NVNA versus LSNA: enemies or friends?

Abstract

N onlinearities are becoming very hot! After some years of hesitation, the high-frequency measurement world fi nally has acknowledged the need to measure the nonlinear behavior of a device or system correctly. Pushed by the modeling world, which clearly needs good nonlinear measurements to obtain good nonlinear models, some "nonlinear" measurement instruments were developed. Two different approaches to design a measurement instrument that is able to measure the nonlinear time domain waveforms correctly can be followed: a samplerbased methodology or a mixer-based methodology.Wendy Van Moer (wendy.vanmoer@vub.ac.be) and Liesbeth Gommé are with Vrije Universiteit Brussel, , over the years, both of the terms LSNA and NVNA have been used interchangeably to describe these and other similar instruments capable of measuring the vector nonlinear behavior of devices, circuits, and systems. A group of interested users formed the NVNA Users' Forum in 2002 to discuss measurement issues related to this broad class of instrumentation. The group currently meets each year at IMS, EuMW, and the fall ARFTG Microwave Measurement conference. For more information, visit http://www.arftg.org/about_ lsna.html.

Wideband radio frequency measurements: From instrumentation to sampling theory

“…1 it can be seen that the phase synchronization during the sweeps is achieved through an additional mixer and a harmonic phase reference located at port two. Such phase synchronization strategy requires accurate calibration and special hardware design which can be expensive [4].…”

“…The main advantage of the sampling-based measurement technique compared to the sweeping-based is the fact that since the whole spectrum of the incident waveform is measured in one single take, there is no need for relative phase synchronization between the spectral components, as is the case for sweepingbased measurement systems. Hence, the receivers hardware architectures are more simple and their respective measurements are much faster [4]. However, on the cost of a lower resolution due to the wide-band characteristic of the measurement which increases the noise level.…”

“…In Fig. 3, the waveforms are first conditioned through attenuators (ATT), down-converted/compressed by wide-band samplers, then amplified by narrow-band linear amplifiers and digitized by high resolution ADCs [4]. It should be noted that the measurement bandwidth of a real-time measurement receiver is set by its sampling rate.…”

A new method to measure pulsed RF time domain waveforms with a sub-sampling system

“…This amplifier was previously measured on a commercial NVNA setup and exhibits the same time domain waveforms for all those duty cycle values. For this kind of characterization, a NVNA needs the duty cycle value in order to correct the power as explained in equation (1), but the LSNA can adaptively sample the pulsed RF and extract automaticaly the correct RF magnitudes and phases within the pulse irrespective of its width. The minimal measurable pulse width has to be larger than the intermediate fundamental frequency period (8p,s in this example).…”

High resolution wideband calibration procedure for RF time-domain measurement of non-linear devices

“…They were developed in the frequency domain due to the lack of voltage and current calibrated probes at RF frequencies. The characterization of non-linear devices excited with CW RF large signals can be performed with calibrated setups using Large Signal Network Analyzers (LSNA) [1], [2] Non Linear Vectors Network Analyzers (NVNA) [3] and Digital Sampling Oscilloscopes (DSO) [4].…”