A modified pulse swallow frequency divider for fractional-N frequency synthesizers was designed and implemented in a 0.18 µm CMOS process. The proposed structure inserts a pulser between D flip-flop 1 (DFF1) and B counter to solve the possible malfunction of the SR latch and the unwanted division ratio offset in the conventional structure. To remarkably improve the operating speed, a D flip-flop 2 (DFF2) was employed to retime the modulus control (MC) signal. The proposed frequency divider can work at an input clock signal frequency up to 7.04 GHz with a power consumption of only 7.59 mW.
A novel time-domain (TD) asymptotic-numerical solution (novel TD-ANS), which provides basic knowledge of engineering applications such as a nondestructive testing of reinforced concrete structures, is proposed for the forward transient scattered magnetic field when an ultra-wideband (UWB) pulse wave is incident on a metal cylinder covered with a homogeneous medium layer (coated metal cylinder). The TD-ANS is represented by multiple reflected and surface diffracted ray (multiple RSD) series solution in the TD. The TD-ANS is useful in understanding forward transient scattering phenomena because it can reproduce any part of a response waveform. The accuracy and validity of the TD-ANS are confirmed by comparing with the reference solution.
Power capacitors are widely used in power systems, and any internal capacitor failures will affect the safe operations of the systems. The most common failures include humidity, partial discharge, aging, or insulating material degradation and structural damage. The purpose of this study is to detect the types of power capacitor failures by using a human-machine interface diagnostic system in order to determine the real-time status of the power capacitors. Partial discharge data measurement and diagnostic analysis were mainly conducted on power capacitors operating at a low voltage for a long time. Defects were pre-processed before capacitance measurement, and then, an electric testing machine was used to conduct a partial discharge test for capacitor enclosures and to continuously apply voltage until the occurrence of a partial discharge. A high frequency oscillograph was used to capture the voltage and partial discharge signals. Subsequently, the empirical mode decomposition (EMD) was applied to identify the characteristics of the discharge signals and to build the chaos and error scatter map by combining the chaotic synchronization detection and analysis method. Moreover, eyes of chaos were taken as the characteristics of fault diagnosis, and an extension algorithm was used to identify capacitance failures. The advantages of this method are to reduce the characteristics’ captured data and to effectively detect the minimum movement of the voltage signal discharged from power capacitors, so that the operating states of the power capacitors can be detected and determined, in order to carry out emergency measures in advance and prevent major disasters. After verification through actual measurement, the proposed method has a detection rate of 84% based on the extension theory, which proves that the method used in this study is applicable to partial discharge detection of power capacitors.
Dramatic advancements have been witnessed for the magnetic resonant coupling wireless power transfer technology used in various portable electronic devices. A novel omnidirectional wireless power transfer system was proposed in this paper. Instead of conventional planar coils, a multidirectional receiver inside the transmitter was designed to receive the electromagnetic energy from all the directions. As expected, the finite element simulation results show that the distribution of magnetic field is uniform at different positions inside the transmitter. And the power transfer efficiency (PTE) of the newly designed system with the multidirectional receiver is obviously greater than that of the conventional system with the planar coil. Effects of the different receiver structural sizes on the system performance were discussed. PTE of the system becomes higher when the receiver is larger. Furthermore, PTE is insensitive to position and angular misalignment of the multidirectional receiver. The experimental measurments show that PTE of the system with the multidirectional receiver is 26% at the frequency of 6.78 MHz. The newly designed magnetic resonant coupling wireless power transfer system will be significative for the electronic devices indoor.
This letter presents a unique printed dipole antenna which can roughly cover an 80% fractional bandwidth (VSWR≤3), and especially possess the omnidirectional radiation patterns similar to those of wire dipole antenna at its all resonant modes. The antenna is simple with a microstrip-fed structure which it is just composed of two arms with each one forming the shape of a conventional “inset-fed” rectangular patch antenna. At the lowest operation frequency for VSWR=3, the antenna size is only 0.3λ×0.008λ, showing its effectiveness in many applications of small antennas.
A linear, high-precision capacitance-to-digital converter (CDC) for grounded-type capacitive sensors is presented in this paper. The designed CDC consists of an analog front-end (AFE) circuit that converts capacitance to voltage signal and a noise-shaping successive approximation register (NS-SAR) analog-to-digital (ADC) that converts voltage to digital output. Firstly, in order to measure very small capacitance with a grounded target electrode in the presence of a large offset capacitance, a variable capacitance multiplier circuit is introduced, which ensures that the final output is independent of the offset capacitance. Secondly, the designed CDC implements a fully differential operational amplifier (FDOA) with two T-networks to reduce non-linearity, which provides an output proportional to the variable capacitance. Accordingly, the design complexity of the analog front-end circuit can be minimized effectively. The interface is designed as an integrated circuit using a standard 0.18 µm CMOS process. The functionality of the proposed CDC is verified first using simulation results, showing that for a sensor capacitance ranging from 1 fF ∼ 1 pF, the minimum measurement accuracy can reach 0.1 fF with a parasitic capacitance up to 100 pF. The whole CDC consumes approximately 0.8 mA from a 1.8 V power supply.
Multicarrier signals are used in many radio frequency and microwave systems. A typical example is the wideband communication satellites. However, it is rare to require the carriers in such multicarrier systems to be coherent due to the fact that their frequencies are different. An exception is the testing system for Multipactor Sensor System (MSS). Compared with existing methods that rely on the heavy use of expensive microwave instruments, in this work, we demonstrate an ultra-wideband coherent multicarrier generator (UCMG) with commercial chips and economic devices, which works from UHF to Ku band. MSS experimental results verified the novelty and effectiveness of the proposed approach. The implemented UCMG would make it affordable for a regular microwave laboratory to conduct quantitative experimental researches on wideband multicarrier multipactors. It can also be widely used in other RF systems such as massive MIMO and large-scale phase array systems.
A self-start circuit with asymmetric inductors reconfigurable technology for dual-output boost converter for energy harvesting is presented in this paper. It is found that the cross-coupled LC oscillator with asymmetric inductors can output much higher voltage than ordinary oscillators. Thus, the asymmetric inductors reconfigurable technology (AIRT) is used in the self-start circuit and a minimum startup voltage of 150mV is achieved. The AIRT realizes dual-output and improves the utilization of chip pins by reusing inductors in the self-start circuit and the boost system. The self-start circuit and the boost system are implemented in a 0.13µm CMOS process and a 73.7% converter efficiency is achieved. The chip area of the boost converter is 0.155mm2. The area occupied by self-start circuit is only of 0.006mm2 without other extra energy sources.
Matching networks for ultra-high frequency chips are susceptible, and accurate extraction of passive devices parameters is essential. For on-chip transmission lines, the authors present a precise method of extracting transmission line propagation constant from two transmission line measurement structures with different lengths. After obtaining the propagation constant based on this method, to get the transmission line’s characteristic impedance, this paper conducts a Y-Z model analysis of the signal pad and gives mathematical expressions. This approximation method can obtain the characteristic impedance of the transmission line without solving the signal pad’s model parameters. The propagation constant and characteristic impedance derived from the methods proposed are compared with the corresponding electromagnetic simulation results, achieving fairly good agreement from 250 MHz to 110 GHz.