Antenna system with receiver diversity and tunable matching circuit

Electronic devices may be provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry and antenna structures. An electronic device may include a display mounted within a housing. A peripheral conductive member may run around the edges of the display and housing. Dielectric-filled gaps may divide the peripheral conductive member into individual segments. A ground plane may be formed within the housing from conductive housing structures, printed circuit boards, and other conductive elements. The ground plane and the segments of the peripheral conductive member may form antennas in upper and lower portions of the housing. The radio-frequency transceiver circuitry may implement receiver diversity using both the upper and lower antennas. The lower antenna may be used in transmitting signals. The upper antenna may be tuned using a tunable matching circuit.

BACKGROUND

This relates generally to wireless communications circuitry, and more particularly, to electronic devices that have wireless communications circuitry.

Electronic devices such as portable computers and cellular telephones are often provided with wireless communications capabilities. For example, electronic devices may use long-range wireless communications circuitry such as cellular telephone circuitry to communicate using cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz. Electronic devices may use short-range wireless communications links to handle communications with nearby equipment. For example, electronic devices may communicate using the WiFi® (IEEE 802.11) bands at 2.4 GHz and 5 GHz and the Bluetooth® band at 2.4 GHz.

To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to implement wireless communications circuitry such as antenna components using compact structures. At the same time, it may be desirable to include conductive structures in an electronic device such as metal device housing components. Because conductive components can affect radio-frequency performance, care must be taken when incorporating antennas into an electronic device that includes conductive structures. Moreover, care must be taken to ensure that the antennas and wireless circuitry in a device are able to operate satisfactorily even in areas of weak radio-frequency signal strength.

It would therefore be desirable to be able to provide improved wireless communications circuitry for wireless electronic devices.

SUMMARY

Electronic devices may be provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry and antenna structures. An electronic device may include a display mounted within a housing. A peripheral conductive member may run around the edges of the display and housing.

The peripheral conductive member may be divided into individual segments by forming gaps in the peripheral conductive member at various points along its length. The gaps may be filled with a dielectric such as plastic and may form an open circuit between opposing portions of the conductive member. With one illustrative configuration, three gaps may be formed in the peripheral conductive member to divide the peripheral conductive member into three respective segments.

A conductive housing member such as a conductive midplate member that spans the width of the housing may be connected to the peripheral conductive member at the left and right edges of the display. The conductive housing member and other conductive structures such as electrical components and printed circuits may form a ground plane. The ground plane and the peripheral conductive member segments may surround dielectric openings to form the antenna structures. For example, an upper cellular telephone antenna may be formed at an upper end of the housing and a lower cellular telephone antenna may be formed at a lower end of the housing. In the upper cellular telephone antenna, a first dielectric opening may be surrounded by at least some of a first peripheral conductive member segment and portions of the ground plane. In the lower cellular telephone antenna, a second dielectric opening may be surrounded by at least some of a second peripheral conductive member segment and portions of the ground plane. The upper cellular telephone antenna may be a two-branch inverted-F antenna. The lower cellular telephone antenna may be a loop antenna.

The radio-frequency transceiver circuitry may be coupled to the upper and lower antennas using matching circuits. A fixed matching circuit may be used to couple the radio-frequency transceiver circuitry to the lower antenna. A fixed matching circuit or a tunable matching circuit may be used to couple the radio-frequency transceiver circuitry to the upper antenna.

During operation of the electronic device, the lower antenna may serve as the primary cellular antenna for the device. Radio-frequency antenna signals may be transmitted and received by the lower antenna in cellular telephone bands such as the bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz. The upper antenna may serve as a secondary antenna that allows the electronic device to implement receiver diversity. When the performance of the lower antenna drops during operation, the radio-frequency transceiver circuitry in the device can receive signals with the upper antenna rather than the lower antenna.

The upper antenna may support only a subset of the bands that are supported by the lower antenna. For example, the upper antenna may support only two receive sub-bands. If desired, the coverage of the upper antenna can be extended by tuning the matching circuit for the upper antenna in real time. This arrangement may allow the upper antenna to cover first and second receive bands during a first mode of operation and third and fourth receive bands during a second mode of operation.

DETAILED DESCRIPTION

Electronic devices may be provided with wireless communications circuitry. The wireless communications circuitry may be used to support wireless communications in multiple wireless communications bands. The wireless communications circuitry may include one or more antennas.

The antennas can include loop antennas, inverted-F antennas, strip antennas, planar inverted-F antennas, slot antennas, hybrid antennas that include antenna structures of more than one type, or other suitable antennas. Conductive structures for the antennas may, if desired, be formed from conductive electronic device structures. The conductive electronic device structures may include conductive housing structures. The housing structures may include a peripheral conductive member that runs around the periphery of an electronic device. The peripheral conductive member may serve as a bezel for a planar structure such as a display, may serve as sidewall structures for a device housing, or may form other housing structures. Gaps in the peripheral conductive member may be associated with the antennas.

An illustrative electronic device of the type that may be provided with one or more antennas is shown inFIG. 1. Electronic device10may be a portable electronic device or other suitable electronic device. For example, electronic device10may be a laptop computer, a tablet computer, a somewhat smaller device such as a wrist-watch device, pendant device, headphone device, earpiece device, or other wearable or miniature device, a cellular telephone, a media player, etc.

Device10may include a housing such as housing12. Housing12, which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of these materials. In some situations, parts of housing12may be formed from dielectric or other low-conductivity material. In other situations, housing12or at least some of the structures that make up housing12may be formed from metal elements.

Device10may, if desired, have a display such as display14. Display14may, for example, be a touch screen that incorporates capacitive touch electrodes. Display14may include image pixels formed form light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electronic ink elements, liquid crystal display (LCD) components, or other suitable image pixel structures. A cover glass layer may cover the surface of display14. Buttons such as button19may pass through openings in the cover glass.

Housing12may include structures such as peripheral member16. Member16may run around the rectangular periphery of device10and display14. Member16or part of member16may serve as a bezel for display14(e.g., a cosmetic trim that surrounds all four sides of display14and/or helps hold display14to device10). Member16may also, if desired, form sidewall structures for device10.

Member16may be formed of a conductive material and may therefore sometimes be referred to as a peripheral conductive member or conductive housing structures. Member16may be formed from a metal such as stainless steel, aluminum, or other suitable materials. One, two, or more than two separate structures may be used in forming member16. In a typical configuration, member16may have a thickness (dimension TT) of about 0.1 mm to 3 mm (as an example). The sidewall portions of member16may, as an example, be substantially vertical (parallel to vertical axis V). Parallel to axis V, member16may have a dimension TZ of about 1 mm to 2 cm (as an example). The aspect ratio R of member16(i.e., the ratio R of TZ to TT) is typically more than 1 (i.e., R may be greater than or equal to 1, greater than or equal to 2, greater than or equal to 4, greater than or equal to 10, etc.).

It is not necessary for member16to have a uniform cross-section. For example, the top portion of member16may, if desired, have an inwardly protruding lip that helps hold display14in place. If desired, the bottom portion of member16may also have an enlarged lip (e.g., in the plane of the rear surface of device10). In the example ofFIG. 1, member16has substantially straight vertical sidewalls. This is merely illustrative. The sidewalls of member16may be curved or may have any other suitable shape. In some configurations (e.g., when member16serves as a bezel for display14), member16may run around the lip of housing12(i.e., member16may cover only the edge of housing12that surrounds display14and not the rear edge of housing12of the sidewalls of housing12).

Display14may include conductive structures such as an array of capacitive electrodes, conductive lines for addressing pixel elements, driver circuits, etc. Housing12also include internal structures such as metal frame members, a planar housing member (sometimes referred to as a midplate) that spans the walls of housing12(i.e., a substantially rectangular member that is welded or otherwise connected between opposing sides of member16), printed circuit boards, and other internal conductive structures. These conductive structures may be located in center CN of housing12(as an example).

In regions22and20, openings may be formed between the conductive housing structures and conductive electrical components that make up device10. These openings may be filled with air, plastic, or other dielectrics. Conductive housing structures and other conductive structures in region CN of device10may serve as a ground plane for the antennas in device10. The openings in regions20and22may serve as slots in open or closed slot antennas, may serve as a central dielectric region that is surrounded by a conductive path of materials in a loop antenna, may serve as a space that separates an antenna resonating element such as a strip antenna resonating element or an inverted-F antenna resonating element from the ground plane, or may otherwise serve as part of antenna structures formed in regions20and22.

Portions of member16may be provided with gap structures. For example, member16may be provided with one or more gaps such as gaps18A,18B,18C, and18D, as shown inFIG. 1. The gaps may be filled with dielectric such as polymer, ceramic, glass, etc. Gaps18A,18B,18C, and18D may divide member16into one or more peripheral conductive member segments. There may be, for example, two segments of member16(e.g., in an arrangement with two gaps), three segments of member16(e.g., in an arrangement with three gaps), four segments of member16(e.g., in an arrangement with four gaps, etc.). The segments of peripheral conductive member16that are formed in this way may form parts of antennas in device10.

In a typical scenario, device10may have upper and lower antennas (as an example). An upper antenna may, for example, be formed at the upper end of device10in region22. A lower antenna may, for example, be formed at the lower end of device10in region20. The antennas may be used separately to cover separate communications bands of interest or may be used together to implement an antenna diversity scheme or a multiple-input-multiple-output (MIMO) antenna scheme.

Antennas in device10may be used to support any communications bands of interest. For example, device10may include antenna structures for supporting local area network communications, voice and data cellular telephone communications, global positioning system (GPS) communications or other satellite navigation system communications, Bluetooth® communications, etc.

A schematic diagram of electronic device10is shown inFIG. 2. As shown inFIG. 2, electronic device10may include storage and processing circuitry28. Storage and processing circuitry28may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in storage and processing circuitry28may be used to control the operation of device10. This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio codec chips, application specific integrated circuits, etc.

Storage and processing circuitry28may be used to run software on device10, such as 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, storage and processing circuitry28may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry28include 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.

Circuitry28may be configured to implement control algorithms that control the use of antennas in device10. For example, to support antenna diversity schemes and MIMO schemes or other multi-antenna schemes, circuitry28may perform signal quality monitoring operations, sensor monitoring operations, and other data gathering operations and may, in response to the gathered data, control which antenna structures within device10are being used to receive and process data. As an example, circuitry28may control which of two or more antennas is being used to receive incoming radio-frequency signals, may control which of two or more antennas is being used to transmit radio-frequency signals, may control the process of routing incoming data streams over two or more antennas in device10in parallel, etc. In performing these control operations, circuitry28may open and close switches, may turn on and off receivers and transmitters, may adjust impedance matching circuits, may configure switches in front-end-module (FEM) radio-frequency circuits that are interposed between radio-frequency transceiver circuitry and antenna structures (e.g., filtering and switching circuits used for impedance matching and signal routing), and may otherwise control and adjust the components of device10.

Input-output circuitry30may be used to allow data to be supplied to device10and to allow data to be provided from device10to external devices. Input-output circuitry30may include input-output devices32. Input-output devices32may 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 device10by supplying commands through input-output devices32and may receive status information and other output from device10using the output resources of input-output devices32.

Wireless communications circuitry34may include radio-frequency (RF) transceiver circuitry formed from one or more integrated circuits, power amplifier circuitry, low-noise input amplifiers, passive RF components, one or more antennas, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications). Wireless communications circuitry34may include satellite navigation system receiver circuitry such as Global Positioning System (GPS) receiver circuitry35(e.g., for receiving satellite positioning signals at 1575 MHz). Transceiver circuitry36may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and may handle the 2.4 GHz Bluetooth® communications band. Circuitry34may use cellular telephone transceiver circuitry38for handling wireless communications in cellular telephone bands such as bands at 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz or other cellular telephone bands of interest. Wireless communications circuitry34can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry34may include global positioning system (GPS) receiver equipment, wireless circuitry for receiving radio and television signals, paging circuits, etc. In WiFi® and Bluetooth® links and other short-range wireless links, wireless signals are typically used to convey data over tens or hundreds of feet. In cellular telephone links and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles.

Wireless communications circuitry34may include antennas40. Antennas40may be formed using any suitable antenna types. For example, antennas40may include antennas with resonating elements that are formed from loop antenna structure, 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. For example, one type of antenna may be used in forming a local wireless link antenna and another type of antenna may be used in forming a remote wireless link.

A cross-sectional side view of device10ofFIG. 1taken along line24-24inFIG. 1and viewed in direction26is shown inFIG. 3. As shown inFIG. 3, display14may be mounted to the front surface of device10. Housing12may include sidewalls formed from member16and one or more rear walls formed from structures such as planar rear housing structure42. Structure42may be formed from a dielectric such as glass, ceramic, or plastic, and/or metals or other suitable materials (e.g., fiber composites). Snaps, clips, screws, adhesive, and other structures may be used in assembling the parts of housing12together.

Device10may contain printed circuit boards such as printed circuit board46. Printed circuit board46and the other printed circuit boards in device10may be formed from rigid printed circuit board material (e.g., fiberglass-filled epoxy) or flexible sheets of material such as polymers. Flexible printed circuit boards (“flex circuits”) may, for example, be formed from flexible sheets of polyimide.

Printed circuit board46may contain interconnects such as interconnects48. Interconnects48may be formed from conductive traces (e.g., traces of gold-plated copper or other metals). Connectors such as connector50may be connected to interconnects48using solder or conductive adhesive (as examples). Integrated circuits, discrete components such as resistors, capacitors, and inductors, and other electronic components may be mounted to printed circuit board46.

Antennas in device10such as illustrative antenna40ofFIG. 3may have antenna feed terminals. For example, each antenna in device10may have a positive antenna feed terminal such as positive antenna feed terminal58and a ground antenna feed terminal such as ground antenna feed terminal54. As shown in the illustrative arrangement ofFIG. 3, a transmission line path such as coaxial cable52may be coupled between the antenna feed formed from terminals58and54and transceiver circuitry in components44via connector50and interconnects48. Components44may include one or more integrated circuits for implementing wireless circuitry34ofFIG. 2(e.g., receiver35and transceiver circuits36and38).

Connectors such as connector50may be used in coupling transmission lines in device10to printed circuit boards such as board46. Connector50may be, for example, a coaxial cable connector that is connected to printed circuit board46using solder (as an example). Cable52may be a coaxial cable or other transmission line. Examples of transmission lines that may be used in device10include coaxial cables, microstrip and stripline transmission lines formed from a flex circuit or rigid printed circuit board, transmission lines that are formed from multiple transmission line structures such as these, etc.

When coupled to the feed of antenna40, transmission line52may be used to transmit and receive radio-frequency signals using antenna40. As shown inFIG. 3, terminal58may be coupled to coaxial cable center connector56. Terminal54may be connected to a ground conductor in cable52(e.g., a conductive outer braid conductor). Other arrangements may be used for coupling transceivers in device10to antenna40if desired. For example, impedance matching circuits may be used in coupling transceiver circuitry to antenna structures. The arrangement ofFIG. 3is merely illustrative.

In the illustrative example ofFIG. 3, device10includes antenna40. To enhance signal quality and to cover multiple bands of interest, device10may contain multiple antennas. With one suitable arrangement, which is sometimes described herein as an example, a WiFi® antenna may be located in region22, a first (e.g., a primary) cellular telephone antenna may be located in region20, and a second (e.g., secondary) cellular telephone antenna may be located in region22. The second cellular telephone antenna may, if desired, be configured to receive GPS signals. Illustrative wireless circuitry34that includes an antenna arrangement of this type is shown inFIG. 4.

As shown inFIG. 4, wireless circuitry34may have input-output ports such as ports100and130for interfacing with digital data circuits in storage and processing circuitry28. Wireless circuitry34may include one or more integrated circuits for implementing transceiver circuits such as baseband processor102and cellular telephone transceiver circuitry38. Port100may receive digital data from storage and processing circuitry28for transmission over antenna40L. Incoming data that has been received by antennas40U and40L, cellular transceiver circuitry38, and baseband processor102may be supplied to storage and processing circuitry28via port100. Port130may be used to handle digital data associated with transmitted and received wireless local area network signals such as WiFi® signals (as an example). Outgoing digital data that is supplied to port130by storage and processing circuitry28may be transmitted using wireless local area network transceiver circuitry36, paths such as path128, and one or more antennas such as antenna40WF. During data reception operations, signals received by antenna40WF may be provided to transceiver36via path128. Transceiver36may convert the incoming signals to digital data. The digital data may be provided to storage and processing circuitry28via port130. If desired, local signals such as Bluetooth® signals may also be transmitted and received via antennas such as antenna40WF.

Transceiver circuitry38may include one or more transmitters and one or more receivers. In the example ofFIG. 4, transceiver circuitry38includes radio-frequency transmitter104and radio-frequency receivers110. Transmitter104and receivers110(i.e., receiver RX1and receiver RX2) may be used to handle cellular telephone communications. Signals that are received by transmitter104over path118may be supplied to power amplifier106by transmitter104. Power amplifier106may strengthen these outgoing signals for transmission over antenna40L. Incoming signals that are received by antenna40L may be amplified by low noise amplifier112and provided to receiver RX1. Receiver RX1may provide data received from antenna40U to processor102via path118. Incoming signals that are received by antenna40U may be amplified by low noise amplifier124and provided to receiver RX2(or to RX1using a switch). Receiver RX2may provide data received from antenna40L to processor102via path118. Circuits such as transmitter104and receivers110may each have multiple ports (e.g., for handling different respective communications bands) and may be implemented using one or more individual integrated circuits.

Antennas40U and40L may be coupled to transceiver circuitry38using circuitry such as impedance matching circuitry, filters, and switches. This circuitry, which is sometimes referred to as front-end module (FEM) circuitry, can be controlled by storage and processing circuitry in device10(e.g., control signals from a processor such as baseband processor102). As shown in the example ofFIG. 4, the front-end circuitry in wireless circuitry34may include impedance matching circuitry108such as matching circuit M1and matching circuit M2. Impedance matching circuitry108may be formed using conductive structures with associated capacitance, resistance, and inductance values, and/or discrete components such as inductors, capacitors, and resistors that form circuits to match the impedances of transceiver circuitry38and antennas40U and40L. Matching circuit M1may be coupled between wireless transceiver circuitry38(including associated amplifier circuitry106and112) and antenna40L. Matching circuit M2may be coupled between transceiver circuitry38(and associated amplifier124) and antenna40U using paths such as paths132and122.

Matching circuits M1and M2may be fixed or adjustable. For example, matching circuit M1may be fixed and matching circuit M2may be adjustable. In this type of configuration, a control circuit such as baseband processor102may issue control signals such as signal SELECT on path116of wireless circuitry34. Signal SELECT may be distributed to matching circuit M2. When SELECT has a first value, matching circuit M2may be placed in a first configuration. When SELECT has a second value, matching circuit M2may be placed in a second configuration. The state of matching circuit M2may serve to tune antenna40U so that different communications bands are covered by antenna40U. By using an antenna tuning scheme of this type, antenna40U may be able to cover a wider range of communications frequencies than would otherwise be possible. The use of tuning for antenna40U may allow a relatively narrow bandwidth (and potentially compact) design to be used for antenna40U, if desired.

Control signals may be provided to receiver circuitry110over path119so that wireless circuitry34can selectively activate one or both of receivers RX1and RX2or can otherwise select which antenna signals are being received in real time (e.g., by controlling a multiplexer in circuitry34that routes signals from a selected one of the antennas to a shared receiver so that the receiver can be shared between antennas). For example, baseband processor102or other storage and processing circuitry in device10can monitor signal quality (bit error rate, signal-to-noise ratio, frame error rate, signal power, etc.) for signals being received by antennas40U and40L. Based on real-time signal quality information or other data (e.g., sensor data indicating that a particular antenna is blocked), signals on path119or other suitable control signals can be adjusted so that optimum receiver circuitry (e.g., receiver RX1or RX2) is used to receive the incoming signals. Antenna diversity schemes such as this in which circuitry34selects an optimum antenna and receiver to use in real time based on signal quality measurements or other information while transmitted signals are transmitted by a fixed antenna and transmitter (i.e., antenna40L and transmitter104) may sometimes be referred to as receiver diversity schemes.

In a receiver diversity configuration (i.e., in a device without transmitter diversity), the radio-frequency transmitter circuitry in a device is configured to receive signals through two or more different antennas, so that an optimum antenna can be chosen in real time to enhance signal reception, whereas the radio-frequency transceiver circuitry is configured to transmit signals through only a single one of the antennas and not others. If desired, wireless circuitry34may be configured to implement both receiver and transmitter diversity and/or may be configured to handle multiple simultaneous data streams (e.g., using a MIMO arrangement). The use of wireless circuitry34to implement a receiver diversity scheme while using a dedicated antenna for handling transmitted signals is merely illustrative.

As shown inFIG. 4, wireless circuitry34may be provided with filter circuitry such as filter circuitry126. Circuitry126may route signals by frequency, so that cellular telephone signals are conveyed between antenna40U and receiver RX2, whereas GPS signals that are received by antenna40U are routed to GPS receiver35.

Illustrative tunable circuitry that may be used for implementing matching circuit M2ofFIG. 4is shown inFIG. 5. As shown inFIG. 5, matching circuit M2may have switches such as switches134and136. Switches134and136may have multiple positions (shown by the illustrative A and B positions inFIG. 5). When signal SELECT has a first value, switches134and136may be put in their A positions and matching circuit MA may be switched into use. When signal SELECT has a second value, switches134and136may be placed in their B positions (as shown inFIG. 5), so that matching circuit MB is connected between paths132and122.

FIG. 6is a top view of the interior of device10showing how antennas40L,40U, and40WF may be implemented within housing12. As shown inFIG. 6, ground plane G may be formed within housing12. Ground plane G may form antenna ground for antennas40L,40U, and40WF. Because ground plane G may serve as antenna ground, ground plane G may sometimes be referred to as antenna ground, ground, or a ground plane element (as examples).

In central portion C of device10, ground plane G may be formed by conductive structures such as a conductive housing midplate member that is connected between the left and right edges of member16, printed circuit boards with conductive ground traces, etc. At ends22and20of device10, the shape of ground plane G may be determined by the shapes and locations of conductive structures that are tied to ground. Examples of conductive structures that may overlap to form ground plane G include housing structures (e.g., a conductive housing midplate structure, which may have protruding portions), conductive components (e.g., switches, cameras, data connectors, printed circuits such as flex circuits and rigid printed circuit boards, radio-frequency shielding cans, buttons such as button144and conductive button mounting structure146), and other conductive structures in device10. In the illustrative layout ofFIG. 6, the portions of device10that are conductive and tied to ground to form part of ground plane G are shaded and are contiguous with central portion C.

Openings such as openings138and146may be formed between ground plane G and respective portions of peripheral conductive member16. Openings138and146may be filled with air, plastic, and other dielectrics. Openings138and146may be associated with antenna structures40.

Lower antenna40L may be formed by a loop antenna structure having a shape that is determined at least partly by the shape of the lower portions of ground plane G and conductive housing member16. In the example ofFIG. 6, opening138is depicted as being rectangular, but this is merely illustrative. In practice, the shape of opening138may be dictated by the placement of conductive structures in region20such as a microphone, flex circuit traces, a data port connector, buttons, a speaker, etc.

Lower antenna40L may be fed using an antenna feed made up of positive antenna feed terminal58-1and ground antenna feed terminal54-1. Transmission line52-1(see, e.g., path122ofFIG. 4) may be coupled to the antenna feed for lower antenna40L. Gap18B may form a capacitance that helps configure the frequency response of antenna40L. If desired, device10may have conductive housing portions, matching circuit elements, and other structures and components that help match the impedance of transmission line52-1to antenna40L (see, e.g., illustrative matching circuit M1ofFIG. 4).

Antenna40WF may have an antenna resonating element formed from a strip of conductor such as strip142. Strip142may be formed from a trace on a flex circuit, from a trace on a rigid printed circuit board, from a strip of metal foil, or from other conductive structures. Antenna40WF may be fed by transmission line52-2(see, e.g., path128ofFIG. 4) using antenna feed terminals58-2and54-2.

Antenna40U may be a two-branch inverted-F antenna. Transmission line52-3(see, e.g., path120ofFIG. 4) may be used to feed antenna40U at antenna feed terminals58-3and54-3. Conductive structure150may be bridge dielectric opening140and may be used to electrically short ground plane G to peripheral housing member16. Conductive structure148and matching circuit M2may be used to connect antenna feed terminal58-3to peripheral conductive member16at point152. Conductive structures such as structures148and150may be formed by flex circuit traces, conductive housing structures, springs, screws, or other conductive structures.

Gaps such as gaps18B,18C, and18D may be present in peripheral conductive member16. (Gap18A ofFIG. 1may be absent or may be implemented using a phantom gap structure that cosmetically looks like a gap from the exterior of device10, but that is electrically shorted within the interior of housing12so that no gap is electrically present in the location of gap18A.) The presence of gaps18B,18C, and18D may divide peripheral conductive member16into segments. As shown inFIG. 6, peripheral conductive member16may include first segment16-1, second segment16-2, and third segment16-3.

Segment16-1may form antenna resonating element arms for antenna40U. In particular, a first portion (segment) of segment16-1(having arm length LBA) may extend from point152(where segment16-1is fed) to the end of segment16-1that is defined by gap18C and a second portion (segment) of segment16-1(having arm length HBA) may extend from point152to the opposing end of segment16-1that is defined by gap18D. The first and second portions of segment16-1may form respective branches of an inverted F antenna and may be associated with respective low band (LB) and high band (HB) antenna resonances for antenna40U.

Antenna40L may cover the transmit and receive sub-bands in five communications bands (e.g., 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz), as shown in the table ofFIG. 7. Antenna40U may be configured to cover a subset of these five illustrative communications bands. For example, antenna40U may be configured to cover a two receive bands of interest and, with tuning, four receive bands of interest.

In arrangements in which matching circuit M2is fixed, for example, antenna40U may be configured to cover receive bands 850 RX (the 850 MHz receive band) and 1900 RX (the 1900 MHz receive band), may be configured to cover receive bands 900 RX (the 900 MHz receive band) and 2100 RX (the 2100 MHz receive band), or may be configured to cover any other suitable pair or set of these bands.

In arrangements in which matching circuit M2is adjustable, antenna40U may be tuned to cover all four of these receive bands. In particular, M2can be placed in state MA to configure antenna40U to cover the 850 RX and 1900 RX communications bands and can be placed in state MB to configure antenna40U to cover the 900 RX and 2100 RX communications bands.

FIG. 8is a circuit diagram of antenna40U. As shown inFIG. 8, gaps18C and18D may be associated with respective capacitances C2and C1. Ground plane G may form antenna ground. Short circuit branch150may form a stub that connects peripheral conductive member segment16-1to ground G to facilitate impedance matching between the antenna feed (formed form feed terminals58-3and54-3) and antenna40U.

The graph ofFIG. 9characterizes the performance of antenna40U by plotting standing wave ratio (SWR) values as a function of antenna operating frequency f. As shown inFIG. 9, there may be two resonances associated with antenna40U of FIG.8—low band LB and high band HB. The values of the frequency ranges covered by bands LB and HB depend on the configuration of antenna40U. With one suitable arrangement, band LB corresponds to a band such as the 850 RX band or the 900 RX band (as examples) and band HB corresponds to a band such as the 1900 RX or 2100 RX band (as examples).

FIG. 10shows the portion of antenna40U that contributes to antenna coverage in band HB (where inactive portions of the antenna are depicted using dashed lines).FIG. 11includes an illustrative SWR plot for the portion of antenna40U that is shown inFIG. 10. The solid line inFIG. 11corresponds to the performance of theFIG. 10circuitry in the absence of matching circuit M2. The dashed line inFIG. 11shows how a GPS resonance (e.g., at 1575 MHz) may be associated with the response of antenna40U when matching circuit M2is present. The frequency range of band HB may coincide with band 1900 RX or band 2100 RX, as described in connection withFIG. 7.

FIG. 12shows the portion of antenna40U that contributes to antenna coverage in band LB (where inactive portions of the antenna are depicted using dashed lines).FIG. 13includes an illustrative SWR plot for the portion of antenna40U that is shown inFIG. 12. The frequency range of band LB may coincide with band 850 RX or band 900 RX, as described in connection withFIG. 7.

FIG. 14includes an illustrative SWR plot for antenna40U ofFIG. 8(e.g., antenna40U ofFIG. 6). The solid line inFIG. 14corresponds to the response of antenna40U when matching circuit M2is in its “MA” configuration. In the MA configuration, antenna40U can cover receive bands 850 RX and 1900 RX and the GPS band at 1575 MHz. When signal SELECT is adjusted to place matching circuit M2in its “MB” configuration, antenna40U may be characterized by the dashed line ofFIG. 14. In the MB configuration, antenna40U can cover receive bands 900 RX and 1900 RX while still covering the GPS band at 1575 MHz (i.e., because the frequency response of antenna40U is not shifted substantially in the vicinity of 1575 MHz as a function of the state of matching circuit M2).