Oscillator Phase Noise and Small-Scale Channel Fading in Higher Frequency Bands

This paper investigates the effect of oscillator phase noise and channel variations due to fading on the performance of communication systems at frequency bands higher than 10GHz. Phase noise and channel models are reviewed and technology-dependent bounds on the phase noise quality of radio oscillators are presented. Our study shows that, in general, both channel variations and phase noise can have severe effects on the system performance at high frequencies. Importantly, their relative severity depends on the application scenario and system parameters such as center frequency and bandwidth. Channel variations are seen to be more severe than phase noise when the relative velocity between the transmitter and receiver is high. On the other hand, performance degradation due to phase noise can be more severe when the center frequency is increased and the bandwidth is kept a constant, or when oscillators based on low power CMOS technology are used, as opposed to high power GaN HEMT based oscillators.Comment: IEEE Global Telecommun. Conf. (GLOBECOM), Austin, TX, Dec. 201

Calculation of the Performance of Communication Systems from Measured Oscillator Phase Noise

Oscillator phase noise (PN) is one of the major problems that affect the performance of communication systems. In this paper, a direct connection between oscillator measurements, in terms of measured single-side band PN spectrum, and the optimal communication system performance, in terms of the resulting error vector magnitude (EVM) due to PN, is mathematically derived and analyzed. First, a statistical model of the PN, considering the effect of white and colored noise sources, is derived. Then, we utilize this model to derive the modified Bayesian Cramer-Rao bound on PN estimation, and use it to find an EVM bound for the system performance. Based on our analysis, it is found that the influence from different noise regions strongly depends on the communication bandwidth, i.e., the symbol rate. For high symbol rate communication systems, cumulative PN that appears near carrier is of relatively low importance compared to the white PN far from carrier. Our results also show that 1/f^3 noise is more predictable compared to 1/f^2 noise and in a fair comparison it affects the performance less.Comment: Accepted in IEEE Transactions on Circuits and Systems-I: Regular Paper

A 24 GHz Sub-Harmonically Pumped Resistive Mixer in GaN HEMT Technology

—This paper presents the design and the characterization of a 24 GHz sub-harmonically pumped resistive mixer (SHM) in an advanced gallium nitride (GaN) high electron mobility transistor (HEMT) technology. The mixer is desired for building up a high-performance phaselocked W-band signal source, and is designed in a singlebalanced configuration, where the balanced LO input is generated by an on-chip first order lattice balun. In measurement, a conversion loss around 12 dB is achieved at the RF bandwidth of 22-28 GHz and the IF bandwidth of 3-6 GHz with a LO power of 10 dBm. The mixer exhibits an RF input P1dB of 13 dBm, and the measured LO to IF isolation achieves 40 dB at the desired LO of 10 GHz. To the best of the author’s knowledge, this is the first sub-harmonically pumped mixer in GaN HEMT technology

25 GHz and 28 GHz Wide Tuning Range 130 nm CMOS VCOs with Ferroelectric Varactors

Two 130nm CMOS VCOs with ferroelectric varactors are presented. The cross-coupled VCO-cores are flip-chip mounted on silicon carriers with integrated inductors and tunable ferroelectric varactors. The output frequency of the first VCO is tunable from 23.4 GHz to 26.1 GHz, corresponding to a tuning range of 11 %. The phase noise of this VCO, tuned to its center frequency, measures -117 dBC/Hz at 1 MHz offset and the power consumption is 18 mW. The second VCO is tunable from 25.8 GHz to 30.5 GHz, corresponding to a tuning range of 17 %. The phase noise at center frequency for this design measures -109 dBc/Hz and the power consumption is 5.3 mW

Towards Machine Learning on data from Professional Cyclists

Professional sports are developing towards increasingly scientific training methods with increasing amounts of data being collected from laboratory tests, training sessions and competitions. In cycling, it is standard to equip bicycles with small computers recording data from sensors such as power-meters, in addition to heart-rate, speed, altitude etc. Recently, machine learning techniques have provided huge success in a wide variety of areas where large amounts of data (big data) is available. In this paper, we perform a pilot experiment on machine learning to model physical response in elite cyclists. As a first experiment, we show that it is possible to train a LSTM machine learning algorithm to predict the heart-rate response of a cyclist during a training session. This work is a promising first step towards developing more elaborate models based on big data and machine learning to capture performance aspects of athletes.Comment: Accepted for the 12th World Congress on Performance Analysis of Sports, Opatija, Croatia, 201

On Models, Bounds, and Estimation Algorithms for Time-Varying Phase Noise

In this paper, first, a new discrete-time model of phase noise for digital communication systems, which is a more accurate model compared to the classical Wiener model, is proposed based on a comprehensive continuous-time representation of time-varying phase noise, and statistical characteristics of this model are derived. Next, the non-data-aided (NDA) and decision-directed (DD) maximum-likelihood (ML) estimators of time-varying phase noise, using the proposed discrete-time model are derived. To evaluate the performance of the proposed estimators, the Cramer-Rao lower bound (CRLB) for each estimation approach is derived and by using Monte-Carlo simulations it is shown that the mean-square error (MSE) of the proposed estimators converges to the CRLB at moderate signal-to-noise ratios (SNR). Finally, simulation results show that the proposed estimators outperform existing estimation methods as the variance of the phase noise process increases

Photoluminescence Properties and Fabrication of Red-Emitting LEDs based on Ca9Eu(VO4)(7) Phosphor

We study the photoluminescence properties of the red-emitting phosphor Ca9Eu(VO4)(7) and establish a strong red emission centered at 613 nm under excitation at 395 nm (near ultra violet light, near-UV light) due to the intra-configurational D-5(0) -> F-7(2) transition within the 4f(6) configuration of the Eu3+ ions. The intensity of the emitted light decreases with increasing temperature and at T = 470 K about 50% of the intensity of the emitted light at room temperature is lost. Five different red-LED prototypes were constructed by applying a mixture of Ca9Eu(VO4)(7) phosphor and silicone gel on the headers of near-UV LED chips. The prototypes showed a color output from violet for the lowest phosphor concentration (133 g phosphor /l silicone gel), reaching an almost pure red-light output for the highest phosphor concentration (670 g phosphor /l silicone gel). The luminous efficiency of optical radiation (LER) was found to decrease slightly with increasing applied current. For the highest phosphor concentration, the LER decreases from 238 lmW(-1) for 1 mA current supply to 235 lmW(-1) for 18 mA current supply. The external quantum efficiency decreased from 7.33% for the lowest phosphor containing LED prototype to 4.13% for the highest one. (C) The Author(s) 2019. Published by ECS

Machine Learning Techniques for Gait Analysis in Skiing

We investigate the use of supervised machine learning on data from ski-poles equipped with force sensors, with the goal of auto- matically identifying which sub-technique the skier is using. Our first contribution is a demonstration that sub-technique identification can be done with high accuracy using only sensors in the pole. Secondly, we also compare different machine learning algorithms (LSTM neural networks and random forests) and highlight their respective strengths and weaknesses, providing practitioners working with sports data some guidance for choice of machine learning algorithms

A MMIC GaN HEMT Voltage-Controlled-Oscillator with high tuning linearity and low phase noise

This paper presents a MMIC GaN HEMT Voltage- Controlled-Oscillator (VCO). The VCO is tunable between 6.45-7.55 GHz with good tuning linearity, average output power about 1 dBm, and a good phase noise with little variation over the tuning range. For a bias of Vd /Id = 6 V/33 mA, the measured phase noise is -98 dBc/Hz @ 100 kHz and -132 dBc/Hz @ 1 MHz offset frequencies, respectively. To the author's best knowledge, this is the lowest phase noise reported for a VCO in GaN HEMT technology with comparable oscillation frequency and tuning range. The 1 MHz offset phase noise is also comparable to state-of-the-art GaAs-InGaP HBT VCOs with similar tuning range

Integrated Lumped Element and Ferroelectrically Tunable Microwave Components

This thesis treats the development of passive circuits for increased integrationlevel in microwave front-ends. The subject is approached from twodifferent directions. On the one hand, emerging materials for microwaveintegrated circuits are studied. On the other hand, novel circuit topologiesare synthesized.Ferroelectric Ba0.25Sr0.75TiO3 (BSTO) varactors are considered for reconfigurablemicrowave circuits. Tunable compact delay lines and metamaterialphase shifters are integrated on highly resistive silicon (HRS) substrate.The circuits are implemented in coplanar configurations, coplanarstrip (CPS) lines and coplanar waveguide (CPW), respectively. The problemof charge accumulation at the Si/SiO2 interface is addressed. Surfacepassivation techniques for HRS substrates covered by ferroelectric films arestudied. It is found that established techniques for surface passivation, i.e.,bombardment with Ar-ions and deposition of poly-Si, are compatible withthe growth of BSTO films. It is also indicated that for millimeter-wavefrequencies, multilayer structures consisting of two metal layers in parallelcoupled through a high permittivity BSTO film exhibit lower loss than asingle metal layer of the same thickness as the two metal layers together.Circuit topologies for generation of differential and quadrature signalsare developed. The second order lattice balun (SOLB), a novel lumpedelementbalun topology based on cross-coupled low-pass and high-pass filters,is synthesized. The circuit provides excellent balancing performanceover bandwidths larger than one octave. For generation of quadraturesignals, lumped quadrature power splitters (LQPSs) based on right/lefthandedtransmission lines are designed. The LQPSs generate well quadraturebalancedsignals with negligible amplitude error. Their bandwidth is restrictedby the phase balance and the input matching. Depending on specifications,up to one octave bandwidth may be reached. Closed-form designequations for component values are derived for both the SOLB and theLQPSs. Both circuits are also validated by experiments. The LQPSs areimplemented at a commercial GaAs MMIC foundry. The SOLB is manufacturedat the same MMIC foundry as well as with surface mounted componentssoldered on a printed circuit board