SwePub - sökning: WFRF:(Fager Christian 1974)

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1.	Bordbar, Alireza, 1998, et al. (författare) Deep-Learning-Based Channel Estimation for Distributed MIMO with 1-bit Radio-Over-Fiber Fronthaul 2024 Ingår i: Proceedings of the International Symposium on Wireless Communication Systems. - 2154-0217 .- 2154-0225. Konferensbidrag (refereegranskat)abstract We consider the problem of pilot-aided, uplink channel estimation in a distributed massive multiple-input multiple-output (MIMO) architecture, in which the access points are connected to a central processing unit via fiber-optical fronthaul links, carrying a two-level-quantized version of the received analog radio-frequency signal. We adapt to this architecture the deep-learning-based channel-estimation algorithm recently proposed by Nguyen et al. (2023), and explore its robustness to the additional signal distortions (beyond 1-bit quantization) introduced in the considered architecture by the automatic gain controllers (AGCs) and by the comparators. These components are used at the access points to generate the two-level analog waveform from the received signal. Via simulation results, we illustrate that the proposed channel-estimation method outperforms significantly the Bussgang linear minimum mean-square error channel estimator, and it is robust against the additional impairments introduced by the AGCs and the comparators.
2.	Fager, Christian, 1974, et al. (författare) High output power, broadband 28-56 GHz MMIC frequency doubler 2000 Ingår i: IEEE MTT-S International Microwave Symposium / Perkins, T.. ; , s. 1589-91 vol.3 Konferensbidrag (refereegranskat)abstract An active single-ended 28-6 GHz MMIC frequency doubler based on a commercial GaAs HEMT process is presented. The presented doubler is broadband and delivers high output power. At 5 dBm input power, the doubler delivers 6 dBm output power. The 3 dB bandwidth is between 48 GHz and 60 GHz. Suppression of the input frequency is better than 23 dB at the design frequency
3.	Sezgin, Ibrahim Can, 1992, et al. (författare) A Flexible Multi-Gbps Transmitter Using Ultra-High Speed Sigma- Delta-over- Fiber 2018 Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. ; 2018-June, s. 1195-1198 Konferensbidrag (refereegranskat)abstract Sigma-delta-over-fiber (SDoF) using high speed-low cost optical components for datacom enables high speed transmission at X-band. This paper examines the limitations of SDoF in terms of maximum frequencies and highest bit rates. Different modulation formats, symbol rates and carrier frequencies are investigated. A high speed 850 nm vertical-cavity surface-emiting-laser (VCSEL) is used as an optical source to transmit the optical signal over a 50 meter, OM4, multimode fiber (MMF). Error vector magnitude (EVM) less than 6% is achieved at a 12-GHz center frequency for a 8-Gbps QAM256 modulated signal.
4.	Sezgin, Ibrahim Can, 1992, et al. (författare) A Low-Complexity Distributed-MIMO Testbed Based on High-Speed Sigma-Delta-Over-Fiber 2019 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 67:7, s. 2861-2872 Tidskriftsartikel (refereegranskat)abstract Distributed multiple-input-multiple-output (D-MIMO) is a very promising technique to improve capacity and quality of service for emerging 5G systems. In this paper, we propose a flexible and low-cost testbed for D-MIMO systems, where a sigma-delta over fiber (SDoF) solution is proposed to address the fundamental challenge of phase-coherent transmission between multiple distributed access points (APs) from a central unit (CU). Employing low-cost standardized optical data interconnects, SDoF, brings a very flexible and software controlled transmission of RF signals over optical fiber. An SDoF-based D-MIMO testbed with a CU feeding 12 distributed APs has been realized and experimentally evaluated. Initial experiments of D-MIMO and conventional colocated MIMO systems at 2.365 GHz have been performed to demonstrate the flexibility and potential of the proposed testbed as a new powerful tool in the design and analysis of emerging communication system concepts.
5.	Sezgin, Ibrahim Can, 1992, et al. (författare) Effect of VCSEL Characteristics on Ultra-High Speed Sigma-Delta-Over-Fiber Communication Links 2019 Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 37:9, s. 2109-2119 Tidskriftsartikel (refereegranskat)abstract State-of-the-art high-speed multi-mode vertical-cavity surface-emitting-lasers (VCSELs) have a 3-dB analog bandwidth of ∼25 GHz and can operate up to 55 Gbps error-free, without need of equalization electronics. This makes them strong candidates as optical sources for ultra-high speed sigma-delta-over-fiber (SDoF) communication links. This paper examines the effects of VCSEL characteristics on a 32-Gbps SDoF communication link with a 50 m, OM4, multimode optical fiber. Three high-speed, 850-nm-wavelength VCSELs with oxide aperture sizes of 8.3, 6.6, and 4.6 μm were tested. The effects of different modulation voltage amplitudes and bias currents were also investigated. The link performance and VCSEL power consumption were used as figures-of-merits. By avoiding sub-laser threshold modulation for the VCSEL, each of three VCSELs could provide similar link performance. We show that, compared to conventional datacom links, eased bit-error-rate requirements enabled by bi-level nature of sigma-delta modulation makes it possible to use significantly lower VCSEL bias currents. This in turn enables a reduced VCSEL power consumption (50% lower heat-to-bit ratio) and a potential longer VCSEL lifespan. For a SDoF modulated, 160-Mbaud, QAM64 signal centered at 12 GHz an error vector magnitude of -28 dB was achieved with the VCSEL having oxide aperture size of 4.6 μm operating at only 2 mA bias current and 0.25 V modulation amplitude. This results in a heat-to-bit ratio of only 0.1 mW/Gb/s (or equivalently 0.1 pJ/b), and a current density in the VCSEL that is less than 10 kA/cm2.
6.	Sezgin, Ibrahim Can, 1992, et al. (författare) Evaluation of Distributed MIMO Communication Using a Low-Complexity Sigma-Delta-over-Fiber Testbed 2019 Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. ; 2019-June, s. 754-757 Konferensbidrag (refereegranskat)abstract Distributing the antennas of a base station is a method to increase the coverage and the capacity of a conventional, co-located MIMO communication system. However, physically separated antennas/access points (AP) creates a fundamental challenge of RF phase synchronization required for joint/coordinated transmission in distributed MIMO (D-MIMO) systems. In this paper we compare co-located-and distributed-MIMO wireless communication thru various measurements using a fully synchronized, low-complexity, twelve-channel testbed based on sigma-delta-over-fiber (SDoF). Single and multi-user measurements are performed in a laboratory environment and the error-vector-magnitude (EVM), the received power and signal-to-interference ratio (SIR) is calculated. We show that distributing the access points improves the received symbol EVM up to 1.6-dB and increases the coverage of the service area by delivering more uniform received power levels.
7.	Aabel, Lise, et al. (författare) A TDD Distributed MIMO Testbed Using a 1-bit Radio-Over-Fiber Fronthaul Architecture 2024 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; In Press Tidskriftsartikel (refereegranskat)abstract We present the uplink and downlink of a time-division duplex distributed multiple-input multiple-output (D-MIMO) testbed, based on a 1-bit radio-over-fiber architecture, which is low cost and scalable. The proposed architecture involves a central unit (CU) that is equipped with 1-bit digital-to-analog and analog-to-digital converters, operating at 10 GS/s. The CU is connected to multiple single-antenna remote radio heads (RRHs) via optical fibers, over which a binary radio frequency (RF) waveform is transmitted. In the uplink, a binary RF waveform is generated at the RRHs by a comparator, whose inputs are the received RF signal and a suitably designed dither signal. In the downlink, a binary RF waveform is generated at the CU via bandpass sigma-delta modulation. Our measurement results show that low error-vector magnitude (EVM) can be achieved in both the uplink and the downlink, despite 1-bit sampling at the CU. Specifically, for point-to-point over-cable transmission between a single user equipment (UE) and a CU equipped with a single RRH, we report, for a 10-MBd signal using single-carrier (SC) 16 quadratic-amplitude modulation (QAM) modulation, an EVM of 3.3% in the downlink, and of 4.5% in the uplink. We then consider a CU connected to three RRHs serving over the air two UEs, and show that, after over-the-air reciprocity calibration, a downlink zero-forcing precoder designed on the basis of uplink channel estimates at the CU achieves an EVM of 6.4% and 10.9% at UE 1 and UE 2, respectively. Finally, we investigate the ability of the proposed architecture to support orthogonal frequency-division multiplexing (OFDM) waveforms, and its robustness against both in-band and out-of-band interference.
8.	Aabel, Lise, 1992, et al. (författare) Distributed Massive MIMO via all-Digital Radio Over Fiber 2020 Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; 2020-November, s. 319-323 Konferensbidrag (refereegranskat)abstract A crucial challenge in the implementation of distributed massive multiple-input multiple-output (MIMO) architectures is to provide phase coherence while, at the same time, limit the complexity of the remote-radio heads (RRHs), which is important for cost-efficient scalability. To address this challenge, we present in this paper a phase-coherent distributed MIMO architecture, based on off-the-shelf, low-cost components. In the proposed architecture, up- and down-conversion are carried out at the central unit (CU). The RRHs are connected to the CU by means of optical fibers carrying oversampled radio-frequency (RF) 1-bit signals. In the downlink, the 1-bit signal is generated via sigma-delta modulation. At the RRH, the RF signal is recovered from the 1-bit signal through a bandpass filter and a power amplifier, and then fed to an antenna. In the uplink, the 1-bit signal is generated by a comparator whose inputs are the low-noise-amplified received RF signal and a suitably designed dither signal. The performance of the proposed architecture is evaluated with satisfactory results both via simulation and measurements from a testbed.
9.	Abdulaziz, Mohammed, 1983, et al. (författare) Improvement of AM-PM in a 33-GHz CMOS SOI Power Amplifier Using pMOS Neutralization 2019 Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 29:12, s. 798-801 Tidskriftsartikel (refereegranskat)abstract This letter presents two highly efficient two-stage power amplifiers (PAs) for 5G applications, implemented in a 22-nm slilicon on insulator (SOI) CMOS technology. High efficiency is achieved by carefully designing the power cells and optimizing the layout. Capacitive neutralization is used to improve the stability and the gain. Both PAs are similar except for the use of nMOS neutralization capacitors in the first one. In the second PA, we propose the use of pMOS capacitors instead to enhance significantly both stability and AM-PM linearity at the same time. For both PAs, the saturated output power is 12.7 dBm andP1 dB is 11.9 dBm from a 0.9-V supply at 33 GHz with a power-added efficiency (PAE) at P1 dB of more than 36%. The PAE at Psat is 38% and 40% for the PA with nMOS and pMOS neutralizations, respectively. The AM-PM up to P3 dB for the PA with nMOS neutralization is 7, and for the one with pMOS neutralization, it is less than 1.3 thanks to the proposed technique.
10.	Afsar Doost, Sepideh, 1983, et al. (författare) Digital Predistortion Using a Vector Switched Model 2012 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:4, s. 1166-1174 Tidskriftsartikel (refereegranskat)abstract Abstract—A switched behavioral model considering memory effects with special focus on ”difficult” amplifier architectures is proposed in this paper. The proposed model is shown to be very simple and linearly identifiable. A digital predistorter based on the proposed model is implemented for a 100–W, 2.6 GHz Doherty power amplifier that has been considered difficult in other reports, and it is shown that the proposed model can succesfully linearize the amplifier. In particular, the proposed model and the digital predistorter is shown to outperform other state-of-the-art models and digital predistorers in terms of computational complexity for a given desired accuracy.
11.	Andersson, Christer, 1982, et al. (författare) A 1-3-GHz Digitally Controlled Dual-RF Input Power-Amplifier Design Based on a Doherty-Outphasing Continuum Analysis 2013 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 61:10, s. 3743-3752 Tidskriftsartikel (refereegranskat)abstract This paper presents a linear multi-harmonic analysis method to evaluate the performance of digitally controlled dual RF-input power amplifiers (PAs). The method enables, due to its low computational cost, optimization of PA efficiency and bandwidth in a complex design space involving two independent inputs. Under the idealized assumption of short-circuited higher harmonics, the analysis is used to prove the existence of a Doherty-outphasing continuum, featuring high average efficiency over 100% fractional bandwidth. With this result as a foundation, a combiner incorporating microwave transistor parasitics is analyzed without assuming short-circuited higher harmonics, showing that high average efficiencies are also achievable under more realistic conditions. A PA is straightforwardly designed from these calculation results using two 15-W GaN HEMTs. The simulated layout-ready (large-signal transistor model) PA average drain efficiency exceeds 50% over 1.1-3.7 GHz for a 6.7-dB peak-to-average power-ratio WCDMA signal. The measured PA has a maximum output power of 44 +/- 0.9 dBm and a 6-dB output power back-off (OPBO) power-added efficiency (PAE) of 45% over 1-3 GHz. After applying digital pre-distortion, excellent linearity is demonstrated when transmitting the WCDMA signal, resulting in an adjacent channel leakage power ratio lower than -57 dBc with corresponding average PAE of 50% and 40% at 1.2 and 2.3 GHz, respectively. This is, to the authors' knowledge, the most wideband OPBO efficiency enhanced PA reported to date, proving the effectiveness of employing linear multi-harmonic analysis in dual-input PA design.
12.	Andersson, Christer, 1982, et al. (författare) A packaged 86 W GaN transmitter with SiC varactor-based dynamic load modulation 2013 Ingår i: 43rd European Microwave Conference, EuMC 2013 - Held as Part of the 16th European Microwave Week, EuMW 2013, Nuremberg, Germany, 7-10 October 2013. - 9782874870316 ; , s. 283-286 Konferensbidrag (refereegranskat)abstract Output power scaling based on class-J dynamic load modulation (DLM) theory is used to design an unprecedentedly high power microwave transmitter with varactor-based DLM functionality. Matching networks are realized on high dielectric constant substrates in order to reduce the form factor. The fully matched DLM PA incorporates a 24-mm GaN HEMT powerbar and a stack of four SiC varactors, all fit into a CuW package (40 mm × 20 mm). Peak output power is reconfigurable by changing the drain voltage, while retaining the DLMeffect. Under pulsed conditions at 40 V the PA delivers a peak power of 86 W at 2.14 GHz. Efficiency enhancement by DLM is 10-15 percentage-units at 6 dB output power back-off (OPBO). Employing digital predistortion (DPD) with a vector switched generalized memory polynomial (VS-GMP) the ACLR is -46 dBc at an average output power of 17 W and a drain efficiency of 34%. These results prove the potential for high output power levels in varactor-based DLM transmitters.
13.	Andersson, Christer, 1982, et al. (författare) Decade bandwidth high efficiency GaN HEMT power amplifier designed with resistive harmonic loading 2012 Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781467310871 Konferensbidrag (refereegranskat)abstract The use of resistive loading at higher harmonics in wideband power amplifier design is proposed. Although the theoretical efficiency of such operation is lower than other classes the significantly simplified load network design potentially allows for multi-octave realizations. A decade bandwidth (0.4-4.1 GHz) GaN HEMT power amplifier was thereby designed, delivering more than 40 dBm output power with 10-15 dB gain and 40-62% drain efficiency. Linearized modulated signal amplification was then successfully demonstrated at multiple frequencies (0.9 to 3.5 GHz), using various downlink signals (LTE, WCDMA, WiMAX), with resulting ACLR lower than 46 dBc.
14.	Andersson, Christer, 1982, et al. (författare) Theory and Design of Class-J Power Amplifiers With Dynamic Load Modulation 2012 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:12, s. 3778-3786 Tidskriftsartikel (refereegranskat)abstract A theory for class-J microwave amplifier operation as a function of drive level and fundamental load impedance is derived. Calculations show that, under appropriate operating conditions, it is sufficient to modulate the transistor load reactance to enable high-efficiency operation (>70%) over a large output power dynamic range (>10 dB) with high transistor power utilization. Such dynamic load modulation (DLM) networks are an ideal application of continuously tunable varactor technologies. Multiharmonic load–pull measurements are performed on a GaN HEMT and experimentally verify the theory of operation. A demonstrator amplifier using an SiC varactor technology is then designed and characterized by static measurements. The amplifier has a peak power of 38 dBm at 2.08 GHz and maintains efficiencies above 45% over 8 dB of power dynamic range. An analysis of the load network losses is performed to show the potential of the class-J DLM transmitter concept.
15.	Andersson, Kristoffer, 1976, et al. (författare) A general procedure for extraction of bias dependent dynamic self heating model parameters 2005 Ingår i: Microwave Symposium Digest, 2005 IEEE MTT-S International. ; , s. 1159-1162 Konferensbidrag (refereegranskat)
16.	Andersson, Kristoffer, 1976, et al. (författare) Oscilloscope based two-port measurement system using error-corrected modulated signals 2012 Ingår i: 2012 Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits, INMMIC 2012. - 9781467329491 Konferensbidrag (refereegranskat)abstract A technique to accurately measure modulated wideband signals in a two-port context is presented. The technique uses a four channel high frequency digital sampling oscilloscope to perform in-situ correction of both amplitude and phase of the modulated stimulus signal. An advantage of the proposed technique is that no assumption about the group delay has to be made. The technique is demonstrated in a source-pull system. The results clearly demonstrate the necessity of using error-correction in tuner based setups due to the large variations in group-delay over the measurement bandwidth. © 2012 IEEE.
17.	Andersson, Kristoffer, 1976, et al. (författare) Statistical Estimation of small signal FET model parameters and their covariance 2004 Ingår i: IEEE MTT-S International Microwave Symposium. Konferensbidrag (refereegranskat)
18.	Andersson, Kristoffer, 1976, et al. (författare) Statistical estimation of the propagation constant in multiline calibrations 2006 Ingår i: 67th ARFTG conference. Konferensbidrag (refereegranskat)
19.	Anjos, Eduardo V.P., et al. (författare) FORMAT: A Reconfigurable Tile-Based Antenna Array System for 5G and 6G Millimeter-Wave Testbeds 2022 Ingår i: IEEE Systems Journal. - 1932-8184 .- 1937-9234. ; 16:3, s. 4489-4500 Tidskriftsartikel (refereegranskat)abstract This article introduces the FORMAT array, a reconfigurable millimeter-wave antenna array platform based on antenna tiles. FORMAT stands for Flexible Organization and Reconfiguration of Millimeter-wave Antenna Tiles, which is a unique hardware solution aiming to implement and demonstrate a variety of antenna array concepts, as well as different array architectures and configurations from the same basic module, providing even benchmark between different solutions and thus valuable insights into fifth-generation (5G) and beyond-5G antenna systems. The combination of a minimum-sized tile with 3D-printed frame parts enables antenna arrays of a variety of sizes, allows multiple beamforming architectures, and a range of different antenna element positioning in the array. The hardware implementation is thoroughly described, with a few different array assemblies being manufactured and measured, validating their antenna performance with over-the-air measurements. Finally, using FORMAT hardware as both base station and user equipment, a 5-m wireless communication link was set up, achieving 4.8 Gbps downlink speed with QAM64 modulation.
20.	Argaez Ramirez, Roger, 1991, et al. (författare) Investigation of power amplifier performance under load mismatch conditions 2021 Ingår i: 2021 IEEE Topical Conference on RF/Microwave Power Amplifiers for Radio and Wireless Applications, PAWR 2021. ; , s. 41-43 Konferensbidrag (refereegranskat)abstract The time-varying loading conditions that power amplifiers (PAs) experience in active antenna systems degrade their overall performance. Consequently, the design of linear and highly-efficient PAs under mismatch is more important than ever. In this paper, different common and promising PA architectures, i.e. class-B, balanced, Doherty (DPA) and load-modulated-power-amplifier (LMBA), are analyzed under mismatch. Their sensitivity in terms of linearity, efficiency and output power is compared under a LTE signal excitation. Average drain efficiency (DE), average output power, normalized-mean-square-error (NMSE) as well as maximum output power variations are presented for each architecture as function of the voltage-standing-waveratio (VSWR). Thereby, the most suitable PA architecture to be integrated in active antenna systems may be identified.
21.	Bagheri, Alireza, et al. (författare) TX Beamforming EVM Performance of a 65 dBm-EIRP Slant-Polarized Gapwaveguide Phased Array at 28 GHz 2023 Ingår i: 17th European Conference on Antennas and Propagation, EuCAP 2023. Konferensbidrag (refereegranskat)abstract The transmit error vector magnitude (EVM) performance measurements of a slant-polarized 28 GHz gapwaveguide-based phased array is analyzed in this paper. The performance is studied by using a large range of signals, with varied powers, symbol rates, and quadrature amplitude modulation (QAM) orders. The measurements have been conducted for four different scanning angles. A non-standardized over-the-air (OTA) link between the phased array and the receiver in a laboratory environment is used. The results show that the phased array antenna supports a 31 dB effective isotropic radiated power (EIRP) dynamic range at a maximum 2% EVM when transmitting a 64QAM modulated signal with 250 MS/s symbol rate at all scanning directions.
22.	Bao, Husileng, 1991, et al. (författare) Automatic Distributed MIMO Testbed for beyond 5G Communication Experiments 2021 Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. ; 2021-June, s. 697-700 Konferensbidrag (refereegranskat)abstract This paper demonstrates an automated testbed suitable for beyond-5G distributed MIMO experiments, where bandwidth, number of transmitters and precoding methods are flexible and configured through a central unit. This is based on an all-digital radio-over-fiber approach to communication through 12 fully coherent, low-complexity remote radio transmitters. An automated robot receiver is implemented to facilitate efficient communication data collection in realistic environments. Using the proposed system, co-located and distributed MIMO communication antenna configurations are compared in a real in-door environment. The results show that distributed MIMO provides more significantly more uniform power distribution and better overall MIMO capacity compared to co-located MIMO.
23.	Bao, Husileng, 1991, et al. (författare) Demonstration of Flexible mm-Wave Digital Beamforming Transmitter Using Sigma-Delta Radio-over-Fiber Link 2022 Ingår i: 2022 52ND EUROPEAN MICROWAVE CONFERENCE (EUMC). - 2325-0305. - 9782874870699 Konferensbidrag (övrigt vetenskapligt/konstnärligt)
24.	Bao, Husileng, 1991, et al. (författare) Demonstration of Flexible mmWave Digital Beamforming Transmitter using Sigma-Delta Radio-Over-Fiber Link 2022 Ingår i: 2022 52nd European Microwave Conference, EuMC 2022. ; , s. 692-695 Konferensbidrag (refereegranskat)abstract This work demonstrates a millimeter-wave digital beamforming transmitter based on a sigma-delta radio-over-fiber link. The digital beamforming is controlled from a central unit and distributed to a remote radio unit using a standardized quad small form-factor pluggable 28 (QSFP28) fiber connection. The experimental results demonstrate 26.2 GHz transmission with high-quality beamforming functionality up to 130 MHz effective radio bandwidth at 2.2 m wireless distance. The solution offers a flexible transmitter solution suitable for millimeter-wave distributed active antenna systems.
25.	Bao, Husileng, 1991, et al. (författare) Flexible Mm-Wave Sigma-Delta-Over-Fiber MIMO Link 2023 Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 41:14, s. 4734-4742 Tidskriftsartikel (refereegranskat)abstract Millimeter-wave and multiple-input-multiple-output (MIMO) technologies combine broad bandwidth with spatial diversity to offer a greater data rate. This paper investigates a flexible millimeter-wave sigma-delta-over-fiber based transmitter solution with digital beamforming MISO and MIMO functionality. Those functions are controlled by a central unit connecting a remote radio head with a standardized QSFP28 fiber link. The central unit generates binary encoded intermediate frequency signals using bandpass sigma-delta modulation. The QSFP28 based fiber link transmits the intermediate frequency bitstreams to the remote radio head. The remote radio head consists of a QSFP28 module, $90^{\circ }$ hybrids, and upconverters. The remote radio head feeds four parallel, independent, coherent, and central-unit controlled 28 GHz signals to a linear array transmitting antenna. The transmitter performance is experimentally verified, demonstrating up to 800 Msym/s at an EVM/NMSE of 6.7%/-23.5 dB when tested with a 64 quadrature amplitude modulation (64-QAM) modulation scheme. Digital over-the-air beamforming MISO functionality is demonstrated up to 700 Msym/s across 1 m wireless distance. MIMO communication capabilities is demonstrated by over-the-air transmission of two independent 500 Msym/s to two spatially separated receivers. The results show that the proposed link can be used for realization of scalable, low-cost and flexible transmitter solution for emerging distributed antenna systems.
26.	Bao, Husileng, 1991, et al. (författare) Wideband mm-wave 6 × 2 Distributed MIMO Transmitter using Sigma-Delta-over-Fiber 2024 Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 42:9, s. 3107-3117 Tidskriftsartikel (refereegranskat)abstract This paper investigates a millimeter-wave sigma-delta-over-fiber distributed multiple-input-multiple-output (D-MIMO) solution, in which a central unit connects two remote radio heads (RRH) with two standardized QSFP28 fiber connections. The four subchannels of the QSFP28 carry three individually controlled intermediate frequency (IF) sigma-delta modulated bitstreams and one local oscillation signal to each RRH. At each RRH, the upconversion to mm-wave frequency is performed while maintaining full phase coherence between all channels and distributed RRHs. This solution offers an effective and scalable way to feed multiple radio heads with coherent signals proper for high performance millimeter-wave D-MIMO systems. Wireless performance of the transmitter is experimentally verified by multiple-input-single-output (MISO) and multiple-user MIMO cases in a 1.4 m × 1.6 m area with 748 MHz wideband signals. The comparison with other publications shows that the proposed system is the first millimeter-wave sigma-delta-over-fiber D-MIMO solution that serves multiple users and reaches the largest bandwidth.
27.	Bao, Husileng, 1991, et al. (författare) Wideband mm-wave Spectrum-Efficient Transmitter Using Low-Pass Sigma–Delta-Over-Fiber Architecture 2023 Ingår i: IEEE Microwave and Wireless Technology Letters. - 2771-9588 .- 2771-957X. ; 33:10, s. 1505-1508 Tidskriftsartikel (refereegranskat)abstract The millimeter-wave band offers large bandwidth and promises high data rates for wireless communication systems. This work proposes a millimeter-wave radio-over-fiber architecture suitable for wideband mm-wave communication, using a lowpass sigma-delta modulation approach. The central unit generates baseband sigma-delta bitstreams, in-phase/quadrature (I/Q) components, which are transported to a remote radio head (RRH) using a standard QSFP28 optical interconnect link connection. In the RRH, the baseband I/Q signals are upconverted to the millimeter-wave band, amplified, and transmitted through an antenna. The performance of the resulting sigma-delta-over-fiber transmitter architecture is experimentally verified at 28 GHz, demonstrating a state-of-the-art symbol rate up to 1.5 Gsym/s. Furthermore, in over-the-air measurements, the architecture is shown to support 1 Gsym/s with 5.9% error vector magnitude for 64/256/1024 quadrature amplitude modulation cases over a 5 m wireless distance. The results demonstrate the feasibility of the proposed architecture for the realization of wideband millimeterwave distributed antenna systems.
28.	Baptista, Emanuel, 1993, et al. (författare) Analysis of thermal coupling effects in integrated MIMO transmitters 2017 Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781509063604 ; , s. 75-78 Konferensbidrag (refereegranskat)abstract This paper presents a detailed analysis of thermal coupling and self-heating effects in highly integrated wireless transmitters. A MIMO transmitter prototype consisting of two closely integrated power amplifiers was built and modelled through microwave and thermal characterizations. The thermal behavior was extracted using FEM software and modelled with an equivalent RC network. The PA model was obtained experimentally using a pulsed setup. An RF-thermal simulator was developed and used with the models to predict joint thermal and electrical behavior. Measurements with modulated communication signals were done and compared with the simulator to demonstrate its feasibility for analysis of thermal effects in highly integrated transmitter applications.
29.	Brynzér, Henrik, et al. (författare) Sustainability and cost efficiency in Supply Chains 2013 Rapport (övrigt vetenskapligt/konstnärligt)abstract The project was formed from three basic observations, which together considerably alter the requirements when designing the supply chains. First, the lean production deployment is now ruling the design of the work cells, e.g. the assembly stations. Second, the focus on sustainability and environmental consideration is calling for new models when designing the supply chains, and third, great cost and time reduction potentials are revealed in the supply chains when applying value stream mapping. The purpose of the project was to contribute to the understanding and to the methods of how to design and evaluate sustainable and cost efficient supply chains that supports lean production processes. The project involved all industrial actors of the FFI programme and relied to a large extent on case studies performed in the companies. These cases often combined the development of models and methods with testing and pilot implementations at the companies. Results were disseminated among the actors through workshops and seminars, which further strengthened the results and understanding of applicability. Among the theoretical contributions is the development of the concept of material exposure, as an interface between materials supply and assembly. This interface realizes the product of the material supply system in the form of an available component for the assembly system to assemble, given the requirements of the customer in form of the assembly system. These requirements govern how material exposure is realized and provides a framework for how materials supply systems can be designed. In this way, the principles of lean production in the assembly is supported by the material supply, while allowing the development of a material supply system that itself is lean.One case study investigated systems for repacking of material between packaging types, that may be necessary to meet the requirements of the assembly system at the same time as the transport costs are kept down. From the case study, a classification of compo¬nents that can be handled manually in this type of repacking were derived, and five different types of components were identified. The case study conclusions include the time to pick these components between different packaging types. These results have been put into further work in the case study company, regarding designing systems for repacking of material.A theoretical model was developed to compare how the choice of packaging affect cost and CO_2 emissions for the supply of materials. A case study chose to compare two different packages with fundamentally different characteristics, one of which was a conventional returnable packaging based on plastics and the other a disposable one-way packaging. In this case the disposable packaging turned out to be clearly advantageous from both a cost and an environmental perspective.A new methodology to describe and evaluate the fulfilment of requirements of material flows was developed within the sub-project ‘Materials Flow Mapping’. This methodol¬ogy provides the ability to better, and in more detail, study material flows and its activi¬ties. Such a level of detail in the analysis proved valuable as a basis for improvement work in the materials supply system, where there is a need to be able to describe the often non-value-added activities that occur.One sub-project was carried out with the aim of developing a cost model for estimating the cost of packaging, transport and in-plant logistics in a supply chain from suppliers to assembly, and to implement this in a software. This is an important contribution to the development of a decision tool for the selection of materials supply set up. The model represents a comparatively fast tool for obtaining cost estimates of various configura¬tions of the materials supply system.Finally, one sub-project has treated materials control, to support the research being done on the physical flows. The focus has been on pull-based materials planning with consid-eration to man, technology and organization (MTO), a need that was identified during the project. The result is two-fold, the first part being a model consisting of MTO factors that are important to take into account in the design and implementation phase of a pull-based system. Secondly, research has provided a better understanding of the potential problems during a process of implementing an external pull system and classified these problems based on the MTO dimensions.
30.	Callebaut, Gilles, et al. (författare) 6G Radio Testbeds: Requirements, Trends, and Approaches 2024 Ingår i: IEEE Microwave Magazine. - 1527-3342 .- 1557-9581. ; 25:4, s. 14-31 Tidskriftsartikel (refereegranskat)abstract The proof of the pudding lies in eating, and that is why 6G testbeds are essential in the progress toward the next generation of wireless networks. Theoretical research toward 6G wireless networks proposes advanced technologies to serve new applications and drastically improve energy performance. Testbeds are indispensable to validate these new technologies under more realistic conditions. This article clarifies the requirements for 6G radio testbeds, reveals trends, and introduces approaches toward their development.
31.	Cao, Haiying, 1982, et al. (författare) Comparison of bandwidth reduction schemes in dynamic load modulation power amplifier architectures 2011 Ingår i: IEEE Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMIC), 2011. - 9781457706509 ; , s. 1-4 Konferensbidrag (refereegranskat)abstract This paper compares bandwidth reduction schemes for baseband control signals used in high efficiency power amplifier (PA) architectures, such as envelope tracking and dynamic load modulation (DLM). The baseband control signal used in such architectures usually has 3–4 times wider bandwidth than the modulated radio frequency (RF) signal. Such a wideband signal brings challenges for practical hardware design. In this paper, two bandwidth reduction schemes originally used in envelope tracking are applied on a DLM PA. The performance of both schemes are investigated by simulation. The results show that the bandwidth of the baseband control signal can be effectively reduced from 12.5 MHz to 4 MHz, while at the same time, maintaining a 49% average power-added and acceptable linearity.
32.	Cao, Haiying, 1982, et al. (författare) Compensation of Transmitter Distortion Using a Nonlinear Modeling Approach 2008 Ingår i: International Workshop on Integrated Nonlinear Microwave and Millimetre-wave Circuits 2008. - 9781424426461 ; , s. 131-134 Konferensbidrag (refereegranskat)abstract In this paper, a nonlinear modeling approach is used to demonstrate a joint compensation scheme for the linear and nonlinear distortions in the I/Q modulator and the power amplifier. Based on this nonlinear model, a digital pre-compensator is constructed. The effects of these two mostdominant nonlinear components in a modern transmitter cantherefore be digitally pre-compensated in a single step. The results are verified by experiments, and the proposed approach shows promising performance.
33.	Cao, Haiying, 1982, et al. (författare) Digital Predistortion for Dual-Input Doherty Amplifiers 2012 Ingår i: RWW 2012 - Proceedings. 2012 IEEE Topical Conference on Power Amplifiers for Wireless and Radio Applications, PAWR 2012. Santa Clara, CA, 15-18 January 2012. - 9781457711541 ; , s. 45-48 Konferensbidrag (refereegranskat)abstract This paper presents a digital predistortion techniquefor dual-input Doherty power amplifiers. The proposedtechnique utilizes both RF inputs of the main and peakamplifiers in the digital predistorter. The effectiveness ofthe resulting dual-input predistorter is evaluated on a twowayDoherty amplifier operating at 2.14 GHz with 53.5 dBmpeak output power. The experimental results demonstratethat the dual-input approach outperforms the conventionalsingle-input predistortion technique by ∼3 dB in terms ofadjacent channel leakage ratio.
34.	Cao, Haiying, 1982, et al. (författare) Digital Predistortion for High Efficiency Power Amplifier Architectures Using a Dual-input Modeling Approach 2012 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:2, s. 361-369 Tidskriftsartikel (refereegranskat)abstract In this paper, a novel model is proposed for dual-input highefficiency power amplifier (PA) architectures, such as envelope tracking (ET) and varactor-based dynamic load modulation (DLM). Compared to the traditional single-input modeling approach, the proposed model incorporates the baseband supply voltage/load control as an input. This advantage makes the new approach capable to achieve maximized average power-added efficiency (PAE) and minimizedoutput distortion simultaneously. Furthermore, the new approach has shown to be robust towards time misalignment between the RF input and baseband supply voltage/load control signals, and it can be applied with a reduced-bandwidth baseband supply voltage/load control.Experiments have been performed in a varactor-based DLM PAarchitecture to evaluate the new modeling approach. The results show that it can achieve 9 dB and 7 dB better performance than the traditional approaches in terms of adjacent channel leakage ratio and normalized mean square error, respectively. At the same time, the average PAE is maximized. Similar results have been achieved with the proposed model even when reduced-bandwidth baseband loadcontrol signal is used or time misalignment between the RF and baseband load control input signals exists. Although the new approach is only tested with DLM architecture in this paper, it is very general and can be applied to ET architectures as well.
35.	Cao, Haiying, 1982, et al. (författare) Dual-Input Nonlinear Modeling for I/Q Modulator Distortion Compensation 2009 Ingår i: 2009 IEEE Radio and Wireless Symposium, RWS 2009; San Diego, CA; United States; 18 January 2008 through 22 January 2008. - 9781424426997 ; , s. 39-42 Konferensbidrag (refereegranskat)abstract This paper focuses on modeling and compensation of both linear and nonlinear distortions in RF I/Q modulators using a dual-input Volterra series-based modeling approach. Moreover, dual-input memory polynomial and dual-input dynamic deviation reduction-based Volterra series models are proposed. The proposed models are evaluated by digital pre-compensation of a high performance I/Q modulator with a wideband input signal. The results show that the proposed dual-input models efficiently compensate for distortion in the I/Q modulator and may therefore greatly improve performance in modern communication systems.
36.	Cao, Haiying, 1982, et al. (författare) I/Q Imbalance Compensation Using a Nonlinear Modeling Approach 2009 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 57:3, s. 513-518 Tidskriftsartikel (refereegranskat)abstract In-phase/quadrature (I/Q) imbalance is one of the main sources of distortion in RF modulators. In this paper, a dual-input nonlinear model based on a real-valued Volterra series is proposed for compensation of the nonlinear frequency-dependent I/Q imbalance. First, different sources of distortion are identified from experimental measurements, then a dual-input nonlinear I/Q imbalance model is developed. Further, the inverse model is used for I/Q imbalance compensation. Finally, the performance of the I/Q imbalance compensator is evaluated with both simulations and experiments. In comparison with previously published results, the proposed I/Q imbalance compensator shows significantly improved performance. Thus, we prove that a complete nonlinear I/Q imbalance compensation can minimize the effects of the RF modulator in high-performance digital communication systems.
37.	Cao, Haiying, 1982, et al. (författare) Identification of Distortions in a RF Measurement System 2008 Ingår i: GHz Symposium 2008. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract Distortions in a RF measurement system can adversely impact the characteristics of the measured signal. In this paper, signal processing techniques are used to identify the sources for distortions. Promising measurement results are shown.
38.	Cao, Haiying, 1982, et al. (författare) Linearization of Efficiency-Optimized Dynamic Load Modulation Transmitter Architectures 2010 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 58:4, s. 873-881 Tidskriftsartikel (refereegranskat)abstract In this paper, a detailed linearization procedure for dynamic load modulation (DLM) transmitter architectures is proposed for the first time. Compared with the conventional single-input/single-output digital predistortion (DPD) approach used with traditional power amplifiers (PAs), the proposed linearization scheme is based on a regular memory DPD in combination with an efficiency-optimized static one-to-two mapping inverse model, which constructs the predistorted input signals to the DLM transmitter. The time-alignment issue, which is very important to this dual-input architecture, is also considered. The proposed technique is demonstrated by a 1-GHz 10-W LDMOS PA that employs a varactor-based tunable matching network. A normalized mean square error of $-{hbox {35 dB}}$, and adjacent channel leakage ratio of $-hbox{43 dBc}$ is achieved, with an average power-added efficiency of 53% for a single-carrier WCDMA signal with 7-dB peak-to-average ratio. Finally, it is shown that the time-alignment sensitivity is relaxed when the proposed linearization scheme is used. This means that the overall complexity of the transmitter implementation can be reduced.
39.	Cao, Haiying, 1982, et al. (författare) Time Alignment in a Dynamic Load Modulation Transmitter Architecture 2009 Ingår i: Proceedings of the 39th European Microwave Conference, EuMC 2009, Sept. 29-Oct. 1 2009, Rome. - 9781424447480 ; , s. 1211 - 1214 Konferensbidrag (refereegranskat)abstract A time alignment algorithm is proposed for a dynamic load modulation transmitter architecture. The effect of time mismatch between the RF input and baseband control signal is investigated by experiments, and it is shown that unsynchronized signals can result in severe distortion of the output signal. In this paper, cross correlation and sinc interpolation techniques are applied to estimate and compensate for the sub-sample delay between the RF signal path and the baseband control signal path in the measurement system. The performance of the dynamic load modulation transmitter architecture with accurate time alignment is shown by experimental results. The measurement shows that, the efficiency is greatly affected by time alignment and the spectral regrowth is suppressed by more than 10 dB.
40.	Cao, Haiying, 1982, et al. (författare) Time Mismatch Effects in a Dynamic Load Modulation Transmitter Architecture 2009 Ingår i: RF Measurement Technology for State of the Art Production and Design(RFMTC09). Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract In this paper, the effect of time mismatch between the RF input and baseband control signals in a dynamic load modulation transmitter is investigated. Experimental results show that even a small time mismatch between the input signals can result in severe distortion of the output signal.
41.	Cao, Wenhui, 1990, et al. (författare) Complexity Optimized Digital Predistortion Model of RF Power Amplifiers 2022 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 70:3, s. 1490-1499 Tidskriftsartikel (refereegranskat)abstract A novel behavioral modeling technique for digital predistortion of radio frequency power amplifiers (PAs) is proposed. The proposed basis-propagating selection (BAPS) model has an advantage on complexity since its basis functions are constructed as delay or a combination of existing basis functions. The BAPS model effectively optimizes the running time complexity while maintaining the generality of a full Volterra series. A greedy search procedure is applied to select the optimal basis functions. Compared with truncated Volterra models and pruned models obtained by popular pruning techniques, the superior performance of the BAPS model, in terms of accuracy and identification stability, has been fairly justified. The linearization measurements on different types of PAs illustrate that the BAPS model can robustly outperform other models from literature while achieving a low running complexity.
42.	Chagtmi, Nadia, et al. (författare) Augmented Hammerstein model for the calibration of six-port based dual band wireless receivers 2019 Ingår i: International Journal of RF and Microwave Computer-Aided Engineering. - : Hindawi Limited. - 1096-4290 .- 1099-047X. ; 29:2 Tidskriftsartikel (refereegranskat)abstract Two architectures of concurrent dual-band six-port-based receiver (SPR), which are modeled and calibrated using the augmented Hammerstein model (AHM) are proposed for the first time in this article. The receivers are based on six-port junctions with one or two local oscillators (LO). The proposed single step calibration algorithms achieve the recovery of the two in-phase (I1 and I2) and quadrature (Q1 and Q2) components of an RF signal with two frequency components (RF1 and RF2). Experimental validations have been performed to verify the performance of the proposed concurrent dual-band receivers and to test the efficiency of the AHM based calibration algorithms. As a performance metric, the Error Vector Magnitude (EVM) has been measured to compare the transmitted and recovered baseband signals and to evaluate the performance and efficiency of the proposed calibration algorithms for the two receiver topologies. The IQ data has been recovered with EVMs no higher than 2% for the two LOs based receiver excited with a QAM modulated dual-band RF signal. The single LO based receiver has been tested with a dual-band LTE signal and the recovered IQ data exhibited EVMs no higher than 4%.
43.	Chani Cahuana, Jessica, 1988, et al. (författare) A new variant of the indirect learning architecture for the linearization of power amplifiers 2015 Ingår i: 2015 European Microwave Conference (EuMIC). - 9782874870408 ; , s. 444-447 Konferensbidrag (refereegranskat)abstract The indirect learning architecture (ILA) is the most commonly used technique for the identification of digital pre-distorters for power amplifiers (PA). A critical issue in ILA is the selection of the normalization gain used to synthesize the predistorter function. In this paper, we investigate the effects that the normalization gain has on the average output power and linearity of PAs. Moreover, we propose a new variant of the ILA that eliminates the need of a normalization gain inside the iterative loop. Experimental results show that the selection of the normalization gain affects the average output power and consequently the linearity performance of the linearized PA. If the normalization gain is not chosen correctly, the average output power of the linearized PA will differ from the average output power obtained before DPD. It is experimentally shown that the proposed ILA variant can maintain the same average output power before and after DPD. Consequently the proposed ILA variant simplifies the linearization process and allows proper evaluation of the DPD performance.
44.	Chani Cahuana, Jessica, 1988, et al. (författare) Digital Predistorter Model Derivation Based on Iterative Learning Control 2016 Ingår i: IEEE European Microwave Conference. Konferensbidrag (refereegranskat)
45.	Chani Cahuana, Jessica, 1988, et al. (författare) Digital Predistortion Parameter Identification for RF Power Amplifiers Using Real-Valued Output Data 2017 Ingår i: IEEE Transactions on Circuits and Systems II: Express Briefs. - 1549-7747 .- 1558-3791. ; 64:10, s. 1227-1231 Tidskriftsartikel (refereegranskat)abstract This brief presents a novel digital predistortion (DPD) parameter identification technique that requires only the acquisition of either the in-phase (I) or the quadrature (Q) component of the power amplifier (PA) output signal. To this end, an approach that allows us to estimate the parameters of a model using only one of the IQ components of the model output is presented. Based on experimental results, it is shown that the proposed real-valued measurements based technique can offer similar linearization capabilities as its complex-valued counterparts. The experimental results also indicate that the proposed technique can be used in combination with other techniques that focus on reducing the speed of analog-to-digital converters (ADCs)
46.	Chani Cahuana, Jessica, 1988, et al. (författare) Iterative Learning Control for RF Power Amplifier Linearization 2016 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9480 .- 1557-9670. ; 64:9, s. 2778-2789 Tidskriftsartikel (refereegranskat)abstract This paper proposes a new technique to identify the parameters of a digital predistorter based on iterative learning control (ILC). ILC is a well-established control theory technique that can obtain the inverse of a system. Instead of focusing on identifying the predistorter parameters, the technique proposed here first uses an iterative learning algorithm to identify the optimal power amplifier (PA) input signal that drives the PA to the desired linear output response. Once the optimal PA input signal is identified, the parameters of the predistorter are estimated using standard modeling approaches, e.g., least squares. To this end, in this paper, we present a complete derivation of an ILC scheme suitable for the linearization of PAs, which includes convergence conditions and the derivation of two learning algorithms. The proposed ILC scheme and parameter identification technique were demonstrated experimentally and compared with the indirect learning architecture (ILA) and direct learning architecture (DLA). The experimental results show that, even for the most difficult cases, the proposed ILC scheme can successfully linearize the PA. The experimental results also indicate that the proposed parameter identification technique is more robust to measurement noise than ILA and can provide better linearity performance when the PA nonlinearities are strong. In addition, the proposed parameter identification technique can achieve similar or better linearity performance than DLA but with a simpler identification process.
47.	Chani Cahuana, Jessica, 1988, et al. (författare) Linearization of dual-input Doherty power amplifiers 2014 Ingår i: International Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits, INMMiC 2014. ; , s. Art. no. 6815085- Konferensbidrag (refereegranskat)abstract This paper studies the linearity of dual-input Doherty power amplifiers. We propose a linearization scheme that uses a combination of an efficiency-optimized static splitter and a vector-switched digital predistorter. The performance of the proposed linearization scheme is evaluated on a dual-input Doherty power amplifier operating at 2.0 GHz with 42 dBm peak output power. Experimental results show that the proposed linearization scheme achieves a normalized mean square error of-43.7 dB and an adjacent channel power ratio of-55.8 dBc with a power added efficiency of 42.4%.
48.	Chani Cahuana, Jessica, 1988, et al. (författare) Lower Bound for the Normalized Mean Square Error in Power Amplifier Linearization 2018 Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 28:5, s. 425-427 Tidskriftsartikel (refereegranskat)abstract The normalized mean square error (NMSE) is a performance criteria commonly used in power amplifier (PA) linearization to quantify the amount of in-band distortion encountered at the output of a PA. This letter presents a closed-form expression for the minimum NMSE that could be obtained in a linearization scenario. The derived expression is verified through numerical simulations and is used to compare the performance of different digital predistortion linearization schemes proposed in the literature.
49.	Chani Cahuana, Jessica, 1988, et al. (författare) Structured Digital Predistorter Model Derivation Based on Iterative Learning Control 2016 Ingår i: 2016 46th European Microwave Conference. - 2325-0305. - 9782874870439 ; , s. 178-181 Konferensbidrag (refereegranskat)abstract A novel approach to derive model structures for digital predistorters based on iterative learning control (ILC) is presented. ILC is a technique used to identify the optimal PA input signal/predistorted signal that drives a PA to a desired output response. The ILC concept is used to derive an analytical expression of the predistorted signal and to identify basis functions for predistorter models. The proposed approach is used to derive a predistorter model structure from the memory polynomial model. Experimental results show that the predistorter model derived with the proposed approach can obtain better linearity performance than conventional models used in digital predistortion.
50.	Deborgies, Francois, et al. (författare) Welcome to the 15th European Microwave Integrated Circuits Conference 2021 Ingår i: EuRAD 2020 - 2020 17th European Radar Conference. Konferensbidrag (övrigt vetenskapligt/konstnärligt)

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