Keysight Technologies, Inc.

Troels Studsgaard Nielsen

Jan Verspecht

Keith Frederick Anderson

Jean-Pierre Teyssier

Felice Francesco Tafuri

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

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

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 system and method sequentially measure phases of selected comb teeth of a comb signal using a local oscillator (LO) signal whose frequency and phase are changed for each sequential measurement, and adjust the measured phases to account for the change of phase in the LO signal from measurement of one selected comb tooth to the next to ascertain reference phase differences between the selected comb teeth. The measured phases of the selected comb teeth are adjusted by applying a phase offset determined from a first phase and a second phase of a pilot tone which are measured using the LO signal, respectively, before and after the frequency and phase of the LO signal change from measurement of one comb tooth to the next. The frequency of the pilot tone is maintained to be substantially the same when measuring the first phase and the second phase of the pilot tone.

Method and system for calibrating phases of comb teeth in comb signal with pilot tone and using calibrated comb teeth phases to measure a device under test

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.

Growing community of inventors

Aalborg, Denmark

Troels Studsgaard Nielsen