Electronic device with over-the-air wireless self-testing capabilities

An electronic device may be provided with wireless circuitry. The wireless circuitry may include antennas. The antennas may include phased antenna arrays for handling millimeter wave signals. Antennas may be located in antenna signal paths. The antenna signal paths may include adjustable components such as adjustable filters, adjustable gain amplifiers, and adjustable phase shifters. Circuitry may be incorporated into an electronic device to facilitate wireless self-testing operations. Wireless self-testing may involve use of one antenna to transmit an over-the-air antenna test signal that is received by another antenna. The circuitry that facilitates the wireless self-testing operations may include couplers, adjustable switches for temporarily shorting antenna signal paths together, mixers for mixing down radio-frequency signals to allow digitization with analog-to-digital converters, and other circuitry for supporting self-testing operations.

BACKGROUND

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

Electronic devices often include wireless communications circuitry. For example, cellular telephones, computers, and other devices often contain antennas and wireless transceivers for supporting wireless communications.

The wireless performance of an electronic device can be affected by manufacturing variations. As a result, many wireless electronic devices are tested during manufacturing. As an example, a wireless device may be placed in a test chamber to that has test antennas coupled to wireless test equipment. Tests may be performed on the wireless device while the wireless device is in the test chamber. Tests measurements such as these may be used to characterize antenna performance and to perform wireless circuit calibration.

It can be challenging to effectively characterize wireless electronic devices during manufacturing. Wireless devices may be produced in large volumes. Unless care is taken, the expense and complexity of installing and operating sufficient wireless test equipment to handle large volumes of devices can be prohibitive.

It would therefore be desirable to be able to provide improved arrangements for wirelessly testing electronic devices.

SUMMARY

An electronic device may be provided with wireless circuitry. The electronic device may be a portable electronic device such as a cellular telephone, laptop computer, or tablet computer, or may be other electronic equipment.

The wireless circuitry may include antennas. The antennas may include phased antenna arrays for handling millimeter wave signals. The wireless circuitry may also include antennas of other types such as cellular telephone antennas, wireless local area network antennas, and satellite navigation system antennas.

Antennas may be located in antenna signal paths. The antenna signal paths may include adjustable components such as adjustable filters, adjustable gain amplifiers, and adjustable phase shifters. During operation, these adjustable components may be adjusted to implement beam steering functions and other wireless functions.

Circuitry may be incorporated into the wireless circuitry of an electronic device to facilitate wireless self-testing operations. Wireless self-testing may involve use of one antenna in an electronic device to transmit an over-the-air antenna signal that is received by another antenna in the electronic device. The circuitry that facilitates the wireless self-testing operations may include couplers, adjustable switches for temporarily shorting antenna signal paths together, mixers for mixing down radio-frequency signals to allow digitization with analog-to-digital converters, and other circuitry for supporting self-testing operations.

DETAILED DESCRIPTION

An electronic device such as electronic device10ofFIG. 1may contain wireless circuitry. The wireless circuitry may include one or more antennas. The antennas may include phased antenna arrays that are used for handling millimeter wave communications. Millimeter wave communications, which are sometimes referred to as extremely high frequency (EHF) communications, involve signals at 60 GHz or other frequencies between about 10 GHz and 400 GHz. Device10may also contain wireless communications circuitry for handling satellite navigation system signals, cellular telephone signals, local wireless area network signals, near-field communications, light-based wireless communications, or other wireless communications.

Electronic device10may be a computing device such as a laptop 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, a device embedded in eyeglasses or other equipment worn on a user's head, or other wearable or miniature device, a television, a computer monitor containing an embedded computer, 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. In the illustrative configuration ofFIG. 1, device10is a portable device such as a cellular telephone, media player, tablet computer, or other portable computing device. Other configurations may be used for device10if desired. The example ofFIG. 1is merely illustrative.

As shown inFIG. 1, device10may include a display such as display14. Display14may be mounted in a housing such as housing12. Housing12, which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing12may be formed using a unibody configuration in which some or all of housing12is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.).

Display14may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures.

Display14may include an array of display pixels formed from liquid crystal display (LCD) components, an array of electrophoretic display pixels, an array of plasma display pixels, an array of organic light-emitting diode display pixels, an array of electrowetting display pixels, or display pixels based on other display technologies.

Display14may be protected using a display cover layer such as a layer of transparent glass, clear plastic, sapphire, or other transparent dielectric. Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button such as button16. An opening may also be formed in the display cover layer to accommodate ports such as a speaker port. Openings may be formed in housing12to form communications ports (e.g., an audio jack port, a digital data port, etc.). Openings in housing12may also be formed for audio components such as a speaker and/or a microphone.

Antennas may be mounted in housing12. To avoid disrupting communications when an external object such as a human hand or other body part of a user blocks one or more antennas, antennas may be mounted at multiple locations in housing12. Sensor data such as proximity sensor data, real-time antenna impedance measurements, signal quality measurements such as received signal strength information, and other data may be used in determining when an antenna (or set of antennas) is being adversely affected due to the orientation of housing12, blockage by a user's hand or other external object, or other environmental factors. Device10can then switch an antenna (or set of antennas) into use in place of the antennas that are being adversely affected.

Antennas may be mounted along the peripheral edges of housing12, on the rear of housing12, under the display cover glass or other dielectric display cover layer that is used in covering and protecting display14on the front of device10, under a dielectric window on a rear face of housing12or the edge of housing12, or elsewhere in device10.

A schematic diagram showing illustrative components that may be used in device10is shown inFIG. 2. As shown inFIG. 2, device10may include control circuitry such as storage and processing circuitry30. Storage and processing circuitry30may 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 circuitry30may be used to control the operation of device10. This processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processor integrated circuits, application specific integrated circuits, etc.

Storage and processing circuitry30may 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 circuitry30may be used in implementing communications protocols. Communications protocols that may be implemented using storage and processing circuitry30include 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, MIMO protocols, antenna diversity protocols, satellite navigation system protocols, etc.

Device10may include input-output circuitry44. Input-output circuitry44may include input-output devices32. Input-output devices32may be used to allow data to be supplied to device10and to allow data to be provided from device10to external devices. Input-output devices32may include user interface devices, data port devices, and other input-output components. For example, input-output devices may include touch screens, displays without touch sensor capabilities, buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, cameras, speakers, status indicators, light sources, audio jacks and other audio port components, digital data port devices, light sensors, accelerometers or other components that can detect motion and device orientation relative to the Earth, capacitance sensors, proximity sensors (e.g., a capacitive proximity sensor and/or an infrared proximity sensor), magnetic sensors, a connector port sensor or other sensor that determines whether device10is mounted in a dock, and other sensors and input-output components.

Input-output circuitry44may include wireless communications circuitry34for communicating wirelessly with external equipment. 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 antennas40, transmission lines, and other circuitry for handling RF wireless signals. Wireless signals can also be sent using light (e.g., using infrared communications).

Transceiver circuitry36may be wireless local area network transceiver circuitry that may handle 2.4 GHz and 5 GHz bands for WiFi® (IEEE 802.11) communications and that may handle the 2.4 GHz Bluetooth® communications band.

Circuitry34may use cellular telephone transceiver circuitry38for handling wireless communications in frequency ranges such as a low communications band from 700 to 960 MHz, a midband from 1710 to 2170 MHz, and a high band from 2300 to 2700 MHz or other communications bands between 700 MHz and 2700 MHz or other suitable frequencies (as examples). Circuitry38may handle voice data and non-voice data.

Millimeter wave transceiver circuitry46may support communications at extremely high frequencies (e.g., millimeter wave frequencies from 10 GHz to 400 GHz or other millimeter wave frequencies).

Wireless communications circuitry34may include satellite navigation system circuitry such as Global Positioning System (GPS) receiver circuitry42for receiving GPS signals at 1575 MHz or for handling other satellite positioning data (e.g., GLONASS signals at 1609 MHz). Satellite navigation system signals for receiver42are received from a constellation of satellites orbiting the earth.

In satellite navigation system links, cellular telephone links, and other long-range links, wireless signals are typically used to convey data over thousands of feet or miles. 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. Extremely high frequency (EHF) wireless transceiver circuitry46may convey signals over these over these short distances that travel between transmitter and receiver over a line-of-sight path. To enhance signal reception for millimeter wave communications, phased antenna arrays and beam steering techniques may be used. Antenna diversity schemes may also be used to ensure that the antennas that have become blocked or that are otherwise degraded due to the operating environment of device10can be switched out of use and higher-performing antennas used in their place.

Wireless communications circuitry34can include circuitry for other short-range and long-range wireless links if desired. For example, wireless communications circuitry34may include circuitry for receiving television and radio signals, paging system transceivers, near field communications (NFC) circuitry, etc.

Antennas40in wireless communications circuitry34may be formed using any suitable antenna types. For example, antennas40may include antennas with resonating elements that are formed from loop antenna structures, patch antenna structures, inverted-F antenna structures, slot antenna structures, planar inverted-F antenna structures, helical antenna structures, hybrids of these designs, etc. If desired, one or more of antennas40may be cavity-backed antennas. 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 antenna. Dedicated antennas may be used for receiving satellite navigation system signals or, if desired, antennas40can be configured to receive both satellite navigation system signals and signals for other communications bands (e.g., wireless local area network signals and/or cellular telephone signals). Antennas40can include phased antenna arrays for handling millimeter wave communications.

Transmission line paths may be used to route antenna signals within device10. For example, transmission line paths may be used to couple antenna structures40to transceiver circuitry90. Transmission lines in device10may include coaxial cable paths, microstrip transmission lines, stripline transmission lines, edge-coupled microstrip transmission lines, edge-coupled stripline transmission lines, transmission lines formed from combinations of transmission lines of these types, etc. Filter circuitry, switching circuitry, impedance matching circuitry, and other circuitry may be interposed within the transmission lines, if desired.

Device10may contain multiple antennas40. The antennas may be used together or one of the antennas may be switched into use while other antenna(s) are switched out of use. If desired, control circuitry30may be used to select an optimum antenna to use in device10in real time and/or to select an optimum setting for adjustable wireless circuitry associated with one or more of antennas40. Antenna adjustments may be made to tune antennas to perform in desired frequency ranges, to perform beam steering with a phased antenna array, and to otherwise optimize antenna performance. Sensors may be incorporated into antennas40to gather sensor data in real time that is used in adjusting antennas40.

In some configurations, antennas40may include antenna arrays. For example, the antennas that are used in handling millimeter wave signals for extremely high frequency wireless transceiver circuits46may be implemented as phased antenna arrays. The radiating elements in a phased antenna array for supporting millimeter wave communications may be patch antennas, dipole antennas, or other suitable antenna elements. Transceiver circuitry can be integrated with the phased antenna arrays to form integrated phased antenna array and transceiver circuit modules.

In devices such as handheld devices, the presence of an external object such as the hand of a user or a table or other surface on which a device is resting has a potential to block wireless signals such as millimeter wave signals or signals at other frequencies. Wireless performance can also be affected by the orientation of an antenna relative to the surroundings of device10. Accordingly, it may be desirable to incorporate multiple antennas within device10, each of which may be placed in a different location within device10. The antennas may be single antennas, phased antenna arrays or antenna elements within a phased antenna array, or other antennas. With this type of arrangement, control circuitry in device10such as control circuitry30may determine which antenna(s) to switch into use during operation to optimize wireless performance (e.g., to switch unblocked antennas into use, to perform beam steering operations for phased antenna arrays, etc.).

FIG. 3is a perspective view of electronic device showing illustrative locations50in which antennas40(e.g., single antennas and/or phased antenna arrays for use with wireless circuitry34such as millimeter wave wireless transceiver circuitry46) may be mounted in device10. As shown inFIG. 3, antennas40may be mounted at the corners of device10, along the edges of housing12such as edge12E, on the upper and lower portions of rear housing portion12R, in the center of rear housing12(e.g., under a dielectric window structure such as plastic logo52), etc. In configurations in which housing12is formed from a dielectric, antennas40may transmit and receive antenna signals through the dielectric. In configurations in which housing12is formed from a conductive material such as metal, slots or other openings may be formed in the metal that are filled with plastic or other dielectric. Antennas40may be mounted in alignment with the dielectric (i.e., the dielectric in housing12may serve as one or more antenna windows for antennas40).

Signal paths such as paths100ofFIG. 4(e.g., transmission lines) may be used to distribute radio-frequency and/or intermediate frequency signals to antennas40. Antennas40may include single antennas (single band, multi-band, etc.) and/or may include antenna arrays (e.g., phased antenna arrays) for handling millimeter wave signals (i.e., radio-frequency signals at RF frequencies such as 60 GHz). If desired, paths100may be configured to form a ring-shaped path. The illustrative network of antenna signal distribution paths100that is shown inFIG. 4is merely illustrative.

Antennas40may be located at the corners of device housing12of device10or may be located elsewhere within device10as described in connection withFIG. 3. Transceiver circuitry46may be located in a central location within housing12(e.g., in the center of housing12as shown inFIG. 4) or may be located in other portions of housing12. For example, portions of transceiver circuitry46may be co-located with antennas40(e.g., in a configuration in which each antenna array has local transceiver circuitry that communicates with a shared baseband processor). The configuration ofFIG. 4is merely illustrative.

To ensure that the wireless performance of device10is satisfactory, device10may be tested. As an example, control circuitry30may be used to run test software that directs wireless communications circuitry34to transmit and receive wireless signals during testing. Some wireless signals may be conveyed to external wireless test equipment. For example, some tests for device10may be performed by placing device10in a shielded wireless test chamber. The chamber may include test antennas. Wireless test equipment that is coupled to the test antennas may be used to wirelessly communicate with device10(e.g., the wireless test equipment and test antennas in the test chamber may be used to perform wireless over-the-air tests on device10). This type of wireless characterization procedure may be performed on representative devices10or on all devices10during manufacturing. Testing may identify faulty devices that are to be reworked or discarded and/or may be used in creating calibration data that is stored within devices10to calibrate devices10.

If desired, device10can also be wirelessly tested using over-the-air wireless test measurements that involve transmission and reception of wireless signals using only a transmitting antenna in device10and receiving antenna in device10. With this type of approach, control circuitry30directs wireless communications circuitry34to transmit test signals with a first antenna40while control circuitry30directs communications circuitry34to simultaneously receive the transmitted test signals with a second antenna40. The transmit and receive antennas of device10may be located at different portions of device10such as at different corners of housing12or may be located at different positions within a common antenna array (i.e., the transmit and receive antennas during a test may both be located within a common phased antenna array). In some tests, the identities of the transmit and receive antennas may be swapped (i.e., the antennas that were used as transmitting and receiving antennas may be used as receiving and transmitting antennas, respectively). Using measurements such as these, wireless circuit components such as phase shifters, filters, and amplifiers may be calibrated, antennas can be tested (e.g., to determine whether the antennas are properly coupled to their signal paths, to calibrate antenna tuning settings, etc.), and other wireless circuit measurements may be made. Examples of tests and measurements that may be performed by circuitry30in device10while transmitting antenna signals with a first antenna in device10and receiving the transmitted antenna signals with a second antenna in device10include, error vector magnitude measurements, radio-frequency bandwidth measurements, S-parameter measurements, receiver noise floor measurements, linearity, receiver blocking, etc.

Wireless circuitry34may include circuitry to facilitate loopback testing. As an example, a loopback circuit may be implemented to facilitate intermediate frequency (IF) signal quality and delay normalization measurements. If desired, an external tester may be used to calibrate a first antenna signal path (e.g., by inserting a probe into the path) before performing over-the-air tests or other wireless tests in which the first antenna signal path transmits signals that are received using a second antenna signal path. Couplers may be incorporated into the antenna signal paths of device10(e.g., to make S-parameter measurements). Mixing circuitry may be used to mix received radio-frequency signals down to direct-current (DC) levels suitable for digitization with analog-to-digital converter circuitry. Digitized signals can then be analyze by control circuitry30.

Using arrangements such as these or other suitable arrangements, multiple antenna signal paths in device10can be characterized and associated calibration data stored in device10. Initially a first path (and the components in that path) may be characterized. Using wireless communications between an antenna in the first path and an antenna in a second path, a second path may be calibrated using the known characteristics of the first path, and so forth, until all desired antenna signal paths in device10have been calibrated.

Consider, as an example, the illustrative configuration ofFIG. 5. As shown inFIG. 5, wireless circuitry34in device10may include multiple antennas such as antennas40-1and40-2. Antennas40-1and40-2may be mounted at different corners of device housing12, may be part of a common phased antenna array, or may be any other two antennas in device10.

Antenna40-1may form part of antenna signal path PATH1and antenna40-2may form part of antenna signal path PATH2. Paths PATH1and PATH2may be coupled to wireless transceiver circuitry118(e.g., transmitter and receiver circuitry and associated baseband processor circuitry) via paths100.

Each of the antenna signal paths ofFIG. 5may include electrical components such as output amplifiers104, input amplifiers102, phase shifters, filters, etc. Switching circuitry107may be coupled to ports a1, b1, a2, and b2of couplers106and may be configured to selectively route signals from any selected one of these ports to a desired output path116. Paths116may be coupled to paths100so that signals from paths116may be received and measured using the receivers of transceiver circuitry118.

Couplers106may be used to measure signals traveling in directions112and114on path PATH1and path PATH2. During testing, switching circuitry107may be adjusted by the control circuitry of device10to couple desired coupler ports to paths116. For example, switching circuitry107may be used to route signals from the coupler in PATH1to the receiver associated with path PATH2via the path116that is coupled to PATH2, so that those signals can be measured by that receiver. Using techniques such as these, S-parameter measurements can be made in wireless circuitry34.

A flow chart of illustrative steps involved in using circuitry of the type shown inFIG. 5to make S-parameter measurements on paths PATH1and PATH2are shown inFIG. 6.

At step120, the transmitter associated with path PATH1may be used to transmit signals through antenna40-1. While transmitting, switch107may be used to couple port a1of the coupler106in path PATH1to the receiver associated with path PATH2, so that the signal from port a1(which is proportional to the PATH1transmitted signal) can be measured.

As illustrated by wireless signals108, the signal that is wirelessly transmitted by path PATH1, is received over the air by antenna40-2in path PATH2. Accordingly, at step122, switch107may be configured to allow signal b2(which is proportional to the PATH2received signal) to be measured.

At step124, control circuitry30may compute S-parameter S21by calculating the ratio of measured values on ports b2and a1.

The S-parameter S12may be measured similarly. Switching circuitry107is first configured to allow the signal on port a2of the coupler in path PATH2to be measured using the receiver in path PATH1(step126). The signal on port b1may then be measured (step128). At step130, the ratio of the measured signals on ports b1and a2may be computed to determine S-parameter S12. As indicated by step132, additional S-parameter measurements can be made in the same fashion (e.g., by transmitting signals on one antenna while receiving signals with another antenna). If desired, all antenna signal paths in device10may be characterized using this type of self-testing scheme, thereby minimizing the use of external test equipment.

Another illustrative configuration for wireless circuitry34is shown inFIG. 7. In the example ofFIG. 7, baseband processor140is used to generate (and receive) antenna signals at intermediate frequencies IF. Paths100may be used to convey intermediate frequency signals IF or other antenna signals between baseband processor140and antenna signal paths (e.g., antenna signal paths in integrated circuit190or other wireless circuitry34). Control signals (e.g., signals from baseband processor140or other control circuitry30and/or direct-current power signals) may also be distributed using paths100.

Each signal path may include an associated antenna. For example, PATH1may include antenna40-1and PATH2may include antenna40-2. Transceiver circuitry118-1and118-2may include transmitter and receiver circuits and upconverters142and downconverters144. Upconverters142may convert IF signals to radio-frequency (RF) signals at higher frequencies. Downconverters144may convert RF signals to IF signals at lower frequencies. Path PATH1may include circuits such as filters F1and F1(e.g., adjustable channel filters to block out-of-band signals), adjustable phase shifter P1, adjustable gain output amplifier A1, and input amplifier A1′. Path PATH2may include circuits such as channel filters F2and F2′, adjustable phase shifter P2, adjustable gain amplifier A2, and amplifier A2′. In some embodiments, a switch such as switch146may be coupled between paths PATH1and PATH2. To measure signals on one of the antenna paths (e.g., PATH2), signals may be tapped from that path (see, e.g., signal path154) that are downconverted to direct-current (DC) frequencies by mixing these tapped signals with signals from radio-frequency local oscillator148using mixer150and digitizing these signals for analysis by control circuitry30using analog-to-digital converter152. As an alternative, mixer150′ may mix signals from path154with signals from path156(e.g., signals tapped from another antenna signal path such as PATH1) and may digitize these signals for control circuitry30using analog-to-digital converter152′.

A flow chart of illustrative steps involved in using wireless circuitry34of the type shown inFIG. 7to perform wireless self-test measurements is shown inFIG. 8. As shown inFIG. 8, a signal such as a modulated test signal may be transmitted on path PATH1at step170. The transmitted signal may be transmitted over the air as over-the-air antenna signal108by antenna40-1and received by antenna40-2in PATH2(step172). At step174, the received signal on path PATH2may be mixed to DC with mixer150or150′ and converted to digital using analog-to-digital converter152or152′.

As shown inFIG. 7, the portion of wireless circuitry34associated with paths PATH1and PATH2may be implemented on one or more integrated circuits such as antenna integrated circuit190. If desired, test results information may be conveyed from integrated circuit190to control circuitry30using intermediate frequency (IF) signal paths such as paths100. The received data may be analyzed using control circuitry30at step178. For example, control circuitry30may determine bit error rates and may otherwise evaluate the performance of wireless circuitry34. If desired, this process may be repeated (i.e., all of the antenna signal paths in circuitry34can be tested in a step-by-step fashion leveraging previously calibrated paths), as indicated by step180(in which a new antenna signal path for testing is selected) and line182.

A flow chart of illustrative steps involved in using wireless circuitry34ofFIG. 7to perform additional wireless self-test measurements is shown inFIG. 9. In the example ofFIG. 9, switch146ofFIG. 7is closed and opened. Initially, at step184, control circuitry30normalizes the path length delay between paths PATH1and PATH2by closing switch SW. In particular, the upconverter142of path PATH1is used to supply a continuous wave (CW) radio-frequency output signal over frequencies in a frequency band of interest to path PATH1while switch SW is turned on to short path PATH1to path PATH2. Phase shifter P2(and other circuit components such as adjustable filters and amplifiers) may be left in a default setting (as an example). At the same time, the downconverter144of PATH2is used by circuitry30to measure the magnitude and phase of signals received at transceiver118-2. The magnitude and phase information that is measured by transceiver118-2in this way may be stored by control circuitry30(e.g., baseband processor140or other control circuitry in device10) and used to define a zero state for each of the frequencies in the band of interest.

At step186, calibration operations are performed using the known zero state. In particular, control circuitry30may open switch SW to force transmitted signals on PATH1to be conveyed between PATH1and PATH2as over-the-air antenna signals108that pass from antenna40-1to antenna40-2. While these signals are being transmitted by the transmitter in transceiver circuit118-1on PATH1and received by the receiver in transceiver circuit118-2on PATH2, the components of PATH1(phase shifter, adjustable gain amplifier, channel filter, etc.) may be adjusted to calibrate these components. As an example, the phase shift setting of phase shifter P1may be adjusted from its default setting (e.g., 0°) through a full range of phase shifts (e.g., through a full 360° or more in phase). The resulting phase and magnitude of the received signals on PATH2may be measured using the downconverter144and receiver of transceiver circuit118-2). In this way, control circuitry30(e.g., baseband processor14) may collect calibration data for phase shifter P1(e.g., data that indicates how much phase shift is produced in path PATH2for a given change in the setting of phase shifter P1in PATH1). The calibration data may be stored in device10and, if desired, may be used to calibrate other devices10that include circuitry34(e.g., other devices10of the same type as device10that are being manufactured using the same type of components).

As indicated by step188, additional antenna signal paths (and, if desired, additional components such as adjustable gain amplifiers, channel filters, etc.) may be calibrated by repeating the operations of steps184and186on additional antenna signal paths in a stepwise fashion.