Oscillator Loop Research Articles

20-pJ/Pulse 250 Mbps Low-Complexity CMOS UWB Transmitter for 3–5 GHz Applications

This letter presents a CMOS on-off keying 3-5 GHz ultra-wideband (UWB) transmitter with low complexity, low power and high speed. In the transmitter, a new differential narrow triangular pulse generator using push and pull integrating technique was designed for reducing quiescent current and common-mode interference, and a new complementary switch mode on-off voltage controlled ring oscillator (VCRO) was proposed by breaking the oscillation loop instead of breaking the power to avoid base-band energy without extra shaping filter. Without using delay resistor and capacitor in the VCRO, the transient response speed of the transmitter can be increased by only utilizing the parasitic resistances and capacitances. The design was successfully implemented with a 0.18 μm CMOS technology. The test results show that the new UWB transmitter can obtain a sidelobe rejection of more than 20 dB, a low energy consumption of 20 pJ/pulse at 250 Mbps, and a small core chip size of 0.08 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Pulsed Digital Oscillators for Electrostatic MEMS

This paper introduces a new actuation scheme for implementing Pulsed Digital Oscillators (PDOs) for electrostatic MEMS resonators. In this scheme, the capacitance of the device is biased with a voltage and it is periodically sampled. Short pulses of zero voltage are applied depending on the decisions taken by the oscillator loop. The paper discusses in detail the implementation of such electrostatic PDO (e-PDO) through a prototype and links the e-PDO to the conventional PDO theory. As an example, it is shown that with this actuation scheme it is possible to excite different resonances of the mechanical structure simply by changing the parameters of the feedback filter of the oscillator.

Simple Optoelectronic Oscillators Using Direct Modulation of Dual-Section Distributed-Feedback Lasers

Dual-section distributed-feedback laser diodes, in which the electrode on the top of the gain medium is split into two electrically isolated sections, can emit multiple optical modes by self-sustained pulsation at gigahertz frequencies. Here, we report that by directly modulating the laser in an optoelectronic oscillator (OEO) loop, a pure OEO signal can be obtained without the need for external modulators. In experiments, we successfully generate an 8-GHz OEO signal with a phase noise of -108 dBc/Hz at a 5-kHz offset and a radio-frequency threshold gain of 29 dB.

Autonomous Oscillation Control Loop Design for Amplitude Controlled, Frequency Read-Out-Type Resonant Sensors

This paper suggests an autonomous oscillation control loop for frequency read-out-type resonant sensors that produces outputs of variable frequency depending on the input of an external physical quantity. The design goal of the oscillation loop is simultaneously to stabilize the resonance characteristics of the sensor and to automatically track the resonant frequency in order to guarantee highly reliable sensor performance. To this end, the concept of automatic gain control (AGC) is applied so that the loop is designed to maintain the oscillation amplitude as one control objective. The second control objective is to achieve resonance condition tracking even when external influences such as disturbance and noise exist. For the verification of the proposed control loop design, an example resonant sensor system is modeled, and a control loop and controller that accompany the system are also designed. Finally, the proposed loop performance was demonstrated via simulations which consider practical noise elements. The theoretical results were further verified via sensor's transient responses and noise analysis.

Stability investigation for InP DHBT mm-wave power amplifier

In this article, we discuss stability issues for mm-wave monolithic integrated power amplifiers using InP double heterojunction bipolar transistor (DHBT) technology targeting E-band applications at 71–76 GHz and 81–86 GHz. Different stability detection methods based on the classical two-port K-Δs pair, linear three-port graphical analysis, system identifications, circuit modal analysis, and normalized determinant function are all reviewed. The corresponding techniques are employed to predict the occurrence of instability at 15 GHz observed during measurements on a fabricated monolithic microwave integrated circuit power amplifier. Experimental results from a redesigned power amplifier with improved stability are presented to confirm that the previously detected oscillation loop is removed using odd-mode stabilization resistors with the correct choice of values and locations. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 662–674, 2013.

Self‐oscillation loop design and measurement for an MEMS resonant accelerometer

SUMMARYThis paper provides detailed information about the dynamic model and closed‐loop control theory of resonant accelerometer based on electrostatic stiffness. After the resonant accelerometer principle based on electrostatic stiffness has been analyzed, a dynamic model was built. According to the requirement of constant stable vibration amplitude for a different applied acceleration, control equations based on self‐sustained oscillation loop technology were also developed for the whole system. By applying the averaging method, the system behaviors were analyzed, and equilibria for the vibration amplitude were achieved. Theoretical analysis and simulation showed that the vibration amplitude became stable and attractive only when the stable criterion was satisfied. Using a PI controller, constant level vibrating amplitude can be achieved when the input acceleration changes. A resonant accelerometer was fabricated using bulk‐silicon dissolved process. Under the aforementioned conditions, the accelerometer was driven and tested using a self‐sustained oscillation loop. When the sensing voltage was 5 V, the sensitivity was 58 Hz/g, and the resolution was 3.5 mg for a single vibrating beam. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Design and characterization of a CMOS MEMS capacitive resonant sensor array

Resonant sensing has been used to detect various physical or chemical quantities, however many reported sensing systems are still bulky and expensive as they rely on external instruments to conduct measurements. For practical applications, it is often desirable to have a low-cost miniaturized sensor chip with multiple sensing devices. This paper presents the first attempt to implement a capacitive resonant sensor array in a complementary metal oxide semiconductor process. The damping loss of all sensors is compensated by placing them in an oscillator loop that contains a phase-locked loop (PLL) driving circuit. The inclusion of a PLL is beneficial for sustaining the oscillation of various resonant frequencies due to the manufacturing tolerance and detected quantity within the PLL capture range. The fabricated micromechanical resonators have a resonant frequency near 200 kHz. To evaluate the sensor performance, a parylene-D thin film was deposited on microstructures and the corresponding frequency shift of 12 devices was on average 33.87 kHz. The resolution for mass detection was estimated to be 23 pg.

Toward a Miniaturized Low-Power Micromechanical Electronic Nose

An electronic nose based on an array of vibrating doubly clamped beams is proposed. These very high aspect ratio (length/thickness) suspended resonators can be individually functionalized by applying polymer coatings with an inkjet printing approach. The absorption of volatile compounds induces a swelling of the polymers that result in axial stress formation and a shift of the resonance frequency. Furthermore, integrated piezoelectric transducers are used for both actuating the resonators, as well as monitoring their resonance frequency in an oscillator loop. This allows for detection at ppm-level concentrations of low molecular weight volatiles. More importantly, the generic resonant transducers can be individually coated with different polymers to allow for selective detection of volatile compounds. Here, we present the first results demonstrating the obtained selectivity by varying the coating chemistry on identical resonators.

System- and circuit-level optimization of PLL designs for DVB-T/H receivers

This article proposes a framework for the optimization of voltage-controlled oscillator (VCO) designs in frequency synthesizers for digital video broadcasting --- terrestrial/handheld (DVB-T/H) receivers. Linear time-invariant phase-domain model of a charge-pump phase-locked loop (PLL) is devised and includes both flicker (1/f) and thermal noise contributions from the loop oscillators. By modeling the entire receiver, it is shown that there are combinations of flicker and thermal noise contributions that result in a constant sum of inter-carrier interference (ICI) and adjacent channel interference, and constant symbol error rate as well. Consequently, optimization of the VCO phase noise spectrum is defined while maintaining the standard-specified symbol-error rate. Link-level performance evaluation is carried out to validate the stipulated trade-off. The effect of ICI mitigation schemes is discussed. Circuit-level VCO design approaches utilizing the derived trade-off are finally presented. The proposed optimization procedure is generic and is also applicable to other systems based on Orthogonal Frequency-Division Multiplexing.

TRANSPOSE RETURN RELATION METHOD FOR DESIGNING LOW NOISE OSCILLATORS

In this paper, a new linear method for optimizing compact low noise oscillators for RF/MW applications will be presented. The first part of this paper makes an overview of Leeson's model. It is pointed out, and it is demonstrates that the phase noise is always the same inside the oscillator loop. It is presented a general phase noise optimization method for reference plane oscillators. The new method uses Transpose Return Relations (RRT) as true loop gain functions for obtaining the optimum values of the elements of the oscillator, whatever scheme it has. With this method, oscillator topologies that have been designed and optimized using negative resistance, negative conductance or reflection coefficient methods, until now, can be studied like a loop gain method. Subsequently, the main disadvantage of Leeson's model is overcome, and now it is not only valid for loop gain methods, but it is valid for any oscillator topology. The last section of this paper lists the steps to be performed to use this method for proper phase noise optimization during the linear design process and before the final non-linear optimization. The power of the proposed RRT method is shown with its use for optimizing a common oscillator, which is later simulated using Harmonic Balance (HB) and manufactured. Then, the comparison of the linear, HB and measurements of the phase noise are compared.

Oscillation Loop for a Vibratory Gyroscope and Its Experiment Study

This paper investigates the design of a self-oscillation loop for the gyroscope system. The dynamic equations describing this system are analyzed using the method of averaging, and a criterion for selecting the circuit parameters is established based on the analysis. The validity of the criterion and the effectiveness of the control scheme are verified by the experimental results obtained from the control parameters that satisfy or violate the stability criterion. The performance of the self-oscillation loop with a z-axis gyroscope is also evaluated in light of the experimental results. The self-oscillation loop based on the auto gain control scheme effectively tracks the resonance frequency of a z-axis gyroscope. This frequency corresponds to a standard Allan variance of 0.04 Hz in 8 min at natural frequency. The output signal-to-noise ratio (SNR) is about 90 dB, and the vibratory velocity amplitude shows a deviation of 0.5% in 8 min.

Power system small‐signal stability as affected by grid‐connected photovoltaic generation

SUMMARYThis paper investigates the impact of a grid‐connected large photovoltaic (PV) power generation station on the power system small‐signal stability. The focus of discussion in the paper is the damping of local‐mode power system oscillations. Hence, a simple single‐machine infinite‐bus power system with the grid‐connected PV generation station is used. Firstly, a comprehensive model of the single‐machine infinite‐bus power system integrated with the PV generation station is established. Then the conventional technique of the damping torque analysis is employed to examine the effect of the PV generation on the damping of power system local‐mode oscillations. Analysis in the paper reveals that there exists a critical operating condition when the damping torque contribution from the PV station to the electromechanical oscillation loop of conventional generator changes sign. Hence, the small‐signal stability of the power system can be affected negatively by the PV penetration when it operates beyond the critical operating condition. In the paper, an example power system is presented. The results of numerical computation and non‐linear simulation demonstrate and confirm all the analytical conclusions obtained. Copyright © 2011 John Wiley &amp; Sons, Ltd.

GENERATION OF CFOA, CCII AND DVCC BASED OSCILLATORS FROM PASSIVE RLC FILTER

In a recent paper the link between the Op Amp-based two integrator loop oscillators and current feedback operational amplifier (CFOA)-based oscillators is detected and clearly explained. It was found that one of the grounded capacitor two CFOA two integrator loop oscillators, however, was not related directly to any of the Op Amp oscillators. In this paper the origin of the two CFOA grounded capacitor oscillator is found to be the passive second-order low-pass filter. It is also found that the differential voltage current conveyor (DVCC) grounded passive element oscillator is generated from the same passive second-order low-pass filter. A new family of grounded capacitor oscillators using current conveyors (CCII) and inverting current conveyors (ICCII) which includes sixteen members is introduced. A second new family of grounded passive elements oscillators using CCII and ICCII which includes eight members is also introduced. A discussion and a comparison with some of the previously reported CCII oscillator circuits is also given at the end of the paper.

Love Wave Bacterial Biosensors and Microfluidic Network for Detection of Heavy Metal Toxicity

The presented work deals with the development of a bacteria-based Love wave sensor platform for the detection of heavy metals in liquid medium. The acoustic delay-line was inserted in an oscillation loop and associated with a Polydimethylsiloxane (PDMS) microfluidic network fabricated using soft photolithography and molding. It resulted in a small platform convenient for fast analysis and detection. Whole bacteria (Escherichia. coli) were fixed as bioreceptors onto the acoustic path of the sensor coated with a polyelectrolyte multilayer (PEM) using a simple and efficient layer by layer electrostatic self-assembly procedure. PEM and bacteria deposition were real-time characterized by monitoring the resonance frequency modification due to mass loading effect. Then when a solution of metal ion (Cd2+, Hg2+) was pumped through the microchannels, a significative frequency variation was observed down to 10-12 mol.l-1 concentration, due to changes of bacteria visco-elastic equivalent parameters in presence of toxic heavy metals.

Design and Implementation of the RF Front-End All-Digital Phase-Locked Loop in the UHF RFID Reader

PLL is an important part of the RF front-end module,its performance is directly related to stability and accuracy of the RF base-band signal extracted. A FPGA-based all-digital PLL is implemented in this thesis, Hilbert digital phase detector (HDPD) ,Numerically controlled oscillator (NCO) and FIR digital loop filter module implemented using Verilog language ensure accuracy and stability to Sample input Baseband signal modulated. The experiments confirmed that the all-digital PLL designed in this thesis can overcome the defects of DPLL based on semi-analog circuits; and has high Operating frequency, exact capture time, precision adjustable, simple interface, and so on; can be widely used in radio frequency identification (RFID) and automatic control system.

Current conveyor based or unity gain cells based two integrator loop oscillators

Four alternative families of oscillators are considered in this paper, three of the families employ CCII or ICCII or combination of both and each family has sixteen oscillator circuit members. The fourth family uses unity gain cells and has four circuit members. Two alternative transformation methods are used in this paper for the generation of oscillators. The first one uses the adjoint circuit theorem to obtain a new family of current mode oscillators from a voltage mode oscillator circuit. The second transformation method uses the nodal admittance matrix (NAM) expansion to generate a grounded passive element oscillator family from an oscillator circuit, which employs a virtually grounded resistor. Although this paper has a tutorial nature it includes two new families of oscillators; one of them provides both current and voltage outputs and the other provides voltage outputs and is based on the use of voltage, current followers and inverters. Simulation results are included to support the analysis.

Clock Jitter Effects on Sampling: A Tutorial

The effect of jitter in data converters is analyzed, with a focus on the frequency domain treatment of the corresponding phase noise. The analysis is mostly intuitive, to give the reader a good feeling for the mechanisms involved. Both open loop oscillators and phase locked loops are considered as clock sources. Several application examples are included to illustrate the concepts. Jitter self-referenced measurements are also covered with their relationships to jitter.

Energy current magnification in coupled oscillator loops

Motivated by studies on current magnification in quantum mesoscopic systems, we consider sound and heat transmission in classical models of oscillator chains. A loop of coupled oscillators is connected to two leads through which one can either transmit monochromatic waves or white-noise signal from heat baths. We look for the possibility of current magnification in this system due to some asymmetry introduced between the two arms in the loop. We find that current magnification is indeed obtained for particular frequency ranges. However, the integrated current shows the effect only in the presence of a pinning potential for the atoms in the leads. We also study the effect of anharmonicity on current magnification.

Love-wave bacteria-based sensor for the detection of heavy metal toxicity in liquid medium

The present work deals with the development of a Love-wave bacteria-based sensor platform for the detection of heavy metals in liquid medium. The acoustic delay-line is inserted in an oscillation loop in order to record the resonance frequency in real-time. A Polydimethylsiloxane (PDMS) chip with a liquid chamber is maintained by pressure above the acoustic wave propagation path. Bacteria ( Escherichia coli) were fixed as bioreceptors onto the sensitive surface of the sensor coated with a polyelectrolyte (PE) multilayer using a simple and efficient layer-by-layer (LbL) electrostatic self-assembly procedure. Poly(allylamine hydrochloride) (PAH cation) and poly(styrene sulfonate) (PSS anion) were alternatively deposited so that the strong attraction between oppositely charged polyelectrolytes resulted in the formation of a (PAH-PSS) n -PAH molecular multilayer. The real-time characterization of PE multilayer and bacteria deposition is based on the measurement of the resonance frequency perturbation due to mass loading during material deposition. Real-time response to various concentrations of cadmium (Cd 2+) and mercury (Hg 2+) has been investigated. A detection limit as low as 10 −12 mol/l has been achieved, above which the frequency increases gradually up to 10 −3 mol/l, after a delay of 60 s subsequent to their introduction onto bacterial cell-based biosensors. Beyond a 10 −3 mol/l a steep drop in frequency was observed. This response has been attributed to changes in viscoelastic properties, related to modifications in bacteria metabolism.

On the generation of CCII and ICCII oscillators from three Op Amps oscillator

A new quadrature oscillator using two current conveyors (CCII) and two inverting current conveyors (ICCII) is generated from a three Op Amp two integrator loop oscillator. The proposed oscillator is generalized and it is found that it is a member of a family of 64 oscillator circuits using combination of CCII and ICCII. Four of the reported oscillators are floating. The three Op Amps oscillator is also found to be the reference oscillator circuit in the generation of two basic CCII two integrator loop grounded passive element oscillators. The nodal admittance matrix (NAM) expansion is used to show the basic steps in the generation of the two alternatives CCII grounded passive element oscillators. Each of the two CCII oscillators is a member of a family of sixteen oscillator circuits using combination of CCII and ICCII. Two of the reported oscillators are floating and their adjoint oscillator circuits are not floating. Simulation results are included.