| 1. |
- del Aguila Pla, Pol, 1990-, et al.
(författare)
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Clock synchronization over networks - Identifiability of the sawtooth model
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, we analyze the two-node joint clocksynchronization and ranging problem. We focus on the case of nodes that employ time-to-digital converters to determine the range between them precisely. This specific design leads to a sawtooth model for the captured signal, which has not been studied in detail before from an estimation theory standpoint. In the study of this model, we recover the basic conclusion of a well-known article by Freris, Graham, and Kumar in clock synchronization. Additionally, we discover a surprising identifiability result on the sawtooth signal model: noise improves the theoretical condition of the estimation of the phase and offset parameters. To complete our study, we provide performance references for joint clock synchronization and ranging. In particular, we present the Cramér-Rao lower bounds that correspond to a linearization of our model, as well as a simulation study on the practical performance of basic estimation strategies under realistic parameters. With these performance references, we enable further research in estimation strategies using the sawtooth model and pave the path towards industrial use.
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| 2. |
- 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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| 3. |
- Händel, Peter, et al.
(författare)
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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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| 4. |
- Landin, Per N., et al.
(författare)
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Peak-power controlled digital predistorters for RF power amplifiers
- 2012
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Ingår i: IEEE transactions on microwave theory and techniques. - 0018-9480 .- 1557-9670. ; 60:11, s. 3582-3590
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the issue of predistorter blow-up, i.e., uncontrolled peak expansion caused by the predistorter. To control the peak expansion, an extension of the multistep indirect learning architecture (MS-ILA) is proposed by adding a constraint that describes the allowed peak power of the predistortion signal. The resulting optimization problem is shown to be convex and an optimization method is formulated to solve it.
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| 5. |
- Landin, Per N., et al.
(författare)
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Two novel memory polynomial models for modeling of RF power amplifiers
- 2015
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Ingår i: International journal of microwave and wireless technologies. - 1759-0795 .- 1759-0787. ; 7:1, s. 19-29
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Tidskriftsartikel (refereegranskat)abstract
- Two novel memory polynomial models are derived based on physical knowledge of a general power amplifier (PA). The derivations are given in detail to facilitate derivations of other model structures. The model error in terms of normalized mean square error (NMSE) and adjacent channel error power ratio (ACEPR) of the novel model structures are compared to that of established models based on the number of parameters using data measured on two different amplifiers, one high-power base-station PA and one low-power general purpose amplifier. The novel models show both lower NMSE and ACEPR for any chosen number of parameters compared to the established models. The low model errors make the novel models suitable candidates for both modeling and digital predistortion.
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| 6. |
- Lundin, Henrik, et al.
(författare)
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Analog-to-Digital Converter Error Correction using Frequency Selective Tables
- 2002
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Ingår i: RadioVetenskap och Kommunikation (RVK). ; , s. 487-490
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Error correction for analog-to-digital converters(ADCs) is considered. The frequency-dependent na-ture of ADC errors motivates the proposal of a novel scheme, incorporating look-up table correction andfast frequency estimation. The method is evaluated using experimental converter data, and the performance, measured in SFDR and SINAD, is found tobe superior to that of non frequency-dependent correction methods.
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| 7. |
- Pla, Pol del Aguila, et al.
(författare)
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Clock synchronization over networks using sawtooth models
- 2020
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Ingår i: 2020 IEEE international conference on acoustics, speech, and signal processing. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 5945-5949
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Konferensbidrag (refereegranskat)abstract
- Clock synchronization and ranging over a wireless network with low communication overhead is a challenging goal with tremendous impact. In this paper, we study the use of time-to-digital converters in wireless sensors, which provides clock synchronization and ranging at negligible communication overhead through a sawtooth signal model for round trip times between two nodes. In particular, we derive Cramer-Rao lower bounds for a linearitzation of the sawtooth signal model, and we thoroughly evaluate simple estimation techniques by simulation, giving clear and concise performance references for this technology.
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| 8. |
- Zenteno, Efrain, et al.
(författare)
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Combating the Dimensionality of Nonlinear MIMO Amplifier Predistortion by Basis Pursuit
- 2014
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Ingår i: Proceedings of the 44th European Microwave Conference. ; , s. 833-836
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Konferensbidrag (refereegranskat)abstract
- A general description of nonlinear dynamic MIMOsystems, given by Volterra series, has significantly larger complex-ity than SISO systems. Modeling and predistortion of MIMOamplifiers consequently become unfeasible due to the largenumber of basis functions. We have designed digital predistortersfor a MIMO amplifier using a basis pursuit method for reducingmodel complexity. This method reduces the numerical problemsthat appear in MIMO Volterra predistorters due to the largenumber of basis functions. The number of basis functions wasreduced from 1402 to 220 in a 2x2 MIMO amplifier and from127 to 13 in the corresponding SISO case. Reducing the numberof basis functions caused an increase of approximately 1 dB ofmodel error and adjacent channel power ratio.
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| 9. |
- 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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| 10. |
- Nader, Charles, 1982-, et al.
(författare)
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OFDM PAPR Reduction by Convex Optimization : A Power Amplifier Point-of-View
- 2010
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Ingår i: 2010 IEEE International Microwave Workshop Series on "RF Front-ends for Software Defined and Cognitive Radio Solutions". - : IEEE. - 9781424457519
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Konferensbidrag (refereegranskat)abstract
- In this paper we evaluate the application of convex optimization for PAPR reduction on OFDM 802.11a signal type. A radio frequency power amplifier is measured and characterized while excited by both original and optimized OFDM signals. A state-of-art test setup was used for the purpose. Improvements in power added efficiency, in-band errors, out-of-band spectral emissions are investigated for their relevance and a study of the power distribution in the excitation signal is evaluated.
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