Abstract: 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.

Abstract: A test system for testing multiple-input and multiple-output (MIMO) systems is provided. The test system may convey radio-frequency (RF) signals bidirectionally between a device under test (DUT) and at least one base station. The DUT may be placed within a test chamber during testing. An antenna mounting structure may surround the DUT. Multiple antennas may be mounted on the antenna mounting structure to transmit and receive RF signals to and from the DUT. A first group of dual-polarized antennas may be coupled to the base station through downlink circuitry. A second group of dual-polarized antennas may be coupled to the base station through uplink circuitry. The uplink and downlink circuitry may each include a splitter/combiner, channel emulators, amplifier circuits, and switch circuitry. The channel emulators and amplifier circuits may be configured to provide desired path loss, spatial interference, and channel characteristics to model real-world wireless network transmission.

Abstract: A test system for testing multiple-input and multiple-output (MIMO) systems is provided. The test system may convey radio-frequency (RF) signals bidirectionally between a base station emulator and a device under test (DUT). The DUT may be placed within a test chamber during testing. An antenna mounting structure may surround the DUT. Multiple antennas may be mounted on the antenna mounting structure to transmit and receive RF signals to and from the DUT. A first group of antennas may be coupled to the base station emulator through downlink circuitry. A second group of antennas may be coupled to the base station emulator through uplink circuitry. The uplink and downlink circuitry may each include a splitter, channel emulators, and amplifier circuits. The channel emulators and amplifier circuits may be configured to provide desired path loss and channel characteristics to model real-world wireless network transmission.

Abstract: An electronic device has wireless communications circuitry including an adjustable antenna system coupled to a radio-frequency transceiver. The adjustable antenna system may include one or more adjustable electrical components that are controlled by storage and processing circuitry in the electronic device. The adjustable electrical components may include switches and components that can be adjusted between numerous different states. The adjustable electrical components may be coupled between antenna system components such as transmission line elements, matching network elements, antenna elements and antenna feeds. By adjusting the adjustable electrical components, the storage and processing circuitry can tune the adjustable antenna system to ensure that the adjustable antenna system covers communications bands of interest.

Abstract: An electronic device such as a cellular telephone may include transceiver circuitry for handling wireless communications. The transceiver circuitry may include a transceiver such as a cellular telephone transceiver or a wireless local area network receiver and may include a satellite positioning system receiver. Radio-frequency circuitry may be used to couple the transceiver circuitry to antenna structures. When operating the transceiver in different modes of operation, the radio-frequency circuitry may be adjusted to optimize performance. Adjustments to the radio-frequency circuitry may impose phase offsets on satellite positioning system signals that are received through the antenna structures and radio-frequency circuitry. These phase offsets which would otherwise cause degradation in the satellite positioning system receiver can be compensated by applying stored compensating phase offset values to the satellite positioning system receiver during operation.

Abstract: A wireless electronic device may serve as a device under test in a test system. The test system may include an array of over-the-air antennas that can be used in performing over-the-air wireless tests on the device under test (DUT). A channel model may be used in modeling a multiple-input-multiple-output (MIMO) channel between a multi-antenna wireless base station and a multi-antenna DUT. The test system may be configured to perform over-the-air tests that emulate the channel model. A design and analysis tool may be used to identify an optimum over-the-air test system setup. The tool may be used in converting a geometric model to a stochastic model for performing conducted tests. The tool may be used in converting a stochastic model to a geometric model and then further convert the geometric model to an over-the-air emulated stochastic model. The over-the-air emulated stochastic model may be used in performing conducted tests.

Abstract: A test system for testing multiple-input and multiple-output (MIMO) systems is provided. The test system may convey signals bidirectionally between two test chambers. Each test chamber may be lined with foam to minimize electromagnetic reflections. Each test chamber may include structure three-dimensional array of test antennas. The test antennas may be mounted in a sphere using an antenna mounting structure. The antenna mounting structure may include multiple rings of different sizes. Test antennas may be embedded in the inner walls of the antenna mounting structure. There may be multiple receiving antennas located in each test chamber. One test chamber may include a device under test inside an array of test antennas and another test chamber may include base station antennas inside another array of test antennas. Signals may be conveyed between the test chambers using channel emulators.