## About

125

Publications

21,668

Reads

**How we measure 'reads'**

A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more

2,173

Citations

Introduction

**Skills and Expertise**

## Publications

Publications (125)

An ultra-wide band measurement method for determining the complex refractive index of large-volume objects is presented. The method is intended for industrial non-destructive testing. It uses a frequency-domain technique in which transmitted radio pulses are analyzed and the effects of near field and coupling on the determined refractive index are...

Experimental characterization of an amplifier's nonlinear properties at 24 GHz is presented in single and dual-band operation using orthogonal frequency-division multiplex signals. A test system for characterizing an amplifier's nonlinear properties at millimeter-wave frequencies for single and dual-band excitation is presented. The use of standard...

We consider backward crosstalk in
$2\times 2$
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...

A novel resonance method for determining the complex permittivity of materials in the X-band is proposed. A distinctive feature of this method is that the sample under test, located in a radio-transparent isotropic and homogeneous dielectric matrix, is both a local inclusion and the excitation element of the resonance in the microwave module ‘waveg...

Crosstalk between the transceiver branches appears in practical multi-antenna transmitters. This paper analyzes the backward crosstalk in 2x2 transmitters, which is caused by crosstalk from the outputs to inputs or by the combination of output crosstalk and impedance mismatch. We consider arbitrarily correlated input signals, while feedback network...

Nonlinear static multiple-input multiple-output (MIMO) systems are analyzed. The matrix formulation of Bussgang's theorem for complex Gaussian signals is rederived and put in the context of the multivariate cumulant series expansion. The attenuation matrix is a function of the input signals' covariance and the covariance of the input and output sig...

Combating the effects of mixer and power amplifier (PA) imperfections on transmitter performance is crucial for the design of wireless systems. PA compression and in-phase/quadrature imbalance are analyzed for a single-input-single-output transmitter model. The influence of the imperfection on the normalized mean squared error (NMSE) of the transmi...

Modern telecommunications are moving towards (massive) multi-input multi-output (MIMO) systems in 5th generation (5G) technology, increasing the dimensionality of the systems dramatically. In this paper, the impairments of radio frequency (RF) power amplifiers (PAs) in a 3 × 3 MIMO system are compensated in both the time and the frequency domains....

A compact multiband diamond-shaped fractal bow-tie terahertz antenna is designed on FR4_epoxy substrate with permittivity 4.4. The dimension of substrate is 4 × 6 × 1.5 mm3. Multi-bands are obtained in S11 versus frequency plots. The effects of creating defects in the ground plane of the antenna were studied and analyzed to get the optimized perfor...

A combined L-S-band antenna module consists of four rectangular patch antennas, two of which operate at the frequencies of the first harmonics (L-band), and two others at the frequencies of the second harmonics (S-band). The module is intended for use in super heterodyne signal reception circuits, for example in studying the various non-linear phen...

A modified symmetric split ring resonator (MSSRR) loaded bowtie antenna with multi-band features over a range of 1.6–7.1 GHz is proposed in this paper. The antenna is designed on FR4 substrate with relative permittivity εr = 4.1 and thickness 1.5 mm. The fabricated antenna size is 40 mm × 58 mm. The Modified Symmetric SRR used beneath the substrate...

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 detai...

A method to determine the pth-order inverse of the Volterra series of multiple-input multiple-output non-linear dynamic systems is presented; it combines time- and frequency-domain techniques to determine the Volterra series of the inverse as a function of the forward system's Volterra series. The method can be used for continuous and discrete time...

This rebuttal is to “On dual-band amplifications using dual two-tone: Clarifications and discussion.” In the following, we provide our reply.

The paper presents a 2D extended envelope memory polynomial (2D-EEMP) model for concurrent dual-band radio frequency (RF) power amplifiers (PAs). The model is derived based on the physical knowledge of a dual-band RF PA. The derived model contains cross-modulation terms not included in previously published models; these terms are found to be of imp...

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 (IIR) fixed pole expansion techniques for the behavioral modeling and digital pre-distortion of single-input-single-output (SISO) and concurrent dual...

Multiple-input multiple-output (MIMO) frequency-domain Volterra kernels of nonlinear order 3 are experimentally determined in bandwidth-limited frequency regions. How the effect of higher nonlinear orders can be reduced and how this affects the estimated errors are discussed. The magnitude and phase of the kernels areKramers-Kronig consistent. The...

There is provided methods and devices for measuring the phase noise of a set of electromagnetic signals, the set comprising at least two electromagnetic signals, in order to construct a representation of the phase noise where the correlated contribution and uncorrelated contribution to the phase noise is determined. There is also provided a device...

This paper presents a multiple-input multiple-output (MIMO) nonlinear mitigation technique for closely spaced concurrent aggregated carrier systems. The transmitter architecture considers band-limited sources, where the predistorter and signal bandwidth are the same, thus reducing transmitter hardware cost and power consumption. The technique relie...

A method is proposed for determining the correlated and uncorrelated parts of phase noise spectra (PNS) of two continuous wave radio signals of different frequencies, ω 1 and ω 2. The PNS of the two signals and of mixed signals are measured. The PNS are modelled as having a correlated part that is the same for both signals, except for a multiplicat...

A compact four-element multi-input-multi-output (MIMO) antenna useful for wireless ultra-wide band (UWB) applications and systems is introduced in this paper. The frequency bandwidth obtained with the proposed UWB antennas is 1.5 to 12.5 GHz. The substrate material used is FR4 with dielectric coefficient of 4.4. The dimension of the substrate is 30...

The combined system with microstrip antennas (f 1 =1.85GHz; f 2 =3.7GHz, f 3 =1.75GHz, f 4 = 3.5GHz) is presented. The measurements of the prototype characteristics have shown that elevation angle of peak directivity of the antennas is oriented to zenith. Simulated S 11 at stated frequencies with the following minimum values of S 11 = −34dB, f=1.85...

In this paper, a novel dual band pass Frequency Selective Surface (FSS) is presented. The FSS is a L9 shaped structure with dimensions 7 × 7mm 2 and substrate thickness h = 0.762 mm. The proposed FSS aims to provide dual pass-bands in X-band. A stacked array FSS is also studied to broaden the transmission band of the structure. An equivalent circui...

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)...

A new two-tone test method for radio frequency power amplifiers is presented. The test signal is a two-tone probing-signal superimposed on large-signals of different amplitude. The amplifier is, thus, excited in different amplitude regions. The amplitude and phase of the 3rd order intermodulation (IM) products are measured vs. frequency spacing and...

An X-band radiator as an open-ended waveguide with a hybrid dielectric insert is proposed. The insert is in the form of a parallelepiped, which fills the entire cross section of the waveguide and constitutes a Teflon matrix with local inhomogeneities in the form of dielectric cylinders with a different permittivity. The design allows for forming va...

Through leakage in the building envelope there is a penetration of air, water vapor and particles. The degree of leakage of air can be quantified by existing methods. However, the location of adventitious openings is often not known. In order to overcome the limitations in existing methods, a non-contact and non-destructive method based on ultra-wi...

The use of “even” order polynomial terms in radio frequency power amplifier behavioral modeling and digital pre-distortion linearization has long been discussed. This contribution mathematically shows that the purely odd polynomials and the odd-even polynomials are equivalent up to the truncation error inherent in the model itself. The choice of od...

Design of low loss with an enhanced thermal profile power divider/combiner for high power dual-band Radio Frequency (RF) power amplifier applications is given. The practical implementation, low loss and substrate characteristics make this type of combiner ideal for high power microwave applications. The combiner operational frequencies are chosen t...

A digital predistortion (DPD) scheme is presented for non-linear distortion mitigation in multi-carrier satellite
communication channels. The proposed DPD has a multiple-input multiple-output architecture similar to data DPD schemes. However, it enhances the mitigation performance of data DPDs using a multi-rate processing algorithm to achieve spec...

A method to characterize the memory effects in a nonlinear concurrent dual-band transmitter is presented. Compared to a SISO nonlinear transmitter, the output signal of a concurrent dual-band transmitter is affected not only by intermodulation products, but also by the cross-modulation products. The characterization of memory effects is done by exc...

Aiming to reduce the power/mass requirements in satellite transponders and to reduce mission costs,
joint amplification of multiple carriers using a single high-power amplifier (HPA) is being considered. In this scenario, a careful investigation of the resulting power efficiency is essential as amplification is nonlinear, and multicarrier signals e...

In this paper, a new design of metafractal antenna is proposed. The dimension of the patch is 44 × 44 mm2 and the FR4 substrate is used for this. The fractal antenna with metamaterial ground plane is used for different iterations. The results show that with the increase of the number of iterations the bandwidth is increased. In the case of higher i...

Using sparse estimation methods, digital predistortion of power amplifiers is presented in this paper comparing SISO and MIMO systems. A general description of MIMO systems, given by Volterra series has larger complexity when compared with SISO systems. In consequence, both Volterra
modelling and predistortion of MIMO amplifiers become complex or u...

This paper proposes three novel models for behavioral modeling and digital pre-distortion (DPD) of nonlinear 2 × 2 multiple-input multiple-output (MIMO) transmitters in the presence of crosstalk. The proposed models are extensions of the single-input single-output generalized memory polynomial model. Three types of crosstalk effects were studied an...

In this paper, we present a method to limit the generation of signal peak power at the output of a digital pre-distorter that is applied to a RF power amplifier (PA) operating in strong compression. The method can be considered as a joint crest-factor reduction and digital pre-distortion (DPD). A challenging characteristic of DPD when applied to a...

The indirect learning architecture (ILA) is the most used methodology for the identification of Digital Predistorter (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 estim...

On-board joint power amplification of multiple-carrier DVB-S2 signals using a single High-Power Amplifier (HPA) is an emerging configuration that aims to reduce flight hardware and weight. However, effects specific to such a scenario degrade power and spectral efficiencies with increased Adjacent Channel Interference caused by non-linear characteri...

In many test and measurement applications, the analogue-to-digital converter (ADC) is the limiting component. Using post-correction methods can improve the performance of the component as well as the overall measurement system. In this paper an ADC is characterised by a Kautz–Volterra (KV) model, which utilises a model-based post-correction of the...

The Volterra theory can be used to mathematically model nonlinear dynamic components such as analog-to-digital converters (ADCs). This paper describes how frequency-domain Volterra kernels of an ADC are determined from measurements. The elements of the Volterra theory are given, and practical issues are considered, such as methods for signal condit...

A stepped three-tone measurement technique based on digitally modulated baseband signals is used in characterizing radio-frequency power amplifiers (PAs). The bandwidths of the stepped measurement were 8.8 MHz for the input signal and 26.4 MHz for the output signal. A PA designed for third-generation mobile telecommunication system was analyzed. Th...

In this paper, a novel method to measure the amplitude and phase of two-tone third-order intermodulation products generated in a high-power amplifier is presented. The method is based on the sampled input and output signals of the amplifier. The presented measurement setup and the associated algorithms for the calculation of the amplitudes and phas...

A nonlinear dynamic behavioral model for radio frequency power amplifiers is presented. It uses orthonormal basis functions, Kautz functions, with complex poles that are different for each nonlinear order. It has the same general properties as Volterra models, but the number of parameters is significantly smaller. Using frequency weighting the out-...

To develop a fast, accurate, objective and nondestructive method for monitoring barley tempeh fermentation.
Barley tempeh is a food made from pearled barley grains fermented with Rhizopus oligosporus. Rhizopus oligosporus growth is important for tempeh quality, but quantifying its growth is difficult and laborious. A system was developed for analys...

In this paper, a method for increasing the bandwidth of a test bed for dynamic characterization of power amplifiers (PAs) is described. The technique is readily implemented using commercially available instruments, which makes it suitable for, e.g., production testing. The bandwidth extension technique is combined with coherent averaging of the mea...

An investigation of the complex-valued parameters of two different dynamic behavioral models due to changes in the drain decoupling network of a PA has been performed. The study is based on complex-envelope measurements on a real PA. The complex coefficients of the parallel Hammerstein (PH) and the optimal pole placements of the Kautz-Volterra (KV)...

In many test and measurement applications, the analogue-to-digital converter (ADC) is the limiting component. Using post-correction methods can improve the performance of the component as well as the over all measurement system. In this paper an ADC is characterised by a Kautz-Volterra (KV) model, which utilises a model-based post-correction of the...

A digital predistortion algorithm for radio frequency power amplifiers based on orthonormal basis functions is presented. It has the same general properties as a Volterra model, but fewer parameters. Experimentally, using a 3.84 MHz wide signal at 2.14 GHz, the adjacent channel power was suppressed 12 to 15 dB, which was 5 to 7 dB more than a polyn...

A Doherty amplifier was investigated using behavioral amplifier modeling techniques. A measurement system for simultaneous wide bandwidth (>100 MHz) and large dynamic range (-70 dBc ACLR) sampled measurements that are needed for the behavioral modeling is presented. Both the measurement system and the performance of the Doherty amplifier are descri...

A new type of behavioral power amplifier (PA) model, a discrete-time Kautz-Volterra (KV) model, is presented. In the model a priori knowledge of the system properties in terms of different poles for different nonlinear orders is used, which is needed for modeling nonlinear and linear memory effects in PAs. An accurate model can thus be achieved wit...

In this paper a method for increasing the bandwidth of a test-bed for dynamic characterization of power amplifiers is described. The technique is readily implemented using commercially available instruments which makes it suitable for, for example, production testing. The bandwidth extension technique is combined with coherent averaging of the meas...

A comparative study of nonlinear behavioral models with memory for radio-frequency power amplifier (PAs) is presented. The models are static polynomial, parallel Hammerstein (PH), Volterra, and radial basis-function neural network (RBFNN). Two PAs were investigated: one was designed for the third-generation (3G) mobile telecommunication systems and...

A radial-basis function neural network (RBFNN) has been used for modeling the dynamic nonlinear behavior of an RF power amplifier for third generation. In the model, the signal's envelope is used. The model requires less training than a model using IQ data. Sampled input and output signals were used for identification and validation. Noise-like sig...

A radial-basis function neural network (RBFNN) is proposed for modeling the dynamic nonlinear behavior of RF power amplifiers. In the model the signal's envelope is used. The model requires less training than a model using both IQ-data. Sampled input and output signals from a power amplifier for 3G were used in the identification and validation. Th...

matlab files for the technical report D. Rönnow ” Software for determining the third order Volterra kernels of radio frequency power amplifiers” Working Paper 33, University of Gävle, Gävle, Sweden, 2005.

Software for determining the third order Volterra kernels of radio frequency power amplifiers is presented. The background theory is included, the source code in Matlab is appended and some examples are given as illustrations and for verification of the code. 2 Contents I.

We report on switching properties in the microwave region of yttrium hydride. A microstrip line of gold on a quartz substrate was used. A gap in the gold had an yttrium hydride layer of 1.0 μm thickness with a cap layer of 5 nm palladium and 2 nm aluminium oxide. The yttrium hydride was switched between a metallic and a semiconducting state with th...

We report a reflectance difference spectroscopy (RDS) study of the optical anisotropy of GaAs:(001) Surface quantum wells consisting of a thin GaAs layer (3-30 nm thick) embedded between an arsenic reconstructed surface and an AlAs barrier. The RDS spectra display anisotropic contributions from the free Surface and from the GaAs/AlAs interface. By...

The strip coating material, Opticlean, which has been reformulated, has been shown to remove 1-5-microm-diameter particles as well as contamination remaining from previous drag wipe cleaning on a used silicon wafer. In addition, no residue that produced scattering was found on a fresh silicon wafer when Opticlean was applied and then stripped off....

Integrated light scattering, from thin, transparent silicon wafers with
different front and backside surface roughness is investigated. The
measurements are made at near normal incidence in the IR wavelength
region 5 to 20 micrometers using an integrating sphere. A method to
separate the scattering contribution from each interface for
measurements...

The scaling of surface roughness in thin spray pyrolyzed fluorinated tin dioxide films of different thicknesses was obtained from atomic force microscopy. The data show that, within experimental uncertainties, the effective dimensionality of the surface is 2; hence no evidence of fractal surface roughness was found. Other methods – based upon light...