We report fixed point variations of a frequency comb generated by a passively mode-locked fiber laser. We measured the pump induced changes in the repetition frequency and the carrier-envelope offset frequency in slightly different intracavity polarization states. The responses of the two frequencies varied by changing the polarization state. Each frequency had a specific polarization state in which it did not depend on the pump power. The fixed point for a pump induced change varied across ∼1 PHz range. This study shows the possibility of realizing a robust and low-noise frequency comb.
A simple and impactful solution to reduce the size and improve the gain of extended hemispherical lens antennas is proposed. A conic extension is used for optimizing the spherical aberration of lenses. The principle is explained by ray-tracing theory, and its model is simulated, optimized and fabricated by nylon. An imaging unit is assembled by patch and the new lens. The radiation patterns are measured at 220 GHz, where close performance of the simulated and measured results is obtained. Imaging experiments have been carried out and good results were achieved.
Realizing both of compact and low energy consumption is technical issue on development of electricity-rich automotive subsystems. In the present work, a 12-V/48-V dual-voltage subsystem using three-port DC/DC converter cells is proposed, and the high power density cell design is studied to achieve ultra-compact subsystem in hybrid-electric-vehicle. A 500 W, 400 kHz prototype is developed with GaN FETs, and its efficiencies are evaluated. The prototype achieves power density of 28 W/cm3 at rated power, and its efficiency is measured more than 91% over a wide output power range, with a maximum efficiency of 93.7%.
A topology optimization method is proposed in this study to miniaturize a Rectangular Microstrip Patch Antenna (RMPA) operates at a frequency of 2.4 GHz using Metamaterials (MTMs) composed of complementary resonator. The metamaterial is placed in an intermediate layer between the patch and the ground, binary pixelation approach is used to build the structure of the complementary resonator and it is optimized using the Genetic Algorithm (GA). The conventional patch antenna and the proposed patch antenna are designed and simulated using High Frequency Electromagnetic Field Simulation (HFSS) software. A comparison between results of the two antennas is done. The area of the proposed patch antenna is reduced about 73.6% compared with the conventional patch antenna, and the return loss is improved from −18 dB to −35 dB.
The use of multi-resonators for medium-range wireless power transfer (WPT) systems is an important concern; the cross-couplings between non-adjacent coils have an adversely impact on the transmission distance and efficiency of the system. This paper proposes a dumbbell-shaped (DS) coil in a WPT system. The DS coil structure was analyzed theoretically and verified experimentally. The proposed scheme eliminates cross-couplings between non-adjacent coils in the multiple resonator system to resolve frequency drift, and improve the transmission distance and efficiency in the multiple resonator system. The scheme features a coplanar structure which can secure direct-coupling and save space when applied in the home, office, and public areas.
A reverse-conducting insulated-gate bipolar transistor (RC-IGBT) with integrated Free-Wheeling Diode (FWD) in edge termination region controlled by metal-oxide-semiconductor field-effect transistor (MOSFET) is proposed. The Field Limiting Ring (FLR) of the edge termination acts as the anode and the N-Collector acts as the cathode of the FWD. The MOSFET makes the FLR conduct reverse current at reverse conduction and float at reverse breakdown. Compared with the conventional RC-IGBT, which integrates the FWD in active cell region, the proposed device can eliminate the snapback easily at forward conduction. In addition, the forward voltage drop can be decreased largely.
We report a 40-GHz harmonically and regeneratively FM mode-locked erbium fiber laser with a phase-locked loop (PLL) circuit operating in the 1.6 µm region. The oscillation wavelength was extended to the L-band by using a 15 m erbium-doped fiber with an Er3+ concentration of 3500 ppm as a gain medium. As a result, a 770 fs transform-limited Gaussian pulse with a 14 mW output power was successfully generated with a timing jitter as low as 88 fs. The wavelength is tunable over 20 nm between 1583 and 1603 nm.
In this paper, a novel structure of One-Third-Mode Substrate Integrated Waveguide Resonator (OTMSIWR) is first proposed, which reduces about 65% size. Based on the OTMSIWR, a single-band bandpass filter (BPF) operats at 4.55 GHz is designed. The single-band BPF has a wide and deep upper stopband. Further, a dual-band BPF using high mode technology based on the single-band filter is designed. The fundamental mode (TM101 mode) and high mode (TM201 mode) are utilized to achieve the dual-band response. The center frequencies locate at the 4.2 GHz and 6.15 GHz, respectively. Two transmission zeros (TZs) are achieved in the dual-band BPF by adjusting the positions of the feeds. To further improve the selectivity of the upper stopband of the dual-band BPF, two pairs of Complementary Split-Ring Resonators (CSRRs) are introduced on the surface of the OTMSIWR, which obtain the desired results. Finally, a single-band BPF and a dual-band BPF are fabricated and tested. The measured results agreed well with the simulated ones, which proved that the proposed structure is a good candidate to design filters.
This paper presents an on-chip antenna integrated with a Ku-band transceiver using a standard 0.18-µm CMOS process. An off-chip guard ring is used to improve the gain of the antenna. As the guard ring is implemented on the test carrier board, this gain improvement technology does not require additional process, and it is easy to implement. It is shown that, a gain improvement of 5.8 dBi can be obtained by using the guard ring with the radiation efficiency improved from 18% to 32%. Additionally, the influence of the CMOS process metal rules and the existence of the transceiver on the antenna performance are studied in this paper. The proposed antenna is fabricated with and without the transceiver, respectively. It is shown that the single-chip antenna (without transceiver) has a gain of 2.4 dBi at 17 GHz, with a 3-dB bandwidth from 14.2 GHz to 21.5 GHz. Meanwhile, the transceiver (with integrated antenna) has a 3-dB bandwidth from 15.8 GHz to 18.0 GHz, with a peak gain of 13.5 dB in the transmitter link and a peak gain of 15.3 dB in the receiver link.
Bandpass sampling (BPS) is a widely used technique where one samples a bandpass-filtered signal at a sampling rate below its Nyquist rate (twice the upper cutoff frequency). For a BPS time-interleaved ADC (TIADC), its dynamic range is subject to the frequency-dependent mismatches generally introduced by the differences of process, supply voltage and temperature between constituent ADCs. This paper proposes a calibration method for frequency-dependent mismatches in BPS TIADCs. The frequency-dependent mismatches is analyzed in both time and frequency domain with the aid of Taylor’s series and binary Hadamard transform (BHT). The calibration is composed of coefficients estimation, equalization and mismatches compensation. The coefficients are estimated by solving a linear equations in the foreground based on least square (LS) algorithm. Equalization is to cancel out the linear distortion ahead of compensation to provide a better approximation of the input signal. The principle of mismatches compensation is to reconstruct the mismatches-induced spurious components and subtract them from the original TIADC’s output. Simulation results are provided to show the improvement of both effective resolution and dynamic range, and investigate the proper length of training signal, the proper order of Taylor approximation, differentiator and Hilbert filter.
An analytical model of channel current for the uniaxial strained Si nanometer NMOSFET has been developed with the degradation due to total dose irradiation taken into consideration. Based on this model, the numerical simulation has been carried out by Matlab, and the influence of the total dose on channel current was simulated. Furthermore, to evaluate the validity of the model, the simulation results were compared with experimental data, and good agreements were confirmed. Thus, the proposed model provides good reference for research on irradiation reliability of uniaxial strained Si nanometer NMOSFET.
An excitation technology of TE40 mode for substrate integrated waveguide (SIW) and its application in designing a slot antenna array is proposed. In order to excite the TE40 mode, a microstrip power divider and two coupling slots driven by microstrip lines in the longitudinal direction of SIW are designed to convert the electromagnetic field pattern from slot lines to SIW. The advantages of the TE40 mode are not only reducing process complexity but also simplifying the feeding network so as to reduce the production bottlenecks at high frequency. A 16-element slot array antenna fed by the TE40 mode SIW is designed based on the standing wave antenna array principle. Experimental results show that a 4×4 antenna array fed by TE40 mode achieves a maximum radiation gain of 15.2 dBi and 85% radiation efficiency at 10.4 GHz and an impedance bandwidth ranging from 9.95 to 10.6 GHz with |S11| below −10 dB. The achieved results demonstrate the superiority of the higher mode excitation technology and it is reasonable to deduce that other higher modes can be achieved based on the proposed technology.