Timing Fluctuation Correction of A Femtosecond Regenerative Amplifier

We report on the long-term correction of a timing fluctuation between the femtosecond regenerative amplifier and the reference oscillator for the seed 100 PW laser system in the Station of Extreme Light (SEL). The timing fluctuation was characterized by a noncollinear balanced optical cross-correlator that maps the time difference to the sum frequency intensity of the amplifier and oscillator laser pulses. A feedback loop was employed to correct the timing jitter by adjusting the time delay line in the amplifier beam path. The timing fluctuation was reduced to 1.26 fs root-mean-square from hundreds of fs over 10 hours. Benefitting from excellent performance and long-term stability, this timing jitter correction scheme, as a component of optical synchronization in the 100 PW laser facility, will be integrated into SEL.

Computer-aided design for analog wireless fronthaul of B5G cellular communication systems

Specialties of an analog fronthaul based on Radio-over-Fiber architecture and key principles of exploiting microwave photonics technology when designing a millimeter-wave Radio Unit (RU) are reviewed and discussed. To clarify, in this paper we perform a comparative simulation for a specific example of developing an obligatory RU's node as a reference oscillator with an output radio frequency (RF) of more than 100 GHz, which is typically implemented by means of a circuit that includes a relatively low-frequency RF oscillator followed by a high-order frequency multiplier. Following the principles and approaches outlined, we propose and describe two alternative schemes for implementing a frequency multiplier from 4.25 to 102 GHz using microwave-electronics or microwave-photonics approach. Further, using Cadence AWRDE software with an additional introduction of the previously proposed models of optoelectronic devices, their main characteristics are considered. To ensure the practical orientation of the model experiments, the parameters of each of the models used are selected based on the specifications of commercially available discrete components.

Sensitivity and Accuracy of Dielectric Measurements of Liquids Significantly Improved by Coupled Capacitive-Dependent Quartz Crystals

A method to measure complex permittivity of liquids by using a capacitive-dependent quartz crystal and two quartz oscillators for temperature compensation in the frequency range of 4–10 MHz is described. Complex permittivity can be detected with high precision and sensitivity through a small change of capacitance and conductance, because a change in reactance in series with the quartz crystal impacts its resonant oscillation frequency. The temperature compensation in the range below 0.1 ppm is achieved by using two quartz oscillators that are made of elements of the same quality and have a temperature–frequency pair of quartz crystals. With the help of a reference oscillator, measurements of frequency are more accurate, because the frequency difference is in the kHz region, which also enables further processing of the signal by a microcontroller. With a proper calibration, the accuracy of this highly sensitive quartz crystal method is ±0.05%, which is an order of magnitude lower than that for a capacitance method without quartz crystals. The improved accuracy is of significant importance in the field of power engineering to monitor coolants and lubricants, oils, liquid fuels and other liquids, the dielectric properties of which are crucial for proper operation of devices.

Detecting Cycle Slips in Carrier-Phase Measurements of Single Frequency Navigation Receivers with Different Instabilities of Reference Oscillators

The use of carrier-phase measurements significantly increases the accuracy of solutions when using the measurements of navigation receivers. One of the problems in carrier-phase measurements is discontinuities (cycle slips) in the measurements. The existing algorithms of detection and compensation of cycle slips in carrier-phase measurements of a singlefrequency navigation receiver either require additional information (for example, Doppler measurements), or operate only in differential mode, or can only detect large cycle slips. The purpose of the research is the development of algorithms for detecting small cycle slips in carrier-phase measurements of single-frequency receivers without using additional information. We use methods of filtering of the trend in the carrier-phase measurements using polynomial or adaptive bases, as well as modified sparse recovery algorithms to estimate cycle slips in the difference between code and carrier-phase measurements. The algorithm which is used to search cycle slips in carrier-phase measurements depends on the quality of the reference oscillator of the navigation receiver. For receivers with high-stability reference oscillators (e.g. active hydrogen maser), one can use polynomial filtering of the trend, the filtering result directly detects discontinuities in carrier-phase measurements with a probability close to unity. For navigation receivers with low-stability reference oscillators (quartz reference oscillators), a modified algorithm for minimization of the total variation with filtering of the trend applied to the difference between the code and carrier-phase single-frequency measurements detects discontinuities in 1 cycle slip against the background of the noise component of comparable magnitude with a probability of 0.8. The results may be applied in navigation systems with single-frequency receivers with low stability reference oscillators, as well as in a posteriori processing of receivers’ measurements to correct carrier-phase measurements on the preprocessing stage.

Управляемая нейроморфная динамика систем фазовой синхронизации

We consider the neuromorphic dynamics of a filter-free phase locked loop with a phase modulation of a reference oscillator. The transition from pulsed single-spike dynamics to the bursting dynamics can be easily controlled by changing the depth and frequency of phase modulation, as well as the gain factor along the ring of the phase locked loop. The possibility of implementing neuromorphic calculations of the "OR" type in the scheme of three phase locked loops mutually coupled through a common control circuit is shown. The presented results can be used in the design of hardware-implemented neuromorphic networks with increased frequency stability, resistant to noise influences.

A Frequency Reference for Carrier Synthesis in Wireless Standard 802.11g

A new approach to a frequency synthesizer is proposed: instead of a fixed frequency reference oscillator and a variable ratio frequency divider we use a variable frequency reference oscillator and a fixed ratio frequency divider. The implementation and characterization of a low phase-noise compensated oscillator used as frequency reference for a wireless transceiver is described. This circuit employs a high Q piezoelectric resonator together with a CMOS cross coupled pair amplifier. A calibration circuit for compensation of frequency errors with respect to process variation is proposed.