Spectrally pure excitation signals: only a dream?

For accurate testing of a nonlinear device-under-test (DUT), the spectral purity of the input signal is utterly important. This paper describes a method to create very pure signals, such as sine waves, dual-tones, or multitones, using only power measurements. The signals are generated with an arbitrary waveform generator. Any unwanted spectral line is removed, independent of its exact origin. This allows to apply the correct signal to the DUT, even if the signal source is not perfect or is followed by filters or amplifiers with a small nonlinear distortion. Measurements are used to demonstrate the capabilities of the method.     

Measuring the sensitivity of microwave components to bias variations

This paper presents a method to measure the sensitivity of microwave components to memory effects caused by the dc biasing circuit. This allows us to determine the required (impedance) properties of the dc biasing circuit to reduce slow dynamics under a certain level. The proposed measurement technique is based on the nonlinear vectorial network analyzer, which allows us to measure not only the absolute magnitude but also the absolute phase relations between the waves. Superimposing a multisine excitation signal on the dc bias allows us to measure the slow dynamics caused by the dc biasing circuit as a function of frequency and input power. Furthermore, it is verified whether or not the measured phenomena depend on the type of excitation signal.     

Experimental characterization of the nonlinear behavior of RF amplifiers

Using specifically designed broadband periodic random excitation signals, the best linear approximation of RF amplifiers is measured. The proposed technique: 1) takes into account the measurement uncertainty and the nonlinear distortions and 2) detects, quantifies, and classifies the nonlinear distortions with confidence bounds. The approach is suitable for the experimental characterization of existing amplifiers.     

Measuring mixed-signal substrate coupling

A measurement method is proposed to characterize the substrate coupling between digital and analog sections of a mixed-signal CMOS chip. Induced noise and spurious signals can be measured by a custom-designed analog sensor. This paper proposes a method that, when given such a sensor, allows to measure the crosstalk between digital and analog chip sections. Calibrated sampling scope measurements illustrate the performance of the measurement setup     

A large-signal network analyzer: Why is it needed?

Good measurements are a major step towards good modeling. However, besides these measurements, modeling a system also requires a good insight in the system behavior. Do harmonics rise above the noise floor? Must they be taken into account during modeling? Is the system essentially dynamic or static? An answer to the above questions lies in the preprocessing of the measured data as obtained by the LSNA. This technique makes nonlinear effects more visible and allows understanding of the energy transport mechanisms behind the device operation     

Identifying the Structure of Nonlinear Perturbations in Mixers using Multisine Signals

The objective of this paper is to identify the position of the nonlinearity, a custom designed multisine signal that can be used to excite the signal path of the mixer. This special random-phase multisine signal with a random harmonic grid contains several carefully selected spectral lines that are left unexcited. These "holes" in the spectrum of the signal act as detectors for the presence and the location of the nonlinearities that deviate from the ideal. First the proposed detection algorithm was tested in a simulation to show that it can work in an ideally controlled environment. Afterwards, measurements are performed on a real mixer excited with a special odd random-phase multisine with a two-port large signal network analyzer (LSNA) and detect the position of the unwanted nonlinearities in the device model.     

Using ANOVA in a Microwave Round-Robin Comparison

This paper describes a procedure for comparing calibrated nonlinear radio-frequency (RF) measurements performed on a nonlinear device by five different measurement laboratories. The device under test (DUT) is a nonlinear active semiconductor device that is designed to generate a maximum number of harmonic tones. The goal is to obtain a simple automated method that detects if some laboratory had measurement problems during the measurement campaign. The developed comparison method is based on the analysis of variance (ANOVA) technique.     

Identification of linear systems in the presence of nonlineardistortions

This paper treats the identification of linear systems in the presence of nonlinear distortions. It extends the theory developed for measurement setups where the input is exactly known and the output is observed with errors (output error framework) to measurement setups where both the input and output are observed with errors (errors-in-variables framework). An appropriate measurement strategy and identification algorithm are presented     

Probability density function for frequency response function measurements using periodic signals

Frequency response function (FRF) measurements are often used to characterize linear dynamic systems. Today, uncertainty bounds on FRF measurements still are based on linear approximations, which are valid for sufficiently large input signal-to-noise-ratios (SNR) only. In this paper, exact uncertainty bounds are calculated, which are valid for any input SNR. These bounds are obtained via an analytic expression of the probability density function (pdf) of the FRF measurements. The results are valid for open- and closed-loop measurements, and the theory is illustrated on a real measurement example.