Browsing by Author "Oliveira, Jorge dos Santos Freitas de"
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- An efficient time-domain simulation method for multirate RF nonlinear circuitsPublication . Oliveira, Jorge dos Santos Freitas de; Pedro, José CarlosThis paper describes a new computer-aided design tool especially conceived for the efficient time-domain simulation of highly heterogeneous nonlinear wireless communication circuits, i.e., combining RF and baseband analog circuitry and digital components. Using multirate Runge–Kutta algorithms within a multitime framework, to benefit from the different rates of variation of slowly varying (latent) and fast-varying (active) currents and voltages (state variables), we managed to solve the envelope transient regime of circuits excited by AM and PM RF carriers, in a highly efficient way. Indeed, with the adoption of convenient sampling rates for the multiple time representations of the slowly varying and fast-varying state variables, gains of more than one order of magnitude in simulation time are reported, even for an illustrative circuit example of very small size.
- An innovative time-domain simulation method for multirate RF circuit simulationPublication . Oliveira, Jorge dos Santos Freitas de; Pedro, J. C.This paper presents an innovative time-domain simulation method, especially conceived for simulating strongly nonlinear RF circuits whose state variables are all fluctuating in a fast-varying time scale, but evidence different time evolution rates in a slow envelope time scale. The method uses the mathematical method of lines based on modern multirate Runge-Kutta (MRK) schemes, and operates within a bivariate framework of an aperiodic slow time scale and a periodic fast time scale. This way, it can attribute different time-steps to slow and fast state variables in the envelope time evolution, considerably reducing the numerical simulation burden. Tests performed in an illustrative application example reveal, however, that its promising efficiency can be constrained by a stiffness restrictive scenario.
- An innovative time-domain simulation technique for strongly nonlinear heterogeneous RF circuits operating in diverse time-scalesPublication . Oliveira, Jorge dos Santos Freitas de; Pedro, José CarlosWith the advent of wireless transceiver reconfigurability, a need has been felt to take profit of digital signal processing tools, this way increasing RF circuits’ complexity and heterogeneity. Having this objective in mind, this paper presents an analytical formulation and a novel numerical method for simulating, in a very efficient way, strongly nonlinear heterogeneous RF circuits running in three different time-scales. In order to reduce the computational workload, a new multi-line double multi-rate shooting technique is proposed to operate within a multi-dimensional warped time framework. Obtained results of an illustrative circuit, reveal significant advantages in speed over previous methods recently proposed for the simulation of the same category of circuits.
- Análise de comportamentos multi-ritmo em sistemas electrónicosPublication . Oliveira, Jorge dos Santos Freitas deEsta tese insere-se na área da simulação de circuitos de RF e microondas, e visa o estudo de ferramentas computacionais inovadoras que consigam simular, de forma eficiente, circuitos não lineares e muito heterogéneos, contendo uma estrutura combinada de blocos analógicos de RF e de banda base e blocos digitais, a operar em múltiplas escalas de tempo. Os métodos numéricos propostos nesta tese baseiam-se em estratégias multi-dimensionais, as quais usam múltiplas variáveis temporais definidas em domínios de tempo deformados e não deformados, para lidar, de forma eficaz, com as disparidades existentes entre as diversas escalas de tempo. De modo a poder tirar proveito dos diferentes ritmos de evolução temporal existentes entre correntes e tensões com variação muito rápida (variáveis de estado activas) e correntes e tensões com variação lenta (variáveis de estado latentes), são utilizadas algumas técnicas numéricas avançadas para operar dentro dos espaços multi-dimensionais, como, por exemplo, os algoritmos multi-ritmo de Runge-Kutta, ou o método das linhas. São também apresentadas algumas estratégias de partição dos circuitos, as quais permitem dividir um circuito em sub-circuitos de uma forma completamente automática, em função dos ritmos de evolução das suas variáveis de estado. Para problemas acentuadamente não lineares, são propostos vários métodos inovadores de simulação a operar estritamente no domínio do tempo. Para problemas com não linearidades moderadas é proposto um novo método híbrido frequência-tempo, baseado numa combinação entre a integração passo a passo unidimensional e o método seguidor de envolvente com balanço harmónico. O desempenho dos métodos é testado na simulação de alguns exemplos ilustrativos, com resultados bastante promissores. Uma análise comparativa entre os métodos agora propostos e os métodos actualmente existentes para simulação RF, revela ganhos consideráveis em termos de rapidez de computação.
- Efficient methods for solving multi-rate partial differential equations in radio frequency applicationsPublication . Oliveira, Jorge dos Santos Freitas deIn telecommunication electronics, radio frequency applications are usually characterized by widely separated time scales. This multi-rate behavior arises in many kinds of circuits and increases considerably the computation costs of numerical simulations. In this paper we are mainly interested in electronic circuits driven by envelope modulated signals and we will show that the application of numerical methods based on a multi-rate partial differential equation analysis will lead to an efficient strategy for simulating this type of problems.
- Envelope transient simulation of nonlinear electronic circuits using multi-rate Runge-Kutta algorithmsPublication . Oliveira, Jorge dos Santos Freitas de; Araújo, A.Time-step integration is a popular technique commonly used for the envelope transient simulation of an electronic circuit. However, many kinds of circuits are characterized by widely separated time scales, which lead to significant computational costs when numerically solving its differential systems. Even so, this situation can be exploited in an efficient way using multi-rate methods, which integrate system components with different step sizes. In this paper two multi-rate Runge-Kutta schemes are studied and tested in terms of computational speed and numerical stability. The results for linear stability analysis here obtained are much more coherent with the characteristics of the methods than the ones previously presented in [6].
- A multiple-line double multirate shooting technique for the simulation of heterogeneous RF circuitsPublication . Oliveira, Jorge dos Santos Freitas de; Pedro, José CarlosThis paper describes a computer-aided design tool especially conceived for the efficient time-domain simulation of strongly nonlinear mixed digital, baseband, and RF circuits operating in multiple time scales. The proposed numerical method is based on a 3-D envelope oriented technique over an innovative multiple-line double multirate shooting strategy, and is tested with an illustrative circuit example. Significant gains in computation speed over previous methods recently proposed for the simulation of this category of circuits are reported, as the technique was tailored to take advantage of the circuits’ heterogeneity and stimulus time-rate disparity.
- A new mixed time-frequency simulation method for nonlinear heterogeneous multirate RF CircuitsPublication . Oliveira, Jorge dos Santos Freitas de; Pedro, J. C.This paper describes a new mixed time-frequency method especially conceived for the efficient simulation of nonlinear multirate RF circuits evidencing some heterogeneity. The proposed method splits the circuit into two subsets, and can be seen as a hybrid scheme combining the popular envelope transient harmonic balance (ETHB) technique with a purely time-marching engine. With this method, the hardest nonlinearities of the circuit are appropriately computed in a strictly time-domain approach, whereas the more moderate ones are processed in the frequency-domain. Simulation tests are performed with an illustrative circuit example, revealing gains in computation speed of more than one order of magnitude over mature ETHB.
- A new time-domain simulation method for highly heterogeneous RF circuitsPublication . Oliveira, Jorge dos Santos Freitas de; Pedro, José CarlosThis paper describes a new time-domain simulation method particularly amenable for highly heterogeneous nonlinear RF circuits as modern wireless transceivers that combine analog RF and both analog and digital base-band circuitry. It uses innovative multi-rate Runge-Kutta algorithms applied to the envelope transient method over a time-domain periodic steady-state technique (shooting), to efficiently resolve strongly nonlinear circuits excited by forcing functions of very distinct time-scales and exhibiting slow (latent) and fast-varying (active) state-variables. Attributing different time-steps to these latent and active state-variables speedup gains of more than 1-to- 7 in simulation time were obtained for even a circuit example of very small size.