Analysis and design of sinusoidal quadrature RC-oscillators

Modern telecommunication equipment requires components that operate in many different frequency bands and support multiple communication standards, to cope with the growing demand for higher data rate. Also, a growing number of standards are adopting the use of spectrum efficient digital modulations, such as quadrature amplitude modulation (QAM) and orthogonal frequency division multiplexing (OFDM). These modulation schemes require accurate quadrature oscillators, which makes the quadrature oscillator a key block in modern radio frequency (RF) transceivers. The wide tuning range characteristics of inductorless quadrature oscillators make them natural candidates, despite their higher phase noise, in comparison with LC-oscillators. This thesis presents a detailed study of inductorless sinusoidal quadrature oscillators. Three quadrature oscillators are investigated: the active coupling RC-oscillator, the novel capacitive coupling RCoscillator, and the two-integrator oscillator. The thesis includes a detailed analysis of the Van der Pol oscillator (VDPO). This is used as a base model oscillator for the analysis of the coupled oscillators. Hence, the three oscillators are approximated by the VDPO. From the nonlinear Van der Pol equations, the oscillators’ key parameters are obtained. It is analysed first the case without component mismatches and then the case with mismatches. The research is focused on determining the impact of the components’ mismatches on the oscillator key parameters: frequency, amplitude-, and quadrature-errors. Furthermore, the minimization of the errors by adjusting the circuit parameters is addressed. A novel quadrature RC-oscillator using capacitive coupling is proposed. The advantages of using the capacitive coupling are that it is noiseless, requires a small area, and has low power dissipation. The equations of the oscillation amplitude, frequency, quadrature-error, and amplitude mismatch are derived. The theoretical results are confirmed by simulation and by measurement of two prototypes fabricated in 130 nm standard complementary metal-oxide-semiconductor (CMOS) technology. The measurements reveal that the power increase due to the coupling is marginal, leading to a figure-of-merit of -154.8 dBc/Hz. These results are consistent with the noiseless feature of this coupling and are comparable to those of the best state-of-the-art RC-oscillators, in the GHz range, but with the lowest power consumption (about 9 mW). The results for the three oscillators show that the amplitude- and the quadrature-errors are proportional to the component mismatches and inversely proportional to the coupling strength. Thus, increasing the coupling strength decreases both the amplitude- and quadrature-errors. With proper coupling strength, a quadrature error below 1° and amplitude imbalance below 1% are obtained. Furthermore, the simulations show that increasing the coupling strength reduces the phase noise. Hence, there is no trade-off between phase noise and quadrature error. In the twointegrator oscillator study, it was found that the quadrature error can be eliminated by adjusting the transconductances to compensate the capacitance mismatch. However, to obtain outputs in perfect quadrature one must allow some amplitude error

A modified multiphase oscillator with improved phase noise performance

This paper investigates the factors that influence the phase noise performance of an oscillator and proposes a modified structure for improved phase noise performance. A single and multiphase oscillator analysis using the harmonic balance method is presented. The modified structure increases the oscillation amplitude without increasing the bias current and leads to improved phase noise performance as well as decreased power consumption. The modification is analyzed and the figure of merit of the oscillator shows a significant improvement of 21 dB. Numerical and analytical solutions are presented to predict the oscillation frequency and phase noise. The analytical solution is used to approximate the first harmonic and can be combined with numerical simulations to extrapolate phase noise performance.The measurements relating to this work were enabled through the support of SAAB Electronic Defence Systems (EDS). Funding was also received from the National Research Foundation (NRF), Department of Science and Technology, South Africa. NRF funding was for measurement equipment – a millimeter-wave vector network analyzer (under grant ID: 72321) and wafer-prober (under grant ID: 78580). NRF funding (under grant ID: 72321) also allowed collaboration with Prof Luca Larcher, Università degli studi di Modena e Reggio Emilia, Italy.http://www.elsevier.com/locate/mejo2018-04-30am2017Electrical, Electronic and Computer Engineerin

350 mV, 5 GHz Class-D Enhanced Swing Differential and Quadrature VCOs in 65 nm CMOS

A new enhanced swing class-D VCO which operates from a supply voltage as low as 300 mV is presented. The architectural advantages are described along with an analysis for the oscillation frequency. Prototype differential and quadrature variants of the proposed VCO have been implemented in a 65 nm RF CMOS process with a 5 GHz VCO oscillation frequency. At a 350 mV supply, the measured phase noise performance for the quadrature VCO with a 5% tuning range is -137.1 dBc/Hz at 3 MHz offset with a power dissipation of 2.1 mW from a 0.35 V supply. The highest resulting figure-of-merit (FoM) is 198.3 dBc/Hz.©2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works

Circuit Design Techniques For Wideband Phased Arrays

University of Minnesota Ph.D. dissertation.June 2015. Major: Electrical Engineering. Advisor: Ramesh Harjani. 1 computer file (PDF); xii, 143 pages.This dissertation focuses on beam steering in wideband phased arrays and phase noise modeling in injection locked oscillators. Two different solutions, one in frequency and one in time, have been proposed to minimize beam squinting in phased arrays. Additionally, a differential current reuse frequency doubler for area and power savings has been proposed. Silicon measurement results are provided for the frequency domain solution (IBM 65nm RF CMOS), injection locked oscillator model verification (IBM 130nm RF-CMOS) and frequency doubler (IBM 65nm RF CMOS), while post extraction simulation results are provided for the time domain phased array solution (the chip is currently under fabrication, TSMC 65nm RF CMOS). In the frequency domain solution, a 4-point passive analog FFT based frequency tunable filter is used to channelize an incoming wideband signal into multiple narrowband signals, which are then processed through independent phase shifters. A two channel prototype has been developed at 8GHz RF frequency. Three discrete phase shifts (0 & +/- 90 degrees) are implemented through differential I-Q swapping with appropriate polarity. A minimum null-depth of 19dB while a maximum null-depth of 27dB is measured. In the time domain solution, a discrete time approach is undertaken with signals getting sampled in order of their arrival times. A two-channel prototype for a 2GHz instantaneous RF bandwidth (7GHz-9GHz) has been designed. A QVCO generates quadrature LO signals at 8GHz which are phase shifted through a 5-bit (2 extra bits from differential I-Q swapping with appropriate polarity) cartesian combiner. Baseband sampling clocks are generated from phase shifted LOs through a CMOS divide by 4 with independent resets. The design achieves an average time delay of 4.53ps with 31.5mW of power consumption (per channel, buffers excluded). An injection locked oscillator has been analyzed in s-domain using Paciorek's time domain transient equations. The simplified analysis leads to a phase noise model identical to that of a type-I PLL. The model is equally applicable to injection locked dividers and multipliers and has been extended to cover all injection locking scenarios. The model has been verified against a discrete 57MHz Colpitt's ILO, a 6.5GHz ILFD and a 24GHz ILFM with excellent matching between the model and measurements. Additionally, a differential current reuse frequency doubler, for frequency outputs between 7GHz to 14GHz, design has been developed to reduce passive area and dc power dissipation. A 3-bit capacitive tuning along with a tail current source is used to better conversion efficiency. The doubler shows FOM$_{T}$ values between 191dBc/Hz to 209dBc/Hz when driven by a 0.7GHz to 5.8GHz wide tuning VCO with a phase noise that ranges from -114dBc/Hz to -112dBc/Hz over the same bandwidth

Proximal-Field Radiation Sensors for Dynamically Controllable and Self-Correcting Integrated Radiators

One of the major challenges in the design of integrated radiators at mm-wave frequencies is the generation of surface waves in the dielectric substrate by the on-chip antennas. Since dielectric substrates are excellent surface waveguides with a fundamental mode with no cutoff frequency, there is always some energy trapped in them due to the surface waves and the excited substrate modes. This phenomenon is a significant cause of reduced radiation efficiency for mm-wave integrated radiators. However, in this thesis, we use this as an opportunity. We show that the excited substrate modes in the dielectric substrate of an integrated antenna contain valuable information regarding its far-field radiation properties. We introduce Proximal-Field Radiation Sensors (PFRS) as a number of small sensing antennas that are placed strategically on the same substrate as the integrated antenna and measure electromagnetic waves in its immediate proximity. These sensors extract the existing information in the substrate modes and use it to predict the far-field radiation properties of the integrated antenna in real-time based on in-situ measurements in the close proximity of the antennas, without any need to use additional test equipment and without removing the antenna from its operating environment or interfering with its operation in a wireless system. In other words, PFRS enables self-calibration, self-correction, and self-monitoring of the performance of the integrated antennas. Design intuition and a variety of data processing schemes for these sensors are discussed. Two proof-of-concept prototypes are fabricated on printed circuit board (PCB) and integrated circuit (IC) and both verify PFRS capabilities in prediction of radiation properties solely based on in-situ measurements. Dynamically controllable integrated radiators would significantly benefit from PFRS, These radiators are capable of controlling their radiation parameters such as polarization and beam steering angle through their actuators and control units. In these cases, PFRS serves as a tool for real-time monitoring of their radiation parameters, so that without direct measurement of the far-field properties through bulky equipment the required information for the control units and the actuators are provided. Dynamically controllable integrated radiators can be designed using the additional design space provided by Multi-Port Driven (MPD) radiator methodology. After a review of advantages of MPD design over the traditional single-port design, we show that a slot-based MPD radiator would have the additional advantage of reduced exclusive use area compared to the original wire-based MPD radiator, through demonstration of a 134.5-GHz integrated slot-based MPD radiator with a measured single-element EIRP of +6.0 dBm and a total radiated power of -1.3 dBm. We discuss how MPD methodology enables the new concept of Dynamic Polarization Control, as a method to ensure polarization matching of the transmitter antenna to the receiver antenna, regardless of the polarization and orientation of the receiver antenna in space. A DPC antenna design using the MPD methodology is described and a 105.5-GHz 2x1 integrated DPC radiator array with a maximum EIRP of +7.8 dBm and a total radiated power of 0.9 mW is presented as the first demonstration of an integrated radiator with DPC capability. This prototype can control the polarization angle across the entire tuning range of 0 to 180 degrees while maintaining axial ratios above 10 dB, and control the axial ratio from 2.4 dB (near circular) to 14 dB (linear). We also demonstrate how simultaneous two-dimensional beam steering and DPC capabilities can even match the polarization to a mobile receiver antenna through a prototype 123-GHz 2x2 integrated DPC radiator array with a maximum EIRP of +12.3 dBm, polarization angle control across the full range of 0to 180 degrees as well as tunable axial ratio down to 1.2 dB and beam steering of up to 15 degrees in both dimensions. We also use slot-based DPC antennas to fabricate a 120-GHz integrated slot-based DPC radiator array, expected to have a maximum EIRP of +15.5 dBm. We also introduce a new modulation scheme called Polarization Modulation (Pol-M) as a result of DPC capability, where the polarization itself is used for encoding the data. Pol-M is a spatial modulation method and is orthogonal to the existing phase and amplitude modulation schemes. Thus, it could be added on top of those schemes to enable creation of 4-D data constellations, or it can be used as the only basis for modulation to increase the stream security by misleading the undesired receivers. We discuss how DPC antenna enables Pol-M and also present PCB prototypes for Pol-M transmitter and receiver units operating at 2.4 GHz.</p

Dynamical Systems

Complex systems are pervasive in many areas of science integrated in our daily lives. Examples include financial markets, highway transportation networks, telecommunication networks, world and country economies, social networks, immunological systems, living organisms, computational systems and electrical and mechanical structures. Complex systems are often composed of a large number of interconnected and interacting entities, exhibiting much richer global scale dynamics than the properties and behavior of individual entities. Complex systems are studied in many areas of natural sciences, social sciences, engineering and mathematical sciences. This special issue therefore intends to contribute towards the dissemination of the multifaceted concepts in accepted use by the scientific community. We hope readers enjoy this pertinent selection of papers which represents relevant examples of the state of the art in present day research. [...

On the synchronization condition of second-harmonic coupled QVCOs

We present a nonlinear analysis of quadrature Voltage-Controlled Oscillators (QVCOs) made up of two VCOs mutually coupled at their second-harmonic frequency through a direct coupling circuit. The analysis of the two VCOs, each of which is considered separately, as an injection locked oscillator, reveals some relevant aspects of their behavior related to the steep nonlinearity of the cross-coupled devices, as well as to common-mode voltage at the drain terminals. These aspects influence the synchronization condition of the overall system of the two VCOs, whose oscillation frequency significantly differs from the resonant frequencies of the individual tanks. ©2010 IEEE