cellular Digital Packet Data), iDEN (integrated Digital Enhanced Network), EvDO (Evolution-Data Optimized) CDMA2000, EDGE (Enhanced Data rates for GSM Evolution), UMTS (Universal Mobile Telecommunication Systems), HSPDA (High-Speed Downlink Packet Access), IEEE 802.16e (also referred to as Worldwide Interoperability for Microwave Access or “WiMAX), or various other networks. Although WWAN is described as a “Wide-Area” network, that term is intended herein also to incorporate wireless Metropolitan Area Networks (WMAN) and other similar technologies for providing coordinated service wirelessly over an area larger than that covered by typical WLANs.

The WLAN comprises a wireless network which, in some embodiments, conforms to IEEE 802.11x standards (sometimes referred to as Wi-Fi) such as, for example, the IEEE 802.11a, 802.11b and/or 802.11g standard. Other communication protocols may be used for the WLAN in other embodiments such as, for example, IEEE 802.11n, IEEE 802.16e (also referred to as Worldwide Interoperability for Microwave Access or “WiMAX”), or IEEE 802.20 (also referred to as Mobile Wireless Broadband Access). The WLAN includes one or more wireless RF Access Points (AP) that collectively provide a WLAN coverage area.