The effect of a variation in tone spacing on the intermodulation performance of Class A and Class AB HBT power amplifiers

McIntosh, P.M.; Snowden, C.M.

doi:10.1109/mwsym.1997.602811

Cited by 14 publications

(7 citation statements)

References 9 publications

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“…This constituted a theoretical confirmation of many of the hypotheses previously anticipated [1]- [4]. However, it also supports experimental observations [6]. In that respect, it is worth telling that the conclusions drawn in [5] for the relation of IMD asymmetries and load termination at the baseband can easily be extrapolated to incorporate the baseband memory effects due to low-frequency dispersion or self heating [7].…”

Section: Introductionsupporting

confidence: 84%

“…A SYMMETRIES in the amplitudes of lower and upper intermodulation distortion (IMD) tones are often observed in real microwave devices subject to two-tone or multitone tests [1]- [6]. That is, two-tone IMD power associated to the response component is distinctly different from the one at .…”

Section: Introductionmentioning

confidence: 99%

“…Previously published works have already dealt with this problem [1]- [6], attributing asymmetric third-order IMD amplitude to various types of memory effects in PAs.…”

Section: Introductionmentioning

confidence: 99%

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A comprehensive explanation of distortion sideband asymmetries

Carvalho

Pedro

2002

IEEE Trans. Microwave Theory Techn.

165

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This paper presents a comprehensive study of intermodulation-distortion response asymmetries often observed in microwave nonlinear systems subject to a two-tone or multitone test. The reasons for the different amplitudes of the two adjacent tones are first investigated under small-and large-signal regimes, using a general circuit with frequency-dependent embedding impedances and resistive and reactive nonlinearities. It is shown that this intriguing phenomenon can be mainly attributed to the terminating impedances at the baseband or difference frequencies.Multitone behavior is also addressed and its main differences from the two-tone case explained. Those theoretical conclusions are then extrapolated for real circuits and validated by measured results obtained from microwave power amplifiers of two different technologies, i.e., a GaAs MESFET and an Si bipolar junction transistor.

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Section: Introductionsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

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A comprehensive explanation of distortion sideband asymmetries

Carvalho

Pedro

2002

IEEE Trans. Microwave Theory Techn.

165

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“…Some other factors contributing to the simulation inaccuracy are the following: (i) the bias decoupling network effect [13] that is not taken into account in a conventional simulation (in principle, this effect can be modeled by the instantaneous quadrature technique [3]), (ii) the difference between static and dynamic AM-AM and AM-PM characteristics [14], (iii) the thermal tone spacing effect [15], (iv) memory feedback effects [14].…”

Section: Approximation Accuracy and Measurement Noisementioning

confidence: 99%

On the accuracy of nonlinear microwave circuit simulation at the behavioral level

Loyka¹

13th International Conference on Microwaves, Radar and Wireless Communications. MIKON - 2000. Conference Proceedings (IEEE Cat.

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. However, for this kind of simulation techniques, the simulation accuracy is of primary concern due to the following reasons: (1) the problem under consideration is a nonlinear one (i.e. we must ensure wide dynamic range of the analysis and reasonable accuracy of the analysis at the same time that is not a simple task), and (2) behavioral-level techniques use the single-tone input-output envelope transfer functions (amplitude-to-amplitude (AM-AM) and amplitudeto-phase (AM-PM)) to characterize the nonlinear circuit operation in multiple-tone regime that gives several additional contributions to the entire simulation error. In this paper, we discuss some factors that influence the accuracy of behavioral-level simulation. For our investigation, we consider mainly two behavioral-level techniques: the quadrature modeling technique and the instantaneous quadrature techniqueThe main principle of these techniques is to use the AM-AM and AM-PM transfer functions obtained from single-tone measurements to simulate the circuit operation. While the quadrature modeling technique uses the complex envelope of a bandpass RF signal and the envelope transfer functions (AM-AM and AM-PM) of a nonlinear element,where A in and ϕ in -are the input signal's amplitude and phase (in the single-tone regime), and A out (A in ) and ϕ out (A in ) -are the same for the output signal (but now they are functions of the input signal amplitude due to the element's nonlinearity), the instantaneous quadrature technique uses instantaneous values of the RF signal and the instantaneous transfer functions of the nonlinear element. A system of two integral equations relates the envelope and instantaneous transfer factors [3]. IMPACT OF THE TRANSFER FUNCTIONS ON SIMULATION ACCURACYThus, the AM-AM and AM-PM transfer functions are the key component of the entire simulation method. When determining these functions (through measurements or circuit-level simulation), one should take into account the following: 1) AM-AM and AM-PM measured (or simulated) data are available for a finite set of points. During simulation, these data are usually required for another set of points. Thus, a mathematical technique is required to transform these data from one set of points to another. Besides, these data must be stored in some form (look-up tables, for example) and that technique can also be used for this purpose. This is a representation problem.2) While the importance of higher-order derivatives of elements' characteristics for the nonlinear circuitlevel simulation is well-recognized [4]-[5], the importance of higher-order d erivatives for the nonlinear behavioral-level simulation is not so well understood [6]. Let us now consider this issue in more details. Measured or circuit-level simulated AM-AM and AM-PM data contains not only the "real" characteristics (without any disturbance), but also measurement (or simulation) noise and distortions due to instruments' (or simulator) noise and inaccuracy. These noise and distortions may severe degrade the entire simulation ...

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“…OFDM signals are obtained by sums of a large number of independently modulated orthogonal carriers and, by the Central Limit Theorem can be modeled as complex Gaussian process with Rayleigh envelope distributim [4]. As a consequence OFDM signals exhibit a practical Peak-to-Mean-Power Ratio (PMPR) of abwr 10 dB and therefore they are very sensitive to nonlinear distortions [SI [6] [7]. The predistortion techniques [S] represent an adequate solution to reduce the AM/AM and AM/PM instantaneous non linearities introduced by HPAs even if the envelope clipping 0-7803-4900-8/98/$10.00 0 1998 IEEE cannot be avoided also for ideal predistortion [9].…”

Section: Introductionmentioning

confidence: 99%

HPA non-linear distortions in DVB-T systems simulation and measurement

Andreoli¹,

Banelli²,

Marrocolo³

et al.

1998 URSI International Symposium on Signals, Systems, and Electronics. Conference Proceedings (Cat. No.98EX167)

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The new digital standards adopted in Europe for broadcast communication systems use the Orthogonal Frequency Division Multiplexing (OFDM) technique [1][2] which is characterised by non constant envelope signals. This fact is in contrast with the employment of RF High Power Amplipers (HPAs) which are typically non linear and utilised with low Output Back Off (OBO) in order to maximise the power efficiency. The consequent generation of InterModulation Products (IMPs) is responsible for Bit Error Rate (BER) degradation and Adjacent Channel Interference (ACI). Aim of this work is to present the Itelco experience in this topics, outlining the DVB-T performance dependence from the OBO. Moreover the improvements achievable by AMIAM-AM/PM predistortion and by RF non-linear memory compensation will be analysed both by simulation and measurements.

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The effect of a variation in tone spacing on the intermodulation performance of Class A and Class AB HBT power amplifiers

Cited by 14 publications

References 9 publications

A comprehensive explanation of distortion sideband asymmetries

A comprehensive explanation of distortion sideband asymmetries

On the accuracy of nonlinear microwave circuit simulation at the behavioral level

HPA non-linear distortions in DVB-T systems simulation and measurement

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