Nuno Miguel Gonçalves Borges de Carvalho

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In this paper, large-signal intermodulation distortion (IMD) sweet spots in microwave power amplifiers are studied and predicted using a new mathematical basis. The variations in the IMD versus drive pattern with active bias point and the terminating matching networks are investigated. This nonlinear distortion model enabled the design of power amplifiers(More)
This work presents a theoretical discussion on the ability of traditional noise power ratio (NPR) setups to characterize the in-band signal distortion of general RF circuits. It is shown that NPR tests are optimistic in estimating co-channel distortion, as they are blind for the signal-correlated components. Therefore, an alternative standard for co-channel(More)
122 June 2008 Multisine signals are used in the laboratory and in the field to provide a periodic, well-characterized waveform that can simulate complex modulated radio frequency (RF) signals. For example, in the field of wireless telecommunications, multisines are often used to provide realistic test signals that have statistics similar to various types of(More)
Analytic expressions are presented to predict the response of a 3rd order memoryless microwave circuit under a relative narrow-band spectrum composed of a general number of equally spaced tones with constant amplitude and correlated or uncorrelated phases. This enabled the study of the relation between two-tone and multi-tone characterization, and showed(More)
Computer simulation of general microwave nonlinear circuits excited by a large number of input tones is addressed. The algorithm, based on the spectral-balance method, uses novel index-vector and convolution-matrix generation techniques. That, in conjunction with a new nonlinear-device modeling approach (which directly takes into account the higher order(More)
The simulation of nonlinear RF circuits driven by digitally-modulated signals with multiple carriers is addressed by combining the Envelope Transient Harmonic Balance Method with the Artificial Frequency Mapping Technique. Specific application examples are considered, in particular the modeling of OFDM-based communications circuits. A mixer subject to a(More)
This paper deals in the integration of additive and nonlinear distortion noise contributions into a single new figure of merit: Noise and Distortion Figure, NDF. In the same way as traditional noise figure, NF, was conceived to be a measure of SNR degradation, NDF is now proposed as its extension to nonlinear systems, as a measure of SINAD degradation. NDF(More)
This article presents a measurement strategy and a characterization bench for the evaluation of Signal to Noise and Distortion Ratio (SNDR) in nonlinear wireless systems when in presence of memory effects. This measurement proposal will be combined with a closed analysis of the nonlinear mechanisms appearing in communication systems presenting memory. The(More)