Patent Application
20150109167
This relates generally to electronic devices and, more particularly, to electronic devices with antennas.
Electronic devices often include antennas. For example, cellular telephones, computers, and other devices often contain antennas for supporting wireless communications.
It can be challenging to form electronic device antennas with desired attributes. In some wireless devices, an antenna is used for satellite communications such as Global Positioning System communications. The antenna is often formed with an unbalanced-fed arrangement having a shorting path to a ground plane. For example, an inverted-F antenna has a resonating element that is directly coupled to the ground plane by a shorting path. However, unbalanced-fed antennas having such shorting paths may produce undesirable antenna radiation characteristics. In particular, the shorting paths allow the formation of substantial antenna ground plane currents that can undesirably alter the radiation patterns of the antenna.
It would therefore be desirable to be able to provide improved antenna structures for electronic devices that are used for satellite communications.
An electronic device may include balanced-fed antenna structures (sometimes referred to herein as balance-fed antenna structures). Balance-fed antenna structures do not have direct paths to ground and therefore are not electrically connected to any ground structures. The balance-fed antenna structures may serve as a Global Positioning System (GPS) antenna and may have a dipole structure having a first and second antenna resonating element arms. An unbalanced transmission line such as a coaxial cable may be coupled to the balance-fed dipole antenna structures and coupled to ground structures. The antenna structures may include a conductive path that conveys antenna signals between a first feed terminal on the first antenna resonating element arm and the unbalanced transmission line. The conductive path may overlap with the second antenna resonating element arm such that current flow through the conductive path induces corresponding current flow in the second antenna resonating element arm (and vice versa). The induced current flow in the second antenna resonating element arm serves to indirectly feed a second antenna feed terminal on the second antenna resonating element arm. The antenna structures may include a short-circuit stub path that couples the first antenna resonating element arm to the second antenna resonating element arm and is configured to match the impedance of the antenna structures to the transmission line.
The antenna structures may be formed on a carrier structure such as a flexible circuit substrate, housing of adjacent circuitry, plastic support structures, or other carrier structures on which the antenna resonating element arms may be formed. For example, the first and second antenna resonating element arms may be formed as first patterned metal layer on a flexible circuit substrate, whereas the conductive path may be formed as a second patterned metal layer that is coupled to the first patterned metal layer by a via that extends through the flexible circuit substrate. As another example, the antenna resonating element arms may be plated onto a plastic carrier.
Circuitry such as microphone circuitry, camera circuitry, or other circuitry may be adjacent to the antenna structures. The adjacent circuitry may be coupled to the ground structures via conductive paths. Choke inductors may be interposed in the conductive paths between the adjacent circuitry and the ground structures and serve to help block indirect paths from the antenna structures to ground while accommodating normal operations of the adjacent circuitry. The choke inductors block radio-frequency antenna signals while passing signals at lower frequencies associated with the adjacent circuitry.
Electronic devices may be provided with antenna structures for satellite communications such as Global Positioning System (GPS) communications and the Global Navigation Satellite System (GLONASS). Satellite antenna structures may have an upper-hemisphere orientation that helps improve reception from GPS satellites located in the upper hemisphere. The GPS antenna structures may have a balance-fed architecture such that antenna currents are focused in antenna resonating elements and ground plane currents are reduced.
Illustrative electronic devices that have antenna structures with balance-fed architectures are shown in
In the example of
Antennas may be provided in other electronic devices if desired. In general, device 10 may be computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. The illustrative configurations for device 10 that are shown in
Housing 12 of device 10, which is sometimes referred to as a case, may be formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other fiber-based composites, metal (e.g., machined aluminum, stainless steel, or other metals), other materials, or a combination of these materials. Device 10 may be formed using a unibody construction in which most or all of housing 12 is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures).
Display 14 of device 10 may be a touch sensitive display that includes a touch sensor or may be insensitive to touch. Touch sensors for display 14 may be formed from an array of capacitive touch sensor electrodes, a resistive touch array, touch sensor structures based on acoustic touch, optical touch, or force-based touch technologies, or other suitable touch sensor components.
A cross-sectional side view of an illustrative electronic device of the type that may be provided with antenna structures is shown in
Display cover layer 40 may cover the surface of display 14 or a display layer such as a color filter layer (e.g., a layer formed from a clear substrate covered with patterned color filter elements) or other portion of a display may be used as the outermost (or nearly outermost) layer in display 14. The outermost display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent member. To hide internal components from view, the underside of the outermost display layer or other display layer surface in inactive area IA may be coated with opaque masking layer 52 (e.g., a layer of opaque ink such as a layer of black ink).
Antenna structures 50 may be mounted under inactive area IA. Antenna structures 50 may include one or more antennas for device 10. Antenna structures 50 may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, closed and open slot antenna structures, planar inverted-F antenna structures, helical antenna structures, strip antennas, monopoles, dipoles, hybrids of these designs, etc. Different types of antennas may be used for different bands and combinations of bands. The example of
Opaque masking layer 52 and display cover layer 40 may be radio-transparent, so that radio-frequency antenna signals can be transmitted and received through display cover layer 40 in inactive area IA and opaque masking layer 52. Housing 12 may be formed from a dielectric such as plastic that is transparent to radio-frequency signals or may be formed from a material such as metal in which an antenna window such as antenna window 56 has been formed. Antenna window 56 may be formed from a dielectric such as plastic, so that antenna window 56 is transparent to radio-frequency signals. During operation, antenna signals associated with antenna structures 50 may pass through the portions of display 14 in inactive area IA that overlap antenna structures 50 and/or through antenna window 56 and/or other dielectric portions of housing 12.
Device 10 may contain electrical components 46. Components 46 may be mounted on one or more substrates such as printed circuit 44. Printed circuit 44 may be a rigid printed circuit board (e.g., a printed circuit formed from a rigid printed circuit board material such as fiberglass-filled epoxy) or a flexible printed circuit (e.g., a flex circuit formed from a sheet of polyimide or other layer of flexible polymer). Electrical components 46 may include integrated circuits, connectors, sensors, light-emitting components, audio components, discrete devices such as inductors, capacitors, and resistors, switches, and other electrical devices. Paths such as path 48 may be used to couple antenna structures 50 to wireless circuitry on substrates such as printed circuit 44. Paths such as path 48 may include transmission line paths such as stripline transmission lines, microstrip transmission lines, coplanar transmission lines, coaxial cable transmission lines, transmission lines formed on flexible printed circuits, transmission lines formed on rigid printed circuit boards, or other signal paths.
Antenna structures 50 may include one or more antennas. Antenna structures 50 may be used for transmitting and receiving wireless signals (as an example). Transceiver circuitry 68 may include transmitters and receivers for transmitting and receiving antenna signals through antenna structures 50. For example, transceiver circuitry 68 may have a transmitter-receiver 72 for transmitting and receiving antenna signals and a receiver such as receiver 70 for receiving antenna signals such as cellular communications signals. Receiver 70 may, as an example, be configured to receive signals at GPS frequencies and/or GLONASS frequencies. Examples of GPS frequencies include 1575 MHz and 1227 MHz, whereas GLONASS frequencies may include 1602 MHz. Transmission line 74 may be used to route signals between transceiver circuitry 68 (e.g., receiver 70) and antenna structures 50. Transmission line 74 may be an unbalanced transmission line such as a coaxial cable. For example, positive antenna feed signals may be conveyed between receiver 70 and antenna structures 50, whereas ground antenna feed signals may be conveyed between receiver 70 and a ground terminal. The ground terminal may be a point on ground structures such as the device housing, a ground plane, or other conductive ground structures. Antenna structures 50 has a balanced-fed configuration in which antenna structures 50 are not electrically connected (i.e., directly coupled by a conductive path) to ground. Balanced signals from the antenna structures may be converted to unbalanced signals for the transmission line using feed structures on antenna structures 50 or using a balun such as a chip balun.
The antennas in device 10 may be used to support any communications bands of interest. For example, device 10 may include antenna structures for supporting GPS communications or other satellite navigation system communications, local area network communications, voice and data cellular telephone communications, Bluetooth® communications, etc.
As shown in
Control circuitry 62 may be used to run software on device 10, such as satellite navigation applications, internet browsing applications, voice-over-internet-protocol (VOIP) telephone call applications, email applications, media playback applications, operating system functions, etc. To support interactions with external equipment, control circuitry 62 may be used in implementing communications protocols. Communications protocols that may be implemented using the storage and processing circuitry of control circuitry 62 include satellite navigation communications protocols, internet protocols, wireless local area network protocols (e.g., IEEE 802.11 protocols—sometimes referred to as WiFi®), protocols for other short-range wireless communications links such as the Bluetooth® protocol, cellular telephone protocols, etc.
Input-output circuitry in device 10 such as input-output devices 64 may be used to allow data to be supplied to device 10 and to allow data to be provided from device 10 to external devices. Input-output devices 64 may include touch screens, buttons, joysticks, click wheels, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device 10 by supplying commands through input-output devices 64 and may receive status information and other output from device 10 using the output resources of input-output devices 64.
Electronic devices such as device 10 may be operated in various orientations such as portrait or landscape. During satellite navigation operations, device 10 of
Antenna structures 50 may include resonating element arms 94 and 96 that form a dipole structure. In the example of
Antenna structures 50 may be fed using a conductive path 100 that is coupled to terminal 78 and antenna resonating element arm 96. Path 100 may be connected to antenna resonating element arm 96 via connection 102. Conductive path 100 may be separated from antenna resonating element arms 94 and 96 by an intervening insulating layer such as a dielectric layer. Path 100 may provide positive antenna feed signals from feed terminal 78 to antenna resonating element arm 96. Path 100 may overlap with segment 104 of antenna resonating element arm 94 so that currents flowing in path 100 generate an electric field that induces corresponding currents in segment 104 (e.g., due to near-field coupling). Similarly, currents flowing in segment 104 generate an electric field that induces corresponding currents in path 100. In other words, the currents flowing through antenna resonating arm 94 are aligned with path 100 and are also therefore aligned with the currents flowing through antenna resonating arm 96. Connection 102 and segment 104 effectively serve as respective first and second antenna feed terminals for antenna structures 50. Segment 104 is indirectly fed via path 100, whereas connection 102 is directly fed by path 100.
Antenna resonating structures 50 may include conductive path 98 that electrically couples arms 94 and 96 and serves as a short-circuit stub path for impedance matching with a transmission line. Conductive path 98 includes a short-circuit portion located at a distance D away from connection 102, which may be adjusted to match the impedance of antenna resonating structures 50 to the impedance of the transmission line coupled to feed terminal 78 at desired operating frequencies. For example, distance D may be selected based on the wavelength of a desired operating frequency for impedance matching.
Antenna feed path 100 may be connected to portion 108 of antenna resonating element arm 96 that is typically oriented towards the upper hemisphere (e.g., that is closer than other portions of arm 96 to satellites 82 in a portrait orientation of device 10 of
Antenna structures 50 may be formed as patterned layers on a substrate.
The example of
Antenna structures 50 may be used in compact electronic devices such as portable electronic devices in which space is limited. In such scenarios, antenna structures 50 may be located adjacent to or within close proximity of nearby circuitry.
During wireless communications, radio-frequency signals received by antenna structures 50 can potentially couple to adjacent circuitry such as camera circuitry 138, path 140, microphone 132, and path 134. For example, electric fields produced by antenna currents can cause near-field coupling to camera circuitry 138, path 140, microphone circuitry 132, and path 134. Current that is induced in paths 134 and 140 by antenna currents may travel to ground plane 92 and cause ground plane 92 to resonate and produce wireless signals. Wireless emissions from ground plane 92 may be typically oriented away from the upper hemisphere during satellite navigation communications (e.g., when the electronic device is operated in a portrait mode). Ground plane emissions may therefore alter the radiation patterns of antenna structures 50, as substantial power may be radiated by ground plane 92 instead of antenna structures 50. Consequently, the antenna performance for satellite communications (e.g., 120° upper hemisphere performance) may be reduced.
Circuitry that is proximate or adjacent to antenna structures 50 may be provided with choke inductors that help to isolate ground structures from antenna currents. The choke inductors serve as high-frequency open circuits and low-frequency short circuits. In the example of
Choke inductor 142 may be coupled between camera 138 and ground plane 92 to block radio-frequency antenna signals without interfering with camera operations (e.g., camera operations using direct-current or signals at frequencies lower than satellite communications frequencies). In general, choke inductors may be used to block indirect antenna current paths to ground, which helps to reduce ground plane currents and maintain the upper-hemisphere orientation of antenna structures 50.
The example of
Antenna structures on a carrier structure may have various configurations.
If desired, carrier structures may include one or more curved surfaces on which antenna structures may be formed.
The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.
