| 31. |
- Björsell, Niclas, 1964-, et al.
(författare)
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Multi-tone design for out-of-band characterization of nonlinear RF modules using harmonic sampling
- 2010
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Ingår i: 2010 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2010. - Piscataway, NJ : IEEE Service Center. - 9781424428335 - 9781424428328 ; , s. 620-623
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Konferensbidrag (refereegranskat)abstract
- In this paper we evaluate the generation of a multi-tone set for characterizing the behavior of nonlinear radio frequency (RF) modules in its out-of-band when harmonic sampling is used as digitizer. The purpose is to provide the reader with a tool to select proper frequencies and record length for a given application and test-bed. The method is based on simulations and the use of Sidon sequences. The proposed method is applicable to sparse discrete frequency multi-tones.
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| 32. |
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| 33. |
- Björsell, Niclas, et al.
(författare)
-
Post-Correction of Under-Sampled Analog to Digital Converters
- 2007
-
Ingår i: IEEE Instrumentation and Measurement Technology Conference.
-
Konferensbidrag (refereegranskat)abstract
- Applications with wide bandwidth and high center frequencies force the analog to digital converter (ADC) to be active in a working range with less dynamic performance in relation to lower frequency bands. However using under-sampling techniques in combination with post-correction methods enable a combination of high sampling rate, wide bandwidth and low distortion. In this paper the employed dynamic post-correction is a combination of look-up tables and model based correction. The results are mainly based on measurements on a 12 bit 210 MSPS ADC. The improvement in total harmonic distortion and spurious free dynamic range are acceptable over a wide frequency range and it is robust to variations in amplitude.
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| 34. |
- Björsell, Niclas, et al.
(författare)
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Truncated Gaussian Noise in ADC Histogram Tests
- 2007
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Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 40:1, s. 36-42
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Tidskriftsartikel (refereegranskat)abstract
- One method to characterize analogue to digital converters (ADCs) is to use a histogram, where Gaussian noise may be used as stimulus signal. However, a Gaussian noise signal that excites all transition levels also generates input values outside working range of the ADC. Modern signal generators can generate arbitrary signals. Hence, excluding undesired values outside the ADC full scale can minimize test sequences. Truncating the signal to the working range gives further advantages, which are explored in this paper. The Cramer-Rao lower bound and a minimum variance estimator for histogram tests with an arbitrary stimulus are derived. These are applied for truncated Gaussian noise and the result is theoretically evaluated and compared to untruncated noise. It is shown that accuracy increases for a fixed sample length and that variation over transition levels decrease.
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| 35. |
- Fritzin, Jonas, et al.
(författare)
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Phase Predistortion of a Class-D Outphasing RF Amplifier in 90 nm CMOS
- 2011
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Ingår i: IEEE Transactions on Circuits and Systems - II - Express Briefs. - 1549-7747 .- 1558-3791. ; 58:10, s. 642-646
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Tidskriftsartikel (refereegranskat)abstract
- This brief presents a behavioral model structure and a model-based phase-only predistortion method that are suitable for outphasing RF amplifiers. The predistortion method is based on a model of the amplifier with a constant gain factor and phase rotation for each outphasing signal, and a predistorter with phase rotation only. The method has been used for enhanced data rates for GSM evolution (EDGE) and wideband code-division multiple-access (WCDMA) signals applied to a Class-D outphasing RF amplifier with an on-chip transformer used for power combining in 90-nm CMOS. The measured peak power at 2 GHz was +10.3 dBm with a drain efficiency and power-added efficiency of 39% and 33%, respectively. For an EDGE 8 phase-shift-keying (8-PSK) signal with a phase error of 3 degrees between the two input outphasing signals, the measured power at 400 kHz offset was -65.9 dB with predistortion, compared with -53.5 dB without predistortion. For a WCDMA signal with the same phase error between the input signals, the measured adjacent channel leakage ratio at 5-MHz offset was -50.2 dBc with predistortion, compared with -38.0 dBc without predistortion.
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| 36. |
- Händel, Peter, et al.
(författare)
-
Dirty MIMO Transmitters : Does It Matter?
- 2018
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Ingår i: IEEE Transactions on Wireless Communications. - : IEEE. - 1536-1276 .- 1558-2248. ; 17:8, s. 5425-5436
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Tidskriftsartikel (refereegranskat)abstract
- The radio frequency transmitter is a key component in contemporary MIMO OFDM systems. A detailed study of a 2×2 MIMO transmitter subjected to correlated input data streams, nonlinear distortion, thermal noise, and crosstalk is provided by stochastic modeling. The effects of correlated input streams, crosstalk and nonlinearities are studied in detail, and exemplified both by approximate expressions and numerical simulations. Key results include exact and approximate expressions for the normalized mean-squared error (NMSE) for systems with or without digital predistortion, the relationship between NMSE and the signal-to-noise-and-distortion ratio, the properties of the distortion noise, and a novel design for power amplifier back-off for MIMO-transmitters subject to crosstalk. The theoretical derivations are illustrated by numerical examples and simulation results, and their relationship to state-of-the-art research are discussed. OAPA
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| 37. |
- Händel, Peter, et al.
(författare)
-
Impact of Backward Crosstalk in 2×2 MIMO Transmitters on NMSE and Spectral Efficiency
- 2020
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Ingår i: IEEE Transactions on Communications. - : IEEE. - 0090-6778 .- 1558-0857. ; 68:7, s. 4277-4292
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Tidskriftsartikel (refereegranskat)abstract
- We consider backward crosstalk in 2×2 transmitters, which is caused by crosstalk from the outputs of the transmitter to the inputs or by the combination of output crosstalk and impedance mismatch. We analyze its impact via feedback networks together with third-order power amplifier non-linearities. We utilize the Bussgang decomposition to express the distorted output signals of the transmitter as a linear transformation of the input plus uncorrelated distortion. The normalized mean-square errors (NMSEs) between the distorted and desired amplified signals are expressed analytically and the optimal closed-form power back-off that minimizes the worst NMSE of the two branches is derived. In the second part of the paper, an achievable spectral efficiency (SE) is presented for the communication from this “dirty” transmitter to another single-antenna receiver. The SE-maximizing precoder is optimally found by exploiting the hardware characteristics. Furthermore, the optimal power back-off is analyzed for two sub-optimal precoders, which either do not exploit any hardware knowledge or only partial knowledge. The simulation results show that the performance of these sub-optimal precoders is close-to-optimal. We also discuss how the analysis in this paper can be extended to transmitters with an arbitrary number of antenna branches.
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| 38. |
- Händel, Peter, et al.
(författare)
-
Maximum likelihood estimation of reverberation chamber direct-to-scattered ratio
- 2009
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 0013-5194 .- 1350-911X. ; 45:25, s. 1285-1286
-
Tidskriftsartikel (refereegranskat)abstract
- The exact maximum likelihood estimator of the direct-to-scattered ratio of the Rician channel in a reverberation chamber is derived and its performance analysed. It is shown that the estimator obeys a non-central F-distribution, the mean value and variance of which are derived. For well stirred chambers, it is shown that the systematic error in the estimated ratio may be significant.
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| 39. |
- Händel, Peter, et al.
(författare)
-
MIMO and Massive MIMO Transmitter Crosstalk
- 2020
-
Ingår i: IEEE Transactions on Wireless Communications. - : IEEE. - 1536-1276 .- 1558-2248. ; 19:3, s. 1882-1893
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of hardware-induced crosstalk in MIMO transmitters, subject to nonlinear power amplifier distortion, are considered in this paper. A methodology that provides tractable results and a clear understanding of the effects of crosstalk on transmitter performance is introduced and applied to different transmitter models. In particular, a physically motivated 2×2 MIMO transmitter model, which is subjected to input and output crosstalk, is studied in detail, as well as a behavior motivated transmitter model, which is subjected to linear crosstalk. For the latter structure, asymptotic results, when the number of transmitters tends to infinity, are derived. These results provide insight into different 1D and 2D transmitter structures in the massive MIMO scenario. The methodology provides tractable analytical results of the performance of the transmitter. It is shown that the transmitter crosstalk degrades the performance in terms of normalized mean squared error with 3 dB going from a 2×2 set-up to a 1D array of a massive amount of transmitters, and an additional 3 dB loss going from a 1D to 2D transmitter structure. Transmitter input power back-off optimization is further studied, with back-off determination that takes the effects of MIMO crosstalk into account in order to increase the energy efficiency of the transmitter.
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| 40. |
- Händel, Peter, 1962-, et al.
(författare)
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Model Based Dynamic Characterization of Analog-Digital-Converters at Radio Frequency
- 2007
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Ingår i: 2007 9th International Symposium on Signal Processing and its Applications, Vol. 1-3. - 9781424407781 ; , s. 1403-1408
-
Konferensbidrag (refereegranskat)abstract
- A dynamic characterization of analog-digital converter integral nonlinearity (INL) is considered. When using a plurality of test frequencies in the measurement set-up, the dynamic errors of the converter are characterized. The INL is modeled by low and high code components - LCF and HCF, respectively. The LCF and HCF are parameterized and a least squares method is derived for the estimation of the parameter values from obtained measurements. A closed form solution to the estimation problem is derived and its performance is illustrated by a numerical example. The proposed method is believed to be fruitful in wide-band characterization of analog-digital converters at radio frequency, and thus of importance for the evaluation of modem and future wireless communication systems.
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