The method of envelope currents for rapid simulation of weakly nonlinear communications circuits

Borich, V.; East, J.R.; Haddad, G.I.

doi:10.1109/mwsym.1999.779550

Cited by 13 publications

(13 citation statements)

References 9 publications

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“…In this paper, an efficient technique proposed by Borich et al [5] for the simulation of weakly nonlinear circuits, the method of EC, is followed. For explanation purposes, let us review its development in a concise way.…”

Section: Theoretical Discussionmentioning

confidence: 99%

“…The predominant technique of harmonic balance (HB) provides precise results, but has the disadvantage of a high computational cost due to the large number of frequency components to be considered in communication systems driven with digitally modulated signals. Another technique, envelop transient analysis [4], decouples RF and baseband spectra, thus gaining computational efficiency but retaining much of the simulation time.Other techniques to simulate nonlinear circuits have recently been presented: the method of envelop currents (EC) [5], which is an alternative solution based on the method of nonlinear currents (NC) that exploits the weakly nonlinear characteristics of communication circuits to accomplish a great improvement in simulation speed; and a new envelope currents method, presented by some of the authors [6], that aims to evaluate nonlinear characteristics of communication circuits which represents a trade-off between precision and computational cost. The most relevant advantage of the EC method is its efficiency, which is especially notable when digitally modulated excitations are used, as in the case of modern mobile and wireless communication systems.…”

mentioning

confidence: 99%

“…However, when the driving sources are narrowband communication signals, solving the NC equation system requires a large simulation time. Borich et al [5] proposed the method of EC as a simple approach to the efficient computation of this equation system in the case of narrowband modulated excitations, taking the form of the real part of the product of the excitation-signal complex envelope and an exponential function at the carrier frequency c ϭ 2f c .With an input signal expressed in terms of its complex envelope, any circuit variable x(t) takes the following general form for the n th -order nonlinear current approximation: (1) where x k (t) is the complex envelope of the signal around the k th harmonic of c .Taking into consideration that the components of x n (t) which are centered at Ϫ c , . .…”

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confidence: 99%

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Circuit‐level simulation of W‐CDMA communication systems applied to the analysis of nonlinear distortion

Madero‐Ayora

Reina‐Tosina

Freire‐Pérez

et al. 2004

Micro & Optical Tech Letters

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Different circuit-level approaches to analyze the effects of nonlinear distortion on coded division multiple access (CDMA) wireless INTRODUCTIONThe interest in a precise approach to analyze the effects of nonlinear distortion in modern mobile and wireless communication systems is still generating a great effort in the development of simulation techniques [1]. Nonlinear devices generate co-channel and adjacent-channel interference due to intermodulation and spectral regrowth. Therefore, the prediction of nonlinear characteristics such as adjacent channel power rejection (ACPR), constellation distortion, and noise power ratio (NPR) in wireless communication systems is an essential task. This paper aims to simulate communications signals in the presence of a channel with mild nonlinearities, where it is necessary to take into account memory effects. A device is said to be memoryless when the output signal at any time sample is only a function of the input at that instant. Unfortunately, many nonlinear devices do not behave like this. Memory effects are defined as variations in the amplitude and phase of the distortion components caused by changes in modulation frequency and are attributed to thermal and electrical effects. It is necessary to emphasize the importance of obtaining an accurate model for the nonlinearities of the device, apart from using an efficient simulation method in order to achieve the best results.A number of models have been reported during the last few years to account for the effects of nonlinear distortion. Starting with the most simple representation, behavioral modeling allows a quick estimation of nonlinear performance. As an example, we can cite Saleh's model [2], which provides AM-AM and AM-PM conversions for a TWT amplifier. However, these conversion characteristics are extracted using a single-tone excitation and cannot accurately model memory effects in amplifiers. Another example of a memoryless formulation for the effects of nonlinear distortion on CDMA communication systems was presented in [3]. Considering that in mobile communications the bandwidth of each RF channel is much smaller than the carrier frequency, the RF signal can be represented as a narrowband passband signal using its complex envelope. In [3], a relation between the input and the output complex envelopes was proposed.Nevertheless, the importance of considering the memory effects on the nonlinearity recommends choosing circuit-level approaches, which present more accurate results at the cost of longer simulation times. The predominant technique of harmonic balance (HB) provides precise results, but has the disadvantage of a high computational cost due to the large number of frequency components to be considered in communication systems driven with digitally modulated signals. Another technique, envelop transient analysis [4], decouples RF and baseband spectra, thus gaining computational efficiency but retaining much of the simulation time.Other techniques to simulate nonlinear circuits have recently been ...

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Section: Theoretical Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Circuit‐level simulation of W‐CDMA communication systems applied to the analysis of nonlinear distortion

Madero‐Ayora

Reina‐Tosina

Freire‐Pérez

et al. 2004

Micro & Optical Tech Letters

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“…The method of envelope simulation combines features of time-and frequency-domain representation, offering a fast and complete analysis of such narrow bandwidth signals [2][3][4][5]. In envelope simulation, the time step for simulation can be as small as 1/2B, where B is the bandwidth of the bandpass signal, compared to the time step of ( )…”

Section: Introductionmentioning

confidence: 99%

Envelope simulation by MATLAB-compatible models of a SAR system

Jiang¹,

Zhang

2009

2009 2nd Asian-Pacific Conference on Synthetic Aperture Radar

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Fast and accurate system behavior simulation is an important technique for developing advanced radar system, Envelope simulation has been proved to be an efficient tool for analyzing and simulating narrow bandwidth system, such as communication system and radar system. In this work a common model for the envelope simulation of the transmitter and receiver of a SAR system is presented. Experimental results validate the reliability and efficiency of the proposed simulation method.

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“…The large nuniber of frequency components to be considered in these systems requires excessive resoiirces and very long simulation Limes using techniques like harmonic balance [I] or time domain techniques 121. A more efficient algorithm has been proposed in [3] extending the Nonlinear Currents method (NC) to the Envelope Currents method (EC). However, since the NC method has poor convergence properties and is an unmanageable technique when the order n of the nonlinearity increases, the method in I31 is limited to nonlinear systems excited by weak input signals.…”

Section: Introductionmentioning

confidence: 99%

Envelope currents method with extended dynamic range for the simulation of nonlinear communication circuits

Crespo‐Cadenas¹,

Reina‐Tosina²

2003

33rd European Microwave Conference Proceedings (IEEE Cat. No.03EX723C)

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Abstmct-A novel approach t o analyze the effects of nonlinear distortion in communication circuits is reported based on a recursive algorithm. I n each iteration a time-varying linear circuit excited by appropriate nonlinear currents obtained from an expansion of the nonlinearity is analyzed. This procedure has been applied to a common-source HEMT amplifier excited with a single tone and results show a very fast convergence together with a high dynamic range. The technique was used in the evaluation of the spectral regrowth and constellation distortion of a QPSK signal with raised cosine and root raised cosine conforming pulses p m duced by the amplifier at 5.8 GHz I . INTRODUCTIONThe design of wireless communications systems requires precise circuit level simulation t o predict nonlinear characteristics like adjacent channel power rejection ( ACPR)? constellation distortion and noise power ratio (NPR). The large nuniber of frequency components to be considered in these systems requires excessive resoiirces and very long simulation Limes using techniques like harmonic balance [I] or time domain techniques 121. A more efficient algorithm has been proposed in [3] extending the Nonlinear Currents method (NC) to the Envelope Currents method (EC). However, since the NC method has poor convergence properties and is an unmanageable technique when the order n of the nonlinearity increases, the method in I31 is limited to nonlinear systems excited by weak input signals. This restriction prevents the application of this technique to circuits operating with signal levels for which the study of nonlinear distortion is more important, i.e. near compression point. In this paper, we propose a new method of nodal analysis instead of the NC method. The basic idea behind this rnetlrod is to express the output of the circuit as a sun1 of incremental voltages, each one of them is the solution of a timevarying linear circuit excited by a nonlinear current. The time dependence of this changeless linear circuit a,nd its exciting noillinear curreiits are updated at cacfi step of the iterative process. This technique exhibits faster THEORETICAL D~SCUSSIONFor the sake of clarity, let consider a single node nonlinear circuit driven by the excitation current I, + is(t). The integrodifferential equation can be symholically expressed aswith w ( t ) being the node voltage, and I ( v ) , c(v)du/dt are the currents across a nonlinear conductance and a nonlinear capacitance, respectively. L[.] represents a linear operator.In the present approach w ( t ) is given 5y 1) = " 0 + 21, + . . . + + sw, = c7, + sun( 2 ) The DC voltage W O is calculated considering that only I, is present in (1). Expanding I(") and c ( v ) in Taylor series about ug and using (2) with n = 1, equation (1) yields + c(u0)-"1 = Zb (3) at dl for the first incremental voltage V I , so that it is computed in the same form as the linear term in the standard NC method. Thus, the first residnal voltage Swl satisfies the equation dv du 1LIbVl] + I(v) + c(n);ii. = q u o ) +g(vo)Vl...

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The method of envelope currents for rapid simulation of weakly nonlinear communications circuits

Cited by 13 publications

References 9 publications

Circuit‐level simulation of W‐CDMA communication systems applied to the analysis of nonlinear distortion

Circuit‐level simulation of W‐CDMA communication systems applied to the analysis of nonlinear distortion

Envelope simulation by MATLAB-compatible models of a SAR system

Envelope currents method with extended dynamic range for the simulation of nonlinear communication circuits

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