Specification of error amplifiers for use in feedforward transmitters

Wilkinson, R.J.; Kenington, P.B.

doi:10.1049/ip-g-2.1992.0075

Cited by 20 publications

(7 citation statements)

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“…The amplitude balance and phase error at a given frequency ultimately governs the resulting cancellation depth [3]. The true time delay determines the cancellation bandwidth that can be maintained at a given cancellation threshold [4,5].…”

Section: A Fundamental Performance Limiting Factorsmentioning

confidence: 99%

Frequency agile bandstop filter (FABSF)

Roussel

Nicholls

Wight

2008

2008 IEEE MTT-S International Microwave Symposium Digest

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The frequency agile bandstop filter (FABSF) is an RF system component that functions as a frequency agile tunable notch filter capable of rejecting the low-level noise in presence of a high-level signal such as the out-of-band noise at the output of a high-power amplifier.The FABSF finds application in a frequency agile duplexer (FAD) system architecture to be implemented in the RF front-end of frequency division duplex (FDD) radio.Index Terms -Flexible radio, base station, tunable filter, feedforward cancellation, frequency agile duplexer.

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Section: A Fundamental Performance Limiting Factorsmentioning

confidence: 99%

Frequency agile bandstop filter (FABSF)

Roussel

Nicholls

Wight

2008

2008 IEEE MTT-S International Microwave Symposium Digest

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“…Although a number of new methods have been proposed, feedforward remains one of the most popular technologies, due to its providing the highest amount of distortion cancellation [3][4][5][6][7][8][9]. Hence, many previous works involving its implementation and analysis have been published, in order to analyze or improve the feedforward system [3][4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…Hence, many previous works involving its implementation and analysis have been published, in order to analyze or improve the feedforward system [3][4][5][6][7][8][9]. Yang et al [9] reported a method of optimizing the 2 nd -loop parameters of a feedforward system using a simple mathematical model.…”

Section: Introductionmentioning

confidence: 99%

Experimental optimization of the 2nd loop configuration for feedforward amplifiers in terms of their efficiency and linearity

Jung

Lee

Yang

et al. 2006

Microw. Opt. Technol. Lett.

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are closely spaced, the quarter-wave transformers were designed corresponding to the geometric mean of the respective resonant frequencies. The simulated radiation patterns obtained using pattern multiplication were compared with the measured radiation pattern, as shown in Figures 4(a) and 4(b). The simulated side lobe levels of Ϫ15.8 dB vary by almost 1 dB, as compared to Ϫ15 dB of the measured side-lobe levels. The measurement was carried out in an open environment and the discrepancy between the simulated and measured results may be attributed to reflections from nearby objects. CONCLUSIONA dual-band linear nonuniform array has been investigated in this paper. An algorithm has been developed for optimizing the sidelobe level of a linear dual-band stub-loaded RMSA array with nonuniform interelement spacing. An eight-element array has been fabricated on glass epoxy substrate and the simulated and measured radiation patterns at both frequencies are shown to be in good agreement. It is shown that the side-lobe levels of a dual-band nonuniform array can be improved by increasing the number of elements.ABSTRACT: In this paper, we report the results of the experimental optimization of the 2 nd -loop configuration for feedforward amplifiers in terms of their efficiency and linearity. We consider two parameters in the 2 nd -loop of a feedforward amplifier: (i) the size ratio between the main and error amplifiers and (ii) the coupling factor of the error signal coupler. Experiments are performed using a multicarrier down-link WC-DMA signal under various configurations. The measured data, which are normalized with respect to the overall power capacity of the main and error amplifiers, show that, among the different 2 nd -loop configurations, the best compromised efficiency (13.4%) at a given adjacent channel leakage ratio (ACLR) level (Ϫ50 dBc) is observed for a size ratio of around 3.0 and a coupling factor of around 7.2 dB.

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“…The reason is the behavior of feedforward technique. AM-AM characteristic of main amplifier by(10) and feedforward amplifier by(42)…”

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confidence: 99%

An analytic approach for CDMA output of feedforward power amplifier

Rahmati

Abdipour

Mohammadi

et al. 2010

Analog Integr Circ Sig Process

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In this paper, a novel method is introduced to predict the Code-Division Multiple-Access (CDMA) output spectrum of an RF power amplifier linearized with feedforward technique based on transfer function. In this method, an RF power amplifier is modeled mathematically by nonlinear complex envelope transfer function based on AM-AM and AM-PM distortion diagrams. Using this model, analytic expressions of CDMA output spectrum of power amplifier is calculated. Having mathematical model of RF power amplifier leads to derive analytic expressions for InterModulation (IM) products in feedforward amplifier. Based on these expressions, IM products are related to nonlinear complex envelope transfer function of feedforward amplifier. Then, CDMA output spectrum of feedforward linearization technique is predicted. The loops imbalances in feedforward technique are considered in analysis. Finally, the results of derived expressions in MATLAB software are compared with ADS simulations results and good agreements were achieved. Employing this method gives insight for feedforward analysis and loops imbalances effects in feedforward amplifier for CDMA applications.

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Specification of error amplifiers for use in feedforward transmitters

Cited by 20 publications

References 1 publication

Frequency agile bandstop filter (FABSF)

Frequency agile bandstop filter (FABSF)

Experimental optimization of the 2nd loop configuration for feedforward amplifiers in terms of their efficiency and linearity

An analytic approach for CDMA output of feedforward power amplifier

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