Abstract: Radio frequency test systems for characterizing antenna performance in various radio coexistence scenarios are provided. In one suitable arrangement, a test system may be used to perform passive radio coexistence characterization. During passive radio coexistence characterization, at least one signal generator may be used to feed aggressor signals directly to antennas within an electronic device under test (DUT). The aggressor signals may generate undesired interference signals in a victim frequency band, which can then be received and analyzed using a spectrum analyzer. During active radio coexistence characterization, at least one radio communications emulator may be used to communicate with a DUT via a first test antenna. While the DUT is communicating with the at least one radio communications emulator, test signals may also be conveyed between DUT 10 and a second test antenna. Test signals conveyed through the second test antenna may be used in obtaining signal interference level measurements.

Abstract: Test systems for characterizing devices under test (DUTs) are provided. A test system for testing a DUT in a shunt configuration may include a signal generator and a matching network that is coupled between the signal generator and the DUT and that is optimized to apply desired voltage/current stress to the DUT with reduced source power. The matching network may be configured to provide matching and desired stress levels at two or more frequency bands. In another suitable embodiment, a test system for testing a DUT in a series configuration may include a signal generator, an input matching network coupled between the DUT and a first terminal of the DUT, and an output matching network coupled between the DUT and a second terminal of the DUT. The input and output matching network may be optimized to apply desired voltage/current stress to the DUT with reduced source power.

Abstract: A test system for testing an antenna tuning element is provided. The test system may include a tester, a test fixture, and a probing structure. The probing structure may include probe tips configured to mate with corresponding solder bumps formed on a device under test (DUT) containing an antenna tuning element. The DUT may be tested in a shunt or series configuration. The tester may be electrically coupled to the test probe via first and second connectors on the test fixture. An adjustable load circuit that is coupled to the second connector may be configured in a selected state so that a desired amount of electrical stress may be presented to the DUT during testing. The tester may be used to obtain measurement results on the DUT. Systematic effects associated with the test structures may be de-embedded from the measured results to obtain calibrated results.

Abstract: Electronic devices may include antenna structures. The antenna structures may form an antenna having first and second feeds at different locations. A first transceiver may be coupled to the first feed using a first circuit. A second transceiver may be coupled to the second feed using a second circuit. The first and second feeds may be isolated from each other using the first and second circuits. The second circuit may have a notch filter that isolates the second feed from the first feed at operating frequencies associated with the first transceiver. The first circuit may include an adjustable component such as an adjustable capacitor. The adjustable component may be placed in different states depending on the mode of operation of the second transceiver to ensure that the first feed is isolated from the second feed.

Abstract: Test systems for characterizing devices under test (DUTs) are provided. A test system for testing a DUT in a shunt configuration may include a signal generator and a matching network that is coupled between the signal generator and the DUT and that is optimized to apply desired voltage/current stress to the DUT with reduced source power. The matching network may be configured to provide matching and desired stress levels at two or more frequency bands. In another suitable embodiment, a test system for testing a DUT in a series configuration may include a signal generator, an input matching network coupled between the DUT and a first terminal of the DUT, and an output matching network coupled between the DUT and a second terminal of the DUT. The input and output matching network may be optimized to apply desired voltage/current stress to the DUT with reduced source power.

Abstract: An electronic device may be provided with a housing. The housing may have a periphery that is surrounded by peripheral conductive structures such as a segmented peripheral metal member. A segment of the peripheral metal member may be separated from a ground by a slot. An antenna feed may have a positive antenna terminal coupled to the peripheral metal member and a ground terminal coupled to the ground and may feed both an inverted-F antenna structure that is formed from the peripheral metal member and the ground and a slot antenna structure that is formed from the slot. Control circuitry may tune the antenna by controlling adjustable components that are coupled to the peripheral metal member. The adjustable components may include adjustable inductors and adjustable capacitors.

Abstract: Radio frequency test systems for characterizing antenna performance in various radio coexistence scenarios are provided. In one suitable arrangement, a test system may be used to perform passive radio coexistence characterization. During passive radio coexistence characterization, at least one signal generator may be used to feed aggressor signals directly to antennas within an electronic device under test (DUT). The aggressor signals may generate undesired interference signals in a victim frequency band, which can then be received and analyzed using a spectrum analyzer. During active radio coexistence characterization, at least one radio communications emulator may be used to communicate with a DUT via a first test antenna. While the DUT is communicating with the at least one radio communications emulator, test signals may also be conveyed between DUT 10 and a second test antenna. Test signals conveyed through the second test antenna may be used in obtaining signal interference level measurements.

Abstract: A test system for testing an antenna tuning element is provided. The test system may include a tester, a test fixture, and a probing structure. The probing structure may include probe tips configured to mate with corresponding solder bumps formed on a device under test (DUT) containing an antenna tuning element. The DUT may be tested in a shunt or series configuration. The tester may be electrically coupled to the test probe via first and second connectors on the test fixture. An adjustable load circuit that is coupled to the second connector may be configured in a selected state so that a desired amount of electrical stress may be presented to the DUT during testing. The tester may be used to obtain measurement results on the DUT. Systematic effects associated with the test structures may be de-embedded from the measured results to obtain calibrated results.

Abstract: A wireless electronic device may contain an antenna tuning element for tuning the device's operating frequency range. The antenna tuning element may include radio-frequency switches, continuously/semi-continuously adjustable components such as tunable resistors, inductors, and capacitors, etc. A test system may be used to measure the radio-frequency characteristics associated with the tuning element assembled with an electronic device. The test system may include a test host, a test chamber, a signal generator, power meters, and radio-frequency testers. The electronic device under test (DUT) may be placed in the test chamber. The signal generator may generate radio-frequency test signals for energizing the antenna tuning element. The power meters and radio-frequency testers may be used to measure conducted and radiated signals emitted from the DUT while the DUT is placed in different desired orientations. A phantom object is optionally placed in the vicinity of the DUT to simulate actual user scenario.

Abstract: A wireless electronic device may contain at least one antenna tuning element for use in tuning the operating frequency range of the device. The antenna tuning element may include radio-frequency switches, continuously/semi-continuously adjustable components such as tunable resistors, inductors, and capacitors, and other load circuits that provide desired impedance characteristics. A test station may be used to measure the radio-frequency characteristics associated with the tuning element. The test station may provide adjustable temperature, power, and impedance control to help emulate a true application environment for the tuning element without having to place the tuning element within an actual device during testing. The test system may include at least one signal generator and a tester for measuring harmonic distortion values and may include at least two signal generators and a tester for measuring intermodulation distortion values.

Abstract: Methods and apparatus for conditioning communications signals based on detection of high-frequency in the polar domain. High-frequency events detected in a phase-difference component of a complex baseband signal in the polar domain are detected and used as a basis for performing hole-blowing on the complex baseband signal in the quadrature domain and/or nonlinear filtering either or both the magnitude and phase-difference components in the polar domain. Alternatively, high-frequency events detected in the phase-difference signal that correlate in time with low-magnitude events detected in a magnitude component of the complex baseband signal are used as a basis for performing hole-blowing on the complex baseband signal in the quadrature domain and/or nonlinear filtering either or both the magnitude and phase-difference components in the polar domain.

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 modulation system includes an amplitude modulation path and a phase modulation path coupled to the amplitude modulation path. One of the amplitude modulation path and the phase modulation path receive a reduced current such that the reduced current reduces power consumption by the system. Preferably, the amplitude modulation path receives the reduced current. The amplitude modulation path has a first set of components and a second set of components. The first set of components consumes less power by using slower operation. The second set of components consumes less power by effectively not operating, or being turned off.

Abstract: This invention, generally speaking, modifies pulse amplitude modulated signals to reduce the ratio of average power to minimum power. The signal is modified in such a manner that the signal quality remains acceptable. The signal quality is described in terms of the Power Spectral Density (PSD) and the Error Vector Magnitude (EVM).

Abstract: Methods and apparatus for conditioning communications signals based on detection of high-frequency in the polar domain. High-frequency events detected in a phase-difference component of a complex baseband signal in the polar domain are detected and used as a basis for performing hole-blowing on the complex baseband signal in the quadrature domain and/or nonlinear filtering either or both the magnitude and phase-difference components in the polar domain. Alternatively, high-frequency events detected in the phase-difference signal that correlate in time with low-magnitude events detected in a magnitude component of the complex baseband signal are used as a basis for performing hole-blowing on the complex baseband signal in the quadrature domain and/or nonlinear filtering either or both the magnitude and phase-difference components in the polar domain.

Abstract: The present invention, generally speaking, provides a VCO linearization technique applicable to advanced loop architectures. In particular, the linearization technique is applicable to a mostly-digital frequency locked loop (FLL), phase locked loop (PLL) or the like using multi-point modulation. In an exemplary embodiment, a correction table is used to form a corrected control variable that affects one modulation point only (e.g., a fast modulation path) of the multi-point modulation circuit. The other modulation point (e.g., a slow modulation path) of the multi-point modulation circuit is controlled in accordance with an error-forming circuit including a loop filter. The use of correction within the fast path enables the VCO to achieve more rapid phase changes than would otherwise be possible, an advantage in high-data-rate communications applications, for example.

Abstract: A modulation system includes an amplitude modulation path and a phase modulation path coupled to the amplitude modulation path. One of the amplitude modulation path and the phase modulation path receive a reduced current such that the reduced current reduces power consumption by the system. Preferably, the amplitude modulation path receives the reduced current. The amplitude modulation path has a first set of components and a second set of components. The first set of components consumes less power by using slower operation. The second set of components consumes less power by effectively not operating, or being turned off.

Abstract: This invention, generally speaking, modifies pulse amplitude modulated signals to reduce the ratio of average power to minimum power. The signal is modified in such a manner that the signal quality remains acceptable. The signal quality is described in terms of the Power Spectral Density (PSD) and the Error Vector Magnitude (EVM).

Abstract: Methods of and apparatus for digitally controlling, with sub-sample resolution, the relative timing of the magnitude and phase paths in a polar modulator. The timing resolution is limited by the dynamic range of the system as opposed to the sample rate. The methods and apparatus of the invention use a digital filter to approximate a sub-sample time delay. Various techniques for approximating a sub-sample time delay using digital signal processing may be used to achieve the approximation. Ideally, the filter will have an all-pass magnitude response and a linear phase response. In practice, the magnitude may be low-pass and the phase may not be perfectly linear. Such deviation from the ideal response will introduce some distortion. However, this distortion may be acceptably small depending on the particular signal being processed.

Abstract: Methods of and apparatus for digitally controlling, with sub-sample resolution, the relative timing of the magnitude and phase paths in a polar modulator. The timing resolution is limited by the dynamic range of the system as opposed to the sample rate. The methods and apparatus of the invention use a digital filter to approximate a sub-sample time delay. Various techniques for approximating a sub-sample time delay using digital signal processing may be used to achieve the approximation. Ideally, the filter will have an all-pass magnitude response and a linear phase response. In practice, the magnitude may be low-pass and the phase may not be perfectly linear. Such deviation from the ideal response will introduce some distortion. However, this distortion may be acceptably small depending on the particular signal being processed.