Showing papers on "Injection locking published in 2007"

The Quadrature LC Oscillator: A Complete Portrait Based on Injection Locking

Abstract: We show that the quadrature LC oscillator is best treated as two strongly coupled, nominally identical oscillators that are locked to the same frequency. Differential equations that extend Adler's description of locking to strong injection reveal the full dynamics of this circuit. With a simplifying insight, the analysis reveals all the modes of the oscillator, their stability, the effects of mismatch on quadrature phase accuracy, and through a novel use of the analysis, phase noise.

Analysis and Design of Wideband Injection-Locked Ring Oscillators With Multiple-Input Injection

Abstract: In this paper, the locking range of the injection-locked ring oscillators is investigated. To improve the injection efficiency and the locking range for superharmonic frequency division, a multiple-injection technique is proposed. Using a 0.18-mum CMOS process, a wideband frequency divider based on a three-stage ring oscillator is implemented for demonstration. With a tunable free-running frequency, the fabricated circuit provides 2:1 and 4:1 frequency division with a single-ended input signal ranging from 13 to 25 and 30 to 45 GHz, respectively. Compared with the case of the single-ended injection, the locking range of the frequency divider almost doubles when multiple-input injection with optimum phases is utilized. The experimental results exhibit good agreement with the theoretical derivation and the circuit simulation.

Transverse Mode Switching and Locking in Vertical-Cavity Surface-Emitting Lasers Subject to Orthogonal Optical Injection

Abstract: In this paper, we report on theoretical and experimental investigation on polarization and transverse mode behavior of vertical-cavity surface-emitting lasers (VCSELs) under orthogonal optical injection as a function of the injection strength and of the detuning between the injection frequency and the free-running frequency of the solitary laser. As the injection strength increases the VCSEL switches to the master laser polarization. We find that the injection power necessary to obtain such polarization switching is minimum at two different values of the frequency detuning: the first one corresponds to the frequency splitting between the two linearly polarized fundamental transverse modes, and the second one appears at a larger positive frequency detuning, close to the frequency difference between the first-order and the fundamental transverse modes of the solitary VCSEL. We show theoretically that both the depth and the frequency corresponding to the second minimum increase when the relative losses between the two transverse modes decrease. Bistability of the polarization switching is obtained for the whole frequency detuning range. Such a bistability is found for the fundamental mode only or for both transverse modes, depending on the value of the detuning. The theoretical and experimental optical spectra are in good agreement showing that the first-order transverse mode appears locked to the external injection

Optical generation of a precise microwave frequency comb by harmonic frequency locking

Abstract: A semiconductor laser under negative optoelectronic feedback is applied to the generation of a microwave frequency comb through the nonlinear dynamics. The laser system is operated in a harmonic frequency-locked pulsing state, where its power spectrum is a microwave frequency comb that consists of multiples of a locking frequency. Every frequency component of the comb can be simultaneously stabilized by simply injecting an external microwave modulation at any component of the comb. This phenomenon can be viewed as a kind of microwave injection locking of the laser dynamics.

A Low Voltage Divide-by-4 Injection Locked Frequency Divider With Quadrature Outputs

Abstract: This letter presents a low voltage quadrature divide-by-4 (divide4) injection-locked frequency divider (QILFD). The QILFD consists of a 1.8-GHz quadrature voltage controlled oscillator (QVCO) and two NMOS switches, which are inserted into the quadrature outputs of the QVCO for signal injection. The low-voltage CMOS divide4 QILFD has been implemented with the TSMC 0.18-mum 1P6 M CMOS technology and the core power consumption is 3.12mW at the supply voltage of 1.2V. The free-running frequency of the QILFD is tunable from 1.73 to 1.99GHz, the measured phase noise of QILFD is -118dBc/Hz at 1-MHz offset from the free running frequency of 1.82GHz. At the input power of 0dBm, the total locking range is from 6.86 to 8.02GHz as the tuning voltage is varied from 0 to 1.2V. The phase noise of the locked output spectrum is lower than that of free running ring oscillator by 11dBc/Hz. The phase deviation of quadrature output is about 0.8deg

A Stabilized and Tunable Single-Frequency Erbium-Doped Fiber Ring Laser Employing External Injection Locking

Abstract: A stabilized and tunable single-longitudinal-mode erbium-doped fiber ring laser has been proposed and experimentally demonstrated. The laser is structured by combining the compound cavity with a fiber Fabry-Peacuterot tunable filter. An injection-locking technique has been used to stabilize the wavelength and output power of the laser. One of the longitudinal modes is stimulated by the injected continuous wave so that this mode is able to win the competition to stabilize the system. A minimum output power of 0.6 dBm and a signal-to-noise ratio of over 43 dB within the tuning range of 1527-1562 nm can be achieved with the proposed technique. A wavelength variation of less than 0.01 nm, a power fluctuation of less than 0.02 dB, and a short-term linewidth of about 1.4 kHz have also been obtained

A 20Gb/s Burst-Mode CDR Circuit Using Injection-Locking Technique

Abstract: The design and experimental verification of a 20Gb/s CDR circuit based on injection-locking technique is presented. Fabricated in 90nm CMOS technology, this circuit achieves a BER of <10-9 for both continuous and burst modes. It has tunability of over 800Mb/s while consuming 175mW. The re-acquisition time of this CDR is 1b interval.

Bifurcation to polarization switching and locking in vertical-cavity surface-emitting lasers with optical injection

Abstract: We unveil the bifurcations underlying polarization switching and injection locking in a vertical-cavity surface-emitting laser subject to optical injection. A Hopf bifurcation, not reported for conventional edge-emitting lasers, delimits the injection locking region and influences the polarization switching conditions. We furthermore theoretically show and experimentally observe periodic dynamics at the relaxation oscillation frequency in the noninjected mode together with wave-mixing dynamics in the injected mode. These dynamics precede the polarization switching leading to injection locking and are attributed to a torus bifurcation arising on a two-polarization mode solution.

Understanding the Transient Behavior of Injection Locked LC Oscillators

Abstract: An analytical framework has been developed to describe the transient behavior of negative resistance injection-locked oscillators based on Adler's equation. Design insights are provided by using a combination of analytical simplifications and graphical interpretation. It has been shown that injection locking can be used to meet the requirements for fast hopping systems like the MBOA-UWB specification. The theoretical analysis and design solutions have been verified by extensive simulations on real CMOS processes.

Demonstration of a 311-GHz Fundamental Oscillator Using InP HBT Technology

Abstract: In this paper, a sub-millimeter-wave HBT oscillator is reported. The oscillator uses a single-emitter 0.3 m15 m InP HBT device with maximum frequency of oscillation greater than 500 GHz. The passive components of the oscillator are realized in a two metal process with benzocyclobutene used as the primary transmission line dielectric. The oscillator is implemented in a common base topology due to its inherent instability. The design includes an on-chip resonator, output matching circuitry, and injection locking port. A free-running frequency of 311.6 GHz has been measured by down-converting the signal. Additionally, injection locking has been successfully demonstrated with up to 17.8 dB of injection-locking gain. This is the first fundamental HBT oscillator operating above 300 GHz.

Optical Properties and Modulation Characteristics of Ultra-Strong Injection-Locked Distributed Feedback Lasers

Abstract: The optical properties and the frequency responses of ultrastrong (injection ratio > 10 dB) injection-locked distributed feedback lasers are investigated experimentally and theoretically. We have observed three distinctive modulation regimes under different frequency detuning between the master and the slave lasers. At large negative frequency detuning, the laser exhibits enhanced modulation efficiency at low frequencies. At intermediate frequency detuning, a flat frequency response with large 3 dB bandwidth is observed. At large positive frequency detuning, the modulation response shows a pronounced resonance peak at high frequencies. These phenomena can be explained by the resonance enhancement of the slave laser cavity mode, with the resonance frequency equal to the difference between the injection-locked frequency and the cavity mode. The experimental results agree well with theoretical calculations based on three coupled rate equations. Depending on the applications, the injection locking conditions can be optimized to achieve high RF link gain, broadband, or high resonance frequency operations.

Analytical Equations for Nonlinear Phase Errors and Jitter in Ring Oscillators

Abstract: In this paper, we present a simple analytical equation for capturing phase errors in 3-stage ring oscillators. The model, based on a simple but useful idealization of the ring oscillator, is provably exact for small noise perturbations. Despite its simplicity and purely analytical form, our model correctly captures the time- dependent sensitivity of oscillator phase to external perturbations. It is thus well suited for estimating both qualitative and quantitative features of ring oscillator phase response to internal noises, as well as to power, ground and substrate interference. The nonlinear nature of the model makes it suitable for predicting injection locking as well. Comparisons of the new model with existing phase models are provided, and its application for correct prediction of thermal jitter demonstrated. Requiring knowledge only of the amplitude and frequency of the oscillator, the model is ideally suited for early design exploration at the system and circuit levels.

Phase locking of an array of three fiber lasers by an all-fiber coupling loop.

Abstract: Constructing a phase-locking array of fiber lasers by an all-fiber coupling loop is presented, and the loop is composed of multiple 2×2 fiber couplers which are connected with the output ends of component fiber lasers of the array. Due to the mutual injection locking among the fiber lasers by the coupling loop, they can achieve the phase-locking states and then are coherently combined in the far field. Phase locking of an array of three fiber lasers with this configuration has been demonstrated experimentally, and obvious interference patterns and stable coherent output have been observed.

Local oscillator with non-harmonic ratio between oscillator and RF frequencies using pulse generation and selection

Abstract: A novel and useful apparatus for and method of local oscillator (LO) generation with non-integer multiplication ratio between the local oscillator and RF frequencies. The LO generation schemes presented are operative to generate I and Q square waves at a designated frequency while avoiding the well known issue of harmonic pulling. The input signal is fed to a synthesizer timed to a rational multiplier of the RF frequency L/N f RF . The clock signal generated is divided by a factor Q to form 2Q phases of the clock at a frequency of L(N*Q) f RF , wherein each phase undergoes division by L. The phase signals are input to a pulse generator which outputs a plurality of pulses. The pulses are input to a selector which selects which signal to output at any point in time. By controlling the selector, the output clock is generated as a TDM based signal. Any spurs are removed by an optional filter.

Phase-locked mutually coupled 1.3 μm quantum-dot lasers

Abstract: Fabry-Perot InAs quantum-dot lasers grown on GaAs substrates are mutually coupled with a delay of several nanoseconds. Stable phase-locked output with narrow linewidth is obtained when the frequency detuning between the two lasers is less than 4 GHz. This simple locking scheme could find application in a variety of photonics applications.

Greater Than 20-dB Supermode Noise Suppression and Timing Jitter Reduction Via CW Injection of a Harmonically Mode-Locked Laser

Abstract: Characterization of the timing and amplitude (AM) noise have shown a greater than 20-dB reduction of the supermode noise spurs from a harmonically mode-locked laser by continuous-wave optical injection. A reduction of the timing jitter and AM noise from 127 to 25 fs and 0.85% to 0.12% (10 Hz-100 MHz), respectively, is demonstrated. A reduction of the optical linewidth, implied by the reduction in the close-in phase noise, is also shown.

A Low Power Injection Locked $LC$ -Tank Oscillator With Current Reused Topology

Abstract: This letter presents a new current reused LC-tank injection locked oscillator (ILO), which is implemented by using a standard TSMC 0.18-mum CMOS process. The ILO, used as a divide-by-two (divide2) divider, is consisted of two switching transistors stacked in series. The injection locking is performed by adding an injection nMOS between the differential outputs of the divider. The divider can operate with a lower power due to the reuse of dc current. The measurement results show that at the supply voltage of 1.5V, the divider free-running frequency is tunable from 2.11 to 2.42GHz, and at the incident power of 0dBm the locking range of the divider in the divide2 mode is about 0.9GHz (19.8%), from the incident frequency 4.1 to 5GHz. The core power consumption is 0.97mW

Behavioral models of frequency pulling in oscillators

Abstract: Based on the state equations of an RLC circuit and hard-limiting characteristics of a transconductor a method is introduced to study and simulate the pulling effect in differential LC oscillators. This method includes phase and amplitude disturbances all at once. The model is validated by measurement results and an example is given to illustrate the application of this method in verifying the real circuits.

Optical-CDMA in InP

Abstract: This paper describes the InP platforms for photonic integration and the development on these platforms of an optical code division multiple access (O-CDMA) system for local area networks. We demonstrate three building blocks of this system: an optical pulse source, an encoder/decoder pair, and a threshold detector. The optical pulse source consists of an integrated colliding pulse-mode laser with nearly transform-limited 10 Gb/s pulses and optical injection locking to an external clock for synchronization. The encoder/decoder pair is based on arrayed waveguide gratings. Bit-error-rate measurements involving six users at 10 Gb/s showed error-free transmission, while O-CDMA codes were calibrated using frequency resolved optical gating. For threshold detection after the decoder, we compared two Mach--Zehnder interferometer (MZI)-based optical thresholding schemes and present results on a new type of electroabsorber-based MZI.

Jitter characteristic in charge recovery resonant clock distribution

Abstract: This paper is focused on analysis and suppression of clock jitter in charge recovery resonant clock distribution networks. In the presented analysis, by considering the data-dependent nature of the generated jitter, the reason for the undesired jitter-peaking phenomenon is investigated. The analysis has been verified by measurements on a test chip fabricated in 0.13-μm standard CMOS process. The chip includes a fully integrated 1.5-GHz LC clock resonator with a passive (bufferless) clock distribution network, which directly drives the clocked devices in pipelined data path circuits. Furthermore, a jitter suppression technique based on injection locking is presented. Measurement results show about 50% peak-to-peak clock jitter reduction from 28.4 ps down to 14.5 ps after injection locking.

Heterodyne Phase Locking: A Technique for High-Speed Frequency Division

Abstract: A phase-locked loop incorporating a cascade of mixers can provide integer or fractional divide ratios at high frequencies. The circuit topology and its variants are presented, and their advantages over static, dynamic, and injection-locked dividers are described. The effect of nonidealities such as the spurious response and noise of the mixers is also analyzed. A divide-by-two prototype realized in 0.13-mum CMOS technology operates from 64 GHz to 70 GHz while consuming 6 mW from a 1.2-V supply.

An Integrated 5–2.5-GHz Direct-Injection Locked Quadrature $LC$ VCO

Abstract: This letter presents an integrated direct-injection locked quadrature voltage controlled oscillator (VCO), consisted of a 5-GHz VCO integrated with injection locked LC frequency dividers for low-power quadrature generation. The circuit is implemented using a standard 0.18-mum CMOS process. The differential VCO is a full PMOS Colpitts oscillator, and the frequency divider is performed by adding an injection nMOS between the differential outputs of complementary cross-coupled np-core LC VCO. The measurement results show that at the supply voltage of 1.8-V, the master 5-GHz VCO is tunable from 4.73 to 5.74GHz, and the slave 2.5-GHz VCO is tunable from 2.36 to 2.87GHz. The measured phase noise of master VCO is -118.2dBc/Hz while the locked quadrature output phase noise is -124.4dBc/Hz at 1-MHz offset frequency, which is 6.2dB lower than the master VCO. The core power consumptions are 7.8 and 8.7mW at master and slave VCOs, respectively

Jitter Characteristic in Charge Recovery Resonant Clock Distribution

Abstract: This paper is focused on analysis and suppression of clock jitter in charge recovery resonant clock distribution networks. In the presented analysis, by considering the data-dependent nature of the generated jitter, the reason for the undesired jitter-peaking phenomenon is investigated. The analysis has been verified by measurements on a test chip fabricated in 0.13-mum standard CMOS process. The chip includes a fully integrated 1.5-GHz LC clock resonator with a passive (bufferless) clock distribution network, which directly drives the clocked devices in pipelined data path circuits. Furthermore, a jitter suppression technique based on injection locking is presented. Measurement results show about 50% peak-to-peak clock jitter reduction from 28.4 ps down to 14.5 ps after injection locking.

Self-calibrating temperature-compensated oscillator

Abstract: A self-calibrating temperature compensated oscillator includes a monolithic structure having a first resonator, a second resonator, and a heating element to heat the first and second resonators. The temperature coefficient of the second resonator is substantially greater than the temperature coefficient of the first resonator. A first oscillator circuit operates with the first resonator and outputs a first oscillator output signal having a first oscillating frequency. A second oscillator circuit operates with the second resonator and outputs a second oscillator output signal having a second oscillating frequency. A temperature determining circuit determines the temperature of the first resonator using the second oscillating frequency. A temperature compensator provides a control signal to the first oscillator in response to the determined temperature to adjust the first oscillating frequency and maintain it at a desired operating frequency.

Scaling of resonance frequency for strong injection-locked lasers.

Abstract: It has been shown that strong optical injection locking can significantly enhance the resonance frequency of semiconductor lasers. In this Letter, we describe the trade-off between the maximum resonance frequency enhancement and the quality factor (Q) of the lossless laser cavity and show that the time-bandwidth product (product of photon lifetime and maximum resonance frequency) is equal to one half the square root of the external power injection ratio. The theoretical model agrees well with our experimental data.

Beat-note jitter suppression in a dual-frequency laser using optical feedback.

Abstract: An efficient locking technique based on optical feedback is demonstrated to suppress jitter on the rf beat note between the two modes of a dual-frequency Yb:Er glass laser. The method consists of a self-injection process in which one selected mode serves as a master oscillator to lock and stabilize the second mode via a frequency-shifted optical feedback. The beat note adjusted near 170 MHz was stabilized with an accuracy of 250 mHz using an optical feedback loop with a double pass through an acousto-optic modulator. The beating note can be tuned over 300 kHz by controlling the reference oscillator. The extensions and limitations of the technique are discussed.

Generation of arbitrary frequency chirps with a fiber-based phase modulator and self-injection-locked diode laser

Abstract: We present a technique for producing pulses of laser light whose frequency is arbitrarily chirped. The output from a diode laser is sent through a fiber-optical delay line containing a fiber-based electro-optical phase modulator. Upon emerging from the fiber, the phase-modulated pulse is used to injection-lock the laser, and the process is repeated. Large phase modulations are realized by multiple passes through the loop, while the high optical power is maintained by self-injection locking after each pass. Arbitrary chirps are produced by driving the modulator with an arbitrary waveform generator. We obtain improved performance, in both chirp rate and chirp range, relative to a diode laser that is injection-locked to a modulated source.

Local oscillator with non-harmonic ratio between oscillator and RF frequencies using XOR operation with jitter estimation and correction

Abstract: A novel and useful apparatus for and method of local oscillator (LO) generation with non-integer multiplication ratio between the local oscillator and RF frequencies. The LO generation schemes presented are operative to generate I and Q square waves at a designated frequency while avoiding the well known issue of harmonic pulling. The use of analog mixers of the prior art is avoided and replaced with an XOR gate configured to generate the correct average frequency. The edges are dynamically adjusted by ±T/12 or zero based on the state of the controlled oscillator down-divided clock.