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  • Resultat 11-20 av 102
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11.
  • Amin, Shoaib, 1985-, et al. (författare)
  • Characterization and modeling of RF amplifiers with multiple input signals
  • 2016
  • Konferensbidrag (refereegranskat)abstract
    • A characterization technique for RF PAs excited with multiple signals is presented. The technique can be used for characterization of memory effects in IM/CM products. The extracted information can in return be of use for modifying behavioral models to better capture memory in IM/CM products.
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12.
  • Amin, Shoaib, et al. (författare)
  • Characterization of concurrent dual-band Power Amplifiers using a dual two-tone excitation signal
  • 2015
  • Ingår i: IEEE Transactions on Instrumentation and Measurement. - : IEEE Press. - 0018-9456 .- 1557-9662. ; :99
  • Tidskriftsartikel (refereegranskat)abstract
    • A method to characterize the memory effects in a nonlinear concurrent dual-band transmitter is presented. It is an extension of the conventional two tone test for power amplifiers to concurrent dual band transmitters. The output signal of a concurrent dual-band transmitter is affected not only by intermodulation products but also by cross-modulation products. In one frequency band, the transmitter is excited by a two tone signal which frequency separation is swept. In the second band the transmitter is concurrently excited by an other two tone signal with slightly wider frequency separation. The frequency difference of the two signals is fixed during the frequency sweep. The two tone test is made at different power levels. The upper and lower third-order inter- and cross-modulation products are measured. The asymmetry between the upper and lower third-order inter- and cross-modulation products are measures of the transmitter's memory effects. The measurement results show that the memory effects are more dominant in the third-order intermodulation products than in the cross modulation products. An error analysis and system calibration was performed and measurement results for two different devices are presented.
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13.
  • Amin, Shoaib, 1985-, et al. (författare)
  • Concurrent dual-band power amplifier model modification using dual two-tone test
  • 2016
  • Ingår i: 46th European Microwave Conference (EUMC) 2016. - : Institute of Electrical and Electronics Engineers (IEEE). - 9782874870439 - 9781509015146 ; , s. 186-189
  • Konferensbidrag (refereegranskat)abstract
    • A dual two-tone technique for the characterization of memory effects in concurrent dual-band transmitters is revisited to modify a 2D-DPD model for the linearization of concurrent dual-band transmitters. By taking into account the individual nonlinear memory effects of the self- and cross-kernels, a new 2D modified digital pre-distortion (2D-MDPD) model is proposed, which not only supersedes the linearization performance but also reduces the computational complexity compared to the 2D-DP Dmodel in terms of a number of floating point operations (FLOPs). Experimental results show an improvement of 1.7 dBin normalized mean square error (NMSE) and a 58% reduction in the number of FLOPs.
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14.
  • Amin, Shoaib, et al. (författare)
  • Digital Predistortion of Single and Concurrent Dual BandRadio Frequency GaN Amplifiers with Strong NonlinearMemory Effects
  • 2017
  • Ingår i: IEEE transactions on microwave theory and techniques. - : IEEE Press. - 0018-9480 .- 1557-9670. ; 65:7, s. 2453-2464
  • Tidskriftsartikel (refereegranskat)abstract
    • Electrical anomalies due to trapping effects in gallium nitride (GaN) power amplifiers (PAs) give rise to long-term or strong memory effects. We propose novel models based on infinite impulse response fixed pole expansion techniques for the behavioral modeling and digital predistortion of single-input single-output (SISO) and concurrent dual-band GaN PAs. Experimental results show that the proposed models outperform the corresponding finite impulse response (FIR) models by up to 17 dB for the same number of model parameters. For the linearization of a SISO GaN PA, the proposed models give adjacent channel power ratios (ACPRs) that are 7-17 dB lower than the FIR models. For the concurrent dual-band case, the proposed models give ACPRs that are 9-14 dB lower than the FIR models.
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15.
  • Amin, Shoaib, 1985-, et al. (författare)
  • Noise Impact on the Identification of Digital Predistorter Parameters in the Indirect Learning Architecture
  • 2012
  • Ingår i: 2012 Swedish Communication Technologies Workshop (Swe-CTW). - : IEEE conference proceedings. - 9781467347631 ; , s. 36-39
  • Konferensbidrag (refereegranskat)abstract
    • The indirect learning architecture (ILA) is the mostused methodology for the identification of Digital Pre-distorter (DPD) functions for nonlinear systems, particularly for high power amplifiers. The ILA principle works in black box modeling relying on the inversion of input and output signals of the nonlinear system, such that the inverse is estimated. This paper presents the impact of disturbances, such as noise in the DPD identification. Experiments were performed with a state-of-art Doherty power amplifier intended for base station operation in current telecommunication wireless networks. As expected, a degradation in the performance of the DPD (measured innormalized mean square error (NMSE)) is found in our experiments. However, adjacent channel power ratio (ACPR) can be a misleading figure of merit showing improvement in the performance for wrongly estimated DPD functions.
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17.
  • Björsell, Niclas, et al. (författare)
  • A Statistical Evaluation of ADC Histogram Tests with Arbitrary Stimuli Signal
  • 2005
  • Ingår i: ADDA 2005. - : IEE. - 0 86341 542 3 ; , s. 259-264
  • Konferensbidrag (refereegranskat)abstract
    • Histogram tests are a commonly used method for characterizing analogue to digital converters. However, different stimuli signals can be used in the histogram test. An overview of common input stimuli for the test is presented. Previous works have analysed the statistical properties of the resulting histograms for different stimuli signals, separately. In this paper, generally applicable results for asymptotically unbiased minimum variance estimator and Cramer-Rao lower bound are derived, irrespective of used input stimuli. Where available, the general expression is compared and found in accordance with signal-specific expressions.
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18.
  • Björsell, Niclas, et al. (författare)
  • Achievable ADC Performance by Post-Correction Utilizing Dynamic Modeling of the Integral Nonlinearity
  • 2008
  • Ingår i: EURASIP Journal on Advances in Signal Processing. - : Springer Science and Business Media LLC. - 1110-8657 .- 1687-6180 .- 1687-6172. ; , s. 497187-1-497187-10
  • Tidskriftsartikel (refereegranskat)abstract
    • There is a need for a universal dynamic model of analog-to-digital converters (ADC’s) aimed for postcorrection. However, it is complicated to fully describe the properties of an ADC by a single model. An alternative is to split up the ADC model in different components, where each component has unique properties. In this paper, a model based on three components is used, and a performance analysis for each component is presented. Each component can be postcorrected individually and by the method that best suits the application. The purpose of postcorrection of an ADC is to improve the performance. Hence, for each component, expressions for the potential improvement have been developed. The measures of performance are total harmonic distortion (THD) and signal to noise and distortion (SINAD), and to some extent spurious-free dynamic range (SFDR).
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19.
  • Björsell, Niclas, et al. (författare)
  • Analog-to-Digital Converters for High-Speed Applications
  • 2005
  • Ingår i: GigaHz 2005. ; , s. 151-154
  • Konferensbidrag (refereegranskat)abstract
    • There is a rapid development of the performance of state-of-the-art analog to digital converters (ADC). Resolution and sampling rate are increasing continuously. Sampling rates in the high intermediate frequency (IF) range with sufficient dynamic range for communication applications were introduced about the turn of the millennium. Post-correction methods enable fast ADCs with modest linearity, and thereby weak dynamic performance, for high-speed applications. A post-correction procedure involves a characterization of the ADC non-linearity and then utilizing this information by processing the ADC output samples to remove the distortion. ADC characterization is usually performed by estimating ADC characteristics from measurements. Consequently, successful characterizations require both developed test methods and high performance test-beds. Characterization and testing ADCs are interesting in many different aspects. Not only that a proper characterization can be used for error compensation, testing is a major factor of cost for manufacturers, and shortening of the test cycle implies large savings. Testing ADCs is complicated, time consuming and demands high-performance instrumentation.
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  • Resultat 11-20 av 102
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