An N/M-Ratio All-Digital Clock Generator with a Pseudo-NMOS Comparator-Based Programmable Divider

A multiplying delay-locked loop (MDLL)-based all-digital clock generator with a programmable N/M-ratio frequency multiplication capability for digital SoC is presented. The proposed digital MDLL provides programmable N/M-ratio frequency multiplication using a new high-speed Pseudo-NMOS comparator-based programmable divider with small area and low power consumption. The proposed MDLL clock generator can also provide a de-skew function by eliminating the phase offset problem caused by the propagation delay of the front divider in conventional N/M MDLL architectures. Fabricated in a 0.13-µm 1.2-V CMOS process, the proposed digital MDLL clock generates fully de-skewed output clock frequencies from 0.3 to 1.137 GHz with programmable N/M ratios of N = 1~32 and M = 1~16. It achieves a measured effective peak-to-peak jitter of 12 ps at 1.0 GHz when N/M = 8/1. It occupies an active area of only 0.034 mm2 and consumes a power of 10.3 mW at 1.0 GHz.

Research on the Dual Modulation of All-Fiber Optic Current Sensor

Acousto-optic modulator (AOM) and electro-optical modulator (EOM) are applied to realize the all-fiber current sensor with a pulsed light source. The pulsed light is realized by amplitude modulation with AOM. The reflected interferometer current sensor is constructed by the mirror and phase modulation with EOM to improve the anti-interference ability. A correlation demodulation algorithm is applied for data processing. The influence of the modulation frequency and duty cycle of AOM on the optical system is determined by modeling and experiment. The duty cycle is the main factor affecting the normalized scale factor of the system. The modulation frequency mainly affects the output amplitude of the correlation demodulation and the system signal-to-noise ratio. The frequency multiplication factor links AOM and EOM, primarily affecting the ratio error. When the frequency multiplication factor is equal to the duty cycle of AOM and it is an integer multiple of 0.1, the ratio error of the system is less than 1.8% and the sensitivity and the resolution of AFOCS are 0.01063 mV/mA and 3 mA, respectively. The measurement range of AFOCS is from 11 mA to 196.62 A, which is excellent enough to meet the practical requirements for microcurrent measurement.

Flat OFC Generation Based on DPMZM Cascaded Dual-Parallel PolM with Frequency Multiplication Circuit

An innovative scheme to generate the high-quality OFC based on DPMZM cascaded dual-parallel PolM with frequency multiplication circuit is proposed and demonstrated. In the scheme, 5 comb lines are generated in the first-stage generator, and the comb line is expanded to 11 times in the second-stage generator. The theoretical model of the overall scheme is established and analyzed. In this scheme, 66-line OFC is generated and the flatness is 0.73 dB, the side mode suppression ratio (SMSR) is 14.19 dB, and the optical signal noise ratio (OSNR) is about 29 dB.

Modeling and dynamic characteristic analysis of dual rotor-casing coupling system with rubbing fault

With the rapid development of aero-engine manufacturing technology, the dual-rotor system has been employed in part of turbofan engine in order to improve the working performance of aircraft more efficiently. In this study, taking the counter-rotation dual-rotor as the research object, the dynamic model of dual rotor-casing coupling system is established by the aid of MATLAB. The dynamic frequency curves are in good agreement with the results in references and calculated by FEM method, that shows the validity and feasibility of the model. The local rub-impact dynamic model of dual rotor-casing coupling system is established, and rubbing analysis is carried out using Newmark- β method. The effects of rotating speed and speed ratio on local rub-impact response are deeply discussed. The results show that with the increase of rotating speed, combined frequencies and frequency multiplication components are more significant. In addition, speed ratio has a great influence on the periodic motion of the system. With the increase of the absolute value of the speed ratio, the whirl radius of the outer rotor and the normal rubbing force increase dramatically.

Investigating the effect of the impeller blade gradient angle on the compressor reliability

Studies show that operating stress and natural frequency of the turbocharger impeller are two key parameters that affect the service life of the turbocharger. In this regard, NREC and ANSYS software are utilized in the present study to design impellers and calculate the impeller stress, natural frequency, and the inertia moment of the impeller for each baseline impeller and their modifications. Furthermore, modal tests are carried out to verify the simulation results. Finally, the compressor characteristic maps before and after the blade gradient angle optimization are compared. Obtained results show that compared with the cantilever length, the blade thickness has a remarkable influence on the blade gradient angle. Moreover, it is found that the correlation between the blade gradient angle and the first-order frequency multiplication ratio is linear. As the blade gradient angle increases, the maximum stress at the blade root of the compressor initially decreases and then increases. The value of the blade gradient angle varies within the range of 2.288°–3.955°. Moreover, the closer the gradient angle to 3.26°, the smaller the maximum equivalent stress of the impeller, and the higher the impeller strength. The greater the thickness of the blade, the longer the cantilever length of the impeller, and the greater the inertia moment. Optimizing the blade gradient angle can improve the efficiency of the compressor without changing the pressure ratio and flow rate. It should be indicated that error between the results from the simulation and the experiment is within the range 1.736%–1.254%. Therefore, the calculation results are reliable. It is concluded that the regular pattern of the blade gradient angle affects the compressor impeller stress and its natural frequency. The present article is expected to provide a helpful theoretical basis for designing an optimized compressor impeller.