Jitter Suppression Research Articles

Low-order wavefront sensing and control for WFIRST-AFTA coronagraph

To maintain the required Wide-Field Infrared Survey Telescope (WFIRST) coronagraph performance in a realistic space environment, a low-order wavefront sensing and control (LOWFS/C) subsystem is necessary. The LOWFS/C uses the rejected stellar light from the coronagraph to sense and suppress the telescope pointing errors as well as low-order wavefront errors (WFEs) due to changes in thermal loading of the telescope and the rest of the observatory. We will present a conceptual design of a LOWFS/C subsystem for the WFIRST-AFTA coronagraph. This LOWFS/C uses a Zernike phase contrast wavefront sensor (ZWFS) with a phase shifting disk combined with the stellar light rejecting occulting masks, a key concept to minimize the noncommon path error. We will present our analysis of the sensor performance and evaluate the performance of the line-of-sight jitter suppression loop, as well as the low-order WFE correction loop with a deformable mirror on the coronagraph. We will also report the LOWFS/C testbed design and the preliminary in-air test results, which show a very promising performance of the ZWFS.

All-Digital 90° Phase-Shift DLL With Dithering Jitter Suppression Scheme

This paper proposes a 90° phase-shift delay-locked loop (DLL) used in dynamic RAM for data sampling clock generation. The proposed DLL alleviates process variation issues, which are mainly caused by the mismatch between the delay line segments in the previous 90° phase-shift DLLs, and reduces area by adopting a multiplying DLL-based structure. In addition, a novel jitter suppression scheme is also proposed to suppress control code dithering. A stochastic analysis is performed to evaluate the effectiveness of the proposed dithering jitter suppression. The proposed DLL is fabricated using a 45-nm CMOS process on an active area of $69.9~\mu \text{m} \times 49.3~\mu \text{m}$ and utilizes a 1.1 V supply voltage. The proposed DLL has an operating frequency ranging from 500 to 800 MHz and consumes 1.32 mW at 800 MHz. The measured rms and peak-to-peak output jitters are improved by 5.42% to 18.75% and 5.52% to 18.31%, respectively, in the entire operating frequency range.

High-bandwidth control of piezoelectric steering mirror for suppression of laser beam jitter

Laser beam steering or pointing, which stabilizes the beam direction, is critical in many areas, such as optical communication systems, astronomy and directed-energy systems etc. However, the disturbances including atmospheric turbulence and mechanical jitter on platform may degrade the pointing accuracy. A proportional-integral (PI) feedback control commonly has been used in the track loop with a fast steering mirror. To compensate dynamic disturbance effectively, the laser beam steering control system must have a larger bandwidth than the disturbance bandwidth. But the control bandwidth is limited by the noise of the sensor, computing latency, and the light energy. So, a simple proportional-integral (PI) feedback controller of a piezoelectric fast steering mirror (PFSM) can only compensate the broadband disturbance of the atmospheric turbulence, but cannot effectively compensate a larger amplitude narrowband jitter because of the low control bandwidth. Moreover, when the control bandwidth is tuned to high, the mechanical resonance of the PFSM can cause the instability of the system. An improved dual two-order filter assisted high-bandwidth control algorithm to improve the pointing accuracy and error attenuation capability is proposed. This method can control a PFSM for suppression of laser beam jitter. The influence of filter parameters on frequency characteristics is analyzed, and then, a practical design method is proposed. The dual two-order filter can combine the characteristics of traditional notch filter and two-order low-pass filter, and can also obtain any desired amplitude in the interesting frequency ragion with little influence on the others. The principle of the proposed filter for suppressing the mechanical resonance of the PFSM and the narrowband disturbance is elaborated. And then, the different dual two-order filters are designed according to the frequency content of the PFSM and the narrowband disturbance. Finally, the proposed dual two-order filter assisted PI control algorithm and classic PI control algorithm are compared with each other. Experimental results show that, in the same conditions, the pointing accuracy of the proposed two-order filter assisted PI control algorithm is nearly 5 times better than that of the classic PI control algorithm, and the error attenuation bandwidth is one time higher. It also indicates that the proposed algorithm does not need an additional sensor; it is simple and effective for the suppression of the mechanical resonance of a PFSM and that of the narrowband disturbance, hence it improves the system error attenuation bandwidth and the beam pointing accuracy.

A 3.12 pJ/bit, 19–27 Gbps Receiver With 2-Tap DFE Embedded Clock and Data Recovery

A 19–27 Gbps receiver comprised of a continuous-time linear equalizer (CTLE) followed by a 2-tap decision feedback equalizer embedded clock and data recovery circuit is implemented. The hybrid CDR is operated at half rate, which is incorporated into a broadband PLL to facilitate ISI and jitter suppression over wide-band operation. To accommodate different channel response, an automatic threshold tracking (ATT) circuit combining with sign-sign least mean square (LMS) adaptive engine is realized. A quadrature relaxation-type oscillator is proposed to provide the sampling phases without bulky inductors. It also provides the advantages of small form factor and wide range operation (19–27 Gbps) to compensate 20 dB channel loss at 12.5 GHz. Fabricated in a 40 nm CMOS technology, the whole receiver manifests an energy efficiency of 3.12 pJ/bit at 27 Gbps operation. The core area is 0.09 mm $^{2}$ only.

Magnetically-controllable optical multi-stability in magneto-optic fiber Bragg gratings with potential applications to multi-level all-optical regeneration

Starting with the nonlinear coupled-mode equations of guided optical waves in the magneto-optic fiber Bragg grating (MFBG), the amplitude transfer curve of the transmitted light is numerically calculated for the incident right-circularly polarized wave, and the multi-stability is analyzed by introducing the parameter of jitter suppression. It is shown that, (i) the performance of amplitude jitter suppression in the stable states of high level is better than that of low level; (ii) the jitter suppression in the multi-stable regions can be enhanced when the magnetic field is applied to the MFBG in the opposite direction of the incident wave; and (iii) by adjusting the applied magnetic field, the multi-stable levels can be tuned flexibly, which is helpful for developing the intelligent all-optical devices for multilevel regeneration.

Full-custom design of split-set data weighted averaging with output register for jitter suppression

A full-custom design of an element selection algorithm, named as Split-set Data Weighted Averaging (SDWA) is implemented in 90nm CMOS Technology Synopsys Library. SDWA is applied in seven unit elements (3-bit) using a thermometer-coded input. Split-set DWA is an improved DWA algorithm which caters the requirement for randomization along with long-term equal element usage. Randomization and equal element-usage improve the spectral response of the unit elements due to higher Spurious-free dynamic range (SFDR) and without significantly degrading signal-to-noise ratio (SNR). Since a full-custom, the design is brought to transistor-level and the chip custom layout is also provided, having a total area of 0.3mm2, a power consumption of 0.566 mW, and simulated at 50MHz clock frequency. On this implementation, SDWA is successfully derived and improved by introducing a register at the output that suppresses the jitter introduced at the final stage due to switching loops and successive delays.

A 10-Gb/s, 1.24 pJ/bit, Burst-Mode Clock and Data Recovery With Jitter Suppression

A burst mode clock and data recovery (BMCDR) circuit for 10 Gbps passive optical network (10G-PON) is presented. The proposed BMCDR is reconfigurable between data gating mode and phase tracking mode to achieve instantaneously phase-locked with jitter suppression capability. Incorporating selectively gating VCO (SGVCO), the BMCDR operates at 1/5-rate and accomplishes 1:5 demultiplexing with a high energy efficiency of 1.24 pJ/bit. With a 4 MHz, 0.22UI pp jitter stressed input data at 10 Gbps, the recovered clock jitter at 2 GHz is 2.94 ps rms . The prototype is fabricated using 55 nm CMOS technology. The core area is 0.03 mm 2 only. It dissipates 12.4 mW from 1 V supply.

Two-photon interference from a quantum dot microcavity: Persistent pure dephasing and suppression of time jitter

We demonstrate the emission of highly indistinguishable photons from a quasi-resonantly pumped coupled quantum dot--microcavity system operating in the regime of cavity quantum electrodynamics. Changing the sample temperature allows us to vary the quantum dot--cavity detuning, and on spectral resonance we observe a three-fold improvement in the Hong--Ou--Mandel interference visibility, reaching values in excess of 80\%. Our measurements off-resonance allow us to investigate varying Purcell enhancements, and to probe the dephasing environment at different temperatures and energy scales. By comparison with our microscopic model, we are able to identify pure-dephasing and not time-jitter as the dominating source of imperfections in our system.

Few-femtosecond-resolution characterization and suppression of excess timing jitter and drift in indoor atmospheric frequency comb transfer

We characterize the timing jitter spectral density of the time-of-flight (TOF) in the indoor atmospheric transfer of optical pulse train over 10 decades of Fourier frequency range (10 μHz - 100 kHz) with sub-100-as resolution using a balanced optical cross-correlator (BOC). Based on the well-known theory for atmospheric transfer of a laser beam, we could fit the measured timing jitter power spectral density to the theory and analyze it with a fairly good agreement from 20 mHz to 10 Hz Fourier frequency range. Moreover, we demonstrate that the BOC-based timing stabilization method can suppress the excess fluctuations in timing from >200 fs (rms) to 2.6 fs (rms) maintained over 130 hours when an optical pulse train is transferred over a 76.2-m long free-space beam path in laboratory environment. The demonstrated stabilization result corresponds to 4 × 10(-20) overlapping Allan deviation at 117,000 s averaging time.

A jitter suppression technique against data pattern dependency on high-speed interfaces for highly integrated SoCs

A jitter suppression technique against data pattern dependency on high-speed interfaces for highly integrated SoCs

Dispersive-cavity actively mode-locked fiber laser for stable radio frequency delivery

We report a novel technique for highly stable transfer of a radio frequency (RF) comb over long optical fiber link, which is highly dispersive and is a part of an actively mode-locked fiber laser. Phase fluctuation along the fiber link, which is mainly induced by physical vibration and temperature fluctuations, is automatically compensated by the self-adapted wavelength shifting. Without phase-locking loop or any tunable parts, stable radio frequency is transferred over a 2-km fiber link, with a time jitter suppression ratio larger than 110.

Design of a semi-passive UHF RFID tag IC with freight security monitoring function

A semi-passive ultra-high-frequency-band radio frequency identification tag IC with freight security monitoring function is proposed. The tag can record the number of times a container has been opened during transport and is compatible with Electronic Product Code Class-1 Generation-2 protocol. A switch-state monitoring unit is presented with power control logic that makes the tag return to sleep mode after each recording operation. An optimized differential rectifier is designed after the analysis and comparison of the different rectifier architectures. The rectifier is designed along with a voltage regulator and a wake-up circuit to comprise a power management unit for generating two output voltages of 1 and 1.8 V at 915 MHz. A baseband processor with a jitter suppression module is employed to improve system reliability. The tag chip is designed in TSMC 0.18m CMOS process and simulated with Spectre. According to the simulation results, the power consumption of the tag is 9.56W under activation mode, and the sleep current is only 645 pA under the typical condition.

A Continuous-Time Delta-Sigma Modulator for RF Subsampling Receivers

We propose a new continuous-time (CT) delta-sigma modulator (DSM) to be utilized in radio-frequency (RF) subsampling receivers for analog-to-digital conversion. Subsampling DSMs employ sub-Nyquist sampling with respect to the input signal frequency and oversampling with respect to the signal bandwidth. The proposed CT-DSM mitigates the effects of subsampling by modifying the feedback path of the modulator to accommodate the RF replica of the feedback signal and by enhancing the quality factor of the loop filter. The novel modulator has significant improvements over previously published subsampling modulators as it provides jitter and image suppression and excess loop delay compensation to improve the dynamic range, thus enabling the modulator to be utilized in subsampling receivers when a relatively low sampling rate is desired.

Active vibration isolation based on model reference adaptive control

High-performance instruments are very sensitive to vibrations and jitters. In this article, a new approach towards multi-degree-of-freedom (DOF) active vibration isolation and its application in spacecraft jitter suppression are presented. Model reference adaptive control (MRAC) with acceleration feedback is used to isolate random disturbances. However, a side effect of this algorithm is that displacements at low frequencies are amplified. Thus, the MRAC is augmented with proportional–integral–differential (PID) displacement feedback to suppress vibration displacements. The MRAC-PID composite control is applied to a 4-leg platform to isolate vibrations and suppress tip/tilt jitters. The scheme is also used to isolate 6-DOF vibrations and steer the payload of a flexible spacecraft. Satisfactory performance of vibration isolation and jitter attenuation has been observed.

Optimized all-optical amplitude reshaping by exploiting nonlinear phase shift in fiber for degenerated FWM

We describe a novel performance optimization method for all-optical amplitude reshaping via degenerated four-wave mixing (FWM) in highly nonlinear optical fiber. The proposed optimization method is achieved by judiciously configuring the FWM operational condition and exploiting the nonlinear phase shift induced by self- and cross-phase modulations to properly influence the FWM conversion efficiency. Through the proposed scheme, fully functional and prevailing reshaping performance, including significant amplitude jitter suppression and extinction ratio improvement, is obtained within a single FWM stage. Results of the present theoretical calculation and numerical simulation verify the feasibility and advantages of the proposed scheme.

A 3-D Low Jitter and Skew Clock Distribution Network Scheme Using LTCC Package Level Interposer With a Planar Cavity Resonator

In this paper, we propose a new three-dimensional (3-D) clock distribution network (CDN) scheme using a low temperature co-fired ceramic (LTCC) package level interposer with a planar cavity resonator to achieve extremely low jitter and skew clock delivery even in severe power supply noise environments, especially for digital chips in 3-D stacked chip packages. It is based on a uniform-phase of the standing wave at the quarter-wavelength planar cavity resonator embedded inside the LTCC interposer. Substantial suppression of the timing jitter and skew was successfully demonstrated through a series of design, fabrication, and measurement processes of test devices and packages.

Optimal Suppression of Laser Beam Jitter by High-Order RLS Adaptive Control

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper demonstrates high-performance adaptive control for a laser-beam steering system, which exhibits high-order unknown jitter dynamics. The adaptive controller, which is based on a recursive least-squares finite-impulse-response lattice filter, has the distinguishing feature that variable and high-order adaptive filters can be realized in the real-time implementation. Varying the order of the adaptive controller produces both fast adaptation and optimal steady-state performance in the experiment, without the large transients often produced by fixed-order recursive least-squares adaptive controllers. The steady-state performance of the high-order adaptive controller approximates closely the theoretically achievable minimum-variance steady-state performance, which is derived from the identified plant and jitter dynamics. Experimental results also illustrate the capability of the adaptive controller to adapt rapidly to changing jitter characteristics. </para>

Jitter Characteristic in Charge Recovery Resonant Clock Distribution

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.

Suppression of pump-induced frequency noise in fiber-laser frequency combs leading to sub-radian f ceo phase excursions

We discuss the origins and the suppression of the large frequency jitter on the carrier-envelope offset frequency (fceo) of fiber-laser frequency combs. While this frequency noise appears most prominently on fceo, its effects are felt across the frequency comb and it is a potential limiting factor in applications of fiber-laser frequency combs. Here we show that its origin lies in the white amplitude noise of the pump laser output. We dramatically reduce this noise by operating the pump laser in a lower-noise state, i.e. at higher pump current, and by more aggressively feeding back to the pump current with an optimal feedback network. We demonstrate instrument-limited fceo linewidths and an integrated fceo phase jitter of 1 rad.

Standard-compliant jitter transfer function of all-optical clock recovery at 40 GHz based on a quantum-dot self-pulsating semiconductor laser

This letter reports on all-optical clock recovery over 40-Gb/s signal using a quantum-dot (QD)-based self-pulsating (SP) laser. In particular, the jitter transfer function from the input signal to the recovered clock is measured for the first time. We clearly demonstrate that, thanks to the narrow spectral linewidth of the free-running SP signal, the QD-based laser allows the suppression of high frequency jitter, and the cutoff frequency is exactly that required by the ITU-T recommendation G825.1 at 40 GHz