Keysight Technologies, Inc.

Agilent Technologies, Inc.

Other

Jan Verspecht

Troels Studsgaard Nielsen

Keith Frederick Anderson

Jean-Pierre Teyssier

Augustine Stav

Bogdan Szafraniec

Joel P Dunsmore

David E Root

Frans Verbeyst

John Wood

Nicholas B Tuffilaro

Ewout Vandamme

A test circuit for measuring phase distortion includes a first laser, a second laser and a photo diode. The first laser is tuned to a first frequency fand generates a first optical signal. The second laser is tuned to a second frequency fand generates a second optical signal and phase modulates the second optical signal with a periodic signal with a repetition frequency fM. The photo diode receives and mixes the first optical signal and the second optical signal, and produces a first tone at a third frequency f, which is a carrier frequency equal to an absolute value of a difference between the second frequency fand the first frequency f, a second tone at a fourth frequency fat a difference between the third frequency fand the repetition frequency fM, and a third tone at a fifth frequency fat a sum of the third frequency fand the repetition frequency fM.

Phase distortion measurement

A system of measuring and correcting for distortions in homodyne systems and a method for operating a data processing system to provide an estimate of distortions in homodyne systems are disclosed. The method for operating a data processing system to provide an estimate of a distortion introduced by a homodyne system when the homodyne system processes a time a multi-tone time domain input signal, x(t), to obtain a time domain output signal, y(t) includes receiving a frequency spectrum, X(f), of the multi-tone time domain input signal, x(t) and measuring an output frequency spectrum, Y(f), when the homodyne system operates on x(t). A plurality of parameters of a model that represents a linear frequency response of the homodyne system when operating on X(f) to arrive at Y(f) by fitting the model to Y(f) and X(f) is determined, and the model is applied to X(f) and Y(f) to estimate the distortions.

Method and apparatus for characterizing homodyne transmitters and receivers

A system and method for operating a data processing system to modify a time domain input signal to a signal generator to correct for distortions introduced by the signal generator are disclosed. The method includes receiving a target signal specifying a signal to be generated by the signal generator and initializing an input signal with the target signal, the method includes

Method and apparatus for reducing non-linear distortion

A receiver-implemented method is for measuring a periodically modulated signal. The method includes applying a received periodically modulated signal to a mixer of a receiver, the periodically modulated signal not synchronized with the receiver, and tuning a local oscillator (LO) of the mixer using an estimate of actual carrier frequency and an estimate of an arbitrary waveform generator (AWG) sampling rate to obtain a digitized intermediate frequency (IF) signal. The method further includes applying a short time Fourier transform (STFT) to the digitized IF signal, extracting a carrier frequency offset and a AWG sampling rate offset based on the applied STFT, compensating for the carrier frequency offset, and applying a digital correction to the STFT to compensate for the AWG sampling rate offset. Compensating for the carrier frequency offset may include retuning the LO to obtain a new digitized IF signal to which the digital correction is applied.

Measurement of periodically modulated signals under non-coherent operating conditions

Nonlinear distortion of a device under test (DUT) is detected by obtaining measurements of a multi-tone input signal from a signal generator to a DUT, to obtain a measured multi-tone input signal. Measurements are also obtained of a multi-tone output signal from the DUT that is generated based on the multi-tone input signal, to obtain a measured multi-tone output signal. A correlated part of the measured multi-tone output signal that is correlated with the measured multi-tone input signal is determined insofar as the correlated part corresponds to a frequency response function of the DUT.

Nonlinear distortion detection

A method for operating a data processing system to determine the actual frequency of a transmitter LO in a transmitter that up converts a repetitive input time domain signal to a repetitive RF signal is disclosed. The method includes receiving a repetitive RF signal resulting from up converting the input time domain signal and assuming a value for the transmitter LO frequency. The received signal is down converted to an IF signal using the transmitter LO frequency, and digitizes to form a time domain record, The time domain record is converted to a sequence of frequency spectra, each frequency spectrum is characterized by a time index and a plurality of plurality of phasors. The frequency difference between the assumed LO transmitter and an actual LO transmitter frequency is determined by fitting the sequence of frequency spectra to a phase tracker function of the time index and the frequency difference.

Method for measuring frequency offset between an RF transmitter and a test receiver

An envelope behavioral model is developed and used in a system and method that simulates and predicts outputs of a non-linear component. An analyzer generates a test signal which is provided as input to the non-linear component. Model kernels representative of static and dynamic parts of the model are extracted from an output of the non-linear component responsive to the test signal. The dynamic part represents memory effects of the non-linear component. The model kernels are then used by a simulator to predict the output of the non-linear component responsive to signals of a modulation type.

Method and system for characterizing, modeling and simulating non-linear components having long term memory effects

A system and method prevent interference caused by images resulting from mixing an incoming periodically modulated RF signal with multiple LO signals generated by a LO in a receiver system. The method includes determining tone frequencies of multiple tones and determining tone spacing between adjacent tones in the periodically modulated RF signal using a known period of modulation of the periodically modulated RF signal; identifying a sampling rate of an ADC of the receiver system; determining a DFT record size of samples provided by the ADC based on at least the tone spacing and the ADC sampling rate; and determining LO frequencies of the multiple LO signals based on at least the DFT record size and the ADC sampling rate, such that images created by respectively mixing the determined LO frequencies with portions of the periodically modulated RF signal avoid interfering with direct mixing components of the plurality of tones.

Method and system of preventing interference caused by images

A method for calibrating a mixer, an apparatus using the calibrated mixer, and a method for using the apparatus to calibrate another mixer are disclosed. The method includes coupling a first RF signal characterized by a first timezero phase and a first RF frequency to the RF signal input. The method includes (a) coupling a first LO signal characterized by a first LO frequency and a first LO timezero phase to the LO signal input terminal; (b) determining an IF tone timezero phase of a tone from the IF signal output corresponding to the first LO signal; and (c) determining a first after LO signal path timezero phase from the IF tone and first LO timezero phase. Steps (a), (b), and (c) are repeated for second and third LO signals. An LO phase change as a function of frequency introduced by the LO signal path is then determined.

Method and apparatus for characterizing local oscillator path dispersion

A system and method sequentially measure the amplitude and phase of a signal in each of two or more noncontiguous spectrum segments (e.g., harmonics) which each include two or more portions which together span the spectrum segment, using a local oscillator (LO) signal whose frequency and phase change for each measurement. The measured phase of the signal for at least one of the portions in each spectrum segment is adjusted to account for the change of phase in the LO signal from measurement of one portion to another, using phases of one or more pilot tones measured in each portion. The phase-adjusted measurements of the output signal in the various portions are stitched together to determine the amplitude and phase of the output signal across the spectrum segment. The phase relationships between the spectrum segments are determined from phases of comb teeth of a comb signal measured in each spectrum segment.

Method and apparatus for spectral stitching discontinuous spectra using reference channel, pilot tones and comb signal

A system and method sequentially measure the amplitude and phase of an output signal of a device under test in each of two or more frequency ranges which together span the output signal spectrum, using a local oscillator (LO) signal whose frequency changes for each measurement. The measured phase of the output signal is adjusted for at least one of the frequency ranges to account for a change of phase in the LO signal from measurement of one frequency range to another frequency range, including applying to the measured phase a phase offset determined by measuring the phase of a pilot tone using the LO signal before and after the frequency of the LO signal changes from measurement of one frequency range to another. The phase-adjusted measurements of the output signal in the two or more frequency ranges are stitched together to determine the amplitude and phase of the output signal across the output signal spectrum.

Method and apparatus for spectral stitching using reference channel and a pilot tone

A system and method supply a test signal having a first tone at a first RF frequency and a second tone at a second RF frequency to a frequency converter; provide a local oscillator (LO) signal to the frequency converter, wherein an IF output signal of the frequency converter is supplied to an input of an intermediate frequency (IF) filter, in response to which the IF filter provides a filtered IF output signal; for each of N&#x3e;1 different LO frequencies, measure the filtered IF output signal at a pair of IF frequencies corresponding to differences between the first and second RF frequencies and the LO frequency, where the measurements of the filtered IF output signal measure time-invariant phase; and ascertain N&#x2212;1 values of phase dispersion D of the IF filter at N&#x2212;1 corresponding IF frequencies from the N measurements of the filtered IF output signal at the N different LO frequencies.

Method and system for characterizing phase dispersion in intermediate frequency channel of receiver

A system for measuring a full spectrum of a modulated output signal provided by a device under test (DUT) includes a signal generating device that provides a radio frequency (RF) stimulus signal to the DUT, and generates a trigger signal, where the DUT outputs the modulated output signal in response. A receiver, having an intermediate frequency (IF) bandwidth less than a total bandwidth of the modulated output signal, includes mixers, an analog-to-digital converter (ADC) triggered by the trigger signal, and a local oscillator (LO) that consecutively generates multiple LO signals having different LO frequencies. A harmonic phase reference (HPR) generator generates a repetitive HPR signal having an HPR bandwidth wider than the total bandwidth of the modulated output signal and a modulation repetition rate the same as that of the RF stimulus signal. The mixers consecutively mix the LO signals with the HPR signal and the modulated output signal to provide IF signals input to channels of the ADC to form ADC data records, respectively, that capture the full spectrum of the modulated output signal.

System and method of measuring full spectrum of modulated output signal from device under test

A method and system for predistorting signals provides a test signal to model a non-linear component. Model kernels representative of static and dynamic parts of the model are extracted from an output of the non-linear component responsive to the test signal. The dynamic part represents memory effects of the non-linear component. The model kernels are then used to calculate an inverse memory model component model. An input signal is predistorted using the inverse memory model.

Method for predistorting signals for non-linear components in the presence of long term memory effects

The present invention includes a method for generating a model of a circuit having an input port and an output port. The method determines an amplitude for current leaving the output port at a frequency &#x3c9;when a signal that includes a carrier at &#x3c9;modulated by a signal V(t) is input to the input port, wherein &#x3c9;is a harmonic of &#x3c9;. The determined amplitude is used to determine values for a set of constants, a, such that a function f(V,a) provides an estimate of the current, I(t), leaving the output port at a frequency &#x3c9;when a signal having the form is input to the input port. Here V(t) is a component of a set of values V. The f(V,a) are used to provide a simulator component adapted for use in a circuit simulator.

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Londerzeel, Belgium

Jan Verspecht