Abstract: A distortion measurement method uses alternative measurements to determine the distortion of a DUT, depending on the ratio of the distortion at an output of the DUT to distortion of a source stimulating the DUT. The method includes calibrating the VNA at a distortion frequency, measuring a first gain of the DUT with the source and the receivers of the VNA set to the distortion frequency, and measuring a second gain of the DUT with the source of the VNA set to a fundamental frequency and the receivers of the VNA set to the distortion frequency. When the second gain is less than a predesignated threshold, a match-corrected source signal is acquired and used with the first gain and the second gain to determine the distortion of the DUT. When the second gain is not less than the predesignated threshold, a match-corrected DUT output signal is measured and used with the first gain and the second gain to determine the distortion of the DUT.

Abstract: The response of a receiver is calibrated using frequency-shifted stimulus signals. A source provides a stimulus signal that has a non-zero bandwidth and an adjustable spectral position. A signal path coupled between the source and the receiver introduces distortion to the stimulus signal. The receiver acquires a first digital representation of the stimulus signal at an output of the signal path with the stimulus signal adjusted to a first spectral position and acquires a second digital representation of the stimulus signal at the output of the signal path with the stimulus signal adjusted to a second spectral position that is shifted from the first spectral position by a predetermined frequency offset. A processor, designates the distortion introduced to the stimulus signal by the signal path to be equivalent at the first spectral position and the second spectral position.

Abstract: A device package has a conductive substrate with at least one mounting site, and an insulating substrate with a first side on the side of the conductive substrate with the one or more mounting sites. The insulating substrate has at least one aperture providing access between a second side of the insulating substrate and the one or more mounting sites. The insulating substrate has one or more signal paths on the second side that couple the one or more apertures to one or more contact sites disposed about the insulating substrate. A series of conductive tabs is coupled to corresponding contact sites.

Abstract: A direct frequency synthesizer provides an output signal derived from a high frequency reference signal that is frequency divided and mixed to satisfy the coarse step synthesis requirements of an offset loop synthesizer. The absence of a VCO within the direct frequency synthesizer, provides the direct frequency synthesizer with lower phase noise than a typical PLL-based coarse step synthesizer. Though applicable to a variety of types of synthesizers and signal generators, the direct frequency synthesizer provides especially advantageous noise performance when used to generate an offset signal for an offset loop synthesizer of the first local oscillator of a spectrum analyzer, where the second local oscillator of the spectrum analyzer provides the reference signal for the direct frequency synthesizer.

Abstract: An optical frequency discriminator includes an interferometer cascaded with an absorption cell that provide a composite signal. A receiver samples a composite signal and maps to the sample positions of the acquired samples, corresponding optical frequencies of an applied optical signal.

Abstract: A pivoting optics mount includes an optical element set on an optics holder that has a pivot element. Three actuators included in the pivoting optics mount maintain a mating of the pivot element with a complementary pivot element. Adjusting the lateral displacement of a tip of one or more of the actuators provides angular adjustment of the optical element. The pivoting optics mount includes a frame that fixes the position of the complementary pivot element relative to the actuators.

Abstract: A high dynamic range receiver includes a detector that produces a current at a pair of terminals. A first gain element, implemented as a current-to-voltage converter for example, is coupled to the first terminal, receiving the current and generating a first output signal corresponding to the current. A second gain element, implemented as a current-to-voltage converter for example, is coupled to the second terminal, receiving the current and generating a second output signal corresponding to the received current. A switch selectively couples the first output signal or the second output signal to a port based on a comparison of at least one of the first output signal and the second output signal to a threshold.

Abstract: In a method for characterizing frequency translation devices (FTDs), a stimulus signal is applied to a first port of a frequency translation device and a drive signal is applied to a second port of the frequency translation device. A third port of the frequency translation device is coupled to an input of a filter. The frequency translation device, at the third port, provides a translated signal having a sum signal component and a difference signal component. A first, second and third reflection response to the applied stimulus signal are obtained with alternative terminations coupled to an output of the filter. The reflection responses include variations in either the sum signal component or the difference signal component as designated by the filter, where the variations depend on which of the alternative terminations is coupled to the output of the filter.

Abstract: A first system includes a converter, complex signal generator, exponentiator, FFT module and processor to estimate carrier frequency of a high symbol rate quadrature amplutide modulated (QAM) signal relative to a target carrier frequency. The converter converts the applied QAM signal to an intermediate frequency (IF) signal and digitizes the IF signal at a predesignated sample rate. The complex signal generator extracts a real component of the digitized IF signal, provides an imaginary component of the digitized IF signal and then combines the real component and the imaginary component in a complex signal. The exponentiator, raises the complex signal to a predesignated power and the FFT module performs a Fast Fourier Transform (FFT), having a predetermined number of samples, on the complex signal as raised to the predesignated power.

Abstract: In a shielding scheme for circuit boards, conductive shields have contoured mating surfaces that become flat, or co-planar, at the circuit board-shield interface when the shields are fastened to opposite sides of the circuit board. The contoured mating surfaces compensate for deformation of the shields resulting from the fastening so that uniform mechanical pressure is applied at all designated points along the circuit board-shield interface even though fastening points are intermittently spaced throughout the shields. When compressible conductive gaskets are optionally interposed between the shields and the circuit board, stops are included to accommodate for the thickness of the gasket. High signal isolation is achieved without correspondingly high contact area on the circuit board and without closely-spaced fastening points. Low assembly time and manufacturing cost results for shielded circuit board assemblies incorporating the shielding scheme.

Abstract: A spectral characterization method accurately characterizes an applied signal spectrum that has multiple, spectrally-separated signal peaks. The method detects signal peaks within the spectrum and measures the spectral content of that spectrum using a first measurement bandwidth that is sufficiently wide to encompass each of the signal peaks and accurately measure a signal component of the spectrum. Spectral content of the spectrum measured using a narrow measurement bandwidth that accurately characterizes a noise component of the spectrum. Signal-to-noise ratio for the signal peaks can be calculated based on the measurements performed using the first and second measurement bandwidths. The spectral characterization method is implemented using a spectral measurement instrument having an adjustable measurement bandwidth.

Abstract: A timebase establishes the timing of samples acquired by a signal sampler relative to a trigger signal that is synchronous with an input signal applied to the signal sampler. The synchronous trigger activates a first pair of samplers included in the timebase to acquire samples of a reference signal and of a shifted version of the reference signal provided within the timebase. A divider receives the reference signal and divides the frequency of the reference signal by a predesignated divisor, and a third sampler included in the timebase acquires samples of this divided reference signal, also according to the synchronous trigger. The samples of the input signal are acquired by the signal sampler according to the divided reference signal. A timing analyzer determines the timing of these acquired samples of the input signal relative to the synchronous trigger, based on the acquired samples of the reference signal, the shifted reference signal and the divided reference signal.

Abstract: A shielded serpentine extension, internal signal path and receptor result in a flexible shielded interface for a circuit board that can be formed consistent with efficient circuit board fabrication processes. The shielded serpentine extension, continuous with the circuit board, has a receptor at an end that is distal from the circuit board. The receptor has a signal contact and a shield contact adapted to receive a surface mount connector. A signal path internal to the serpentine extension couples the signal contact of the receptor to the circuit board. The serpentine extension has shielding disposed about the signal path that couples the shield contact to the circuit board.

Abstract: Compliance margin of a waveform is determined relative to a standard, indicating the extent to which the waveform either complies or fails to comply with the standard. An acquisition system captures the waveform of an applied signal in a display space, and a memory stores a representation of a series of scaled masks in the display space. Each scaled mask in the series is a version of the standard that is scaled relative to the standard according to a corresponding scale factor. A comparator determines which scaled masks in the series coincide with the waveform at one or more predesignated locations in the display space by comparing the waveform to the represented series of scaled masks at the one or more locations. An output device indicates the compliance margin of the waveform based on the corresponding scale factors of the scaled masks that coincide with the waveform at the one or more locations in the display space.

Abstract: A timebase establishes the timing of samples acquired by a signal sampler relative to a trigger signal that is synchronous with a signal applied to the signal sampler. A first pair of samplers included in the timebase acquires samples of a reference signal and of a shifted version of the reference signal provided within the timebase, according to a synchronous trigger, to establish a first time position on the reference signal. A second pair of samplers included in the timebase acquires samples of the reference signal and the shifted reference signal according to the synchronous trigger as delayed by a programmed time interval, to establish a second time position on the reference signal. While the programmed time interval is adjusted to designate timing of the sample acquisitions by the signal sampler, the two pairs of samplers in conjunction with a timing analyzer accurately determine the timing of these sample acquisitions based on the established time positions on the reference signal.

Abstract: A zero calibration system and method for an optical receiver include an illuminated photodetector, switchably coupled to an amplifier. The photodetector is de-coupled from the amplifier while illumination of the photodetector is maintained and an error signal is measured at the output of the amplifier The photodetector is then coupled to the amplifier and subsequent signals measured at the output of the amplifier are corrected according to the measured error signal, based on a comparison of the relative values of a feedback resistor, coupled between the output and an input of the amplifier, and an equivalent resistance of the photodetector. When the ratio of the feedback resistor to the equivalent resistance does not exceed a predetermined threshold, the subsequently measured signals at the output of the amplifier are corrected by offsetting the subsequently measured signals by the measured error signal.

Abstract: A method and apparatus accommodate for wavelength drift of optical sources. The apparatus includes an optical source having a wavelength control port and an output port, providing one or more optical signals that drift at a first rate. A signal generator within the apparatus provides a control signal to the wavelength control port of the optical source that causes wavelength variations to be superimposed on the wavelength drift of the one or more optical signals. The superimposed wavelength variations occur at a second rate that exceeds the first rate. The apparatus also includes a receiver coupled to the output port of the optical source, that receives the one or more optical signals having the superimposed wavelength variations. The receiver accommodates for the wavelength variations caused by the control signal, enabling a received wavelength to be distinguished from the drifting wavelength of the optical source. A corresponding method accommodates for wavelength drift of optical sources.

Abstract: A reflection measurement method and apparatus measures reflection characteristics of a device under test (DUT) when access to the DUT is through a dispersive element. The method and apparatus measure a composite reflection response of a network that includes the DUT and the dispersive element coupled to the DUT via a transmission line. A reflection response of the dispersive element is isolated from a remainder of the composite reflection response of the network. A set of transmission parameters for the dispersive element is generated from the isolated reflection response of the dispersive element and is then applied to the remainder of the composite reflection response of the network to extract the reflection characteristic of the DUT.

Abstract: Absolute delay of a FTD is characterized by applying a stimulus signal to a first port of the FTD. A second port of the FTD is coupled to a delay element having a known delay and a reflective termination. A drive signal is applied to a third port of the FTD. A time domain reflection response to the stimulus signal is obtained and a signal peak within the response that corresponds to a return signal from the reflective termination is identified. Absolute delay of the frequency translation device is then extracted based on the known delay of the delay element and a time that corresponds to the occurrence of the identified signal peak. Delay versus frequency is characterized by isolating a segment of the obtained time domain reflection response that corresponds to a return signal from the reflective termination. Inverse frequency transforming the isolated segment of the time domain reflection response provides delay characteristics of the FTD versus frequency.

Abstract: A vector stimulus/response system enables the vector responses of frequency translation devices (FTDs) to be accurately characterized. The system includes a source, having a predetermined source match, reflection tracking and directivity, that generates a stimulus signal. A receiver having a predetermined load match is also included in the system. The receiver measures a first series of responses of a reference translator to the stimulus signal, when the reference translator is coupled between the source and receiver. The reference translator has predetermined transmission characteristics, input match and output match. The receiver measures a second series of responses of a FTD to the stimulus signal. A processor generates a correction array from the first series of responses, the predetermined transmission characteristics, input match output match, source match, and the directivity, reflection tracking and load match.